AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 138 PM MST WED JUL 23 2008 SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA FORECAST DISCUSSION .UPDATE...UPDATED AVIATION DISCUSSION && .SYNOPSIS... A WEAK WEATHER SYSTEM WILL MOVE THROUGH SOUTHERN ARIZONA AND MEXICO TODAY...CONTINUING A THREAT FOR SHOWERS AND THUNDERSTORMS MAINLY OVER THE HIGHER TERRAIN TO OUR EAST. ACROSS THE DESERTS... DRIER AIR FROM THE WEST HAS MOVED INTO THE VALLEY FLOORS... DECREASING THE DAILY THREAT FOR SHOWERS AND THUNDERSTORMS WHILE AIDING IN A CONTINUED WARMING TREND. A CHANGE IN WEATHER MIGHT BE LURKING AROUND THE CORNER...AS THE REMNANTS OF TROPICAL STORM DOLLY EJECTS A SIGNIFICANT AMOUNT OF MOISTURE FROM THE EAST BACK INTO THE LOWER DESERTS THIS WEEKEND. && .DISCUSSION... AREA OF SHOWERS AND THUNDERSTORMS DEVELOPED OVER SOUTHERN GILA COUNTY AND HAS BEEN MOVING NORTHEAST TO SOUTHWEST ACROSS THE REGION DURING THE LAST FEW HOURS. THIS SEEMS TO BE ASSOCIATED WITH A VORTICITY LOBE WHICH HAS DEVELOPED IN AN AREA OF UPPER LEVEL DEFORMATION...JUST EAST OF THE UPPER LEVEL RIDGE ORIENTED SOUTHWEST TO NORTHEAST ACROSS SOUTHEAST ARIZONA. BOTH THE NAM12 AND RUC12 DO A DECENT JOB IN INITIALIZING THIS FEATURE. THIS ALSO APPEARS TO COINCIDE CLOSELY WITH THE APPROXIMATE POSITION OF AN INVERTED TROUGH...WHICH HAS BEEN PROGGED OVER THE LAST SEVERAL DAYS TO MOVE EAST TO WEST ACROSS SOUTHERN ARIZONA TODAY. BOTH SHORT RANGE FORECAST MODELS...HOWEVER LOSE THIS FEATURE AS IT ATTEMPTS TO PUSH FURTHER TOWARD THE WEST THROUGH THE DAY. TODAYS FORECAST IS ANOTHER CHALLENGING ONE. MORNING SOUNDING SHOWS SIGNIFICANT DRYING FROM THE SURFACE TO AROUND 700 MB. THIS COULD HINDER STORM DEVELOPMENT OVER MOST OF THE FORECAST AREA. NAM...GFS...AND LOCAL WRF WANT TO KEEP AFTERNOON DEVELOPMENT CONFINED TO THE MORE FAVORABLE HIGHER TERRAIN REGIONS NORTH AND EAST OF PHOENIX. THE RUC HOWEVER BRINGS THE PRECIPITATION A LITTLE FURTHER WEST...THOUGH STILL EAST OF PHOENIX. THE REAL QUESTION WILL BE...HOW MUCH DO THE LOWER LEVELS MOISTEN UP THROUGH THE DAY...AND HOW MUCH STORM DEVELOPMENT OCCURS TO OUR SOUTHEAST LATER TODAY. SIGNIFICANT ACTIVITY TO OUR SOUTHEAST COULD RESULT IN OUTFLOW BOUNDARIES PROPAGATING NORTHWARD...BRINGING ADDITIONAL MOISTURE INTO THE AREA AND PROVIDING THE FOCUS FOR STORM DEVELOPMENT. THESE BOUNDARIES COULD ALSO INTERACT WITH THOSE PRODUCED BY STORMS OVER THE HIGHER TERRAIN TO THE EAST AND NORTH. THIS MORNINGS SOUNDING ALSO SHOWED WEAK STEERING FLOW ALOFT...THOUGH THE MODELS INDICATE THAT STORM MOTION WILL BE OUT OF THE NORTHEAST LATER THIS AFTERNOON AND EVENING. CAN THEREFORE NOT RULE OUT STORMS THAT DEVELOP ON THE MOUNTAINS MOVING DOWN INTO THE VALLEYS. MADE SOME MINOR ADJUSTMENT TO TODAYS TEMPS AND POPS...PRIMARILY IN EAST AND SOUTHEAST PORTION OF THE FORECAST AREA...WHERE SHOWERS...ADDITIONAL CLOUDINESS AND MORE MOISTURE EXISTS THIS MORNING. && .PREV DISCUSSION... ISSUED AT 535 AM MST WED JUL 23 2008 SAT IMAGERY EARLY THIS MORNING SHOWS ANTICYCLONIC SPIN OVER MUCH OF THE GREATER SOUTHWEST...AS HIGH PRESSURE EXTENDS FROM CO SOUTHWESTWARD INTO SRN CA. A PERSISTENT WESTERLY FLOW IN THE LOW LEVELS OVER THE PAST DAY OR SO HAS LEAD TO A SIGNIFICANT DECREASE IN LOW LEVEL MOISTURE FROM THE SFC THROUGH ABOUT 750MB (10K FT) ACROSS THE WRN CWA AND INTO THE SOUTH-CNTRL AZ DESERTS. AS OF 00UTC...THE KPSR RAOB HAD A PWATER OF 1.43 INCHES COMPARED TO 1.81 INCHES 24 HOURS PREVIOUS. TEMPERATURES HAVE ALSO CONTINUED TO WARM SEVERAL DEG EACH DAY THIS WEEK...WITH ANOTHER COUPLE DEG OF WARMING EXPECTED TODAY. MEANWHILE...A MORE NORTHEASTERLY FLOW FROM 750MB-500MB HAS KEPT OUR FAR ERN HIGHER TERRAIN PLENTY MOIST...WHICH IS WHERE SHOWERS/TSTMS HAVE PRETTY MUCH BEEN CONFINED THE PAST DAY OR SO. TODAY AND THURSDAY...WE ARE STILL WATCHING THE WEAK INVERTED TROF OF LOW PRESSURE THAT HAS BEEN OVER W TX THIS WEEK AS IT SLOWLY INCHES ITS WAY WESTWARD. MODELS CONTINUE SHOW THIS FEATURE MOVING ACROSS FAR SOUTHERN AZ AND MAINLY MEXICO TODAY AND THURSDAY. WITH EACH PASSING RUN...THIS SYSTEM HAS BEEN SHUNTED FURTHER SOUTH...LIMITING THE MOISTURE TRANSPORT INTO OUR LOWER DESERTS...AS WELL AS KEEPING THE BEST FORCING ALOFT OVER SOUTHEAST AZ. FCST TREND THE PAST 24 HOURS HAS BEEN BACKING OFF ON THE PROBABILITY OF SHOWERS/TSTMS TODAY...AND THIS MORNING`S PACKAGE IS NO EXCEPTION. I`VE LEFT SCATTERED WORDING IN THE FCST TODAY AND EARLY THIS EVENING FOR THE HIGHER TERRAIN EAST OF PHOENIX IN ZONE 23...BUT OTHERWISE...POPS HAVE BEEN CUT BACK TO LOW TEENS ACROSS THE DESERT VALLEY FLOORS...WITH NEXT TO NO CHANCE OF ACTIVITY OVER THE WRN CWA THROUGH AT LEAST THE EARLY EVENING HOURS. NOW...WHAT HAPPENS AFTER ABOUT MIDNIGHT MIGHT BE ANOTHER STORY. EVEN WITH THE BULK OF THE DYNAMICS...AND CERTAINLY MOISTURE...STAYING WELL SOUTH/SOUTHEAST OF OUR AREA TODAY...IF THINGS COME TOGETHER NICELY OVER SE AZ (TWC CWA) LATER...WITH A POSSIBLE MCS DEVELOPING WITH THE IMPORT OF COOLER AND MORE MOIST AIR IN THEIR MORE EASTERLY FLOW...WE COULD SEE THIS FEATURE MARCH ACROSS OUR CENTRAL AND WESTERN DESERTS OVERNIGHT TONIGHT. BECAUSE OF THAT...I`VE DECIDED TO KEEP SLIGHT CHANCE (ABOUT 25%) IN THE FCST FROM THE CO RIVER VALLEY EASTWARD FROM MIDNIGHT THROUGH EARLY MORNING HOURS. IF THIS ENDS UP BEING THE CASE...WE WOULD EXPECT THE LOW LEVELS TO MOISTEN SIGNIFICANTLY...WHICH COULD LEAD TO A BETTER CHANCE FOR VALLEY SHOWERS/TSTMS THURSDAY AFTERNOON AS WELL. STILL A LOT OF UNCERTAINTIES WITH THE SHORT TERM PORTION OF THE FCST...BUT BOTTOM LINE IS A MUCH MORE BENIGN WEATHER PATTERN IS IN STORE FOR OUR AREA THAN PREVIOUS MODEL RUNS AND FCSTS WERE SHOWING. FRIDAY THROUGH THE WEEKEND...AFTER THE INVERTED TROF PASSES WELL TO THE WEST...THE HIGH CENTER WILL SHIFT OVER THE PLAINS...MAKING ROOM FOR THE REMNANTS OF TS DOLLY TO MOVE EASTWARD. WITH THE CLOCKWISE CIRCULATION AROUND THE HIGH...AND THE COUNTERCLOCKWISE CIRCULATION FROM THE TS COMING TOGETHER...WE COULD END UP WITH A PRETTY LONG FETCH OF VERY MOIST SUBTROPICAL AIR MOVING INTO THE REGION UNDER AN EASTERLY FLOW. MODELS ARE INDICATING LOWER LEVEL MEAN MIXING RATIOS TO INCREASE BACK TO NEAR 12/13 G/KG (COMPARED TO 7/8 G/KG NOW). WITH THE MORE FAVORABLE STEERING FLOW...AND ADDED MOISTURE...FELT IT PRUDENT TO SHOW AN INCREASING THREAT FOR SHOWER/THUNDERSTORMS THIS WEEKEND (AND CURRENT FCST NOW REFLECTS THIS). BEYOND THE WEEKEND...IT IS REALLY ANYONE`S GUESS. AT THIS POINT IN TIME...THERE DOESN`T APPEAR TO BE ANYTHING UPSTREAM TO WIPE OUT OUR MOISTURE...SO WE`LL CONTINUE A LOW GRADE MONSOON FCST THOUGH THE EXTENDED...WITH SHOWERS/THUNDERSTORMS FAVORING THE HIGHER TERRAIN AND TEMPS RUNNING A COULD DEG BELOW AVERAGE FOR LATE JULY. && .AVIATION... SOUTH-CENTRAL ARIZONA...KPHX/KIWA AND SURROUNDING AIRFIELDS... AIRMASS WEST OF KPHX TO THE LOWER COLORADO RIVER HAS DRIED OUT CONSIDERABLY...EAST OF KPHX INTO THE HIGHER TERRAIN STILL MAINTAINS SUFFICIENT MOISTURE AND INSTABILITY. WITH A WEAK NORTHEAST STEERING FLOW...THERE IS ONLY A SLIGHT CHANCE FOR STORMS TO MOVE SW OFF THE HIGHER TERRAIN AND INTO THE DESERTS THROUGH 03Z THURSDAY. HOWEVER ...ANY STORM THAT MOVES INTO THE DESERTS NEAR KIWA/KPHX HAS THE POTENTIAL TO PRODUCE GUSTY OUTFLOW WINDS UP TO 35 KTS. DUE TO UNCERTAINTIES/LOW POPS...WILL NOT MENTION WEATHER AT THIS TIME. WINDS SHOULD BE GENERALLY LIGHT AND DIURNAL OVERNIGHT THROUGH 12Z THURSDAY. SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA...KNYL/KBLH AND KIPL... AIRMASS MUCH DRIER AND MORE STABLE WITH NO THREAT OF THUNDERSTORMS THROUGH 18Z THURSDAY. EXPECT LIGHT WINDS FAVORING THE SOUTH THROUGHOUT THE DAY ...LIGHT AND VARIABLE OVERNIGHT. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... NO SIGNIFICANT FIRE WEATHER CONCERNS FRIDAY THOUGH THE WEEKEND...AND INTO EARLY NEXT WEEK. AIRMASS WILL BE GRADUALLY WETTING UP FRIDAY THROUGH SUNDAY AS MOISTURE FROM HURRICANE DOLLY WORKS WESTWARD AND INTO THE STATE...LEADING TO A CHANCE FOR SHOWERS/THUNDERSTORMS ACROSS SOUTH-CENTRAL AZ BY SATURDAY...WITH POSSIBLY A BETTER CHANCE SUNDAY. AS HUMIDITIES RISE...MAX TEMPS WILL LOWER...LIKELY TO WELL BELOW NORMAL VALUES BY SUNDAY. WITH NO SIGNIFICANT MECHANISM TO REALLY DRY THINGS OUT NEXT WEEK...WE WILL KEEP AT LEAST A STANDARD GRADE MONSOON FORECAST GOING...WITH MAX TEMPS TO CLIMB TO NEAR NORMAL BY THE END OF THE PERIOD. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...MCLANE/WANEK AVIATION...MEYERS FIRE WEATHER...CB az AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RENO NV 330 AM PDT TUE JUL 22 2008 .SHORT TERM... THE UPPER LOW RESPONSIBLE FOR THE EXCEPTIONAL AMOUNT OF SEVERE WEATHER MONDAY WILL FILL AND EXIT INTO SOUTHEAST OREGON THIS MORNING. WITH A JET STREAK AND UPPER DIFFLUENCE MOVING INTO EXTREME NORTHERN PORTIONS OF THE CWA JUST AHEAD OF THE UPPER LOW...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE STILL POSSIBLE THIS MORNING...MOSTLY NORTH OF GERLACH. AS FAR AS SEVERITY...WHILE WIND SHEAR ALOFT REMAINS STRONG...INSTABILITY IS WANING ACCORDING TO RUC MODEL FORECASTS SO ANY STORMS MAY TEND TO TEAR APART SOMEWHAT AND/OR REMAIN MODEST IN STRENGTH. AS FAR AS FLASH FLOODING...WITH FAST MOVING THUNDERSTORMS I AM NOT TOO CONCERNED WITH FLASH FLOODING. THEREFORE...I HAVE CANCELLED THE FLASH FLOOD WATCH A COUPLE HOURS EARLY TO COINCIDE WITH THE MORNING FORECAST PACKAGE. AFTER THE UPPER LOW EXITS THIS MORNING...THE REGION WILL SETTLE INTO A DRY SOUTHWEST FLOW ALOFT THROUGH THURSDAY. TEMPERATURES WILL SLOWLY WARM AS AN UPPER RIDGE BUILDS OVERHEAD...WITH HIGHS WINDING UP 5-10 DEGREES ABOVE NORMAL BY THURSDAY. SNYDER .LONG TERM...FRIDAY THROUGH MONDAY... MODELS STILL SHOWING SIMILAR TRENDS THROUGH THE EXTENDED WITH SATURDAY LOOKING TO BE THE MOST INTERESTING DAY ACROSS THE SOUTHERN AND EASTERN ZONES. CENTRAL CONUS RIDGE IS FORECAST TO BUILD INTO THE SOUTHWESTERN U.S. ON FRIDAY HELPING TO TURN OUR FLOW SOUTHERLY WHILE A SHORTWAVE TROUGH DEVELOPS OFF THE NORTHERN CALIFORNIA COAST. MOISTURE WILL BEGIN TO SURGE NORTHWARD INTO SOUTHERN AND EASTERN NEVADA ON FRIDAY. MAINTAINED SLIGHT CHANCE THUNDERSTORMS FOR MONO/MINERAL COUNTIES ON FRIDAY AFTERNOON. THERE ARE TIMING DIFFERENCES BETWEEN THE GFS AND EC...THE EC IS ABOUT 12 HOURS FASTER IN EJECTING THE SHORTWAVE TROUGH THAN THE GFS ON SATURDAY AFTERNOON. WENT AHEAD AND INTRODUCED SLIGHT CHANCE OF THUNDERSTORMS FOR THE SOUTHERN AND FAR EASTERN PORTIONS OF OUR ZONES DURING THE AFTERNOON AS INSTABILITY ASSOCIATED WITH THE UPPER WAVE INCREASES ACROSS THE AREA. KEPT SLIGHT CHANCE WORDING THROUGH SATURDAY NIGHT WITH LOWER CONFIDENCE IN TIMING OF THE UPPER SYSTEM. UPPER WAVE FLATTENS PUSHES RIDGE EASTWARD AND TURNS OUR FLOW SOUTHWESTERLY ON SUNDAY AND MONDAY. EXPECT DRY CONDITIONS ACROSS THE FORECAST AREA WITH ONLY SLIGHT CHANCE OF THUNDERSTORMS OVER MONO AND MINERAL COUNTIES EACH AFTERNOON. CENTRAL CONUS RIDGE IS FORECAST TO BUILD BACK INTO THE DESERT SOUTHWEST ON TUESDAY TURNING THE FLOW ONCE AGAIN MORE SOUTHERLY INCREASING MOISTURE ACROSS SOUTHERN AND EASTERN NEVADA. INCREASED TO SLIGHT CHANCE OF THUNDERSTORMS TUESDAY AFTERNOON ACROSS THE SOUTHERN AND FAR EASTERN PORTIONS OF THE FORECAST AREA. TEMPS WILL REMAIN WARM THROUGH THE WEEKEND WITH HIGHS REACHING TO NEAR 100 THROUGH SUNDAY ACROSS WESTERN NEVADA WHILE THE HIGH SIERRA WILL REACH THE MID 80S. THINGS WILL COOL OFF SLIGHTLY EARLY NEXT WEEK WITH HIGHS INTO THE LOWER TO MID 90S IN WESTERN NEVADA AND LOWER 80S IN THE SIERRA. MOZLEY && .AVIATION... SHOWERS AND THUNDERSTORMS HAVE ENDED OVER MOST OF THE FORECAST AREA EXCEPT FOR AREAS NORTH OF SUSANVILLE AND LOVELOCK WHERE ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH 18Z. QUIET DAY AT THE TERMINALS WITH THE AFTERNOON/EVENING WEST WINDS OFF THE SIERRA. BRONG && .REV WATCHES/WARNINGS/ADVISORIES... NV...NONE. CA...NONE. && $$ HTTP://WEATHER.GOV/RENO ca AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 305 PM MDT TUE JUL 22 2008 .SHORT TERM...CONVECTION CURRENTLY CONFINED TO HIGHER TERRAIN EAST OF THE CONTINENTAL DIVIDE AS SHOWN BY LATEST RADAR LOOPS. SOME STORMS BEGINNING TO DEVELOP ALONG AND WEST OF THE DIVIDE. NO STORMS YET OVER THE PLAINS. WITH CONTINUED HEATING...SHOULD SEE COVERAGE OF MOUNTAIN STORMS INCREASE BY THE EVENING...WILL CONTINUE THE CURRENT SCATTERED POPS THERE. HARD TO SEE ANY SIGN OF A SHORTWAVE ON SATELLITE WHICH WOULD HELP TO INCREASE COVERAGE. AS FOR PLAINS... AIRMASS STILL SLIGHTLY CAPPED THOUGH LAPS SURFACE ANALYSIS SHOWING CIN ALL BUT GONE. ALSO...ACARS SOUNDINGS INDICATING VERY MINIMAL CIN. SO...POTENTIAL FOR STORMS TO DEVELOP AND MOVE ACROSS PLAINS SLIGHTLY BETTER THAN PREVIOUS DAYS. LOW LEVEL SOUTHEAST FLOW PROVIDING A BOUNDARY ACROSS EASTERN WELD...MORGAN AND CENTRAL ADAMS COUNTIES. CUMULUS HAD BEEN DEVELOPING ALONG THIS BOUNDARY DURING THE PAST HOUR. COULD SEE A FEW STORMS FIRE ALONG THIS BOUNDARY. IN ADDITION...OUTFLOW FROM MOUNTAIN STORMS COULD ALSO BECOME FOCUS FOR CONVECTION. THOUGH RUC KEEPS MOST IF NOT ALL OF THE QPF OVER THE MOUNTAINS TONIGHT...THE NAM AND GFS SPREAD SOME QPF OVER THE PLAINS. GIVEN CURRENT TRENDS...WILL UP THE EVENING POPS TO 30 PERCENT FOR THE URBAN CORRIDOR AND ADJACENT PLAINS. CURRENT INTEGRATED PRECIPITABLE WATER VALUES HOVERING AROUND NINE TENTHS OF AN INCH...COULD ACTUALLY SEE SOME RAINFALL WITH THE STORMS. STEERING WINDS ARE LIGHT...SO STORMS WILL BE SLOW MOVING WITH THE POTENTIAL FOR LOCALLY HEAVY RAIN. MOST ACTIVITY WILL BE ENDING BY MIDNIGHT... THOUGH COULD SEE A FEW STORMS LINGER PAST MIDNIGHT OVER THE MOUNTAINS. ON WEDNESDAY...LITTLE CHANGE IN OVERALL PATTERN EXCEPT THE UPPER LEVEL RIDGE AXIS SHIFTS SLIGHTLY EAST INTO EASTERN COLORADO. THIS COULD BRING MORE OF THE MOISTURE PLUME ACROSS OUR AREA. IN ADDITION..LATEST NAM SHOWING A BATCH OF QG ASCENT IN THE 700-500 MB LAYER ROTATING ACROSS EASTERN COLORADO DURING THE AFTERNOON. THIS FEATURE COULD BE ENOUGH TO AID IN INCREASING CONVECTION CHANCES. FOR NOW WILL LEAVE THE SLIGHT CHANCE POPS ACROSS PLAINS AS FORECAST SOUNDINGS STILL SHOW QUITE A BIT OF CIN DURING THE AFTERNOON. AS FOR MOUNTAINS...SCATTERED POPS SUFFICIENT FOR NOW. FORECAST SOUNDINGS SHOWING PRECIPITABLE WATER VALUES OVER AN INCH ACROSS THE PLAINS...WITH AROUND SEVEN TENTHS OF AN INCH ACROSS THE MOUNTAINS. POTENTIAL EXISTS FOR HEAVY RAIN WITH THE STORMS. TEMPERATURE AND THICKNESS PROGS SHOW LITTE CHANGE FROM TODAY`S PATTERN. HIGHS COULD BE A FEW DEGREES COOLER GIVEN A BIT MORE CLOUD COVER. GUIDANCE INDICATING HIGHS IN THE LOWER AND MID 90S ACROSS THE PLAINS. THIS SEEMS REASONABLE. CURRENT TEMPERATURE GRIDS IN LINE WITH GUIDANCE...LITTLE IF ANY CHANGES NEEDED AT THIS POINT. .LONG TERM...UPPER LEVEL RIDGE WILL REMAIN CENTERED OVER THE SOUTHWESTERN U.S. THROUGH THE WEEKEND AND INTO NEXT WEEK. VERY WARM AND MOSTLY DRY CONDITIONS WILL CONTINUE TO PREVAIL IN THIS PATTERN. BEST CHANCE FOR MOISTURE DURING THE EXTENDED PERIOD WILL BE WEDNESDAY EVENING. MODELS SHOW MOISTURE INCREASING ACROSS THE AREA...LEADING TO GREATER INSTABILITY WHICH SHOULD BE ABLE TO BREAK THE CAP ACROSS THE PLAINS. MOISTURE TO DECREASE THURSDAY AND WE`LL BE BACK TO THE SAME OLD PATTERN OF MOSTLY MOUNTAIN AND FOOTHILL SHOWERS AND THUNDERSTORMS. MODELS HINTING AT SOME SORT OF SHORT WAVE PASSING THROUGH THE RIDGE SUNDAY OR MONDAY. EXPECT AN INCREASE IN THUNDERSTORMS WITH THIS. WILL HOLD FROM INCREASING THE POPS FOR THIS BECAUSE OF THE UNCERTAINTY WITH THE TIMING AND TRACK. HIGH TEMPERATURES WILL REMAIN IN THE 90S ACROSS THE PLAINS EACH DAY. && .AVIATION...ISOLATED THUNDERSTORMS POSSIBLE THROUGH 04Z...WHICH COULD AFFECT AREA AIRPORTS. GUSTY WINDS AND BRIEF HEAVY RAIN POSSIBLE IF STORMS TRACK OVER THE AIRPORTS. VFR CONDITIONS WILL PREVAIL. SOUTHEAST SURFACE GRADIENT TO WEAKEN THIS EVENING...WITH SURFACE WINDS BECOMING DRAINAGE BY 06Z. ISOLATED THUNDERSTORMS POSSIBLE AFTER 18Z WEDNESDAY...PRODUCING GUSTY OUTFLOW WINDS. HEAVY RAIN POSSIBLE WITH THE STORMS...WHICH MAY BRIEFLY LOWER CEILINGS AND VISIBILITY INTO THE MVFR CATEGORY. && .BOU WATCHES/WARNINGS/ADVISORIES...NONE. && D-L/MEIER co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 335 AM EDT WED JUL 23 2008 .SYNOPSIS...WATER VAPOR IMAGERY SHOWS A MID TO UPPER TROUGH FROM THE GREAT LAKES TO THE LOWER MS VALLEY AND A WEAK SHORTWAVE OFF THE SE U.S. COAST PER RUC AND NAM GUIDANCE. AT SFC...RIDGE AXIS IS ACROSS CENTRAL FL AND ANTICIPATE LITTLE CHANGE IN THIS FEATURE FOR THE NEXT 3 DAYS. JAX SOUNDING FROM 00Z SHOWED PWAT OF ABOUT 2 INCHES AND MEAN 0-6KM WINDS FROM THE NW AT 5 KT. CONSIDERABLE MID AND UPPER LEVEL DEBRIS CLOUDINESS BLANKETS PORTIONS OF THE AREA FROM EARLIER CONVECTION OVER THE SE CONUS. ANTICIPATE A FEW AREA PLACES OVER THE SRN ZONES TO DEVELOP PATCHY FOG THROUGH SUNRISE DUE TO WET GROUNDS FROM YESTERDAYS RAINFALL. RADAR IMAGERY SHOWS A FEW SHOWERS AND STORMS ALREADY FORMING JUST S OF THE FORECAST AREA. .SHORT TERM...TODAY...CLOUDINESS AND LOWER HEIGHTS WILL TRANSLATE INTO LOWER MAX TEMPS THAN THE PAST FEW DAYS. ANTICIPATE HIGHS OF UPPER 80S TO LOWER 90S. MAV POPS HAVE JUMPED UP TO 70-80% FOR TODAY WHICH LOOKS TOO HIGH. WILL GO CLOSER TO NAM GUIDANCE AND HAVE LOW END LIKELY OVER MOST AREAS. NAM SHOWS MORE THAN 2 IMPULSES AFFECTING THE REGION TODAY COMING IN FROM THE NW AND WITH DAYTIME HEATING AND SEA BREEZES THE LIKELY POPS SEEM REASONABLE. MODIFIED SOUNDING YIELDS CAPE VALUES CLOSE TO 2500 J/G AND LI OF -6. GIVEN THE RELATIVE HIGH PWAT AIR AND WEAK 0-6KM WINDS MAIN THREATS TODAY APPEAR TO BE LOCALLY HEAVY RAINFALL AND MARGINALLY SEVERE DOWNBURST WINDS. IN ADDITION...STORMS DON`T LOOK TO BE AS INTENSE AS THEY WERE ON TUE DUE TO WARMER TEMPS AT 500 MB AND GENERALLY LOWER INSTABILITY VALUES. TONIGHT...SHORTWAVE IMPULSES CONT TO AFFECT THE AREA TONIGHT AND BEST DYNAMIC LIFT WILL BE OVER NE FL. WILL GO WITH A BLEND OF THE GUIDANCE BUT LEAN A BIT TOWARD THE MAV POPS WHICH HAVE BEEN CONSISTENTLY AROUND 40% FOR TONIGHT. THURSDAY...THE WEAK TROUGH THAT IS N OF THE AREA WILL BE SAGGING SWD AND RESULT IN CONTINUED MOISTURE POOLING OVER THE AREA...MOST FAVORED OVER NE FL. WILL GO WITH POPS AROUND 40-50% OVER NE FL AND 30-40% FOR SE GA WHICH IS A CONSENSUS OF THE GUIDANCE. TEMPS SHOULD BE A BIT WARMER AS HEIGHTS RISE A BIT. THU NIGHT...MID LEVEL RIDGING TRIES TO BUILD IN AND SFC TROUGH WILL DRIFT INTO CENTRAL GA. PLANNING ON POPS AT 20-30% FOR MAINLY EVENING CONVECTION. FRIDAY...MID LEVEL HEIGHTS CONT TO BUILD AS THE SE CONUS TROUGHING WANES. ENOUGH MOISTURE TO WORK WITH FOR SCT POPS AREA WIDE...THOUGH LOWER CHANCES FOR SE GA WHERE WEAKER FORCING AND LOWER MOISTURE IS LOCATED. TEMPS IN THE LOWER 90S EXPECTED WITH FEW POCKETS OF MID 90S. .LONG TERM...SAT-TUE. SFC RIDGE CONTS OVER CENTRAL FL FOR THE WEEKEND. LATEST GFS SHOWS ERN COAST TROUGHING TO BECOME RE-ESTABLISHED WITH LOWERING HEIGHTS AND THUS SUSTAINING A CHANCE OF SHOWERS AND THUNDERSTORMS FOR THE EXTENDED FORECASTS. FOR NOW WILL KEEP POPS IN THE 30-40% RANGE EACH DAY AND SHOW JUST A SLIGHT CHANGE IN TEMPS MOVING CLOSE TO OR JUST BELOW CLIMO. && .AVIATION...MAY SEE BRIEF PERIOD OF MVFR VISIBILITY EARLY THIS MORNING (09Z-12Z) DUE TO FOG. OTHERWISE AN ACTIVE AFTERNOON EXPECTED ACROSS THE AREA AS THE NEXT SHORT WAVE MOVES IN. CONFIDENCE IS HIGH THAT THUNDERSTORMS WILL BE IMPACTING ALL OF THE TERMINALS AND HAVE INCLUDED VCTS BY 18Z AND TEMPO GROUPS FOR TS AND GUSTY WINDS BETWEEN 19Z-22Z. && .MARINE...SW TO S WINDS EXPECTED FOR MUCH OF THE WEEK AS HIGH PRESSURE RIDGE REMAINS NEAR CENTRAL FLORIDA. NOCTURNAL SURGES AT NIGHT BUT BELOW SCEC CRITERIA. SEAS 2-4 FT. MAIN CONCERN WILL BE SCATTERED AFTERNOON STORMS WITH STRONG WIND POTENTIAL MOVING OFFSHORE. && .PRELIMINARY POINT TEMPS/POPS... AMG 91 71 93 72 / 60 30 30 20 SSI 88 75 89 76 / 50 40 30 20 JAX 90 71 91 73 / 60 40 40 30 SGJ 87 71 88 74 / 60 40 40 30 GNV 89 71 90 73 / 60 40 50 30 OCF 89 71 90 72 / 60 40 50 30 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...NONE. && $$ SHASHY/PETERSON fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 310 PM EDT TUE JUL 22 2008 .SHORT TERM...TONIGHT THROUGH FRIDAY. THE LATEST SATELLITE IMAGERY SHOWS A SHARP MID TO UPPER LEVEL SHORTWAVE SPINNING JUST NORTH OF OUR GEORGIA ZONES. IN FACT...THE LATEST RUC ANALYSIS SHOWS A CLOSED 500MB CIRCULATION ASSOCIATED WITH THIS FEATURE. THIS WAVE IS PROGGED TO EXPAND SOUTH THIS AFTERNOON AND REMAIN INFLUENTIAL THROUGH MUCH OF THE NIGHT. MODERATE TO STRONG INSTABILITY EXISTS ACROSS MUCH OF THE LOCAL FORECAST AREA AND AMPLE MOISTURE RESIDES THROUGH THE COLUMN. THIS WILL SET THE STAGE FOR STRONG AFTERNOON THUNDERSTORMS TO CARRY INTO THE EVENING AND POSSIBLY EVEN AFTER MIDNIGHT. SEVERE THUNDERSTORMS ARE POSSIBLE...ESPECIALLY GIVEN LARGE CAPE DENSITY VALUES AND COLD TEMPERATURES ALOFT. BOTH LARGE HAIL AND DAMAGING WIND GUSTS WILL BE CONCERNS. SLOW STORM MOVEMENT WILL ALSO RESULT IN VERY HEAVY RAINFALL IN SOME AREAS. GIVEN THE LATEST MODEL DATA WITH UPPER LEVEL SUPPORT REMAINING OVER THE AREA TONIGHT...HAVE DECIDED TO BUMP EVENING POPS UP A LITTLE...INTO THE 40 TO 50 PERCENT RANGE OVER NORTHEAST FLORIDA. EAST COAST SURFACE TROUGH WILL EXTEND SOUTH THROUGH THE LOCAL FORECAST AREA ON WEDNESDAY. UPPER LEVEL PERTURBATIONS WILL ALSO BRUSH THE AREA AS THEY ROTATE AROUND THE BASE OF UPPER TROUGH WHICH WILL BE DIGGING THROUGH THE GREAT LAKES REGION. 850MB WIND MAXIMA WILL APPROACH 20 KNOTS OUT OF THE NORTHWEST BEHIND 850 TROUGH AND THIS WILL AID IN THUNDERSTORM DEVELOPMENT. DEEP CYCLONIC FLOW...AMPLE MOISTURE...AND SUFFICIENT INSTABILITY WILL ALL COMBINE TO PRODUCE SCATTERED TO NUMEROUS THUNDERSTORMS WEDNESDAY AFTERNOON. SEVERE WEATHER WILL AGAIN BE POSSIBLE BUT DEPENDENT ON AMOUNT OF INSOLATION AND REALIZED INSTABILITY. CAPES WILL PROBABLY BE HELD MUCH BELOW TODAYS VALUES GIVEN THE EXTRA CLOUD COVERAGE EXPECTED...HOWEVER...ISOLATED SEVERE THUNDERSTORMS ARE A DECENT BET GIVEN UNSEASONABLY COLD AIR ALOFT. BY THURSDAY...HIGH PRESSURE WILL BEGIN TO BUILD BACK IN. THE NAM AND GFS CONTINUE TO DISAGREE ON POPS THURSDAY AFTERNOON. THE GFS IS MUCH MORE BULLISH (40 TO 60 PERCENT) OPPOSED TO THE NAM SOLUTION OF LESS THAN 20 PERCENT POPS. THE NAM ADVECTS IN MUCH DRIER AIR BEHIND DEPARTING UPPER TROUGH AXIS IN NORTHWEST FLOW ALOFT. WILL CONTINUE TO SIDE CLOSER TO THE GFS. ENOUGH MOISTURE IS EXPECTED TO REMAIN OVER THE AREA FOR TYPICAL SUMMERTIME CONVECTION TO INITIATE ALONG MESOSCALE (SEABREEZE/OUTFLOW) BOUNDARIES. .LONG TERM...SATURDAY THROUGH TUESDAY. LATEST GFS NOW SHOWS AN INTERESTING SOLUTION FOR THE UPCOMING WEEKEND. IT SHOWS THE LARGE UPPER TROUGH OVER THE EAST COAST ATTEMPTING TO DIG BACK DOWN ALL THE WAY INTO FLORIDA ONCE AGAIN...WITH THE ATTENDANT SURFACE TROUGH IN TOW. THIS WOULD RESULT IN ELEVATED CHANCES OF PRECIP WITH POPS HIGHER THAN CLIMO VALUES. WILL CONTINUE WITH 40 PERCENT AFTERNOON POPS FOR NOW BUT IF THE GFS IS CORRECT...THESE VALUES ARE LIKELY A LITTLE ON THE LOW SIDE. NEAR NORMAL TEMPS ARE EXPECTED THROUGH THE EXTENDED PERIOD. && .AVIATION...HAVE CONTINUED TEMPO THUNDER AT ALL SITES THRU THE AFTN...WITH VCTS THRU MID TO LATE EVENING. MAY BE SOME FOG IN RECENT RAIN AREAS TONIGHT AND EVENING SHIFT CAN EVALUATE FURTHER FOG MODIFICATIONS. && .MARINE...HAVE MADE FEW CHANGES TO ONGOING FORECAST. WINDS AND SEAS SHOULD CONTINUE BELOW HEADLINE CRITERIA. && .PRELIMINARY POINT TEMPS/POPS... AMG 73 95 71 94 / 30 40 40 30 SSI 77 92 75 89 / 40 40 40 30 JAX 74 93 73 91 / 40 40 40 30 SGJ 75 91 73 88 / 40 40 40 30 GNV 73 91 72 90 / 50 50 40 40 OCF 72 90 71 88 / 50 50 30 40 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...NONE. && $$ SHULER/CARROLL fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MELBOURNE FL 318 AM EDT TUE JUL 22 2008 .DISCUSSION... TODAY/TONIGHT...WEAK SURFACE HIGH PRESSURE ACROSS FLORIDA EARLY THIS MORNING. A FEW LINGERING DEBRIS CLOUDS OVER THE PENINSULA...AND WHILE TC DOLLY IS FAR AWAY OVER WESTERN GULF...SOME CIRRUS FROM SYSTEM BEING CARRIED TOWARD FL VIA ANTICYCLONE ALOFT. LATEST WATER VAPOR IMAGES/RUC ANALYSIS INDICATING SOME CONFLUENCE AND DRIER AIR ALOFT OVER REGION AT PRESENT AND 00Z RUNS OF GFS AND ESPECIALLY NAM ARE INDICATING SOME LOWER PWAT AIR TODAY ESPECIALLY ACROSS NORTHERN SECTIONS. THIS HAS RESULTED IN MODEL POPS COMING IN LOWER THAN PREVIOUS RUNS. WEAK WIND FIELDS WILL ALLOW SEA AND LAKE BREEZES TO FORM WITH DAYTIME HEATING. ENOUGH MOISTURE AND SOME WEAK VORT ENERGY ROTATING DOWN BACK SIDE OF ATLANTIC TROF LATER TODAY TO HELP AID IN STORM DEVELOPMENT BY MID TO LATE AFTERNOON. HAVE DISTRIBUTED POPS FROM SLGT CHC/ISOLATED NORTHERN COASTAL SECTIONS TO LOW END CHC/SCT REMAINDER OF THE AREA WITH ISOLATED ACTIVITY LINGERING INTO EARLY EVENING OVER THE INTERIOR. MORE WARM TEMPS ON TAP WITH SOME MID 90S EXPECTED AGAIN ACROSS THE INTERIOR SECTIONS WHILE SEA BREEZE ONSET SHOULD CAP MAXES NEAR THE EAST COAST IN THE LOWER 90S. WED-MON...VORTICITY MAXIMA ROTATING AROUND AN UPPER LOW THAT IS WOBBLING ABOUT THE UPPER GREAT LAKES/ONTARIO/QUEBEC REGION WILL PUSH THE SURFACE RIDGE/WEAK HIGH PRESSURE UP AND DOWN THE PENINSULA. JUST HOW FAR THE SEA BREEZE PUSHES INLAND EACH DAY REMAINS A BIT TENUOUS. TIME HEIGHT CROSS SECTION RELATIVE HUMIDITY FIELD(S) SHOWED MOST OF THE MOISTURE BELOW 700MB FOR MUCH OF THE FORECAST PERIOD THEREFORE WENT WITH CLIMO POP OF 30/40 DURING THE AFTERNOON AND 20S OVERNIGHT WHICH DID NOT STRAY FAR FROM LATEST EXTENDED (MEX MOS) GUIDANCE. TEMPERATURES AROUND THEIR NORMAL HIGHS OF LOW 90S INLAND AND UPPER 80S ALONG THE COAST DUE TO SEA BREEZE STOPPING DAY TIME HEATING... AND OVERNIGHT LOWS IN THE LOW/MID 70S. && .AVIATION...VFR THROUGH ~18Z THEN TSRA PRODUCING CIG/VSBY REDUCTIONS THROUGH 00Z WILL BE MORE COMMON INTERIOR TAF SITES AND HAVE TEMPO INDICATED INLAND SITES VERSUS A VCTS OR PROB30 EAST COAST LOCATIONS. && .MARINE...WEAK PRESSURE GRADIENT RESULTS IN LIGHT/MODERATE WINDS WITH DAILY SEA BREEZE CIRCULATIONS BEGINNING BY MID AFTERNOON EACH DAY THROUGH THE REMAINDER OF THE WEEK. WINDS LESS THAN 15 KNOTS WITH SOME SEA BREEZE ENHANCE DURING THE AFTERNOON AND EARLY EVENING. SEAS ON THE AVERAGE 3 FEET OR LESS. LONG PERIOD SWELLS STILL NOTED AT OFFSHORE BUOYS AND WILL KEEP RIP CURRENT RISK ELEVATED AGAIN TODAY. && .PRELIMINARY POINT TEMPS/POPS... DAB 93 74 89 72 / 20 20 40 20 MCO 93 74 90 73 / 30 20 40 20 MLB 89 73 89 71 / 30 20 30 20 VRB 90 74 89 73 / 30 10 30 20 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. && $$ SHORT TERM/AVIATION...GLITTO LONG TERM....WIMMER fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 127 AM EDT WED JUL 23 2008 .SYNOPSIS... A TROUGH OF LOW PRESSURE WILL REMAIN INLAND TONIGHT...BUT WILL SHIFT CLOSER TO THE COAST ON WEDNESDAY AND WEDNESDAY NIGHT AS A COLD FRONT APPROACHES FROM THE NORTHWEST. THE COLD FRONT WILL STALL NEAR THE AREA THURSDAY INTO FRIDAY. ATLANTIC HIGH PRESSURE WILL THEN PERSIST INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... SHOWERS/THUNDERSTORMS ARE MOVING INTO THE GEORGIA ZONES FROM THE SOUTHWEST...SO I HAD TO UPDATE THE GRIDS AND TEXT PRODUCTS A BIT EARLY. I RAISED POPS IN THE GEORGIA ZONES AND LOWERED THEM IN THE SOUTH CAROLINA ZONES TO ACCOUNT FOR CURRENT TRENDS. LATEST RUC GUIDANCE SUGGESTS THE THREAT FOR RAIN IN GEORGIA WILL GO ON UNTIL MIDNIGHT OR SHORTLY THEREAFTER BEFORE WINDING DOWN...AND THIS SEEMS REASONABLE GIVEN THE AMOUNT OF INSTABILITY STILL AVAILABLE THERE. I ALSO HAD TO MAKE SOME ADJUSTMENTS TO THE EVENING TEMPS AND CLOUDS RELATED TO THE CONVECTION. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/... A COLD FRONT WILL APPROACH FROM THE NORTHWEST ON WEDNESDAY...WHILE IT APPEARS THAT A LEE SIDE TROUGH WILL SHIFT CLOSER TO THE COAST SOUTH OF THE FRONT. DEEPER MOISTURE AND THE PROXIMITY OF THE TROUGH/FRONT WILL RESULT IN INCREASED CHANCES OF PRECIPITATION WEDNESDAY INTO WEDNESDAY EVENING...GENERALLY AROUND 40 PERCENT ACROSS THE AREA. PRECIPITABLE WATER VALUES RANGING FROM 2-2.25 INCHES COULD RESULT IN LOCALLY HEAVY RAINFALL. WITH THE LOSS OF HEATING...EXPECT THE COVERAGE OF ANY SHOWERS/THUNDERSTORMS TO DIMINISH SOME WEDNESDAY NIGHT. HIGH TEMPERATURES WEDNESDAY SHOULD BE IN THE MID 90S AWAY FROM THE COAST...WITH LOWS WEDNESDAY NIGHT IN THE LOWER TO MID 70S. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... THERE CONTINUES TO BE SOME DISAGREEMENT BETWEEN THE MODELS CONCERNING THE PROGRESSION OF THE COLD FRONT THROUGH THE AREA ON THURSDAY. 12Z GFS KEEPS THE FRONTAL BOUNDARY TO THE NORTH AND SOUTHERLY SURFACE FLOW OVER THE AREA. 12Z NAM PUSHES THE COLD FRONT TO THE GEORGIA/SOUTH CAROLINA COASTAL BORDER BY THURSDAY MORNING...BEFORE STALLING IT OVER NORTHERN FLORIDA BY THURSDAY NIGHT. LATEST ECMWF RUN SHOWS A SIMILAR STALLED FRONT TO THE GFS...BUT ALLOWS DEEPER LAYER DRY AIR TO PUSH INTO THE REGION WITHIN THE INLAND SURFACE TROUGH. WILL LEAN TOWARD THE MORE SEASONAL SOLUTION PROVIDED BY THE GFS. HAVE MAINTAINED SOUTHERLY WINDS ON THURSDAY...WITH POPS IN THE 30 PERCENT RANGE DURING THE AFTERNOON...WHEN INSTABILITY AND SEABREEZE FORCING WILL BE MAXIMIZED. HIGH TEMPERATURES WILL BE A FEW DEGREES COOLER THAN WEDNESDAY...REACHING THE LOWER 90S AWAY FROM THE COAST. UPPER LEVEL RIDGING WILL LINGER OVER THE SOUTHWESTERN STATES THROUGH THE LONG TERM PERIOD...WHILE UPPER TROUGHING REMAINS OVER THE NORTHEAST STATES. A SERIES OF WEAK SHORTWAVES WILL MOVE ALONG THE BASE OF THE UPPER TROUGH OVER THE WEEKEND. THIS UPPER LEVEL ENERGY WILL KEEP A SUFFICIENT MOISTURE PROFILE TO SPARK CONVECTION WITHIN THE AFTERNOON SEABREEZE FORCING. WILL THUS CONTINUE TO REPRESENT A MORE CLIMATOLOGICAL POP SCHEME OF A CHANCE FOR SHOWERS AND THUNDERSTORMS EACH AFTERNOON...DIMINISHING TO NO MORE THAN A SLIGHT CHANCE OVERNIGHT. GFS AMPLIFIES THE UPPER LEVEL ACTIVITY BY LATE SUNDAY...AS ANOTHER WEAK SURFACE FRONT APPROACHES FROM THE NORTHWEST. THERE APPEARS TO BE SOME TIMING AND SENSIBLE WEATHER DIFFERENCES BETWEEN THE ECMWF AND GFS SOLUTIONS THAT LEND UNCERTAINTY IN THE DETAILS FOR LATE WEEKEND INTO THE EARLY NEXT WEEK TIME FRAME. HAVE OPTED TO CONTINUE WITH A MORE GENERAL CONVECTIVE FORECAST OF CHANCE POPS DURING THE DAYTIME HOURS...UNTIL MORE CONSISTENT TRENDS ARE SEEN IN THE MODEL FORECASTS. HIGH TEMPERATURES THROUGH THE PERIOD WILL RANGE WITHIN A FEW DEGREES OF SEASONAL NORMS...WARMING INTO THE LOWER 90S EACH AFTERNOON. HEAT INDICES WILL GENERALLY REMAIN BELOW 103 DEGREES THROUGH THE WEEKEND...WITH INDICES AS HIGH AS 105 IN SOME AREAS BY EARLY NEXT WEEK. && .AVIATION /05Z WEDNESDAY THROUGH SUNDAY/... KCHS - WE ARE CAREFULLY MONITORING VISIBILITY TRENDS EARLY THIS MORNING. DEWPOINTS HAVE POOLED INTO THE MID 70S WITH FAIRLY LIGHT WINDS. IR SATELLITE IMAGERY SUGGESTS SKIES WILL REMAIN CLEAR WITH THINNING CONVECTIVE DEBRIS HIGH CLOUDINESS REMAINING WEST AND NORTH OF THE TERMINAL. THERE IS A GOOD CHANCE THAT SHALLOW GROUND FOG MAY TEMPORARILY REDUCE VISIBILITIES TO HIGH END MVFR BETWEEN 08Z-11Z. ANY FOG WILL QUICKLY BURN OFF AFTER 13Z WITH VFR CONDITIONS PREVAILING. EXPECT ISOLATED SHOWERS AND THUNDERSTORMS TO INITIATE ALONG THE SEA BREEZE JUST NORTH OF THE TERMINAL BY LATE MORNING OR EARLY AFTERNOON WITH ADDITIONAL ACTIVITY FORMING FARTHER INLAND. WILL CARRY A MENTION OF CB/S FROM 16Z-21Z TO HOLD FOR NOW. ADDITIONAL ACTIVITY COULD IMPACT THE TERMINAL LATER THIS EVENING IF CONVECTION THAT DEVELOPS OVER THE MIDLANDS ORGANIZES AND MAKES A RUN FOR THE COAST. KSAV - CONVECTIVE DEBRIS HIGH CLOUDINESS WILL TEND TO THIN OUT WITH TIME BUT SHOULD REMAIN PREVALENT ENOUGH TO PRECLUDE FOG FORMATION AT THE TERMINAL THIS MORNING. EXPECT VFR CONDITIONS TO PREVAIL FOR THE NEXT 24 HOURS. SCATTERED SHOWERS AND THUNDERSTORMS WILL LIKELY FIRE AHEAD OF THE SEA BREEZE THIS AFTERNOON SO WILL CARRY A MENTION OF CB/S FROM 20Z-01Z TO COVER THIS POSSIBILITY. EXTENDED AVIATION OUTLOOK...A CHANCE OF MVFR VSBYS EACH MORNING DUE TO HIGH LOW LEVEL MOISTURE AND LIGHT WINDS...OTHERWISE VFR CONDITIONS EXPECTED OUTSIDE OF MAINLY AFTERNOON/EVENING CONVECTION. && .MARINE... FAIRLY TRANQUIL CONDITIONS EXPECTED THROUGH SUNDAY. THE MARINE ZONES WILL REMAIN ON THE WESTERN PERIPHERY OF ATLANTIC HIGH PRESSURE. WINDS WILL GENERALLY MAINTAIN A SOUTHERLY COMPONENT THROUGH THE PERIOD. SPEEDS WILL REMAIN AT OR BELOW 15 KNOTS OUTSIDE OF ANY THUNDERSTORM ACTIVITY...WITH SEAS AT OR BELOW 4 FEET. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...NONE. && $$ ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 215 PM CDT WED JUL 23 2008 .DISCUSSION... 335 AM CDT QUIET WEATHER WILL CONTINUE TODAY AND TONIGHT...AND THEN ATTENTION WILL SHIFT TO NEXT CHANCE OF PRECIP FOR LATE THURSDAY AFTERNOON...AND ESPECIALLY INTO THURSDAY NIGHT. WATER VAPOR IMAGERY/RUC ANALYSES INDICATING LAST IN SERIES OF STRONGER UPPER LEVEL SHORT WAVES ROTATING THROUGH SOUTHERN LOWER MICHIGAN/NORTHERN INDIANA EARLY THIS MORNING. ANOTHER SHORT WAVE TROUGH ACROSS JAMES BAY IS ROTATING BACK WESTWARD AROUND THE LONGWAVE TROUGH...BUT THE EXPECTED TRACK OF THIS VORT WILL KEEP IT WELL EAST OF THE AREA. OTHERWISE...BROAD SURFACE ANTICYCLONE ACROSS SOUTHERN ONTARIO WILL CONTINUE TO SETTLE INTO WESTERN GREAT LAKES TODAY. FORECAST SOUNDINGS SUGGEST STRENGTHENING INVERSION IN THE 800-750 HPA LAYER THIS AFTERNOON WHICH SEEMS REASONABLE GIVEN STRENGTHENING SYNOPTIC SCALE SUBSIDENCE BEHIND THIS AFOREMENTIONED VORT MAX TODAY. WITH RELATIVELY DRY LOW LEVELS/SUBSIDENCE...CU COVERAGE SHOULD BE LIMITED TODAY AND FORMING MOSTLY LIKELY AWAY FROM LAKE MICHIGAN. LOW LEVEL THERMAL PROGS SUGGEST HIGHS TODAY IN THE BALLPARK FROM YESTERDAY...PERHAPS A FEW DEGREES WARMER IN MOST LOCATIONS GIVEN SLIGHTLY DEEPER MIXED LAYER TODAY. NORTH WINDS WILL CONTINUE TO PROVIDE LAKE COOLING AND HIGHS NEAR THE LAKE MICHIGAN SHORELINE SHOULD ONCE AGAIN RISE INTO MID 70S. ELSEWHERE HIGH TEMPERATURES OF AROUND 80 ARE EXPECTED. DECOUPLING WILL OCCUR EARLY THIS EVENING...AND WITH A RELATIVELY DRY AIR MASS IN PLACE TEMPERATURES WILL DROP OFF FAIRLY SHARPLY EARLY THIS EVENING WITH A GOOD RADIATIONAL COOLING SETUP. HAVE CONTINUED IDEA OF MID TO UPPER 50S FOR LOWS TONIGHT...ALTHOUGH SOME LOCALLY COOLER READINGS ARE POSSIBLE IN THE 50 TO 55 DEGREE RANGE. ATTENTION FOR THURSDAY WILL THEN SHIFT TO INCREASINGLY FAVORABLE SETUP FOR PRECIPITATION. MOISTURE PROFILE WILL BE INITIALLY QUITE MEAGER ACROSS THE AREA EARLY THURSDAY AND GIVEN FAIRLY LARGE AMPLITUDE TROUGH TO THE EAST...THE SFC RIDGE AXIS WILL BE RATHER SLOW TO EXIT. NAM OVER PAST FEW DAYS HAS BEEN CONSIDERABLY FASTER IN BRINGING SIGNIFICANT LOW LEVEL WARM/MOIST ADVECTION INTO NORTHERN ILLINOIS DURING THE DAY THURSDAY. HOWEVER LATEST FEW RUNS OF NAM ARE SEEMINGLY COMING AROUND TO MORE OF A GFS IDEA IN A SLOWER ONSET OF WAA/THETA-E ADVECTION FORCING. HAVE CONTINUED TO FOLLOW GFS IDEA WITH BRINGING HIGHER CHANCE POPS INTO NORTHERN ILLINOIS BY THURSDAY EVENING. DID MAINTAIN SOME LOW CHANCE POPS ACROSS FAR WESTERN PORTIONS OF THE CWA FOR THURSDAY AFTERNOON...ALTHOUGH ANY INSTABILITY WILL BE QUITE ELEVATED AND INITIAL WAA/MID LEVEL FRONTO FORCING WILL LIKELY BE SPENT WITH IN LOW/MID LEVEL SATURATION. CONCERN FOR THURSDAY NIGHT MAY END UP BEING MORE TOWARD HEAVY RAINFALL POTENTIAL WITH PWATS INCREASING BACK INTO THE 1.75 TO 2.00 INCH RANGE AGAIN...ESPECIALLY ACROSS SOUTHERN PORTIONS OF THE AREA. LARGER SCALE PATTERN DOES APPEAR TO CONTINUE TO FAVOR SOUTHEAST PROPAGATION OF ANY MCS THAT FORMS TO THE WEST THURSDAY EVENING...SO NORTH-SOUTH POP GRADIENT FOR THURSDAY NIGHT SEEMS APPROPRIATE AT THIS TIME. DID CONTEMPLATE GOING WITH LIKELY POPS ACROSS THE FAR SOUTH BUT AT THIS DISTANCE HAVE INCREASED TO HIGHER END CHANCE POPS. WITH MAIN LOW LEVEL THERMAL RIDGE REMAINING OFF TO THE WEST OF THE AREA THURSDAY NIGHT...MID LEVEL LAPSE RATES SHOULD BE ON THE WEAK SIDE AND INSTABILITY PROGS AT THIS TIME DO NOT SEEM SUPPORTIVE OF A SUBSTANTIAL SEVERE WEATHER THREAT. ON FRIDAY...DETAILS ON PRECIP POTENTIAL BECOME MORE BLURRY DUE TO THE EFFECTS OF THURSDAY NIGHT CONVECTION ON MESOSCALE FACTORS. GFS/NAM ARE IN GENERAL AGREEMENT IN WEAK SFC TROUGH APPROACHING FAR NORTHERN ILLINOIS DURING THE AFTERNOON ASSOCIATED WITH AN UPPER LEVEL SHORT WAVE APPROACHING THE NORTHERN GREAT LAKES. MAY ALSO HAVE ANOTHER BOUNDARY TO THE SOUTH LEFT OVER FROM OVERNIGHT CONVECTION. MAGNITUDE OF INSTABILITY ALSO IN QUESTION DEPENDING IN EXTENT OF REMNANT CLOUD COVER. GIVEN ALL THESE UNCERTAINTIES...MAINTENANCE OF BROADBRUSH LOW END CHANCE POPS STILL SEEM IN ORDER FOR FRIDAY. MAIN SURFACE FRONT WILL LIKELY STALL OUT SOMEWHERE JUST SOUTH OF THE FORECAST AREA ON SATURDAY AS MAIN MID/UPPER LEVEL FORCING RACES EAST INTO THE NORTHEAST US. LATER FORECASTS MAY NEED TO CONSIDER ADDING LOW POPS ACROSS THE SOUTH FOR FIRST PART OF THE WEEKEND...BUT WILL CONTINUE TO LEAN TOWARD MODEL CONSENSUS WITH A DRY SATURDAY WITH EXPECTATION MORE FAVORED PRECIP CHANCES WILL BE SOUTH OF THE AREA. NO CHANGES TO REMAINDER OF EXTENDED WITH BEST CHANCE OF MCS DEVELOPMENT LIKELY REMAINING SOUTH OF THE AREA GIVEN LITTLE CHANGE IN LARGE SCALE WESTERN RIDGE/EASTERN TROUGH PATTERN AND SFC BOUNDARY SOUTH OF THE AREA. MARSILI && .AVIATION... 18Z TAFS...QUIET WEATHER EXPECTED THRU THURSDAY MORNING. HIGH PRESSURE OVER THE WESTERN LAKES WILL CONTINUE TO BUILD SOUTH ACROSS THE AREA THIS AFTERNOON AND TONIGHT...THEN MOVE SOUTHEAST ACROSS THE SOUTHERN LAKES AND OH VALLEY THURSDAY. NORTHEAST WINDS 10-15KTS WILL DIMINISH UNDER 10KTS EARLY THIS EVENING THEN BECOME CALM AT MOST LOCATIONS BY LATE EVENING. GRADIENT HAS SUPPORTED A FEW HIGHER GUSTS TO 18-20KTS. NOT SURE HOW LONG THESE WILL LAST BUT HAVE AMENDED ORD TO INCLUDE GUSTS THIS AFTERNOON AND WILL WATCH OTHER TAFS FOR PREVAILING GUSTS. A FEW HIGH BASED CU TODAY THEN THIN CIRRUS INCREASING TONIGHT AND SCT/BKN MID CLOUDS THURSDAY MORNING. CMS && .MARINE... 215 PM...LARGE HIGH PRESSURE EXTENDS FROM ONTARIO SOUTH ACROSS THE WESTERN LAKES. THIS HIGH WILL MOVE SOUTHEAST TONIGHT AS IT SLOWLY WEAKENS...REACHING THE OHIO VALLEY THURSDAY. LOW PRESSURE NEAR THE U.S. AND CANADIAN BORDER WILL MOVE NORTHEAST ACROSS NORTHERN ONTARIO THURSDAY NIGHT AND FRIDAY. SOUTHERLY FLOW WILL DEVELOP BETWEEN THIS LOW AND THE HIGH PRESSURE WHICH WILL CONTINUE TO SLIDE SOUTHEAST OFF THE ATLANTIC COAST FRIDAY. A WEAK TRAILING COLD FRONT WILL TURN WINDS WESTERLY OR NORTHWESTERLY FRIDAY NIGHT INTO SATURDAY ACROSS THE WESTERN LAKES. CMS && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...SMALL CRAFT ADVISORY UNTIL 4 PM CDT THIS AFTERNOON FOR LMZ740- LMZ741-LMZ742-LMZ743-LMZ744-LMZ745. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 1157 PM CDT TUE JUL 22 2008 .UPDATE... UPDATED FOR 06 UTC AVIATION. && .DISCUSSION... SEE PREVIOUS DISCUSSION. && .AVIATION... WARM AIR ADVECTION INTO TONGUE OF LOW LEVEL MOISTURE MAY BRING A FEW SHOWERS AND STORMS TO THE AREA OVERNIGHT...BUT SHOULD REMAIN ISOLATED AND NOT WORTHY OF TAF MENTION. THIS MOISTURE WILL BRING SOME CONCERN FOR LOWERED VISIBILITIES BUT BELIEVE WIND SPEEDS NEAR THE BOUNDARY LAYER WILL BE ENOUGH OF KEEP THEM AT VFR LEVELS. CONVECTIVE THREAT NOT ZERO FOR WEDNESDAY AFTERNOON/EVENING BUT WELL TO LOW FOR INCLUSION AT THIS POINT. && .PREV DISCUSSION... /ISSUED 344 PM CDT TUE JUL 22 2008/ DISCUSSION... WEAK SURFACE BOUNDARY JUST SOUTH OF I70 AT 20Z. MESOANALYSES SHOW SOME SURFACE CONVERGENCE ALONG BOUNDARY...AND WEAK CAP. DEWPOINTS HAVE POOLED JUST NORTH OF FRONT...WITH MIXED LAYER CAPES NEAR 4000 J/KG. HOWEVER...NO SIGNIFICANT CONVECTION HAS FIRED AND NOTHING APPEARS IMMINENT ON SATELLITE IMAGERY. RUC ANALYSIS AND PROFILER WINDS SHOWS WEAK VORT MAX OVER ERN NEBRASKA MOVING SE. HOWEVER...SUBSIDENCE IN WAKE OF THIS MORNINGS MISSOURI MCS HAS HELPED WITH OVERALL CONVECTIVE SUPPRESSION. WITH BOUNDARY REMAINING IN AREA...EXPECT ISOLATED CONVECTION TO STILL BE POSSIBLE TONIGHT INTO WEDNESDAY AS WEAK POSITIVE 850 MB THETA-E ADVECTION CONTINUES. POPS KEPT AOB 20 PERCENT TONIGHT AND WEDNESDAY. RELATIVELY HIGH DEWPOINTS ACROSS ERN KS SHOULD KEEP LOW TEMPS IN THE UPPER 60S TO LOWER 70S. ON WEDNESDAY...GFS MOS GUIDANCE WARMER THAN NAM OR NGM AND HAVE GONE CLOSER TO THIS BASED ON RECENT PERFORMANCE. PHILLIPS WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...THE UPPER RIDGE WILL AMPLIFY ACROSS THE SOUTHERN PLAINS WHILE AN UPPER LEVEL TROUGH MOVES EAST ACROSS THE NORTHERN PLAINS INTO THE UPPER MIDWEST. WEDNESDAY NIGHT INTO THURSDAY MORNING THERE MAY BE A SLIGHT CHANCE FOR ELEVATED SHOWERS AND THUNDERSTORMS TO DEVELOP AS WAA/ISENTROPIC LIFT INCREASES ACROSS THE NORTHERN AND EASTERN PORTIONS OF THE CWA...BUT BEING UNDER THE 5H RIDGE AXIS MAY INHIBIT THE DEVELOPMENT OF ELEVATED THUNDERSTORMS. AS THE 5H TROUGH MOVES ACROSS THE NORTHERN HIGH PLAINS THEN DIGS SOUTHEAST INTO THE GREAT LAKES...A WEAK COLD FRONT WILL MOVE SOUTHWARD ACROSS NE AND INTO NORTH CENTRAL KS DURING THE AFTERNOON HOURS. THERE MAY BE ENOUGH SFC CONVERGENCE FOR ISOLATED THUNDERSTORMS TO DEVELOP THURSDAY AFTERNOON ACROSS THE NORTH CENTRAL KANSAS ALONG THE COLD FRONT. HIGHS ON THURSDAY MAY BE CLOSE TO 100 DEGREES ACROSS THE SOUTHWEST AND WEST CENTRAL CWA...WITH LOWER 90S ACROSS THE NORTHEAST COUNTIES OF THE CWA. THE FRONT WILL MOVE SOUTHEAST ACROSS THE NORTHERN AND EASTERN CWA PROVIDING AT LEAST A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THURSDAY NIGHT. FRIDAY THROUGH SATURDAY NIGHT...THE WEAK FRONT WILL MOVE SOUTHWARD AND STALL OUT AND WEAKEN ALONG I-70. THE 5H TROUGH OVER THE MIDWEST WILL DIG SOUTHEAST INTO THE GREAT LAKES STATES. BOTH THE ECMWF AND GFS SHOW THE SOUTHERN PLAINS 5H RIDGE RE-AMPLIFYING. SYNOPTIC SCALE SUBSIDENCE UNDER THE 5H RIDGE SHOULD CREATE AN ENVIRONMENT UNFAVORABLE FOR DEEP MOIST CONVECTION...BUT I CANNOT RULE OUT PULSE STORMS DEVELOPING ALONG OR NORTH OF THE BOUNDARY DURING THE LATE AFTERNOON HOURS FRIDAY...GIVEN DEEP MOISTURE AND STRONG SFC HEATING. THEREFORE...I KEPT A 14 POP DURING THE DAY FRIDAY AND 15 POPS FRIDAY EVENING. TEMPERATURES ACROSS THE NORTHERN COUNTIES MAY ONLY REACH THE LOWER TO MID 90S NORTH OF THE WEAK SFC BOUNDARY. SOUTH OF THE SFC BOUNDARY HIGHS WILL BE IN THE UPPER 90S...POSSIBLY NEAR 100 DEGREES OVER THE SOUTHERN COUNTIES OF THE CWA. ON SATURDAY BOTH THE ECMWF AND GFS SHOW THE 5H RIDGE AXIS RETROGRADING INTO THE WEST CENTRAL CONUS AS A LONGER WAVE LENGTH 5H TROUGH OVER THE EASTERN CONUS AMPLIFIES. HIGH TEMPERATURES MAY BE A FEW DEGREES COOLER AS THE CENTER OF THE RIDGE AXIS SHIFTS WEST OF THE SOUTHERN PLAINS. HIGHS ON SATURDAY WILL BE IN THE MID 90S ACROSS MOST OF THE CWA. SATURDAY NIGHT THROUGH TUESDAY...BOTH THE ECMWF AND GFS KEEP A LONGER WAVE LENGTH 5H TROUGH ACROSS THE EASTERN CONUS AND A BROAD 5H RIDGE ACROSS THE WEST CENTRAL CONUS. THE ECMWF IS A BIT MORE AMPLIFIED WITH THE 5H TROUGH OVER THE EASTERN CONUS...AND BRINGS A COLD FRONT SOUTHWESTWARD INTO THE CWA SUNDAY INTO MONDAY. THIS WOULD PROVIDE THE CWA WITH A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS SATURDAY NIGHT THROUGH SUNDAY NIGHT. HOWEVER...THE GFS IS NOT AS AMPLIFIED WITH THE EASTERN CONUS 5H TROUGH AND KEEPS THE FRONT NEARLY STATIONARY ACROSS EASTERN NE...SOUTHEAST INTO WESTERN MO. IF THE GFS WERE TO VERIFY THE BEST RAIN CHANCES WILL REMAIN NORTH AND EAST OF THE CWA. THEREFORE...I PLACED IN SLIGHT CHANCES FOR THUNDERSTORMS SATURDAY NIGHT THROUGH SUNDAY NIGHT ACROSS THE CWA. THE ECMWF MODEL FORECAST SHOWS THE FRONT MOVING SOUTHWARD INTO NORTHERN OK MONDAY AND TUESDAY...AND THE GFS MODEL SOLUTION KEEPS THE FRONT NORTHEAST OF THE CWA...THEREFORE I KEPT POPS AT 14 PERCENT MONDAY NIGHT AND TUESDAY. HIGHS SUNDAY THROUGH TUESDAY WILL ONLY REACH THE LOWER TO MID 90S...SINCE THE 5H RIDGE AXIS WILL SHIFT FARTHER WEST. HIGH MAY BE A BIT COOLER ON SUNDAY AND MONDAY IF THE ECMWF SOLUTION WERE TO VERIFY BRING THE SFC COLD FRONT SOUTHWEST ACROSS THE CWA. GARGAN && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ 65 ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 1054 PM MDT TUE JUL 22 2008 .UPDATE... 714 PM MDT TUE JUL 22 2008 JUST COMPLETED AN UPDATE. MAIN CHANGE WAS TO REMOVE PRECIPITATION. CAP IS STRENGTHENING OVER THE AREA AND IS ALREADY STRONG ON TOP OF OUR STATIONARY FRONT. ALSO HEIGHTS/RIDGE BUILDING OVER THE AREA WITH LITTLE IF ANY LIFT NOTED ON SATELLITE. ADJUSTED CLOUD COVER TO ACCOUNT FOR MUCH LESS IN THE EVENING AND MORE OVERNIGHT. KEPT THE AREAS OF FOG IN EVEN THOUGH NAM/RUC NOT AS AGGRESSIVE TONIGHT WITH FOG FORMATION. HOWEVER...MODELS UNDERDID MOISTURE ADVECTION LAST NIGHT AND HAVE DECENT UPSLOPE FLOW. OTHERWISE DID MINOR TWEEKS ON OTHER ELEMENTS BASED ON CURRENT TRENDS. BULLER && .DISCUSSION...FORECAST CONCERNS ARE ON EXTENT OF FOG TONIGHT FOLLOWED BY TEMPERATURES AND PRECIPITATION THROUGH THE NEXT 7 DAYS. STATIONARY BOUNDARY CURRENTLY ALONG OR JUST NORTH OF THE INTERSTATE AND WILL ACT AS A FOCUS FOR SHOWERS AND THUNDERSTORMS THIS EVENING. AFTER MIDNIGHT FOG WILL REDEVELOP AND BASED ON THE NAM (WHICH ACTUALLY VERIFIED THIS WELL ON YESTERDAYS MODEL RUN) WILL COVER THE NORTHEAST 1/2 OF THE AREA THROUGH 15Z OR SO BEFORE LIFTING NORTHEAST AND DISSIPATING. FOR TUESDAY NIGHT THROUGH FRIDAY UPPER LEVEL FLOW WILL INCREASE A BIT WHILE ALSO FLATTENING OUT ALLOWING FOR AN INCREASED CHANCE OF PRECIPITATION...MAINLY ACROSS THE NORTHWEST AND WESTERN PARTS OF THE AREA. AFTERNOON TEMPERATURES WILL BE HOT AGAIN WEDNESDAY WITH HIGHS AROUND 100 BUT A VERY SLIGHT COOLING TREND IS EXPECTED AS INCREASING CLOUDINESS WITH THE DEAMPLIFIED TROUGH MOVES IN. BY THURSDAY LOW TO MID 90S ARE EXPECTED. SATURDAY THROUGH TUESDAY...A GENERAL BROAD UPPER RIDGE BUILDS SLIGHTLY ON SATURDAY AND CONTINUES THROUGH TUESDAY WITH TEMPERATURES REMAINING IN THE 90S. TYPICAL OF THIS TIME OF YEAR AFTERNOON AND EVENING THUNDERSTORMS ARE POSSIBLE. WITHOUT A STRONG SIGN OR AGREEMENT ON ANY DISTURBANCES TO KICK THEM OFF WILL MAINTAIN SLIGHT CHANCE POPS. DDT && .AVIATION... 1048 PM MDT TUE JUL 22 2008 FOR THE 06Z TAFS...FRONT HAS SAGGED FURTHER SOUTH AND WEST SINCE 00Z...AND HAS MOVED PASSED KGLD. NAM/RUC HAVE STARTED TO INDICATE VISIBILITY RESTRICTIONS AND LOWER CEILINGS WITH NEWER RUNS. OF HIGHER PROBABILITY TO SEE MVFR/IFR CEILINGS/VISIBILITIES WILL BE KMCK. KGLD APPEARS TO BE ON THE EDGE OF THE FOG AND STRATUS. HOWEVER...BELIEVE THE MODELS ARE NOT FAR ENOUGH WEST. WILL HIT THE STRATUS HARDER HERE THAN THE FOG. SINCE KGLD APPEARS TO BE ON THE EDGE...CEILINGS/VISIBILITIES COULD BE HIGHLY VARIABLE. SOUTHERLY WILL INCREASE INTO THE BREEZY CATEGORY BY 18Z. AT THIS TIME...ANY THUNDERSTORMS THAT DEVELOP IN THE AFTERNOON AND EVENING LOOK TO STAY TO THE WEST OF BOTH TAF SITES. BULLER && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 553 PM MDT TUE JUL 22 2008 .DISCUSSION...FORECAST CONCERNS ARE ON EXTENT OF FOG TONIGHT FOLLOWED BY TEMPERATURES AND PRECIPITATION THROUGH THE NEXT 7 DAYS. STATIONARY BOUNDARY CURRENTLY ALONG OR JUST NORTH OF THE INTERSTATE AND WILL ACT AS A FOCUS FOR SHOWERS AND THUNDERSTORMS THIS EVENING. AFTER MIDNIGHT FOG WILL REDEVELOP AND BASED ON THE NAM (WHICH ACTUALLY VERIFIED THIS WELL ON YESTERDAYS MODEL RUN) WILL COVER THE NORTHEAST 1/2 OF THE AREA THROUGH 15Z OR SO BEFORE LIFTING NORTHEAST AND DISSIPATING. FOR TUESDAY NIGHT THROUGH FRIDAY UPPER LEVEL FLOW WILL INCREASE A BIT WHILE ALSO FLATTENING OUT ALLOWING FOR AN INCREASED CHANCE OF PRECIPITATION...MAINLY ACROSS THE NORTHWEST AND WESTERN PARTS OF THE AREA. AFTERNOON TEMPERATURES WILL BE HOT AGAIN TUESDAY WITH HIGHS AROUND 100 BUT A VERY SLIGHT COOLING TREND IS EXPECTED AS INCREASING CLOUDINESS WITH THE DEAMPLIFIED TROUGH MOVES IN. BY THURSDAY LOW TO MID 90S ARE EXPECTED. SATURDAY THROUGH TUESDAY...A GENERAL BROAD UPPER RIDGE BUILDS SLIGHTLY ON SATURDAY AND CONTINUES THROUGH TUESDAY WITH TEMPERATURES REMAINING IN THE 90S. TYPICAL OF THIS TIME OF YEAR AFTERNOON AND EVENING THUNDERSTORMS ARE POSSIBLE. WITHOUT A STRONG SIGN OR AGREEMENT ON ANY DISTURBANCES TO KICK THEM OFF WILL MAINTAIN SLIGHT CHANCE POPS. DDT && .AVIATION... 542 PM MDT TUE JUL 22 2008 FOR THE 00Z TAFS...CURRENTLY HAVE STATIONARY FRONT DRAPED FROM NORTHWEST TO SOUTHEAST ACROSS THE CENTER OF THE FORECAST AREA. WOULD THINK THIS WOULD BE A GOOD FOCUS FOR THUNDERSTORMS. HOWEVER PER LAPS AND SATELLITE...LOW LEVEL AIR MASS APPEARS TO BE CAPPED ESPECIALLY ON TOP OF THE FRONT. LITTLE IF ANY LIFT IN PLACE ALOFT AND ONLY GETS WORSE WITH RISING HEIGHTS THROUGH THE EVENING. AS A RESULT AM PESSIMISTIC ABOUT ANY THUNDERSTORMS DEVELOPING. LEFT THE MENTION OF CB IN THE KMCK TAF SINCE IT IS CLOSEST TO THE FRONT. NEXT PROBLEM WILL BE HOW MUCH STRATUS AND FOG REDEVELOP TONIGHT. WITH FRONT AND EASTERLY WINDS TO STAY IN PLACE...WOULD THINK THAT A REPEAT IS IN STORE. BUT EVEN THE NAM/RUC WHICH GOT IT RIGHT LAST NIGHT IS NOT SHOWING ANY REDUCTIONS IN VISIBILITY. MADE THE KGLD TAF MORE OPTIMISTIC...AND PUT THE LOWER CEILINGS AND VISIBILITY AT THE KMCK TAF. WILL HAVE TO FINE TUNE THESE WITH THE NEXT ISSUANCE. BULLER && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 635 PM CDT TUE JUL 22 2008 .UPDATE... UPDATED FOR 00 UTC AVIATION. && .DISCUSSION... SEE PREVIOUS DISCUSSION. && .AVIATION... PRESENCE OF OUTFLOW BOUNDARIES...A WEAK UPPER WAVE...AND PLENTY OF INSTABILITY SUGGEST SOME CONVECTIVE CONCERNS FOR THE TERMINALS. WILL GO WITH CB FOR THE EARLY EVENING UNTIL INSTABILITY WANES AS THE CHANCES OF A TS IN THE AERODROMES SEEM REMOTE. WINDS SHOULD GENERALLY BE LIGHT AND EASTERLY...WITH AN INCREASE IN SPEEDS BY LATE WEDNESDAY MORNING. VFR CONDITIONS ARE EXPECTED THROUGHOUT THE 00Z CYCLE. && .PREV DISCUSSION... /ISSUED 344 PM CDT TUE JUL 22 2008/ DISCUSSION... WEAK SURFACE BOUNDARY JUST SOUTH OF I70 AT 20Z. MESOANALYSES SHOW SOME SURFACE CONVERGENCE ALONG BOUNDARY...AND WEAK CAP. DEWPOINTS HAVE POOLED JUST NORTH OF FRONT...WITH MIXED LAYER CAPES NEAR 4000 J/KG. HOWEVER...NO SIGNIFICANT CONVECTION HAS FIRED AND NOTHING APPEARS IMMINENT ON SATELLITE IMAGERY. RUC ANALYSIS AND PROFILER WINDS SHOWS WEAK VORT MAX OVER ERN NEBRASKA MOVING SE. HOWEVER...SUBSIDENCE IN WAKE OF THIS MORNINGS MISSOURI MCS HAS HELPED WITH OVERALL CONVECTIVE SUPPRESSION. WITH BOUNDARY REMAINING IN AREA...EXPECT ISOLATED CONVECTION TO STILL BE POSSIBLE TONIGHT INTO WEDNESDAY AS WEAK POSITIVE 850 MB THETA-E ADVECTION CONTINUES. POPS KEPT AOB 20 PERCENT TONIGHT AND WEDNESDAY. RELATIVELY HIGH DEWPOINTS ACROSS ERN KS SHOULD KEEP LOW TEMPS IN THE UPPER 60S TO LOWER 70S. ON WEDNESDAY...GFS MOS GUIDANCE WARMER THAN NAM OR NGM AND HAVE GONE CLOSER TO THIS BASED ON RECENT PERFORMANCE. PHILLIPS WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...THE UPPER RIDGE WILL AMPLIFY ACROSS THE SOUTHERN PLAINS WHILE AN UPPER LEVEL TROUGH MOVES EAST ACROSS THE NORTHERN PLAINS INTO THE UPPER MIDWEST. WEDNESDAY NIGHT INTO THURSDAY MORNING THERE MAY BE A SLIGHT CHANCE FOR ELEVATED SHOWERS AND THUNDERSTORMS TO DEVELOP AS WAA/ISENTROPIC LIFT INCREASES ACROSS THE NORTHERN AND EASTERN PORTIONS OF THE CWA...BUT BEING UNDER THE 5H RIDGE AXIS MAY INHIBIT THE DEVELOPMENT OF ELEVATED THUNDERSTORMS. AS THE 5H TROUGH MOVES ACROSS THE NORTHERN HIGH PLAINS THEN DIGS SOUTHEAST INTO THE GREAT LAKES...A WEAK COLD FRONT WILL MOVE SOUTHWARD ACROSS NE AND INTO NORTH CENTRAL KS DURING THE AFTERNOON HOURS. THERE MAY BE ENOUGH SFC CONVERGENCE FOR ISOLATED THUNDERSTORMS TO DEVELOP THURSDAY AFTERNOON ACROSS THE NORTH CENTRAL KANSAS ALONG THE COLD FRONT. HIGHS ON THURSDAY MAY BE CLOSE TO 100 DEGREES ACROSS THE SOUTHWEST AND WEST CENTRAL CWA...WITH LOWER 90S ACROSS THE NORTHEAST COUNTIES OF THE CWA. THE FRONT WILL MOVE SOUTHEAST ACROSS THE NORTHERN AND EASTERN CWA PROVIDING AT LEAST A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THURSDAY NIGHT. FRIDAY THROUGH SATURDAY NIGHT...THE WEAK FRONT WILL MOVE SOUTHWARD AND STALL OUT AND WEAKEN ALONG I-70. THE 5H TROUGH OVER THE MIDWEST WILL DIG SOUTHEAST INTO THE GREAT LAKES STATES. BOTH THE ECMWF AND GFS SHOW THE SOUTHERN PLAINS 5H RIDGE RE-AMPLIFYING. SYNOPTIC SCALE SUBSIDENCE UNDER THE 5H RIDGE SHOULD CREATE AN ENVIRONMENT UNFAVORABLE FOR DEEP MOIST CONVECTION...BUT I CANNOT RULE OUT PULSE STORMS DEVELOPING ALONG OR NORTH OF THE BOUNDARY DURING THE LATE AFTERNOON HOURS FRIDAY...GIVEN DEEP MOISTURE AND STRONG SFC HEATING. THEREFORE...I KEPT A 14 POP DURING THE DAY FRIDAY AND 15 POPS FRIDAY EVENING. TEMPERATURES ACROSS THE NORTHERN COUNTIES MAY ONLY REACH THE LOWER TO MID 90S NORTH OF THE WEAK SFC BOUNDARY. SOUTH OF THE SFC BOUNDARY HIGHS WILL BE IN THE UPPER 90S...POSSIBLY NEAR 100 DEGREES OVER THE SOUTHERN COUNTIES OF THE CWA. ON SATURDAY BOTH THE ECMWF AND GFS SHOW THE 5H RIDGE AXIS RETROGRADING INTO THE WEST CENTRAL CONUS AS A LONGER WAVE LENGTH 5H TROUGH OVER THE EASTERN CONUS AMPLIFIES. HIGH TEMPERATURES MAY BE A FEW DEGREES COOLER AS THE CENTER OF THE RIDGE AXIS SHIFTS WEST OF THE SOUTHERN PLAINS. HIGHS ON SATURDAY WILL BE IN THE MID 90S ACROSS MOST OF THE CWA. SATURDAY NIGHT THROUGH TUESDAY...BOTH THE ECMWF AND GFS KEEP A LONGER WAVE LENGTH 5H TROUGH ACROSS THE EASTERN CONUS AND A BROAD 5H RIDGE ACROSS THE WEST CENTRAL CONUS. THE ECMWF IS A BIT MORE AMPLIFIED WITH THE 5H TROUGH OVER THE EASTERN CONUS...AND BRINGS A COLD FRONT SOUTHWESTWARD INTO THE CWA SUNDAY INTO MONDAY. THIS WOULD PROVIDE THE CWA WITH A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS SATURDAY NIGHT THROUGH SUNDAY NIGHT. HOWEVER...THE GFS IS NOT AS AMPLIFIED WITH THE EASTERN CONUS 5H TROUGH AND KEEPS THE FRONT NEARLY STATIONARY ACROSS EASTERN NE...SOUTHEAST INTO WESTERN MO. IF THE GFS WERE TO VERIFY THE BEST RAIN CHANCES WILL REMAIN NORTH AND EAST OF THE CWA. THEREFORE...I PLACED IN SLIGHT CHANCES FOR THUNDERSTORMS SATURDAY NIGHT THROUGH SUNDAY NIGHT ACROSS THE CWA. THE ECMWF MODEL FORECAST SHOWS THE FRONT MOVING SOUTHWARD INTO NORTHERN OK MONDAY AND TUESDAY...AND THE GFS MODEL SOLUTION KEEPS THE FRONT NORTHEAST OF THE CWA...THEREFORE I KEPT POPS AT 14 PERCENT MONDAY NIGHT AND TUESDAY. HIGHS SUNDAY THROUGH TUESDAY WILL ONLY REACH THE LOWER TO MID 90S...SINCE THE 5H RIDGE AXIS WILL SHIFT FARTHER WEST. HIGH MAY BE A BIT COOLER ON SUNDAY AND MONDAY IF THE ECMWF SOLUTION WERE TO VERIFY BRING THE SFC COLD FRONT SOUTHWEST ACROSS THE CWA. GARGAN && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ 65 ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 344 PM CDT TUE JUL 22 2008 .DISCUSSION... WEAK SURFACE BOUNDARY JUST SOUTH OF I70 AT 20Z. MESOANALYSES SHOW SOME SURFACE CONVERGENCE ALONG BOUNDARY...AND WEAK CAP. DEWPOINTS HAVE POOLED JUST NORTH OF FRONT...WITH MIXED LAYER CAPES NEAR 4000 J/KG. HOWEVER...NO SIGNIFICANT CONVECTION HAS FIRED AND NOTHING APPEARS IMMINENT ON SATELLITE IMAGERY. RUC ANALYSIS AND PROFILER WINDS SHOWS WEAK VORT MAX OVER ERN NEBRASKA MOVING SE. HOWEVER...SUBSIDENCE IN WAKE OF THIS MORNINGS MISSOURI MCS HAS HELPED WITH OVERALL CONVECTIVE SUPPRESSION. WITH BOUNDARY REMAINING IN AREA...EXPECT ISOLATED CONVECTION TO STILL BE POSSIBLE TONIGHT INTO WEDNESDAY AS WEAK POSITIVE 850 MB THETA-E ADVECTION CONTINUES. POPS KEPT AOB 20 PERCENT TONIGHT AND WEDNESDAY. RELATIVELY HIGH DEWPOINTS ACROSS ERN KS SHOULD KEEP LOW TEMPS IN THE UPPER 60S TO LOWER 70S. ON WEDNESDAY...GFS MOS GUIDANCE WARMER THAN NAM OR NGM AND HAVE GONE CLOSER TO THIS BASED ON RECENT PERFORMANCE. PHILLIPS WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...THE UPPER RIDGE WILL AMPLIFY ACROSS THE SOUTHERN PLAINS WHILE AN UPPER LEVEL TROUGH MOVES EAST ACROSS THE NORTHERN PLAINS INTO THE UPPER MIDWEST. WEDNESDAY NIGHT INTO THURSDAY MORNING THERE MAY BE A SLIGHT CHANCE FOR ELEVATED SHOWERS AND THUNDERSTORMS TO DEVELOP AS WAA/ISENTROPIC LIFT INCREASES ACROSS THE NORTHERN AND EASTERN PORTIONS OF THE CWA...BUT BEING UNDER THE 5H RIDGE AXIS MAY INHIBIT THE DEVELOPMENT OF ELEVATED THUNDERSTORMS. AS THE 5H TROUGH MOVES ACROSS THE NORTHERN HIGH PLAINS THEN DIGS SOUTHEAST INTO THE GREAT LAKES...A WEAK COLD FRONT WILL MOVE SOUTHWARD ACROSS NE AND INTO NORTH CENTRAL KS DURING THE AFTERNOON HOURS. THERE MAY BE ENOUGH SFC CONVERGENCE FOR ISOLATED THUNDERSTORMS TO DEVELOP THURSDAY AFTERNOON ACROSS THE NORTH CENTRAL KANSAS ALONG THE COLD FRONT. HIGHS ON THURSDAY MAY BE CLOSE TO 100 DEGREES ACROSS THE SOUTHWEST AND WEST CENTRAL CWA...WITH LOWER 90S ACROSS THE NORTHEAST COUNTIES OF THE CWA. THE FRONT WILL MOVE SOUTHEAST ACROSS THE NORTHERN AND EASTERN CWA PROVIDING AT LEAST A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THURSDAY NIGHT. FRIDAY THROUGH SATURDAY NIGHT...THE WEAK FRONT WILL MOVE SOUTHWARD AND STALL OUT AND WEAKEN ALONG I-70. THE 5H TROUGH OVER THE MIDWEST WILL DIG SOUTHEAST INTO THE GREAT LAKES STATES. BOTH THE ECMWF AND GFS SHOW THE SOUTHERN PLAINS 5H RIDGE RE-AMPLIFYING. SYNOPTIC SCALE SUBSIDENCE UNDER THE 5H RIDGE SHOULD CREATE AN ENVIRONMENT UNFAVORABLE FOR DEEP MOIST CONVECTION...BUT I CANNOT RULE OUT PULSE STORMS DEVELOPING ALONG OR NORTH OF THE BOUNDARY DURING THE LATE AFTERNOON HOURS FRIDAY...GIVEN DEEP MOISTURE AND STRONG SFC HEATING. THEREFORE...I KEPT A 14 POP DURING THE DAY FRIDAY AND 15 POPS FRIDAY EVENING. TEMPERATURES ACROSS THE NORTHERN COUNTIES MAY ONLY REACH THE LOWER TO MID 90S NORTH OF THE WEAK SFC BOUNDARY. SOUTH OF THE SFC BOUNDARY HIGHS WILL BE IN THE UPPER 90S...POSSIBLY NEAR 100 DEGREES OVER THE SOUTHERN COUNTIES OF THE CWA. ON SATURDAY BOTH THE ECMWF AND GFS SHOW THE 5H RIDGE AXIS RETROGRADING INTO THE WEST CENTRAL CONUS AS A LONGER WAVE LENGTH 5H TROUGH OVER THE EASTERN CONUS AMPLIFIES. HIGH TEMPERATURES MAY BE A FEW DEGREES COOLER AS THE CENTER OF THE RIDGE AXIS SHIFTS WEST OF THE SOUTHERN PLAINS. HIGHS ON SATURDAY WILL BE IN THE MID 90S ACROSS MOST OF THE CWA. SATURDAY NIGHT THROUGH TUESDAY...BOTH THE ECMWF AND GFS KEEP A LONGER WAVE LENGTH 5H TROUGH ACROSS THE EASTERN CONUS AND A BROAD 5H RIDGE ACROSS THE WEST CENTRAL CONUS. THE ECMWF IS A BIT MORE AMPLIFIED WITH THE 5H TROUGH OVER THE EASTERN CONUS...AND BRINGS A COLD FRONT SOUTHWESTWARD INTO THE CWA SUNDAY INTO MONDAY. THIS WOULD PROVIDE THE CWA WITH A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS SATURDAY NIGHT THROUGH SUNDAY NIGHT. HOWEVER...THE GFS IS NOT AS AMPLIFIED WITH THE EASTERN CONUS 5H TROUGH AND KEEPS THE FRONT NEARLY STATIONARY ACROSS EASTERN NE...SOUTHEAST INTO WESTERN MO. IF THE GFS WERE TO VERIFY THE BEST RAIN CHANCES WILL REMAIN NORTH AND EAST OF THE CWA. THEREFORE...I PLACED IN SLIGHT CHANCES FOR THUNDERSTORMS SATURDAY NIGHT THROUGH SUNDAY NIGHT ACROSS THE CWA. THE ECMWF MODEL FORECAST SHOWS THE FRONT MOVING SOUTHWARD INTO NORTHERN OK MONDAY AND TUESDAY...AND THE GFS MODEL SOLUTION KEEPS THE FRONT NORTHEAST OF THE CWA...THEREFORE I KEPT POPS AT 14 PERCENT MONDAY NIGHT AND TUESDAY. HIGHS SUNDAY THROUGH TUESDAY WILL ONLY REACH THE LOWER TO MID 90S...SINCE THE 5H RIDGE AXIS WILL SHIFT FARTHER WEST. HIGH MAY BE A BIT COOLER ON SUNDAY AND MONDAY IF THE ECMWF SOLUTION WERE TO VERIFY BRING THE SFC COLD FRONT SOUTHWEST ACROSS THE CWA. GARGAN && .AVIATION... FEW WEAK ELEVATED SHOWERS AND TSTMS THIS MORNING HAVE MOSTLY DISSIPATED. EASTERLY WINDS IN EAST CENTRAL AND NORTHEAST KS KEEPING DEWPOINTS IN THE UPPER 60S TO LOWER 70S. ATMOSPHERE DOES DESTABILIZE LATE THIS AFTERNOON/EVENING IN THE VICINITY OF A FRONTAL BOUNDARY. ISOLATED TSTMS AGAIN POSSIBLE AND HAVE KEPT VCTS IN KTOP/KFOE TAFS. FRONTAL BOUNDARY SHIFTS FARTHER SOUTH OVERNIGHT WITH CONTINUED EAST TO NORTHEAST SURFACE WINDS. VFR CONDITIONS WILL CONTINUE. STARK && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PHILLIPS/GARGAN/STARK ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 1208 PM CDT TUE JUL 22 2008 .UPDATE... UPDATED FOR 18 UTC AVIATION && .DISCUSSION... SEE PREVIOUS DISCUSSION BELOW... && .AVIATION... FEW WEAK ELEVATED SHOWERS AND TSTMS THIS MORNING HAVE MOSTLY DISSIPATED. EASTERLY WINDS IN EAST CENTRAL AND NORTHEAST KS KEEPING DEWPOINTS IN THE UPPER 60S TO LOWER 70S. ATMOSPHERE DOES DESTABILIZE LATE THIS AFTERNOON/EVENING IN THE VICINITY OF A FRONTAL BOUNDARY. ISOLATED TSTMS AGAIN POSSIBLE AND HAVE KEPT VCTS IN KTOP/KFOE TAFS. FRONTAL BOUNDARY SHIFTS FARTHER SOUTH OVERNIGHT WITH CONTINUED EAST TO NORTHEAST SURFACE WINDS. VFR CONDITIONS WILL CONTINUE. STARK && .PREV DISCUSSION... /ISSUED 350 AM CDT TUE JUL 22 2008/ DISCUSSION... 08Z WATER VAPOR SHOWS A TROUGH ALONG THE PACIFIC NORTHWEST COAST AND THE GREAT LAKES/NORTHEAST U.S. AN UPPER LEVEL RIDGE WAS CENTERED OVER THE SOUTHERN ROCKIES AND EXTENDED NORTH INTO THE CENTRAL HIGH PLAINS. A SHORTWAVE MOVING THROUGH THE UPPER MID WEST WAS ROTATING THROUGH IA WITH ANOTHER SHORTWAVE OVER MN. ELEVATED CONVECTION HAS DEVELOPED ALONG A MOISTURE AXIS BETWEEN 800 AND 700MB FROM SOUTHEAST NEB INTO NORTHERN MO. ISENTROPIC LIFT ON THE 310K SFC DEPICTED BY THE RUC SHOWS THIS NARROW CORRIDOR OF MOISTURE REMAINING JUST NORTHEAST OF BROWN COUNTY. GFS ALSO KEEPS ITS QPF JUST TO THE NORTHEAST. WITH THE RUC SHOWING SOME DRYER AIR OVER CENTRAL KS...THINK BULK OF ELEVATED CONVECTION WILL REMAIN JUST TO THE NORTHEAST OF THE FORECAST AREA WITH MOST OF THE LIFT OVERHEAD GOING INTO SATURATING PARCELS AS THEY LIFT INTO NORTHERN MO. NEVERTHELESS WILL MAINTAIN LOW POPS THROUGH 12Z. AFTER 12Z...LEFT LOOKS TO DIMINISH AND PRECIP MAY BE PUSHING OFF TO THE EAST. FOR THE REST OF TODAY THROUGH WEDNESDAY...THE ATMOSPHERE WILL BE CHARACTERIZED AS CONDITIONALLY UNSTABLE WITH NO REAL FORCING TO SPEAK OF AS THE UPPER RIDGE REMAINS JUST TO THE WEST OVER THE HIGH PLAINS. WHILE MID LEVEL TEMPS ARE NOT OVERWHELMING IN TERMS OF A CAP...WEAK LOW LEVEL CAA WITH THE EASTERLY WIND WILL PREVENT THE BOUNDARY LAYER FROM MIXING AS DEEP AS IT HAS THE PAST COUPLE DAYS OVER EASTERN KS WHERE LOW LEVEL MOISTURE IS EXPECTED TO POOL. SO THE QUESTION IS WHETHER THERE WILL BE ENOUGH HEATING AND LOW LEVEL CONVERGENCE ALONG THE FRONT TO ALLOW A STORM TO DEVELOP. IN GENERAL DO NOT FEEL CONFIDENT TO REMOVE POPS GIVEN THE AMOUNT OF INSTABILITY THERE COULD BE WITH DEWPOINTS POOLING AROUND 70 DEGREES. KEPT SOME CHANCE POPS THIS AFTERNOON OVER EAST CENTRAL KS WHERE THE BOUNDARY AND GREATEST INSTABILITY SHOULD BE CO-LOCATED. FOR TONIGHT THROUGH WEDNESDAY NIGHT FELT CHANCE POPS WERE A LITTLE OVERDONE GIVEN LITTLE IF ANY FORCING PROGGED BY THE MODELS. KEPT SLIGHT CHANCE POPS FOR THE POSSIBILITY OF ISOLATED CONVECTION TO FORM. BY WEDNESDAY...THE BOUNDARY SHOULD BEGIN TO WASH OUT AND PRECIP CHANCES SHOULD SHIFT BACK NORTH. HIGHS TODAY AND WEDNESDAY ACROSS EASTERN KS SHOULD BE COOLER GIVEN THE DIMINISHED MIXING AND THE EASTERLY WINDS. PARTS OF NORTH CENTRAL KS AHEAD OF THE WEAK BOUNDARY SHOULD STILL REACH THE UPPER 90S. FORECAST REMAINS IN TACT FOR THURSDAY THROUGH MONDAY. THE GFS LOOKS TO SUFFER FROM FEEDBACK ISSUES ON THURSDAY WITH A CONVECTIVELY INDUCED VORT MAX PROPAGATING ACROSS NORTHEAST KS DURING THE DAY. HAVE LITTLE CONFIDENCE IN THIS SO MAINTAINED SLIGHT CHANCE POPS. UNCERTAINTY IN SFC FEATURES FOR THE WEEKEND AND BEYOND PRECLUDED ANY CHANGES. WOLTERS && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 1039 AM CDT TUE JUL 22 2008 .UPDATE... WIDELY SCATTERED CONVECTION CONTINUES TO WANE AS BETTER ISENTROPIC LIFT IN THE 310K LAYER MOVES TO THE EAST INTO MISSOURI. THE WEAK CONVECTION NEAR COUNCIL GROVE IS STILL SOMEWHAT ROOTED ON THE TAIL END OF THE SHORTWAVE CURRENTLY MOVING THROUGH CENTRAL MO. SHORT TERM MODELS STILL SHOWS LOTS OF ML CAPE (3000-3500 J/KG) ACROSS ERN KS THIS AFTERNOON...WITH FORECAST SOUNDINGS SHOWING SOME UNSTABLE AIR BELOW 700H. BUT WARMER AIR ALOFT WILL PROBABLY KEEP CONVECTION FROM REGENERATING OR BECOMING WIDESPREAD AS IT MOVES EAST INTO THIS SURFACE BASED INSTABILITY. COULD STILL SEE A FEW ISOLATED SHRA/TSRA NEAR THE ALLEN AND WILSON CO LINE....SO WILL KEEP A LOW POP FOR THIS INTO THE AFTERNOON HOURS. WILL ALSO LEAVE A LOW POP INTO SOUTHEAST KS FOR THE EVENING HOURS AS WELL...AS BACKDOOR SURFACE BOUNDARY DRIFTS SOUTHWEST INTO THIS AREA. STILL SOME CONCERN ABOUT MID LEVEL CAP KEEPING CONVECTION FROM DEVELOPING SO WILL KEEP POP IN THE SLIGHT CATEGORY FOR NOW. THE MAIN CONCERN ELSEWHERE WILL BE HOT TEMPS. SOME AREAS WILL APPROACH THE CENTURY MARK ESPECIALLY ACROSS CENTRAL KS WHERE SOMEWHAT DRIER AIR WILL LEAD TO A NICE DIURNAL TEMP SWING WITH SOME HEAT INDICES APPROACHING 105. .AVIATION... FOR THE 18Z TAF SUITE. MAINLY VFR CONDITIONS EXPECTED FOR MOST TAF SITES...WITH THE MAIN CONCERN BEING THIS AFTERNOON/EVENING NEAR THE KCNU TAF SITE. WILL KEEP SOME MID LEVEL CEILING MENTIONED IN THIS AREA...AS WANING CONVECTION STAYS JUST TO THE NORTH OF THIS AREA. WILL NOT INCLUDE A VCTS MENTION EITHER FOR NEAR KCNU...BUT COULD SEE THIS ADDED LATER. KETCHAM && .PREV DISCUSSION... /ISSUED 700 AM CDT TUE JUL 22 2008/ UPDATE... AVIATION... 12Z TAF ISSUANCE: SCT ACCAS CONTS TO DEVELOP OVER C & ERN KS EARLY THIS MORNING IN REGION OF ISENTROPIC ASCENT IN 305-310K LAYER JUXTAPOSED WITH NEARLY STATIONARY 925-MB FRONT DRAPED IN NEARLY W-E MANNER OVER THESE AREAS. SHRA/TSRA HAVE YET TO DEVELOP BUT CONTINUE TO MONITOR CLOSELY. WITH STATIONARY FRONT LURKING ABOUT SCT-ISOLATED TSRA POSSIBLE THIS AFTERNOON & EVENING OVER PRIMARILY NE KS WHERE CLOSER TO TRACK OF SECONDARY MID-LEVEL SHORTWAVE SWINGING ALMOST DUE S OVER MS VALLEY. WITH EXPECTED COVERAGE OVER C KS TO BE MORE ISOLATED IN NATURE...HAVE OPTED TO KEEP "VCTS" OUT OF KSLN FOR TIME BEING. PREV DISCUSSION... /ISSUED 454 AM CDT TUE JUL 22 2008/ UPDATE... LATEST IR LOOP/FOG IMAGERY CONTINUES TO SHOW THE ALTOCUMULUS CASTELLANEOUS INCREASING IN COVERAGE IN AREAS BETWEEN SALINA AND CONCORDIA. THIS IS IN ASSOCIATION WITH AN AREA OF ISENTROPIC ASCENT/MOISTURE TRANSPORT AROUND 310K MOVING THROUGH WESTERN KANSAS...ACCORDING TO THE LATEST RUC. LATEST LAPS DATA IS SHOWING 0-3KM MOST UNSTABLE CAPES AROUND 1200 J/KG. THIS COULD LEAD TO THE DEVELOPMENT OF A FEW THUNDERSTORMS ACROSS AREAS MAINLY NORTH OF INTERSTATE 70 BEFORE 12Z. WE MAY EXTEND THE POPS BEYOND 12Z...BUT WE WILL MONITOR FOR A LITTLE LONGER BEFORE MAKING THAT DECISION. COX PREV DISCUSSION... /ISSUED 258 AM CDT TUE JUL 22 2008/ DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE WILL BE THE HEAT AND HOW LONG IT LAST. THE OTHER CONCERN IS THE THUNDERSTORM CHANCES BEGINNING THIS AFTERNOON AND CONTINUING THROUGH WEDNESDAY. TODAY AND TONIGHT: LATEST IR LOOP IS SHOWING ANOTHER ATMOSPHERIC FIREWORKS SHOW MOVING THROUGH THE MISSISSIPPI VALLEY TONIGHT. THIS COMPLEX OF STORMS IS ASSOCIATED WITH A FAIRLY STRONG SHORTWAVE MOVING THROUGH EASTERN IOWA. AS THIS SHORTWAVE CONTINUES TO TRACK EAST...IT WILL CAUSE THE FRONTAL BOUNDARY CURRENTLY NEAR THE KANSAS AND NEBRASKA BORDER TO PUSH SLOWLY SOUTH TODAY. THIS BOUNDARY COULD SET OFF A FEW PULSE SEVERE THUNDERSTORMS MAINLY IN NORTHEAST KANSAS THIS AFTERNOON DUE TO MIXED LAYER CAPES AROUND 2500-3000J/KG AND WEAK SHEAR. THESE STORMS WILL ALSO CREATE SEVERAL COLD POOL BOUNDARIES WHICH WILL ACT AS A FOCUS MECHANISM FOR MORE ACTIVITY EARLY THIS EVENING. THE MODELS ARE SHOWING A FAIRLY WEAK LOW LEVEL JET IN SOUTHEAST KANSAS...SO WE WOULD EXPECT MOST OF THE ACTIVITY TO DRIVE ALONG THE MEAN MID LEVEL FLOW INTO MISSOURI. HOWEVER...A FEW OF THESE STORMS COULD CLIP THE NORTHEAST PORTION OF OUR FORECAST AREA THIS LATE THIS AFTERNOON AND TONIGHT. THEREFORE...WE HAVE KEPT A CHANCE OF THUNDERSTORMS IN THE PICTURE MAINLY EAST OF A SALINA TO EL DORADO TO INDEPENDENCE LINE. TEMPERATURES THIS AFTERNOON AND TONIGHT WILL BE FAIRLY SIMILAR TO YESTERDAY AND THIS MORNING. WEDNESDAY: THE MODELS ARE SHOWING THE FRONTAL BOUNDARY BEGINNING TO WASH OUT AS THE UPPER LEVEL RIDGE BEGINS TO FLATTEN OVER THE PLAINS. HOWEVER...THE ECMWF/GFS AND UKMET ARE SHOWING AN INSTABILITY AXIS EXTENDING FROM SALINA TO SOUTHEAST KANSAS. WE ARE NOT EXPECTING MUCH ACTIVITY IN THIS INSTABILITY AXIS DUE TO LIMITED LOW LEVEL FORCING...BUT WE CANNOT RULE OUT AN ISOLATED STRONG STORM OR TWO. THEREFORE...WE KEPT A SLIGHT CHANCE OF THUNDERSTORMS IN THE PICTURE. WEDNESDAY NIGHT-SATURDAY: THE HOT AND DRY PATTERN WILL PERSIST INTO THE WEEKEND WITH AFTERNOON TEMPERATURES STAYING CLOSE TO THE CENTURY MARK. WE DID RAISE TEMPERATURES AND LOWERED DEWPOINTS A FEW NOTCHES IN THIS TIMEFRAME. COX AVIATION... 06Z TAF UPDATE...VFR CONDITIONS ARE EXPECTED TO PREVAIL FOR TONIGHT INTO TOMORROW FOR ALL TERMINALS...HOWEVER A FRONTAL BOUNDARY WILL BEGIN TO SAG SLOWLY SOUTHWARD ACROSS KANSAS FOR TUESDAY AFTERNOON. WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP NEAR THE FRONT FOR THE MID TO LATE AFTERNOON HOURS. JAKUB && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 99 72 99 72 / 10 10 0 10 HUTCHINSON 99 71 100 72 / 10 10 10 10 NEWTON 98 71 98 72 / 10 20 10 10 ELDORADO 97 71 98 72 / 10 20 10 10 WINFIELD-KWLD 98 73 99 72 / 10 10 0 10 RUSSELL 100 68 99 69 / 10 10 10 10 GREAT BEND 99 68 100 69 / 10 10 0 10 SALINA 98 70 99 71 / 10 20 20 10 MCPHERSON 99 70 98 71 / 10 10 10 10 COFFEYVILLE 98 73 95 72 / 10 20 20 10 CHANUTE 98 71 95 72 / 10 20 20 10 IOLA 98 71 95 72 / 20 20 20 10 PARSONS-KPPF 98 72 95 72 / 10 20 20 10 && .ICT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 723 AM CDT TUE JUL 22 2008 .UPDATE... UPDATED FOR 12 UTC AVIATION && .DISCUSSION... SEE PREVIOUS DISCUSSION BELOW... && .AVIATION... AN AREA OF ACCAS AT 12 KFT HAS PERSISTED FOR MOST OF THE MORNING HOURS. MOST AREAS SHOULD REMAIN DRY AND VFR CONDITIONS WITH A FEW ISOLATED SHOWERS POSSIBLE THIS MORNING. OTHERWISE...A FEW THUNDERSTORMS MAY DEVELOP LATE THIS AFTERNOON INTO TONIGHT IN THE VICINITY OF A FRONTAL BOUNDARY. FOE/TOP LOOK TO HAVE A BETTER SHOT AT SEEING AT LEAST VCTS...WITH MODELS SUGGESTING THE HIGHEST PROBABILITY ACROSS FAR EASTERN KANSAS. EASTERLY SFC WIND WILL BE THE DOMINANT VECTOR DURING THE TAF FORECAST PERIOD WITH SPEEDS UNDER 12 KTS. BLAIR && .PREV DISCUSSION... /ISSUED 350 AM CDT TUE JUL 22 2008/ DISCUSSION... 08Z WATER VAPOR SHOWS A TROUGH ALONG THE PACIFIC NORTHWEST COAST AND THE GREAT LAKES/NORTHEAST U.S. AN UPPER LEVEL RIDGE WAS CENTERED OVER THE SOUTHERN ROCKIES AND EXTENDED NORTH INTO THE CENTRAL HIGH PLAINS. A SHORTWAVE MOVING THROUGH THE UPPER MID WEST WAS ROTATING THROUGH IA WITH ANOTHER SHORTWAVE OVER MN. ELEVATED CONVECTION HAS DEVELOPED ALONG A MOISTURE AXIS BETWEEN 800 AND 700MB FROM SOUTHEAST NEB INTO NORTHERN MO. ISENTROPIC LIFT ON THE 310K SFC DEPICTED BY THE RUC SHOWS THIS NARROW CORRIDOR OF MOISTURE REMAINING JUST NORTHEAST OF BROWN COUNTY. GFS ALSO KEEPS ITS QPF JUST TO THE NORTHEAST. WITH THE RUC SHOWING SOME DRYER AIR OVER CENTRAL KS...THINK BULK OF ELEVATED CONVECTION WILL REMAIN JUST TO THE NORTHEAST OF THE FORECAST AREA WITH MOST OF THE LIFT OVERHEAD GOING INTO SATURATING PARCELS AS THEY LIFT INTO NORTHERN MO. NEVERTHELESS WILL MAINTAIN LOW POPS THROUGH 12Z. AFTER 12Z...LEFT LOOKS TO DIMINISH AND PRECIP MAY BE PUSHING OFF TO THE EAST. FOR THE REST OF TODAY THROUGH WEDNESDAY...THE ATMOSPHERE WILL BE CHARACTERIZED AS CONDITIONALLY UNSTABLE WITH NO REAL FORCING TO SPEAK OF AS THE UPPER RIDGE REMAINS JUST TO THE WEST OVER THE HIGH PLAINS. WHILE MID LEVEL TEMPS ARE NOT OVERWHELMING IN TERMS OF A CAP...WEAK LOW LEVEL CAA WITH THE EASTERLY WIND WILL PREVENT THE BOUNDARY LAYER FROM MIXING AS DEEP AS IT HAS THE PAST COUPLE DAYS OVER EASTERN KS WHERE LOW LEVEL MOISTURE IS EXPECTED TO POOL. SO THE QUESTION IS WHETHER THERE WILL BE ENOUGH HEATING AND LOW LEVEL CONVERGENCE ALONG THE FRONT TO ALLOW A STORM TO DEVELOP. IN GENERAL DO NOT FEEL CONFIDENT TO REMOVE POPS GIVEN THE AMOUNT OF INSTABILITY THERE COULD BE WITH DEWPOINTS POOLING AROUND 70 DEGREES. KEPT SOME CHANCE POPS THIS AFTERNOON OVER EAST CENTRAL KS WHERE THE BOUNDARY AND GREATEST INSTABILITY SHOULD BE CO-LOCATED. FOR TONIGHT THROUGH WEDNESDAY NIGHT FELT CHANCE POPS WERE A LITTLE OVERDONE GIVEN LITTLE IF ANY FORCING PROGGED BY THE MODELS. KEPT SLIGHT CHANCE POPS FOR THE POSSIBILITY OF ISOLATED CONVECTION TO FORM. BY WEDNESDAY...THE BOUNDARY SHOULD BEGIN TO WASH OUT AND PRECIP CHANCES SHOULD SHIFT BACK NORTH. HIGHS TODAY AND WEDNESDAY ACROSS EASTERN KS SHOULD BE COOLER GIVEN THE DIMINISHED MIXING AND THE EASTERLY WINDS. PARTS OF NORTH CENTRAL KS AHEAD OF THE WEAK BOUNDARY SHOULD STILL REACH THE UPPER 90S. FORECAST REMAINS IN TACT FOR THURSDAY THROUGH MONDAY. THE GFS LOOKS TO SUFFER FROM FEEDBACK ISSUES ON THURSDAY WITH A CONVECTIVELY INDUCED VORT MAX PROPAGATING ACROSS NORTHEAST KS DURING THE DAY. HAVE LITTLE CONFIDENCE IN THIS SO MAINTAINED SLIGHT CHANCE POPS. UNCERTAINTY IN SFC FEATURES FOR THE WEEKEND AND BEYOND PRECLUDED ANY CHANGES. WOLTERS && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 700 AM CDT TUE JUL 22 2008 .UPDATE... .AVIATION... 12Z TAF ISSUANCE: SCT ACCAS CONTS TO DEVELOP OVER C & ERN KS EARLY THIS MORNING IN REGION OF ISENTROPIC ASCENT IN 305-310K LAYER JUXTAPOSED WITH NEARLY STATIONARY 925-MB FRONT DRAPED IN NEARLY W-E MANNER OVER THESE AREAS. SHRA/TSRA HAVE YET TO DEVELOP BUT CONTINUE TO MONITOR CLOSELY. WITH STATIONARY FRONT LURKING ABOUT SCT-ISOLATED TSRA POSSIBLE THIS AFTERNOON & EVENING OVER PRIMARILY NE KS WHERE CLOSER TO TRACK OF SECONDARY MID-LEVEL SHORTWAVE SWINGING ALMOST DUE S OVER MS VALLEY. WITH EXPECTED COVERAGE OVER C KS TO BE MORE ISOLATED IN NATURE...HAVE OPTED TO KEEP "VCTS" OUT OF KSLN FOR TIME BEING. && .PREV DISCUSSION... /ISSUED 454 AM CDT TUE JUL 22 2008/ UPDATE... LATEST IR LOOP/FOG IMAGERY CONTINUES TO SHOW THE ALTOCUMULUS CASTELLANEOUS INCREASING IN COVERAGE IN AREAS BETWEEN SALINA AND CONCORDIA. THIS IS IN ASSOCIATION WITH AN AREA OF ISENTROPIC ASCENT/MOISTURE TRANSPORT AROUND 310K MOVING THROUGH WESTERN KANSAS...ACCORDING TO THE LATEST RUC. LATEST LAPS DATA IS SHOWING 0-3KM MOST UNSTABLE CAPES AROUND 1200 J/KG. THIS COULD LEAD TO THE DEVELOPMENT OF A FEW THUNDERSTORMS ACROSS AREAS MAINLY NORTH OF INTERSTATE 70 BEFORE 12Z. WE MAY EXTEND THE POPS BEYOND 12Z...BUT WE WILL MONITOR FOR A LITTLE LONGER BEFORE MAKING THAT DECISION. COX PREV DISCUSSION... /ISSUED 258 AM CDT TUE JUL 22 2008/ DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE WILL BE THE HEAT AND HOW LONG IT LAST. THE OTHER CONCERN IS THE THUNDERSTORM CHANCES BEGINNING THIS AFTERNOON AND CONTINUING THROUGH WEDNESDAY. TODAY AND TONIGHT: LATEST IR LOOP IS SHOWING ANOTHER ATMOSPHERIC FIREWORKS SHOW MOVING THROUGH THE MISSISSIPPI VALLEY TONIGHT. THIS COMPLEX OF STORMS IS ASSOCIATED WITH A FAIRLY STRONG SHORTWAVE MOVING THROUGH EASTERN IOWA. AS THIS SHORTWAVE CONTINUES TO TRACK EAST...IT WILL CAUSE THE FRONTAL BOUNDARY CURRENTLY NEAR THE KANSAS AND NEBRASKA BORDER TO PUSH SLOWLY SOUTH TODAY. THIS BOUNDARY COULD SET OFF A FEW PULSE SEVERE THUNDERSTORMS MAINLY IN NORTHEAST KANSAS THIS AFTERNOON DUE TO MIXED LAYER CAPES AROUND 2500-3000J/KG AND WEAK SHEAR. THESE STORMS WILL ALSO CREATE SEVERAL COLD POOL BOUNDARIES WHICH WILL ACT AS A FOCUS MECHANISM FOR MORE ACTIVITY EARLY THIS EVENING. THE MODELS ARE SHOWING A FAIRLY WEAK LOW LEVEL JET IN SOUTHEAST KANSAS...SO WE WOULD EXPECT MOST OF THE ACTIVITY TO DRIVE ALONG THE MEAN MID LEVEL FLOW INTO MISSOURI. HOWEVER...A FEW OF THESE STORMS COULD CLIP THE NORTHEAST PORTION OF OUR FORECAST AREA THIS LATE THIS AFTERNOON AND TONIGHT. THEREFORE...WE HAVE KEPT A CHANCE OF THUNDERSTORMS IN THE PICTURE MAINLY EAST OF A SALINA TO EL DORADO TO INDEPENDENCE LINE. TEMPERATURES THIS AFTERNOON AND TONIGHT WILL BE FAIRLY SIMILAR TO YESTERDAY AND THIS MORNING. WEDNESDAY: THE MODELS ARE SHOWING THE FRONTAL BOUNDARY BEGINNING TO WASH OUT AS THE UPPER LEVEL RIDGE BEGINS TO FLATTEN OVER THE PLAINS. HOWEVER...THE ECMWF/GFS AND UKMET ARE SHOWING AN INSTABILITY AXIS EXTENDING FROM SALINA TO SOUTHEAST KANSAS. WE ARE NOT EXPECTING MUCH ACTIVITY IN THIS INSTABILITY AXIS DUE TO LIMITED LOW LEVEL FORCING...BUT WE CANNOT RULE OUT AN ISOLATED STRONG STORM OR TWO. THEREFORE...WE KEPT A SLIGHT CHANCE OF THUNDERSTORMS IN THE PICTURE. WEDNESDAY NIGHT-SATURDAY: THE HOT AND DRY PATTERN WILL PERSIST INTO THE WEEKEND WITH AFTERNOON TEMPERATURES STAYING CLOSE TO THE CENTURY MARK. WE DID RAISE TEMPERATURES AND LOWERED DEWPOINTS A FEW NOTCHES IN THIS TIMEFRAME. COX AVIATION... 06Z TAF UPDATE...VFR CONDITIONS ARE EXPECTED TO PREVAIL FOR TONIGHT INTO TOMORROW FOR ALL TERMINALS...HOWEVER A FRONTAL BOUNDARY WILL BEGIN TO SAG SLOWLY SOUTHWARD ACROSS KANSAS FOR TUESDAY AFTERNOON. WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP NEAR THE FRONT FOR THE MID TO LATE AFTERNOON HOURS. JAKUB && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 99 72 99 72 / 10 10 0 10 HUTCHINSON 99 71 100 72 / 10 10 10 10 NEWTON 98 71 98 72 / 10 20 10 10 ELDORADO 97 71 98 72 / 10 20 10 10 WINFIELD-KWLD 98 73 99 72 / 10 10 0 10 RUSSELL 100 68 99 69 / 10 10 10 10 GREAT BEND 99 68 100 69 / 10 10 0 10 SALINA 98 70 99 71 / 20 20 20 10 MCPHERSON 99 70 98 71 / 10 10 10 10 COFFEYVILLE 98 73 95 72 / 10 20 20 10 CHANUTE 98 71 95 72 / 10 20 20 10 IOLA 98 71 95 72 / 20 20 20 10 PARSONS-KPPF 98 72 95 72 / 10 20 20 10 && .ICT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WICHITA KS 454 AM CDT TUE JUL 22 2008 .UPDATE... LATEST IR LOOP/FOG IMAGERY CONTINUES TO SHOW THE ALTOCUMULUS CASTELLANEOUS INCREASING IN COVERAGE IN AREAS BETWEEN SALINA AND CONCORDIA. THIS IS IN ASSOCIATION WITH AN AREA OF ISENTROPIC ASCENT/MOISTURE TRANSPORT AROUND 310K MOVING THROUGH WESTERN KANSAS...ACCORDING TO THE LATEST RUC. LATEST LAPS DATA IS SHOWING 0-3KM MOST UNSTABLE CAPES AROUND 1200 J/KG. THIS COULD LEAD TO THE DEVELOPMENT OF A FEW THUNDERSTORMS ACROSS AREAS MAINLY NORTH OF INTERSTATE 70 BEFORE 12Z. WE MAY EXTEND THE POPS BEYOND 12Z...BUT WE WILL MONITOR FOR A LITTLE LONGER BEFORE MAKING THAT DECISION. COX && .PREV DISCUSSION... /ISSUED 258 AM CDT TUE JUL 22 2008/ DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE WILL BE THE HEAT AND HOW LONG IT LAST. THE OTHER CONCERN IS THE THUNDERSTORM CHANCES BEGINNING THIS AFTERNOON AND CONTINUING THROUGH WEDNESDAY. TODAY AND TONIGHT: LATEST IR LOOP IS SHOWING ANOTHER ATMOSPHERIC FIREWORKS SHOW MOVING THROUGH THE MISSISSIPPI VALLEY TONIGHT. THIS COMPLEX OF STORMS IS ASSOCIATED WITH A FAIRLY STRONG SHORTWAVE MOVING THROUGH EASTERN IOWA. AS THIS SHORTWAVE CONTINUES TO TRACK EAST...IT WILL CAUSE THE FRONTAL BOUNDARY CURRENTLY NEAR THE KANSAS AND NEBRASKA BORDER TO PUSH SLOWLY SOUTH TODAY. THIS BOUNDARY COULD SET OFF A FEW PULSE SEVERE THUNDERSTORMS MAINLY IN NORTHEAST KANSAS THIS AFTERNOON DUE TO MIXED LAYER CAPES AROUND 2500-3000J/KG AND WEAK SHEAR. THESE STORMS WILL ALSO CREATE SEVERAL COLD POOL BOUNDARIES WHICH WILL ACT AS A FOCUS MECHANISM FOR MORE ACTIVITY EARLY THIS EVENING. THE MODELS ARE SHOWING A FAIRLY WEAK LOW LEVEL JET IN SOUTHEAST KANSAS...SO WE WOULD EXPECT MOST OF THE ACTIVITY TO DRIVE ALONG THE MEAN MID LEVEL FLOW INTO MISSOURI. HOWEVER...A FEW OF THESE STORMS COULD CLIP THE NORTHEAST PORTION OF OUR FORECAST AREA THIS LATE THIS AFTERNOON AND TONIGHT. THEREFORE...WE HAVE KEPT A CHANCE OF THUNDERSTORMS IN THE PICTURE MAINLY EAST OF A SALINA TO EL DORADO TO INDEPENDENCE LINE. TEMPERATURES THIS AFTERNOON AND TONIGHT WILL BE FAIRLY SIMILAR TO YESTERDAY AND THIS MORNING. WEDNESDAY: THE MODELS ARE SHOWING THE FRONTAL BOUNDARY BEGINNING TO WASH OUT AS THE UPPER LEVEL RIDGE BEGINS TO FLATTEN OVER THE PLAINS. HOWEVER...THE ECMWF/GFS AND UKMET ARE SHOWING AN INSTABILITY AXIS EXTENDING FROM SALINA TO SOUTHEAST KANSAS. WE ARE NOT EXPECTING MUCH ACTIVITY IN THIS INSTABILITY AXIS DUE TO LIMITED LOW LEVEL FORCING...BUT WE CANNOT RULE OUT AN ISOLATED STRONG STORM OR TWO. THEREFORE...WE KEPT A SLIGHT CHANCE OF THUNDERSTORMS IN THE PICTURE. WEDNESDAY NIGHT-SATURDAY: THE HOT AND DRY PATTERN WILL PERSIST INTO THE WEEKEND WITH AFTERNOON TEMPERATURES STAYING CLOSE TO THE CENTURY MARK. WE DID RAISE TEMPERATURES AND LOWERED DEWPOINTS A FEW NOTCHES IN THIS TIMEFRAME. COX AVIATION... 06Z TAF UPDATE...VFR CONDITIONS ARE EXPECTED TO PREVAIL FOR TONIGHT INTO TOMORROW FOR ALL TERMINALS...HOWEVER A FRONTAL BOUNDARY WILL BEGIN TO SAG SLOWLY SOUTHWARD ACROSS KANSAS FOR TUESDAY AFTERNOON. WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP NEAR THE FRONT FOR THE MID TO LATE AFTERNOON HOURS. JAKUB && .PRELIMINARY POINT TEMPS/POPS... WICHITA-KICT 99 72 99 72 / 10 10 0 10 HUTCHINSON 99 71 100 72 / 10 10 10 10 NEWTON 98 71 98 72 / 10 20 10 10 ELDORADO 97 71 98 72 / 10 20 10 10 WINFIELD-KWLD 98 73 99 72 / 10 10 0 10 RUSSELL 100 68 99 69 / 10 10 10 10 GREAT BEND 99 68 100 69 / 10 10 0 10 SALINA 98 70 99 71 / 20 20 20 10 MCPHERSON 99 70 98 71 / 10 10 10 10 COFFEYVILLE 98 73 95 72 / 10 20 20 10 CHANUTE 98 71 95 72 / 10 20 20 10 IOLA 98 71 95 72 / 20 20 20 10 PARSONS-KPPF 98 72 95 72 / 10 20 20 10 && .ICT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 350 AM CDT TUE JUL 22 2008 .DISCUSSION... 08Z WATER VAPOR SHOWS A TROUGH ALONG THE PACIFIC NORTHWEST COAST AND THE GREAT LAKES/NORTHEAST U.S. AN UPPER LEVEL RIDGE WAS CENTERED OVER THE SOUTHERN ROCKIES AND EXTENDED NORTH INTO THE CENTRAL HIGH PLAINS. A SHORTWAVE MOVING THROUGH THE UPPER MID WEST WAS ROTATING THROUGH IA WITH ANOTHER SHORTWAVE OVER MN. ELEVATED CONVECTION HAS DEVELOPED ALONG A MOISTURE AXIS BETWEEN 800 AND 700MB FROM SOUTHEAST NEB INTO NORTHERN MO. ISENTROPIC LIFT ON THE 310K SFC DEPICTED BY THE RUC SHOWS THIS NARROW CORRIDOR OF MOISTURE REMAINING JUST NORTHEAST OF BROWN COUNTY. GFS ALSO KEEPS ITS QPF JUST TO THE NORTHEAST. WITH THE RUC SHOWING SOME DRYER AIR OVER CENTRAL KS...THINK BULK OF ELEVATED CONVECTION WILL REMAIN JUST TO THE NORTHEAST OF THE FORECAST AREA WITH MOST OF THE LIFT OVERHEAD GOING INTO SATURATING PARCELS AS THEY LIFT INTO NORTHERN MO. NEVERTHELESS WILL MAINTAIN LOW POPS THROUGH 12Z. AFTER 12Z...LEFT LOOKS TO DIMINISH AND PRECIP MAY BE PUSHING OFF TO THE EAST. FOR THE REST OF TODAY THROUGH WEDNESDAY...THE ATMOSPHERE WILL BE CHARACTERIZED AS CONDITIONALLY UNSTABLE WITH NO REAL FORCING TO SPEAK OF AS THE UPPER RIDGE REMAINS JUST TO THE WEST OVER THE HIGH PLAINS. WHILE MID LEVEL TEMPS ARE NOT OVERWHELMING IN TERMS OF A CAP...WEAK LOW LEVEL CAA WITH THE EASTERLY WIND WILL PREVENT THE BOUNDARY LAYER FROM MIXING AS DEEP AS IT HAS THE PAST COUPLE DAYS OVER EASTERN KS WHERE LOW LEVEL MOISTURE IS EXPECTED TO POOL. SO THE QUESTION IS WHETHER THERE WILL BE ENOUGH HEATING AND LOW LEVEL CONVERGENCE ALONG THE FRONT TO ALLOW A STORM TO DEVELOP. IN GENERAL DO NOT FEEL CONFIDENT TO REMOVE POPS GIVEN THE AMOUNT OF INSTABILITY THERE COULD BE WITH DEWPOINTS POOLING AROUND 70 DEGREES. KEPT SOME CHANCE POPS THIS AFTERNOON OVER EAST CENTRAL KS WHERE THE BOUNDARY AND GREATEST INSTABILITY SHOULD BE CO-LOCATED. FOR TONIGHT THROUGH WEDNESDAY NIGHT FELT CHANCE POPS WERE A LITTLE OVERDONE GIVEN LITTLE IF ANY FORCING PROGGED BY THE MODELS. KEPT SLIGHT CHANCE POPS FOR THE POSSIBILITY OF ISOLATED CONVECTION TO FORM. BY WEDNESDAY...THE BOUNDARY SHOULD BEGIN TO WASH OUT AND PRECIP CHANCES SHOULD SHIFT BACK NORTH. HIGHS TODAY AND WEDNESDAY ACROSS EASTERN KS SHOULD BE COOLER GIVEN THE DIMINISHED MIXING AND THE EASTERLY WINDS. PARTS OF NORTH CENTRAL KS AHEAD OF THE WEAK BOUNDARY SHOULD STILL REACH THE UPPER 90S. FORECAST REMAINS IN TACT FOR THURSDAY THROUGH MONDAY. THE GFS LOOKS TO SUFFER FROM FEEDBACK ISSUES ON THURSDAY WITH A CONVECTIVELY INDUCED VORT MAX PROPAGATING ACROSS NORTHEAST KS DURING THE DAY. HAVE LITTLE CONFIDENCE IN THIS SO MAINTAINED SLIGHT CHANCE POPS. UNCERTAINTY IN SFC FEATURES FOR THE WEEKEND AND BEYOND PRECLUDED ANY CHANGES. WOLTERS && .AVIATION... OUTFLOW BOUNDARY NEARING THE TAF SITES LATE THIS EVENING BUT CONVECTION HAS PUSHED TO THE EAST AND CHANCES FOR ADDITIONAL DEVELOPMENT IN THE LOCAL AREA SEEM LOW GIVEN MEAGER 850MB MOISTURE PER 00Z UPPER AIR DATA. MAY SEE SOME LINGERING MID CLOUD THROUGH MUCH OF THIS CYCLE WITH SOME CHANCE FOR ADDITIONAL CONVECTION DURING AFTERNOON/EVENING HOURS THURSDAY WITH FRONT/OUTFLOW IN THE VICINITY...BUT CHANCES APPEAR TOO LOW FOR A MENTION AT THIS TIME. 65 && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 1230 AM MDT TUE JUL 22 2008 .DISCUSSION... 1230 AM MDT TUE JUL 22 2008 THE SUBTROPICAL RIDGE IS PROGGED TO BREAK DOWN OVER MUCH OF THE NORTHERN PLAINS STATES ON WEDNESDAY AS A SHORTWAVE TROUGH OVER NORTHERN CALIFORNIA TRANSLATES EAST/NORTHEAST INTO THE NORTHERN ROCKIES/NORTHERN PLAINS NEAR THE CANADIAN BORDER. FURTHER SOUTH...LOW LEVEL MOISTURE HAS POOLED ALONG A SLOW MOVING COLD FRONT OVER PORTIONS OF THE CENTRAL PLAINS ALLOWING DEWPOINT TEMPERATURES TO RISE INTO THE MID 70S ACROSS SOUTH CENTRAL NEBRASKA. AS THIS FRONT BACKS SLOWLY INTO THE AREA THIS MORNING...EXPECT FOG STRATUS TO EXPAND IN COVERAGE. THE PREVIOUS FORECAST CAPTURED THIS SCENARIO WITH ONLY SUBTLE CHANGES PLANNED. LOW LEVEL WIND TRAJECTORIES SUPPORT LOWERING MAXIMUM TEMPERATURES ACROSS THE NORTHEAST ZONES WHERE A LULL IN DEEP VERTICAL MIXING IS ANTICIPATED GIVEN MOIST EASTERLY POST-FRONTAL REGIME. NAM/GFS FORECAST SOUNDINGS SUPPORT THE PREVIOUS FORECAST WITH ISOLATED THUNDERSTORMS WEIGHTED ACROSS THE NORTHEAST ZONES WHERE MLCAPE IS MAXIMIZED WITH MINIMAL CINH. WEDNESDAY-THURSDAY...THE SUBTROPICAL RIDGE CONTINUES TO SPRAWL OVER THE SOUTHERN ROCKIES WITH SIMILAR TEMPERATURES IN THE UPPER 90S/AROUND 100 EXPECTED ACROSS THE TRI-STATE AREA. THE STALLED FRONT MAY LIFT NORTHEAST OF THE AREA...BUT UNCERTAINTY REMAINS RATHER HIGH SO LEANED A LITTLE COOLER TOWARD THE KMCK AREA. INCREASING H7 TEMPERATURES SUGGEST VERY LIMITED CHANCES FOR DEEP MOIST CONVECTION AND PULLED POPS FROM PREVIOUS FORECAST ACROSS MUCH OF THE AREA WITH THE EXCEPTION BEING THE FAR NORTHWEST ZONES WHERE AN ISOLATED THUNDERSTORM MAY DRIFT ENE OFF THE FAVORED TERRAIN OUT WEST. A COLD FRONT MAY SURGE SOUTH LATE THURSDAY...HOWEVER CAPPING CONCERNS AND SOUTHERN EXTENT OF FRONT REMAIN UNCERTAIN. TRIMMED POPS TO THE FAR NORTHWEST ZONES GIVEN CAPPING CONCERNS. HIGHS ON EITHER SIZE OF 100 ARE EXPECTED ONCE AGAIN. DAYS 4 THROUGH 7...NO CHANGES. && .AVIATION... 1056 PM MDT MON JUL 21 2008 FOR THE 06Z TAFS...INITIAL PROBLEM WILL BE FOG AND STRATUS POTENTIAL FOR KMCK. NAM/RUC SIMILAR IN BRINGING IN FOG AND STRATUS AROUND 09Z. FEEL MORE CONFIDENT OF THIS HAPPENING DUE TO DEWPOINT/TEMPERATURE SPREADS VERY NARROW UPSTREAM WITH FOG ALREADY DEVELOPING. MODEL GUIDANCE SAYS THERE IS POTENTIAL TO GO TO LIFR ON THE VISIBILITY. HOWEVER...DID NOT WANT TO GO THAT FAR YET. SO KEPT MVFR VISIBILITY AND IFR CEILING. AFTER THAT...SHOULD BE VFR AT KMCK FOR THE REMAINDER OF THE PERIOD. KGLD WILL REMAIN VFR FOR THE ENTIRE PERIOD. AFTER 18Z THERE IS POTENTIAL FOR ISOLATED TSRA. AT THIS TIME NOT CONFIDENT IS LOCATION OF CONVECTION SO PUT NO MENTION OF IT IN THE TAFS WITH THE KMCK TAF HAVING THE BEST CHANCE. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 1058 PM MDT MON JUL 21 2008 .UPDATE... 824 PM MDT MON JUL 21 2008 JUST COMPLETED AN UPDATED. LOW LEVEL AIR MASS HAS BECOME CAPPED PER LAPS AND AREA SOUNDINGS. NO SIGNIFICANT LOW LEVEL JET OR LIFT AT MID LEVELS SEEN SO LOOKS LIKE NO ELEVATED TSRA DEVELOPING LATER TONIGHT. BASED ON EASTERLY WINDS AND INCREASING MOISTURE BEHIND SAGGING COLD FRONT...INSERTED PATCHY FOG INTO THE FORECAST PLUS INCREASED CLOUD COVER IN THE FAR NORTH LATER TONIGHT AND TOMORROW MORNING. ALSO ADJUST MINS UP A LITTLE BIT IN THE NORTHEAST AS WELL. TWEEKED WIND...TEMPERATURE...AND DEWPOINT GRIDS BASED ON REALITY AND LATEST GUIDANCE. BULLER && .DISCUSSION...FORECAST CONCERNS ARE TEMPERATURES AND PRECIPITATION CHANCES. SHOWERS AND THUNDERSTORMS WILL RETURN TO THE NORTHERN HALF OF THE AREA (PRIMARILY) OVER THE NEXT FEW DAYS AS A FRONTAL BOUNDARY SLOWLY SAGS SOUTH INTO THE AREA. THE FRONT COMBINED WITH INCREASING MID AND UPPER LEVEL MOISTURE VIA MONSOONAL MOISTURE AND SUFFICIENT INSTABILITY WILL BE THE DRIVING FORCE FOR THE PRECIPITATION CHANCES. STILL SOME TIMING AND POSITION DIFFERENCES WITH REGARD TO LOCATION OF THE ABOVE MENTIONED FEATURES SO FOR NOW WILL KEEP POPS ON THE SLIGHT CHANCE SIDE AND GO FROM THERE. TEMPERATURES WILL REMAIN ABOVE NORMAL WITH READINGS WELL INTO THE 90S AND PROBABLY LOW 100S FOR A FEW LOCATIONS. NAM STILL TRYING TO SUGGEST SATURATED BOUNDARY LAYER CONDITIONS ALONG THE NEARLY STATIONARY FRONTAL BOUNDARY WHILE THE GFS KEEPS IT OUT OF THE AREA. SHOULD THE NAM VERIFY STRATUS/FOG AND SOME AVIATION CONCERNS WILL DEVELOP. WILL KEEP THE FOG OUT OF THE FORECAST AGAIN TODAY UNTIL SOME CONSISTENCY DEVELOPS WITH THE PLACEMENT OF THE BOUNDARY. FRIDAY-MONDAY...LARGE AREA OF UPPER LEVEL HIGH PRESSURE WILL COVER MUCH OF THE CENTRAL AND SOUTHERN PLAINS THROUGH SATURDAY BEFORE SHIFTING WEST TOWARD THE FOUR CORNERS SUNDAY AND MONDAY AS A STATIONARY FRONTAL BOUNDARY BACKS INTO THE AREA. MONSOONAL MOISTURE AND NEAR TO ABOVE NORMAL DAYTIME TEMPERATURES WILL PROMOTE A CHANCE OF PRECIPITATION JUST ABOUT EVERY DAY. DDT && .AVIATION... 1056 PM MDT MON JUL 21 2008 FOR THE 06Z TAFS...INITIAL PROBLEM WILL BE FOG AND STRATUS POTENTIAL FOR KMCK. NAM/RUC SIMILAR IN BRINGING IN FOG AND STRATUS AROUND 09Z. FEEL MORE CONFIDENT OF THIS HAPPENING DUE TO DEWPOINT/TEMPERATURE SPREADS VERY NARROW UPSTREAM WITH FOG ALREADY DEVELOPING. MODEL GUIDANCE SAYS THERE IS POTENITAL TO GO TO LIFR ON THE VISIBILITY. HOWEVER...DID NOT WANT TO GO THAT FAR YET. SO KEPT MVFR VISIBILITY AND IFR CEILING. AFTER THAT...SHOULD BE VFR AT KMCK FOR THE REMAINDER OF THE PERIOD. KGLD WILL REMAIN VFR FOR THE ENTIRE PERIOD. AFTER 18Z THERE IS POTENTIAL FOR ISOLATED TSRA. AT THIS TIME NOT CONFIDENT IS LOCATION OF CONVECTION SO PUT NO MENTION OF IT IN THE TAFS WITH THE KMCK TAF HAVING THE BEST CHANCE. BULLER && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 858 PM CDT WED JUL 23 2008 .UPDATE... BAND OF CIRRUS CLOUDS MOVING SOUTH ACROSS THE MISSISSIPPI VALLEY WILL PERSIST MUCH OF THE NIGHT. SURFACE WINDS FROM THE EAST TO NORTHEAST ARE STAYING UP THIS EVENING...AND 21Z RUC FORECASTS SOME WIND TO CONTINUE AT THE SURFACE THROUGH 09Z. UPDATED FORECAST FOR THESE SLIGHT CHANGES. WITH THE CLOUDS AND WIND...RAISED TEMPS A COUPLE DEGREES IN MOST PLACES /EXCEPT SW INDIANA AND ADJACENT COUNTIES/. && .PREVIOUS DISCUSSION /ISSUED 300 PM CDT WED JUL 23 2008/... SHORT TERM /TONIGHT THROUGH SATURDAY/... DRY SURFACE HIGH PRESSURE HAS OVERSPREAD ALL BUT FAR SOUTHWEST COUNTIES IN SOUTHEAST MISSOURI. PLENTY OF STRATOCU IN THAT AREA...BUT APPARENTLY NOT ENOUGH INSTABILITY FOR CONVECTION TO DEVELOP. NO MODELS LINGER ANYTHING BEYOND 00Z...SO WILL KEEP TONIGHT DRY...WITH CLEAR SKIES OVER MUCH OF THE AREA. MAIN QUESTION THURSDAY IS WHETHER A CONVECTIVE COMPLEX WILL DIVE SOUTHEAST ALONG THE MISSISSIPPI RIVER INTO THE AREA. THE 12Z GFS HAS THE BEST HANDLE ON ONGOING WEAK CONVECTION NEAR SIOUX CITY IOWA ALONG NORTHWEST EXTENSION OF MOISTURE BAND THAT EXTENDS INTO SOUTHEAST MISSOURI. BASED ON ITS BETTER HANDLING OF CURRENT SITUATION WILL LEAN TOWARD ITS SOLUTION FOR THURSDAY AND THURSDAY NIGHT. IF THE SYSTEM DEVELOPS AND MOVES TOWARD THE AREA...IT IS LIKELY THAT IT WILL OUTRUN RETURN FLOW MOISTURE UPON ENTERING THE AREA...AS SURFACE RIDGE HOLDS FIRM. THUS WILL KEEP POPS TO SLIGHT CHANCE ALONG THE NORTHWESTERN FRINGE OF THE AREA THURSDAY. THE 12Z MODELS ALL WEAKEN AND PUSH THE SURFACE HIGH EAST OF THE AREA THURSDAY NIGHT INTO FRIDAY...ALLOWING FOR RETURN FLOW IN THE LOW LEVELS AND INCREASING MOISTURE...ESPECIALLY IN WESTERN ZONES. THE GFS HAS A MORE WESTERN PATH TO THE CONVECTIVE COMPLEX ON THURSDAY NIGHT THAN THE NAM OR ECMWF...BUT GIVEN CURRENT LOCATION OF BAROCLINIC ZONE...AM NOT READY TO DISCOUNT IT AT THIS TIME. WILL HAVE CHANCE POPS OVER MUCH OF THE AREA THURSDAY NIGHT WITH BEST CHANCES OVER NORTHERN PORTIONS OF SOUTHERN ILLINOIS. FRIDAY CONTINUES TO HAVE THE BEST CHANCE OF CONVECTION OVER THE QUAD STATE NO MATTER WHICH MODEL IS PREFERRED. EITHER A COMPLEX WILL BE MOVING THROUGH THE AREA AS THE GFS SUGGESTS...OR THERE WILL BE DEVELOPMENT ALONG THE OUTFLOW OF A SYSTEM THAT SKIRTS BY TO OUR NORTH AND NORTHEAST...AS THE NAM AND ECMWF SUGGEST. WILL KEEP POPS AT CHANCE LEVELS FRIDAY...WITH BEST CHANCES NORTHEAST. PRECIPITATION SHOULD BE EXITING THE SOUTHEAST PORTIONS OF THE AREA FRIDAY NIGHT. COULD HAVE A DRY PERIOD FROM LATE FRIDAY NIGHT THROUGH MUCH OF SATURDAY...BEFORE YET ANOTHER COLD FRONT REACHES THE AREA LATE SATURDAY AND SATURDAY NIGHT. DECIDED TO GO WITH LOW CHANCE POPS TO BE SAFE FOR SATURDAY. TEMPERATURES WILL CONTINUE TO RUN NEAR NORMAL OR JUST A BIT BELOW THROUGH THE REMAINDER OF THE WEEK. LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT IN THE OVERALL SYNOPTIC PATTERN OVER THE COUNTRY...WITH AN UPPER RIDGE OVER ROCKY MOUNTAINS...AND A TROUGH IN THE EAST. THE QUAD STATE WILL BE UNDER THE INFLUENCE OF NORTHWEST FLOW ALOFT...WHICH TRADITIONALLY LEADS TO A LOW CONFIDENCE PRECIPITATION FORECAST...AS THE MODELS HAVE A DIFFICULT TIME WITH TIMING AND PLACEMENT OF IMPULSES WHICH WILL EITHER TOUCH OFF MCS/S OR WILL BRING A FRONT THROUGH THE REGION. WILL LEAN ON THE HPC SOLUTION...WHICH IS HIGHLY BASED ON NCEP/ECMWF ENSEMBLE MEANS. THIS APPROACH TENDS TO WASH OUT SOME OF THE DETAILS AND LEADS TO A SIMPLIFIED SOLUTION. AN EAST/WEST ORIENTED FRONT BISECTING THE QUAD STATE SATURDAY NIGHT WILL SLOWLY SAG SOUTH OF THE AREA BY MONDAY MORNING...WHERE IT WILL REMAIN THROUGH MIDWEEK. WILL HAVE LOW CHANCE POPS SATURDAY NIGHT AND SUNDAY AND THEN SHOW A DRYING TREND FROM NORTH TO SOUTH SUNDAY NIGHT AND MONDAY. THE FORECAST IS DRY FROM MONDAY NIGHT THROUGH WEDNESDAY. COULD SEE A SWATH OF HEAVY RAINALL AND SOME GUSTY WINDS WITH AN MCS AT SOME POINT SATURDAY NIGHT THROUGH MONDAY...BUT SEVERE STORMS SEEM UNLIKELY AT THIS TIME. WOULD NOT BE SURPRISED TO SEE POPS ADDED IN FOR NEXT WEEK...BUT AT THIS TIME...WITH THE FRONT STAYING TO OUR SOUTH AND EASTERLY LOW LEVEL FLOW...CANNOT JUSTIFY ANYTHING BUT A DRY FORECAST. TEMPERATURES WILL REMAIN AT OR JUST A BIT ABOVE NORMAL THROUGH THE PERIOD. OF COURSE...A POORLY TIMED MCS COULD HAVE A SIGNIFICANT IMPACT ON TEMPERATURES...SIMILAR TO WHAT HAPPENED ACROSS THE AREA YESTERDAY. && .AVIATION... VFR CONDITIONS WILL PREVAIL THROUGH THURSDAY. INTERVALS OF CIRRUS WILL BEGIN TO OVERSPREAD THE AREA OVERNIGHT INTO THURSDAY...BUT NO PRECIPITATION IS ANTICIPATED. NORTHEAST WINDS AS HIGH AS 10 KNOTS WILL SUBSIDE TO NEAR CALM THIS EVENING...THEN BECOME SOUTHEASTERLY THURSDAY MORNING WITH AN INCREASINGLY SOUTHERLY COMPONENT. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ UPDATE...MY SHORT TERM......DRS LONG TERM.......DRS AVIATION........RP ky AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PADUCAH KY 1140 AM CDT WED JUL 23 2008 .DISCUSSION... REVISED FORECAST TO ELIMINATE ANY MENTION OF PRECIPITATION EXCEPT FOR LOCATIONS NEAR THE ARKANSAS BORDER...NAMELY ALONG AND SOUTH OF A GREENVILLE MISSOURI TO HICKMAN KENTUCKY LINE. THIS AREA HAS YET TO EXPERIENCE THE INFILTRATION OF LOW 60S DEW POINT AIR THAT HAS MADE ITS WAY ACROSS THE REST OF THE FORECAST AREA THIS MORNING. BOUNDARY LAYER DRYING WILL BE SLOW TO OCCUR THIS AFTERNOON IN THE AFOREMENTIONED AREAS...SO MAINTAINED A SLIGHT CHANCE TO ACCOUNT FOR ANY CONVECTION THAT MAY DEVELOP BETWEEN NOW AND NEXT ROUTINE FORECAST ISSUANCE. ALSO TWEAKED TEMPERATURE AND DEW POINT GRIDS DOWN A FEW DEGREES TO ACCOUNT FOR ONGOING TRENDS. && .AVIATION... VFR CONDITIONS WILL PREVAIL THROUGH THURSDAY. ANY THUNDERSTORM DEVELOPMENT SHOULD STAY SOUTH OF AREA FORECAST TERMINALS THIS AFTERNOON. DEVELOPMENT OF FEW-SCT CU IS STILL EXPECTED TODAY... WITH NEARLY CLOUD-FREE SKIES TONIGHT. NORTHEAST WINDS AS HIGH AS 10 KNOTS WILL PREVAIL THE REST OF TODAY...THEN BECOME NEARLY CALM TONIGHT. && .PREV DISCUSSION... /ISSUED 334 AM CDT WED JUL 23 2008/ DISCUSSION... RADARS EARLY THIS MORNING INDICATED A TSTM CLUSTER MOVING SEWD THROUGH THE MO OZARK FOOTHILLS REGION NEAR AN 850 MB WIND CONVERGENCE BOUNDARY. THE RUC MODEL SHOWS THIS PATTERN DISAPPEARING BY 12Z OR SO...AS DRIER AIR FILTERS IN ON THE NOSE OF A SFC HIGH PRESSURE AREA. THIS SHOULD ALL BUT ELIMINATE CHCS OF PCPN BY AFTN EVEN NEAR THE AR/TN BORDER. THE PAH FCST AREA WILL BE RAIN FREE THROUGH THU AFTN...THEN THE MID LEVEL FLOW OVER OUR REGION IS PROGGED TO TAKE ON A MORE WRLY COMPONENT AS AN ERN GREAT LAKES LOW DEPARTS INTO CANADA. THIS SHOULD RESULT IN THE EWD EXPANSION OF THE SWRN CONUS MID LEVEL RIDGE AND THE REINTRODUCTION OF WARM MOIST AIR FROM THE SW ON THU NIGHT/FRI. SCT SHWS/TSTMS WILL PROBABLY RESULT IN THE VICINITY OF THE WARM FRONT. FRI NIGHT PCPN CHCS WILL DECREASE SOME... ESPECIALLY IN SERN MO AS SHRTWV ENERGY EVENTUALLY TURNS LOW LEVEL WINDS BACK TO THE NORTH...TENDING TO DRY OUT THE ATMOSPHERIC COLUMN. THIS WRN RIDGE/ERN TROF PATTERN IS EXPECTED TO CONTINUE...WITH AN ON AND OFF PCPN PATTERN LASTING AT LEAST THROUGH THE WEEKEND AS SHRTWV ENERGY IMPULSES MOVE THROUGH THE NWLY MID LEVEL PATTERN. ALL IN ALL...POPS ARE NOT VERY HIGH. FURTHER INTO NEXT WEEK...MODELS ARE IN GOOD AGREEMENT THAT DRIER NWRLY FLOW APPEARS TO WIN OUT FOR MUCH OF THE WEEK. TEMPS WILL BE MODERATE FOR THIS TIME OF YEAR && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ RJP/DB ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 334 AM CDT WED JUL 23 2008 .DISCUSSION... RADARS EARLY THIS MORNING INDICATED A TSTM CLUSTER MOVING SEWD THROUGH THE MO OZARK FOOTHILLS REGION NEAR AN 850 MB WIND CONVERGENCE BOUNDARY. THE RUC MODEL SHOWS THIS PATTERN DISAPPEARING BY 12Z OR SO...AS DRIER AIR FILTERS IN ON THE NOSE OF A SFC HIGH PRESSURE AREA. THIS SHOULD ALL BUT ELIMINATE CHCS OF PCPN BY AFTN EVEN NEAR THE AR/TN BORDER. THE PAH FCST AREA WILL BE RAIN FREE THROUGH THU AFTN...THEN THE MID LEVEL FLOW OVER OUR REGION IS PROGGED TO TAKE ON A MORE WRLY COMPONENT AS AN ERN GREAT LAKES LOW DEPARTS INTO CANADA. THIS SHOULD RESULT IN THE EWD EXPANSION OF THE SWRN CONUS MID LEVEL RIDGE AND THE REINTRODUCTION OF WARM MOIST AIR FROM THE SW ON THU NIGHT/FRI. SCT SHWS/TSTMS WILL PROBABLY RESULT IN THE VICINITY OF THE WARM FRONT. FRI NIGHT PCPN CHCS WILL DECREASE SOME... ESPECIALLY IN SERN MO AS SHRTWV ENERGY EVENTUALLY TURNS LOW LEVEL WINDS BACK TO THE NORTH...TENDING TO DRY OUT THE ATMOSPHERIC COLUMN. THIS WRN RIDGE/ERN TROF PATTERN IS EXPECTED TO CONTINUE...WITH AN ON AND OFF PCPN PATTERN LASTING AT LEAST THROUGH THE WEEKEND AS SHRTWV ENERGY IMPULSES MOVE THROUGH THE NWLY MID LEVEL PATTERN. ALL IN ALL...POPS ARE NOT VERY HIGH. FURTHER INTO NEXT WEEK...MODELS ARE IN GOOD AGREEMENT THAT DRIER NWRLY FLOW APPEARS TO WIN OUT FOR MUCH OF THE WEEK. TEMPS WILL BE MODERATE FOR THIS TIME OF YEAR. && .AVIATION... CONVECTION SHOULD STAY WEST OF THE TAF SITES EARLY TODAY. SOME MID CLOUDS MAY AFFECT THE SITES EARLY ON...FOLLOWED BY A CHANCE OF CU FORMATION. WINDS WILL BE LIGHT NE DURING THE DAY...NEARLY CALM AT NIGHT. SOME BRIEF VSBYS 3-5SM CANNOT BE RULED OUT EARLY THIS MORNING. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ PUBLIC....DB AVIATION...CN ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PADUCAH KY 935 PM CDT TUE JUL 22 2008 .UPDATE... SINCE 00Z...ISOLATED SHOWERS ALONG THE INTERSTATE 64 CORRIDOR HAVE ACTUALLY INCREASED SLIGHTLY. THE AIR MASS ACROSS THE REGION REMAINS VERY MOIST AND SLIGHTLY UNSTABLE. WATER VAPOR IMAGERY INDICATES A SHORTWAVE TROUGH APPROACHING THE LOWER OHIO VALLEY FROM THE NORTHWEST. RUC MODEL HINTS AT A SECONDARY SURFACE BOUNDARY MOVING SOUTH INTO THE LOWER OHIO VALLEY OVERNIGHT...WHICH WILL MARK THE LEADING EDGE OF DRIER AIR. BASED ON THESE SYNOPTIC FEATURES...EXPECT ISOLATED SHOWERS TO PERSIST THROUGH THE NIGHT. WOULD NOT BE SURPRISED TO SEE SOME LIGHTNING STRIKES. FORECAST WILL BE UPDATED TO REFLECT LATEST RADAR AND SATELLITE TRENDS. && .PREVIOUS DISCUSSION /ISSUED 308 PM CDT TUE JUL 22 2008/... FOR THE VERY SHORT TERM/TONIGHT/...CURRENT CONVECTIVE COMPLEX MOVING ACROSS SOUTHEAST MISSOURI SHOULD SCOUR OUT ANY REMAINING EFFECTIVE THETA-E AIR IMPINGING ON THE WFO PAH FORECAST AREA. THE CIRRUS SHIELD FROM THIS COMPLEX SHOULD ALSO RETARD ANY SIGNIFICANT RISE IN LOW LEVEL/SURFACE TEMPERATURES ENOUGH TO REACH CONVECTIVE VALUES THROUGH SOUTHERN IL...SOUTHWEST IN...NORTHWEST KY FOR THE REMAINDER OF THE AFTERNOON. TO HANDLE REMNANTS OF THE SERN MO MCS AND ISOLATED CONVECTION THROUGH THE EVENING...I HAVE LEFT A SMALL POP ACROSS THE SOUTHERN 2/3RDS OF THE WFO PAH FORECAST AREA THROUGH 10 PM...TAPERING RAIN CHANCES OFF RAPIDLY FROM 10 PM TUESDAY THROUGH 1 AM WEDNESDAY. BY THAT TIME...WIND FIELDS PER THE GFS/MOS GUIDANCE SUGGEST WEAK CONVERGENT FLOW WITH THE SWD MOVING SURFACE FRONT. BY 12Z THE SURFACE CONVERGENCE LINE SHOULD BE NEARING THE SOUTHERN BORDER COUNTIES OF MO/KY...WITH THE 925/850 MB FRONT CUTTING W-E ACROSS THE SOUTHERN 1/3 OF THE WFO PAH FORECAST AREA WEDNESDAY MORNING. WITH MOST OF THE LOWER LEVEL MOISTURE EFFECTIVELY SCOURED OUT...AND THE SHORTWAVE SHEARING AWAY FROM THE WFO PAH FORECAST AREA LATE TONIGHT...I DECIDED TO PULL ANY MENTION OF MEASURABLE POPS FROM THE FORECAST AFTER MIDNIGHT. WITH THE FRONTAL CONVERGENCE ZONE NEARBY AND WEAK WINDS...I DID...HOWEVER...ADD THE MENTION OF PATCHY FOG TO FAVORED LOCATIONS IN THE WFO PAH FORECAST AREA. FOR WEDNESDAY...INSOLATION AND WEAK LIFT ACROSS THE FRONTAL BOUNDARY WILL SUPPORT AT LEAST ISOLATED CONVECTION ALONG THE SOUTHERN EDGE OF THE WFO PAH FORECAST AREA BETWEEN THE SURFACE AND 925/850 MB FRONTAL BOUNDARY. WITH DRIER AND SOMEWHAT COOLER AIR INFILTRATING THE AREA...MAX TEMPERATURES SHOULD NOT RISE MUCH HIGHER THAN TODAYS RAIN-COOLED VALUES. FOR WEDNESDAY NIGHT INTO THURSDAY...A SHARPER NWLY FLOW ALOFT WILL IMPINGE ON THE AREA...WITH A GRADUAL SHARPENING/INCREASE OF THICKNESS/MOISTURE ALONG THE FRONTAL BOUNDARY OVER MO/AR...SETTING UP THE STAGE FOR WARM AIR ADVECTION PRECIPITATION TO MOVE BACK ACROSS SERN MO LATER THURSDAY MORNING/AFTERNOON. FOR THURSDAY NIGHT AND INTO EARLY NEXT WEAK...THE WFO PAH FORECAST AREA WILL BE POISED IN A QUASI-STATIONARY BAROCLINIC ZONE...WITH FASTER FLOW TO THE NORTHEAST ASSOCIATED WITH THE SEMI-PERMANENT CYCLONIC VORTEX ROTATING OVER EASTERN CANADA AND THE NORTHEAST QUARTER OF THE UNITED STATES...WITH A BROAD RIDGE CENTERED OVER WRN TX/OK...ERN CO/NM. IN BETWEEN...THE WFO PAH FORECAST AREA WILL BE ON THE RECEIVING END OF PERIODIC MESOSCALE CONVECTIVE SYSTEMS MOVING SEWD IN NW FLOW ALOFT. THE AMOUNT OF RETURN FLOW BETWEEN EACH SYSTEM WILL DETERMINE THE COVERAGE/INTENSITY/SEVERITY OF EACH SYSTEM DURING THIS TIME PERIOD. && .AVIATION... A COMPLEX OF THUNDERSTORMS THAT MOVED THROUGH MUCH OF THE QUAD STATE REGION THIS MORNING HAS EFFECTIVELY STABILIZED THE ATMOSPHERE FOR THIS AFTERNOON AND LIKELY TONIGHT AS WELL. ANOTHER COMPLEX OF THUNDERSTORMS WILL DIVE SOUTH SOUTHEAST THIS AFTERNOON ACROSS MUCH OF SOUTHEAST MISSOURI WITH THE POTENTIAL FOR BRIEF IFR CONDITIONS AND A PERIOD OF GUSTY NORTHWEST WINDS AT KPOF AND POINTS FURTHER EAST. THIS COMPLEX MAY BRING A PERIOD OF LIGHT RAIN TO KCGI...BUT THUNDER IS VERY UNLIKELY ALONG AND EAST OF THE MISSISSIPPI RIVER THIS AFTERNOON. HOWEVER...THESE AREAS MAY FEEL A WIND SHIFT TO THE WEST OR NORTHWEST...AS THE OUTFLOW BOUNDARY PUSHES EAST SOUTHEAST THROUGH THE REGION. TONIGHT A COLD FRONT WILL TRY TO PUSH THROUGH THE AREA...HOWEVER INSTABILITY WILL BE LACKING...SO THUNDER IS NOT ANTICIPATED WITH IT TONIGHT. COULD SEE SOME MVFR TO IFR FOG AHEAD OF THE FRONT AFTER 06Z TONIGHT...IF CLEAR AND CALM CONDITIONS DEVELOP AS FORECAST. MOST OF THE AREA SHOULD BE BEHIND THE FRONT BY 14Z WEDNESDAY...SO SCATTERED TO BROKEN LOW VFR TO MVFR CLOUDS WILL BE POSSIBLE ALONG WITH SOME LINGERING MVFR VISIBILITIES IN THE MORNING. HOWEVER...THESE CONDITIONS SHOULD BE SHORT-LIVED EAST OF THE MISSISSIPPI RIVER...AS NORTHEAST WINDS BRING IN DRIER CONDITIONS. IN SOUTHEAST MISSOURI...CLOUDS MAY LINGER THROUGH MIDDAY...AND WINDS MAY BE MORE VARIABLE...AS THE PROGRESS OF THE FRONT IS LESS CERTAIN IN THAT AREA. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ UPDATE...MY PREVIOUS SHORT TERM...DRS/SMITH PREVIOUS LONG TERM....SMITH AVIATION...DRS ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 154 PM EDT TUE JUL 22 2008 .SHORT TERM ...MESOSCALE UPDATE... REMNANTS...OUTFLOW BOUNDARY FROM CONVECTIVE COMPLEX OVER WESTERN KENTUCKY THIS MORNING IS PRODUCING SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTH CENTRAL KY THIS AFTERNOON. MCVS APPARENT ON SAT LOOP AS WELL AS TWO CONVECTIVE OUTFLOW BOUNDARIES JUST WEST OF OUR CWA. AT PRESENT...ACTIVITY SEEMS ESPECIALLY CONCENTRATED IN THIS AREA. RUC ANALYSIS AND GOES SOUNDING DATA SUGGEST ACTIVITY WILL CONTINUE TO MOVE INTO EASTERN KENTUCKY AS CAPE INCREASES...TO AROUND 2000 J/KG ACROSS SOUTHERN PORTIONS OF OUR CWA THIS AFTERNOON. RTMA SFC ANALYSIS IS ALSO PICKING UP ON GOOD SFC CONVERGENCE IN THE VICINITY OF INTERSECTING OUTFLOW BOUNDARIES. ATTM EXPECT THE BULK OF ANY SEVERE WEATHER TO BE RESTRICTED TO AREAS SOUTH AND EAST OF EACH OUTFLOW BOUNDARY...OR GENERALLY ALONG AND EAST OF THE I75 CORRIDOR AND SOUTH OF THE MOUNTAIN PARKWAY. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /THE REST OF TODAY/ DECREASED SKY COVER SLIGHTLY ACROSS THE BOARD PER LATEST VISIBLE SATELLITE IMAGERY. INSPITE OF AN OVERCAST OF CIRROSTRATUS...THE OVERALL OPAQUE CLOUD COVER IS MUCH LESS THAN THE NUMBERS THAT WERE IN THE SKY COVER GRIDS PREVIOUSLY...SO APPROPRIATED ADJUSTMENTS WERE MADE. THE PRIMARY CHANGE HERE WAS DOWNGRADING A FEW OF THE ZONE BREAKUPS FROM MOSTLY CLOUDY TO PARTLY CLOUDY SKIES THROUGH MID AFTERNOON. ALSO DECREASED PRECIPITATION CHANCES QUITE A BIT THROUGH 18Z...AS THERE SIMPLY ISNT ANYTHING HAPPENING ACROSS EASTERN KENTUCKY RIGHT NOW CONVECTIVE LY SPEAKING. STILL ANTICIPATING SHOWERS AND STORMS TO FIRE LATER THIS AFTERNOON AND BECOME QUITE NUMEROUS ALONG A SLOWLY SOUTHWARD MOVING FRONTAL BOUNDARY...WITH A FEW STRONG TO SEVERE STORMS POSSIBLE ALONG THE WAY. THE CIRROSTRATUS LAYER IS KEEPING TEMPERATURES FROM INCREASING VERY MUCH AT ALL SO FAR TODAY. THE 14 AND 15Z SURFACE OBSERVATIONS INDICATE THAT HOURLY TEMPS ARE RUNNING SEVERAL DEGREES COOLER THAN THE PREVIOUS FORECAST INDICATED. MADE ADJUSTMENTS HERE PER THE TEMP TRENDS OBSERVED SO FAR THIS MORNING. ALSO RECALCULATED TODAYS MAX TEMPS BASED ON THE CHANGES MADE TO DIURNAL TREND...WITH TODAYS HIGHS 4 TO 6 DEGREES COOLER ACROSS THE BOARD. CORRESPONDING ADJUSTMENTS WERE ALSO NECESSARY WITH THE WEATHER AND QPF FORECASTS...BASED ON THE DECREASED POPS DURING THE LATE MORNING TO EARLY AFTERNOON PERIOD. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /THE REST OF TODAY/ CONVECTION HAS DISSIPATED AS EXPECTED AS IT MOVED INTO THE MORE STABLE AIRMASS OVER EASTERN KENTUCKY. WILL REMOVE THE WATCH HEADLINE FROM THE ZONE FORECAST PRODUCT BUT WILL LEAVE EVERYTHING ELSE AS IS FOR NOW AS IT CONTINUES TO APPEAR LIKE THUNDERSTORM ACTIVITY WILL INCREASE ONCE AGAIN LATER THIS AFTERNOON. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /TODAY THROUGH THURSDAY/ DEEP UPPER LEVEL TROUGH WILL BECOME ESTABLISHED OVER THE EASTERN GREAT LAKES BY THURSDAY. SURFACE COLD FRONT IS EXPECTED TO PROGRESS SOUTHEAST ACROSS THE AREA LATER TONIGHT WITH A COUPLE OF ROUNDS OF CONVECTION ANTICIPATED BEFORE IT PUSHES TO OUR SOUTH AND HIGH PRESSURE BUILDS INTO THE REGION LATE WEDNESDAY INTO THURSDAY. IT IS TOUCH TO GAGE WHAT WILL HAPPEN WITH THE INITIAL MCS ONGOING TO OUR NORTHWEST. THE AIRMASS OVER SOUTHEAST KENTUCKY IS ACTUALLY FAIRLY STABLE WITH LOWER SURFACE DEWPOINTS LEFT OVER AFTER THE CONVECTION EARLIER ON MONDAY. THE SYSTEM MAY ACTUALLY JUST DELIVER A GLANCING BLOW AS THE EASTERN END PROGRESSES ACROSS NORTHERN KENTUCKY/SOUTHERN OHIO AND THE WESTERN HALF DIVES SOUTH OR REDEVELOPS IN THE MORE UNSTABLE AIRMASS OVER THE WESTERN HALF OF THE STATE. THIS SCENARIO SEEMS TO BE SUPPORTED BY MCS MAINTENANCE PROBABILITIES BUT WE WILL JUST HAVE TO WATCH RADAR/SATELLITE TRENDS OVER THE NEXT HOUR OR TWO TO SEE HOW THIS SYSTEM HOLDS TOGETHER AS IT CONTINUES TOWARD THE AREA. WHATEVER HAPPENS WITH THE MCS EARLY THIS MORNING PRECIP WISE... THERE WILL LIKELY BE A LOT OF DEBRIS CLOUDINESS DURING THE MORNING HOURS BUT THIS SHOULD THIN AND SCATTER OUT ALLOWING FOR GOOD HEATING AND DESTABILIZATION DURING THE AFTERNOON HOURS... ESPECIALLY FOR SOUTHEAST KENTUCKY. ADDITIONAL MCS ACTIVITY SHOULD THEN DEVELOP ALONG THE FRONT AND PROGRESS SOUTHEAST INTO THE AREA LATE IN THE AFTERNOON INTO THE OVERNIGHT HOURS. THERE CONTINUES TO BE A SLIGHT RISK FOR SEVERE THUNDERSTORMS THROUGHOUT THE DAY TODAY AND OVERNIGHT TONIGHT WITH LARGE HAIL AND DAMAGING WINDS POSSIBLE. ANOTHER THING TO NOTE TODAY IS THE LARGE DIFFERENCES IN MOS GUIDANCE TEMPS WITH AN 8 DEGREE SPREAD BETWEEN THE MAV AND MET NUMBERS AT JKL AND LOZ. GFS SEEMS TO BE WARMING THE AREA TOO MUCH AT 850 MB POSSIBLY DUE TO CONVECTIVE FEEDBACK AND OVER DEVELOPMENT OF AN AREA OF LOW PRESSURE ON THE FRONT. NAM IS PROBABLY OVERDOING THE AMOUNT OF CLOUD COVER TODAY. OVERALL... EXPECT READINGS TO COME IN SIMILAR TO YESTERDAY OVER SOUTHEAST KENTUCKY BUT REMAIN SEVERAL DEGREES COOLER UP NORTH WHERE MORE CLOUDS ARE ANTICIPATED. WILL LINGER LOW CHANCE POPS ACROSS THE AREA ON WEDNESDAY AS THE FRONT SLOWLY WORKS INTO THE TENNESSEE VALLEY BUT SKIES SHOULD CLEAR WEDNESDAY NIGHT WITH SUNNY SKIES EXPECTED ON THURSDAY. A MUCH DRIER AIRMASS IS PROGGED TO FILTER IN BEHIND THE FRONT WITH SURFACE DEWPOINTS FALLING INTO THE 50S. THIS SHOULD ALLOW TEMPS TO FALL INTO THE UPPER 50S WEDNESDAY NIGHT IN OUR ORDINARILY COOLER VALLEY LOCATIONS AND KEEP CONDITIONS PLEASANT ON THURSDAY. .LONG TERM.../THURSDAY NIGHT THROUGH MONDAY/ GENERAL MODEL AGREEMENT CONTINUES WITH ADVERTISING NORTHWEST FLOW ALOFT ACROSS THE OHIO VALLEY AND NEW ENGLAND AS REINFORCING NORTHERN STREAM ENERGY ALLOWS FOR DEEPER CUTOFF LOWS TO DEVELOP ACROSS EASTERN CANADA. EASTERN KENTUCKY WILL BEGIN THE LONG TERM UNDER THE INFLUENCE OF HIGH PRESSURE. A SLOW MOVING COLD FRONT WILL THEN BRING DAILY CHANCES OF AFTERNOON AND EVENING ISOLATED TO SCATTERED CONVECTION TO THE AREA THROUGH THE REST OF THE WEEK AND INTO EARLY NEXT WEEK AS THE FRONT IS SLOW TO EXIT OFF TO THE SOUTHEAST. GIVEN THE NORTHWEST FLOW ALOFT...TEMPERATURES WILL RUN NEARLY SEASONAL FOR THIS TIME OF YEAR. THE HPC NUMBERS LOOKED REASONABLE ONCE AGAIN AND ONLY MADE A FEW TWEAKS TO THESE. && .AVIATION.../18Z TO 18Z/...UPDATED CLUSTER OF STRONG TO SEVERE THUNDERSTORMS IS HEADED FOR OUR SW COUNTIES AT TAF ISSUANCE TIME. HAVE TIMED THESE ACROSS KLOZ AND KSME AT MID AFTERNOON NEAR THE BEGINNING OF TAF VALID TIME. HAVE ONLY USED VCTS AT KJKL...WITH NORTHWARD DEVELOPMENT NOT TAKING PLACE SO FAR. AFTER THE CURRENT BATCH OF STORMS MOVES ACROSS OUR SOUTHERN COUNTIES THIS AFTERNOON...ADDITIONAL PRECIP THROUGH TONIGHT IS MUCH MORE QUESTIONABLE. ON WEDNESDAY...WILL LOOK FOR MORE DEVELOPMENT OF CONVECTION AS HEATING OCCURS AND A COLD FRONT MOVEST SOUTHEAST THROUGH THE AREA. ANY PRECIP SHOULD SWEEP SE OUT OF THE STATE WITH COLD FRONTAL PASSAGE IN THE AFTERNOON. OUTSIDE OF PRECIP...MAINLY VFR CONDITIONS ARE EXPECTED...WITH THE POSSIBLE EXCEPTION OF VALLEY FOG LATE TONIGHT INTO EARLY WEDNESDAY. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...ABE/AR/RAY LONG TERM....GEOGERIAN AVIATION...HAL ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 136 PM EDT TUE JUL 22 2008 .SHORT TERM...UPDATED ...MESOSCALE UPDATE... REMNANTS...OUTFLOW BOUNDARY FROM CONVECTIVE COMPLEX OVER WESTERN KENTUCKY THIS MORNING IS PRODUCING SEVERE THUNDERSTORMS ACROSS PORTIONS OF SOUTH CENTRAL KY THIS AFTERNOON. MCVS APPARENT ON SAT LOOP AS WELL AS TWO CONVECTIVE OUTFLOW BOUNDARIES JUST WEST OF OUR CWA. AT PRESENT...ACTIVITY SEEMS ESPECIALLY CONCENTRATED IN THIS AREA. RUC ANALYSIS AND GOES SOUNDING DATA SUGGEST ACTIVITY WILL CONTINUE TO MOVE INTO EASTERN KENTUCKY AS CAPE INCREASES...TO AROUND 2000 J/KG ACROSS SOUTHERN PORTIONS OF OUR CWA THIS AFTERNOON. RTMA SFC ANALYSIS IS ALSO PICKING UP ON GOOD SFC CONVERGENCE IN THE VICINITY OF INTERSECTING OUTFLOW BOUNDARIES. ATTM EXPECT THE BULK OF ANY SEVERE WEATHER TO BE RESTRICTED TO AREAS SOUTH AND EAST OF EACH OUTFLOW BOUNDARY...OR GENERALLY ALONG AND EAST OF THE I75 CORRIDOR AND SOUTH OF THE MOUNTAIN PARKWAY. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /THE REST OF TODAY/ DECREASED SKY COVER SLIGHTLY ACROSS THE BOARD PER LATEST VISIBLE SATELLITE IMAGERY. INSPITE OF AN OVERCAST OF CIRROSTRATUS...THE OVERALL OPAQUE CLOUD COVER IS MUCH LESS THAN THE NUMBERS THAT WERE IN THE SKY COVER GRIDS PREVIOUSLY...SO APPROPRIATED ADJUSTMENTS WERE MADE. THE PRIMARY CHANGE HERE WAS DOWNGRADING A FEW OF THE ZONE BREAKUPS FROM MOSTLY CLOUDY TO PARTLY CLOUDY SKIES THROUGH MID AFTERNOON. ALSO DECREASED PRECIPITATION CHANCES QUITE A BIT THROUGH 18Z...AS THERE SIMPLY ISNT ANYTHING HAPPENING ACROSS EASTERN KENTUCKY RIGHT NOW CONVECTIVE LY SPEAKING. STILL ANTICIPATING SHOWERS AND STORMS TO FIRE LATER THIS AFTERNOON AND BECOME QUITE NUMEROUS ALONG A SLOWLY SOUTHWARD MOVING FRONTAL BOUNDARY...WITH A FEW STRONG TO SEVERE STORMS POSSIBLE ALONG THE WAY. THE CIRROSTRATUS LAYER IS KEEPING TEMPERATURES FROM INCREASING VERY MUCH AT ALL SO FAR TODAY. THE 14 AND 15Z SURFACE OBSERVATIONS INDICATE THAT HOURLY TEMPS ARE RUNNING SEVERAL DEGREES COOLER THAN THE PREVIOUS FORECAST INDICATED. MADE ADJUSTMENTS HERE PER THE TEMP TRENDS OBSERVED SO FAR THIS MORNING. ALSO RECALCULATED TODAYS MAX TEMPS BASED ON THE CHANGES MADE TO DIURNAL TREND...WITH TODAYS HIGHS 4 TO 6 DEGREES COOLER ACROSS THE BOARD. CORRESPONDING ADJUSTMENTS WERE ALSO NECESSARY WITH THE WEATHER AND QPF FORECASTS...BASED ON THE DECREASED POPS DURING THE LATE MORNING TO EARLY AFTERNOON PERIOD. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /THE REST OF TODAY/ CONVECTION HAS DISSIPATED AS EXPECTED AS IT MOVED INTO THE MORE STABLE AIRMASS OVER EASTERN KENTUCKY. WILL REMOVE THE WATCH HEADLINE FROM THE ZONE FORECAST PRODUCT BUT WILL LEAVE EVERYTHING ELSE AS IS FOR NOW AS IT CONTINUES TO APPEAR LIKE THUNDERSTORM ACTIVITY WILL INCREASE ONCE AGAIN LATER THIS AFTERNOON. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /TODAY THROUGH THURSDAY/ DEEP UPPER LEVEL TROUGH WILL BECOME ESTABLISHED OVER THE EASTERN GREAT LAKES BY THURSDAY. SURFACE COLD FRONT IS EXPECTED TO PROGRESS SOUTHEAST ACROSS THE AREA LATER TONIGHT WITH A COUPLE OF ROUNDS OF CONVECTION ANTICIPATED BEFORE IT PUSHES TO OUR SOUTH AND HIGH PRESSURE BUILDS INTO THE REGION LATE WEDNESDAY INTO THURSDAY. IT IS TOUCH TO GAGE WHAT WILL HAPPEN WITH THE INITIAL MCS ONGOING TO OUR NORTHWEST. THE AIRMASS OVER SOUTHEAST KENTUCKY IS ACTUALLY FAIRLY STABLE WITH LOWER SURFACE DEWPOINTS LEFT OVER AFTER THE CONVECTION EARLIER ON MONDAY. THE SYSTEM MAY ACTUALLY JUST DELIVER A GLANCING BLOW AS THE EASTERN END PROGRESSES ACROSS NORTHERN KENTUCKY/SOUTHERN OHIO AND THE WESTERN HALF DIVES SOUTH OR REDEVELOPS IN THE MORE UNSTABLE AIRMASS OVER THE WESTERN HALF OF THE STATE. THIS SCENARIO SEEMS TO BE SUPPORTED BY MCS MAINTENANCE PROBABILITIES BUT WE WILL JUST HAVE TO WATCH RADAR/SATELLITE TRENDS OVER THE NEXT HOUR OR TWO TO SEE HOW THIS SYSTEM HOLDS TOGETHER AS IT CONTINUES TOWARD THE AREA. WHATEVER HAPPENS WITH THE MCS EARLY THIS MORNING PRECIP WISE... THERE WILL LIKELY BE A LOT OF DEBRIS CLOUDINESS DURING THE MORNING HOURS BUT THIS SHOULD THIN AND SCATTER OUT ALLOWING FOR GOOD HEATING AND DESTABILIZATION DURING THE AFTERNOON HOURS... ESPECIALLY FOR SOUTHEAST KENTUCKY. ADDITIONAL MCS ACTIVITY SHOULD THEN DEVELOP ALONG THE FRONT AND PROGRESS SOUTHEAST INTO THE AREA LATE IN THE AFTERNOON INTO THE OVERNIGHT HOURS. THERE CONTINUES TO BE A SLIGHT RISK FOR SEVERE THUNDERSTORMS THROUGHOUT THE DAY TODAY AND OVERNIGHT TONIGHT WITH LARGE HAIL AND DAMAGING WINDS POSSIBLE. ANOTHER THING TO NOTE TODAY IS THE LARGE DIFFERENCES IN MOS GUIDANCE TEMPS WITH AN 8 DEGREE SPREAD BETWEEN THE MAV AND MET NUMBERS AT JKL AND LOZ. GFS SEEMS TO BE WARMING THE AREA TOO MUCH AT 850 MB POSSIBLY DUE TO CONVECTIVE FEEDBACK AND OVER DEVELOPMENT OF AN AREA OF LOW PRESSURE ON THE FRONT. NAM IS PROBABLY OVERDOING THE AMOUNT OF CLOUD COVER TODAY. OVERALL... EXPECT READINGS TO COME IN SIMILAR TO YESTERDAY OVER SOUTHEAST KENTUCKY BUT REMAIN SEVERAL DEGREES COOLER UP NORTH WHERE MORE CLOUDS ARE ANTICIPATED. WILL LINGER LOW CHANCE POPS ACROSS THE AREA ON WEDNESDAY AS THE FRONT SLOWLY WORKS INTO THE TENNESSEE VALLEY BUT SKIES SHOULD CLEAR WEDNESDAY NIGHT WITH SUNNY SKIES EXPECTED ON THURSDAY. A MUCH DRIER AIRMASS IS PROGGED TO FILTER IN BEHIND THE FRONT WITH SURFACE DEWPOINTS FALLING INTO THE 50S. THIS SHOULD ALLOW TEMPS TO FALL INTO THE UPPER 50S WEDNESDAY NIGHT IN OUR ORDINARILY COOLER VALLEY LOCATIONS AND KEEP CONDITIONS PLEASANT ON THURSDAY. .LONG TERM.../THURSDAY NIGHT THROUGH MONDAY/ GENERAL MODEL AGREEMENT CONTINUES WITH ADVERTISING NORTHWEST FLOW ALOFT ACROSS THE OHIO VALLEY AND NEW ENGLAND AS REINFORCING NORTHERN STREAM ENERGY ALLOWS FOR DEEPER CUTOFF LOWS TO DEVELOP ACROSS EASTERN CANADA. EASTERN KENTUCKY WILL BEGIN THE LONG TERM UNDER THE INFLUENCE OF HIGH PRESSURE. A SLOW MOVING COLD FRONT WILL THEN BRING DAILY CHANCES OF AFTERNOON AND EVENING ISOLATED TO SCATTERED CONVECTION TO THE AREA THROUGH THE REST OF THE WEEK AND INTO EARLY NEXT WEEK AS THE FRONT IS SLOW TO EXIT OFF TO THE SOUTHEAST. GIVEN THE NORTHWEST FLOW ALOFT...TEMPERATURES WILL RUN NEARLY SEASONAL FOR THIS TIME OF YEAR. THE HPC NUMBERS LOOKED REASONABLE ONCE AGAIN AND ONLY MADE A FEW TWEAKS TO THESE. && .AVIATION.../12Z TO 12Z/ WITH THE DISSIPATION OF THE EARLIER MCS TO OUR NORTH ATTENTION NOW TURNS TO THE TIMING FOR THE RENEWAL OF ACTIVITY. THIS WILL BE HARD TO PIN DOWN SO...BASED ON RECOVERY TIME AND DIURNAL HEATING...HAVE INCLUDED A PREVAILING VCTS FROM 18Z ON...INTENDING TO PROVIDE MORE SPECIFICS VIA FUTURE UPDATES OR AMENDMENTS. DID TRY TO TIME A NEW ROUND OF THUNDERSTORM ACTIVITY FOR LATER THIS EVENING FROM 01Z INTO THE EARLY MORNING HOURS. WINDS STILL LOOK TO BE MAINLY LIGHT FROM THE SOUTHWEST...OUTSIDE OF ANY STORMS. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...ABE/AR/RAY LONG TERM....GEOGERIAN AVIATION...GREIF ky AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE CARIBOU ME 929 PM EDT WED JUL 23 2008 .SYNOPSIS... LOW PRESSURE OVER THE EASTERN GREAT LAKES WILL SLOWLY MOVE TO THE EAST. THIS SYSTEM IS EXPECTED TO SPREAD SHOWERS ACROSS THE REGION LATER TONIGHT AND THURSDAY. A SLOW MOVING COLD FRONT WILL CROSS THE REGION THURSDAY NIGHT AND FRIDAY BRINGING RAIN WITH A CHANCE OF THUNDERSTORMS. && .NEAR TERM /THROUGH THURSDAY/... BIG CHGS TO NEAR TERM. FIRST LATEST RADAR IMAGERY NECESSITATED HIGHER POPS ACROSS THE FA...SPCLY WRN AREAS WHERE WIDESPREAD SHWRS WERE IMMINENT. OVR THE WATERS AND ADJACENT COASTAL WATERS...WE ADDED MORE TSTM CVRG WITH A LITTLE LINE OF TSTMS APCHNG THESE AREAS. MODELS INDICATE ELEVATED CAPE UP TO A 1000 J OR SO WITH ASSOCIATED ADVANCING WARM FRONT AND MOISTURE FLUX ADVCN/CNVRG ALG THE FRONT. ADDTIONAL CHGS WERE TO LOWER POPS FOR THU MIDDAY INTO AFT...AS MUCH OF THE FA IS INDICATED BY THE MODELS TO BE IN THE WARM SECTOR JUST E OF THE HVY RN BAND FURTHER W IN NEW ENG. MERGED CHGS IN POPS AND CLDS TO THE MIDDLE OF PD 3 (THU NGT) FROM PREVIOUS FCST... WHERE POPS ARE SHOWN TO INCREASE WITH THE ARRIVAL OF THE MAIN COLD FRONT BAND OF SHWRS AND TSTMS. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... A SLOW MOVING COLD FRONT WILL CROSS THE REGION LATER THURSDAY NIGHT THROUGH EARLY FRIDAY AFTERNOON. MODELS CONTINUE TO INDICATE A LOW LEVEL JET TRANSPORTING ABUNDANT MOISTURE NORTH IN ADVANCE OF THE FRONT...WITH PRECIPITABLE WATER VALUES APPROACHING 2 INCHES. ALONG WITH THE FRONTAL LIFT...AN UPPER LEVEL JET WILL ENHANCE LIFT ACROSS THE REGION IN ADVANCE OF THE FRONT. THE COMBINATION OF ABUNDANT MOISTURE...ENHANCED LIFT AND UPSLOPING OF MOISTURE INTO HIGHER TERRAIN AREAS WILL LEAD TO THE POSSIBILITY OF HEAVY RAIN ALONG THE FRONT ACROSS PORTIONS OF THE REGION LATER THURSDAY NIGHT THROUGH EARLY FRIDAY AFTERNOON...THOUGH UNCERTAINTY STILL EXISTS REGARDING PRECIPITATION AMOUNTS AND THE LOCATION OF THE HEAVIEST PRECIPITATION. AN AREA OF RAIN WILL CROSS THE REGION IN ADVANCE OF THE FRONT...ALONG WITH A CHANCE OF THUNDERSTORMS...THURSDAY NIGHT THROUGH EARLY FRIDAY AFTERNOON WITH PRECIPITATION TAPERING TO SHOWERS IN THE WAKE OF THE FRONT LATER FRIDAY AFTERNOON. SHOWERS COULD LINGER ACROSS MOSTLY NORTHERN AREAS FRIDAY NIGHT. UNSETTLED CONDITIONS WILL PERSIST SATURDAY INTO SATURDAY NIGHT WITH AN UPPER LEVEL DISTURBANCE CROSSING THE REGION SATURDAY AND A COLD FRONT APPROACHING SATURDAY NIGHT. TEMPERATURES WILL BE AT NEAR NORMAL LEVELS FRIDAY AND SATURDAY. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... UPPER LEVEL PATTERN FORECAST NOT ALL THAT DIFFERENT THAN YESTERDAYS FORECAST GUIDANCE. A BROAD UPPER LEVEL RIDGE WILL REMAIN PARKED OVER THE MIDWEST THROUGH THE PERIOD. COMPUTER MODELS DIFFER SOMEWHAT BEYOND MONDAY. ENSEMBLE MEAN MEMBERS FROM THE GFS INDICATE A MORE AMPLIFIED RIDGE IN THE MIDWEST THAT ITS OPERATIONAL COUNTERPART. HPC NOTED A COMMON OPERATIONAL BIAS CONCERNING THIS TYPE OF SCENARIO. HAVE INITIALIZED THE EXTENDED FORECAST WITH GMOS. HOWEVER...ON DAYS 6 AND 7 DECIDED TO GO WITH GFS ENSEMBLE GUIDANCE. THE AFFECT OF THIS WAS TO RAISE POPS BACK ABOVE CLIMO FOR NORTHERN TIER ZONES. ALL IN ALL...THERE IS A MODERATE DEGREE && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... EXPECT MVFR/IFR CONDITIONS MAINLY DUE TO CEILINGS TO PERSIST TONIGHT AND THURSDAY. SOME FOG IS POSSIBLE KBGR AND KBHB AFTER 06Z. CEILINGS/VISIBILITIES WILL BE REDUCED IN RAIN AND FOG...WITH A CHANCE OF THUNDERSTORMS...THURSDAY NIGHT THROUGH EARLY FRIDAY AFTERNOON. IFR/LIFR CONDITIONS WILL BE COMMON ACROSS THE REGION LATER THURSDAY NIGHT THROUGH EARLY FRIDAY AFTERNOON. CONDITIONS WILL THEN IMPROVE LATER FRIDAY AFTERNOON. GENERALLY VFR CONDITIONS ARE EXPECTED FRIDAY NIGHT THROUGH SATURDAY...THOUGH THERE WILL BE A CONTINUING CHANCE OF SHOWERS AND POSSIBLE THUNDERSTORMS. CEILINGS/VISIBILITIES SHOULD BEGIN TO LOWER AGAIN LATER SATURDAY NIGHT WITH MORE EXTENSIVE SHOWERS DEVELOPING. && .MARINE... NEAR TERM: HAVE INITIALIZED THE WIND GRIDS WITH THE RUC13 OUT TO 03Z THEN TRANSITION TO A 50/50 BLEND OF THE NAM12 AND GFS40 FOR THE REMAINDER OF THE FORECAST PERIOD. EXPECT SLIGHTLY HIGH WIND SPEED BIAS...ESPECIALLY AS AIR TEMPERATURES INCREASE RELATIVE TO COLD SEA SURFACE TEMPERATURES THURSDAY. SO WILL LOWER SPEEDS 1 TO 2 KNOTS. FOR WAVES: A PERSISTENT SOUTHERLY FLOW WILL CONTINUE TO DEVELOP TO THE EAST AND SOUTH OF NEW ENGLAND. DUE TO THIS SOUTHERLY FETCH A COMBINATION OF WIND WAVE AND LONGER PERIOD SWELL WILL CONTINUE. HAVE INITIALIZED WAVE GRIDS WITH WNA WAVES TONIGHT AND EARLY THURSDAY THEN TRANSITION TO THE NAM VERSION OF SWAN. EXPECT HIGH BIAS FOR WAVE MODEL WINDS IN LOCAL WATERS THURSDAY...SO WILL LOWER WAVE HEIGHTS TO COMPENSATE. DEW POINTS EXPECTED TO INCREASE TONIGHT SO WILL TRANSITION FROM AREAS TO WIDE SPREAD FOG AFTER 06Z. SHORT TERM: SEAS COULD BE AT MARGINAL SMALL CRAFT ADVISORY LEVELS THURSDAY NIGHT INTO SATURDAY...IN MOSTLY A SOUTH SWELL. WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS THURSDAY NIGHT THROUGH SATURDAY NIGHT. VISIBILITIES WILL BE REDUCED IN RAIN AND FOG WITH A CHANCE OF THUNDERSTORMS THURSDAY NIGHT THROUGH FRIDAY...WITH LINGERING SHOWERS POSSIBLE FRIDAY EVENING. SHOWERS AND POSSIBLE THUNDERSTORMS ARE THEN EXPECTED SATURDAY INTO SATURDAY NIGHT. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...NONE. && $$ NEAR TERM...VJN SHORT TERM...NORCROSS LONG TERM...LERICOS AVIATION...MIGNONE MARINE...VJN me AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 204 PM EDT TUE JUL 22 2008 .SYNOPSIS... AN APPROACHING COLD FRONT WILL RESULT IN SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS INTO WEDNESDAY. HIGH PRESSURE WILL BUILD INTO THE REGION FOR LATE IN THE WEEK...BRINGING DRY AND SEASONABLY COOL CONDITIONS. THE NEXT FRONTAL SYSTEM WILL IMPACT THE AREA OVER THE WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/... SCATTERED SHOWERS/ISOLATED TSTMS ARE DEVELOPING ACROSS NORTHEAST OH/NORTHWEST PA ALONG A LAKE INDUCED BOUNDARY...OTHERWISE THE NEXT WAVE IS APPROACHING FROM THE WESTERN GREAT LAKES. THIS WAVE WILL ROTATE ACROSS THE AREA EARLY THIS EVENING ACROSS EASTERN OHIO...AND ACROSS WESTERN PA EASTWARD LATE THIS EVENING/OVERNIGHT. AS HAS BEEN THE CASE THE LATE COUPLE OF DAYS...THE POTENTIAL FOR STORMS TO PRODUCE LOCALLY STRONG WINDS WILL CONTINUE. NAM/GFS/SREF ALL DEPICT A SLOWER EXIT OF THE FORCING...ESPECIALLY ALONG THE SE RIDGES...THUS WILL KEEP HIGH END CHC POPS THROUGH MOST OF WEDNESDAY THERE...WITH DIMINISHING PRECIP COVERAGE FURTHER NORTH AND WEST. NOTICEABLY COOLER AND DRIER CONDITIONS WILL WORK IN ACROSS NORTHERN SECTIONS WEDNESDAY WITH HIGHS IN THE MID 70S WITH DEWPOINTS FALLING INTO THE 50S. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... RESIDUAL ISOLATED SHWRS WILL END WEDNESDAY EVENING ACROSS THE RIDGES AS THE UPPER LOW EXITS TO THE EAST. HIGH PRESSURE WILL BUILD IN FOR THE REMAINDER OF THE WORK WEEK...BRINGING DRY AND COOLER CONDITIONS...WITH MOST LOCATIONS IN THE 50S WEDNESDAY NIGHT AND THURSDAY NIGHT. && .LONG TERM /SATURDAY THROUGH TUESDAY/... MEDIUM RANGE MODELS CONTINUE TO BE IN DECENT AGREEMENT BRINGING THE NEXT FRONTAL BOUNDARY ACROSS THE REGION SATURDAY...WITH PERHAPS A SECONDARY FEATURE FOR SUNDAY. WILL KEEP CHANCE POPS FOR SAT/SUN. SOME DIFFERENCES FOR EARLY NEXT WEEK...WITH THE GFS SHOWING YET ANOTHER WAVE CROSSING THE AREA...AND THE ECMWF SHOWING THE FEATURE DEPARTING TO THE SOUTH. WILL KEEP MINIMAL RESIDUAL CHANCES FOR MONDAY...WITH DRY CONDITIONS FOR TUESDAY. NEAR NORMAL TEMPERATURES WILL PREVAIL FOR THE LONG TERM. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... BLEND OF MOST RECENT RUC NAM AND SREF MODEL RUNS SUGGEST A BAND OF SCATTERED TO NUMEROUS THUNDERSTORMS CAN MOVE THROUGH THE UPPER OHIO VALLEY BETWEEN 19Z AND 02Z. A SECOND BAND OF SHOWERS AND SCATTERED THUNDERSTORMS CAN MOVE THROUGH THIS AREA LATE TONIGHT. RECENT RADAR DATA SHOWING ISOLATED THUNDERSTORMS SPROUTING WITHIN THE LAKE ERIE BREEZE ZONE TO THE VICINITY OF THE I-80 CORRIDOR SUPPORTS THE CONTENTION OF THE INITIAL THUNDERSTORM BAND. SREF DEEP LAYER BULK SHEAR AND CAPE VALUES SUPPORT SPC THINKING THE STORMS MAY DEVELOP SEVERE CHARACTERISTICS. SO THUNDERSTORM GUSTS NEAR 30 KTS INCLUDED WITH 3-HOUR WINDOW OF THUNDERSTORM ONSET ALONG WITH MVFR. THIS WILL BE MONITORED FOR UPWARD ADJUSTMENT AS NEEDED. THE DEGREE OF DESTABILIZATION WITH THE FRONTAL BAND OF SHOWERS AND THUNDERSTORMS WILL DEPEND ON SEVERAL FACTORS THAT INCLUDE HOW MUCH CAPE IS USED TO SUPPORT PROPOSED INITIAL BAND AND EXACT TIMING OF SLOW COLD FRONTAL PASSAGE. SO AT THIS TIME HAVE FORECASTED A PERIOD OF SHOWERS LATE TONIGHT ALBEIT THERE CAN ALSO BE SUFFICIENT RESIDUAL LIFT AND INSTABILITY TO GENERATE SCATTERED THUNDERSTORMS AND MVFR. WITH THE EXPECTED RAIN MOISTENING OF THE SURFACE LAYER...HAVE FORECASTED LATE NIGHT FOG WITH WIDESPREAD MVFR AND SCATTERED IFR. BY WEDNESDAY NIGHT...EXPECT THE SURFACE LAYER TO SUFFICIENTLY DRY TO END SHOWER CHANCES TO INDUCE WIDESPREAD VFR. BASED ON BLEND OF SREF AND GEFS MODEL RUNS EXPECT VFR TO BE PREVALENT THURSDAY AND FRIDAY WITH ONLY IFR POSSIBILITY IN ISOLATED EARLY MORNING FOG PATCHES. LATEST GEFS MODEL RUN SHOWS ANOTHER FRONT AFFECTING THE UPPER OHIO VALLEY SATURDAY AND SUNDAY RAISING THE CHANCES OF SHOWERS AND THUNDERSTORMS AND AT LEAST MVFR CONDITIONS. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$ md AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 429 AM EDT TUE JUL 22 2008 .SYNOPSIS... A COLD FRONT OVER OHIO WILL BRING A CHANCE FOR SHOWERS AND THUNDERSTORMS TODAY AND WEDNESDAY. THIS FRONT WILL STALL OUT TO OUR SOUTH THURSDAY...AND INCH NORTHWARD TOWARD THE END OF THE WEEK. && .NEAR TERM /TODAY/... LOOKS LIKE A FAIRLY ACTIVE PATTERN OVER THE NEXT COUPLE OF DAYS. MCS OVER OH HAS MAINTAINED ITSELF RLVTLY WELL THRU THE OVRNGT HRS. HRRR RUC SHOWS A SOMEWHAT INTERESTING PSBLTY W/ THIS...THAT THE MCS WL DETERIORATE AS IT MOVES ACROSS W.V. BUT THAT A LN A RW/TRW WL MAKE IT E OF THE MTNS EARLY THIS AFTN. NEXT SHIFT WL KEEP AN EYE ON THIS. SPC HAS ENTIRE MID ATLC IN A SLT RISK FOR THIS AFTN. THE MCS HAS HAD A NGT OF PRODUCING WATCHES...AND IF IT IS ABLE TO REGENERATE THIS AFTN THIS COULD AGN BE THE CASE FOR OUR RGN. ANOTHER VERY WARM DAY...ALTHO THIS HAS CERTAINLY NOT BEEN AS OPPRESSIVE AS MANY OF THE LATE JULS I HV SPENT HERE. TEMPS 90-95 THIS AFTN...HEAT INDEX VALUES 95-100. CLD WISE DAY SHOULD START OUT BTWN THE SHORT WV THAT PRODUCED THE RW AFTR MDNGT AND THE MCS...SO MAINLY SUNNY THIS MRNG THEN INCRSG CLDS W/ CHC-LKLY POPS THIS AFTN. && .SHORT TERM /TONIGHT/... UPPER TROF OVER ERN ONTARIO BEGINS TO DIG OVER THE NERN U.S. TNGT FORMING A SOMEHAT ATYPICAL LATE JUL PATTERN. BEING ON THE ERN SIDE OF THE TROF CHCS OF PCPN WL EXIST AGN TNGT. POPS MAINLY 40-50...BUT THESE MAY NEED TO BE INCRSD BASED ON HOW THINGS DVDLP TDA. TEMPS RANGE FM THE M60S HIGHLANDS TO MU70S IN CITIES AND ALONG CHES BAY. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... WED LOOKS TO BE ACTIVE...ONE OF THOSE SITUATIONS WHERE TOO MUCH OF A LOW LEVEL MOISTURE SURGE DRNG THE MRNG HRS MAY LIMIT OR STABILIZE THE ENVRMNT FOR AFTN CONVECTION. FORCING HOWEVER DOESN/T LOOK TO BE AN ISSUE. A STRONG POSITIVELY TILTED AND APRCHNG UPPER TROF AXIS WILL DIG VERY FAR SOUTH /FOR A LATE-JULY SYSTEM/ INTO THE TN VLY AND SRN APLCHNS INTO WED AFTN. ALL ALONG THE ERN SEABOARD /IN THE WARM SECTOR OF THE APRCHNG SHRTWV/...A FAIRLY INTENSE MID SUMMER LL JET MAX LOOKS TO DEVELOP. THIS FEATURE...ALONG W/ HIGH DWPNTS AND MID LEVEL SUBSIDENCE BEHIND THE SYSTEM...COULD LIKELY DEVELOP SOME AREAS OF INTENSE CONVECTION UP/DOWN THE ERN SEABOARD. OVRNGHT WED INTO THURS MRNG THE TROF AXIS WILL SHARPLY TURN NE/WRD AND PUSH THE REMAINING ACTIVITY OFF THE ATLNC COAST. THE BIG CHANGE IN LR MODELS FROM 24 HRS AGO IS THE WEEKEND SET-UP FOR THE UPPER LOW OVER THE GREAT LAKES. A DECENT AGREEMENT IS HELD AMONGST GUIDANCE ABOUT THE SHARP TROF AXIS THAT GRADUALLY WORKS IT/S WAY ACROSS THE ERN HALF OF THE COUNTRY...INITIALLY POSITIVELY TILTED OVER THE WRN GREAT LAKES AND MID MS VALLEY...THEN BECOMES PHASES N/S OVER THE APLCHN CHAIN ON THURS /DRIVING THE ACTIVITY OFF THE COAST/. THEN THE UPPER TROF AXIS GRADUALLY TILTS NEGATIVELY AS IT MOVES UP THE NORTHEAST COAST. PREV RUNS FROM THIS POINT PUSHED THE UPPER LOW OUT /FROM ERN QUEBEC OUT INTO THE NRN ATLNC/ BY A DEVELOPING UPPER ON THE LEE OF THE CANADIAN ROCKIES...INTO THE PLAINS OF S CNTL CANADA. LATEST GFS/ECMWF RUNS NOW COMBINING THE TWO SYSTEMS JUST NORTH OF THE GREAT LAKES REGION OVER THE WEEKEND...MAKING FOR ONE LAST PASS OF ACTIVE WEATHER BEFORE EXITING NORTH AMERICA. AT THIS POINT...THE MAIN EFFECT ON THE MID ATLNC LOOKS TO BE DAILY INSTABILITY INCREASES AND SCT/D CONVECTION EACH AFTN...PSBLY INTO THE WEEKEND IF THE SFC FRONT STALLS OR SLOWS IT/S PROGRESS ACROSS THE REGION. && .AVIATION /TODAY THROUGH SATURDAY/... VFR CONDS THIS MRNG. TSTM ACTVTY IS PSBL THIS AFTN WICH COULD GNR8 STRONG WINDS. FOR TIME BEING ONLY HV VCTS REMARK IN TAFS. THIS WL NEED TO BE REFINED LATER THIS MRNG/THIS AFTN. TSTM WL BE PSBL DURG OVRNGT HRS AS WELL. MUCH OF WED WILL HAVE THE PSBLY OF EITHER SHRA/TSTM ACTIVITY. BY WED AFTN...MUCH OF THE AREA WILL BE UNDER SOME RISK OF TSTMS...ESPC THE I-95 CRDR BY EVNG. THIS ACTIVITY WILL GRADLY PUSH OFF THE MID ATLNC COAST EARLY THURS. DRY WX WILL RETURN FOR MUCH OF THURS AND INTO FRI. THE WEEKEND LOOKS TO BE ACTIVITY AGAIN W/ SCTD TSTMS PSBLE INTO EARLY NEXT WEEK...W/ A PSBLE COLD FRONTAL PASSAGE ON MON. && .MARINE... NOP PROB WIND WISE TDA-TNGT. AFTN AND EVE TSTMS WL BE THE BIGGEST PROBS FOR MARINERS. WINDS ON WED MAY APRCH SCA CRIT W/ BRIEF PERIODS OF S/RLY CHANNELING FROM AN APRCHNG UPPER LOW PRES SYSTEM. TSTM ACTIVITY WILL BE THE MAIN CONCERN GOING INTO WED AFTN/EVNG. LITTLE CONCERN FOR THE END OF THE WEEK...THO ANOTHER UPPER DISTURBANCE WILL CROSS THE REGION THIS WEEKEND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ PRODUCTS...WOODY!/GMS md AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 145 PM EDT WED JUL 23 2008 UPDATED FOR THE 18Z TAFS .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SLOWLY DEPARTING UPR TROF OVER SE ONTARIO DOWNSTREAM OF HI AMPLITUDE RDG EXTENDING FM THE PLAINS INTO SCNTRL CAN. AT THE SFC/H85...SPRAWLING HI PRES CENTERED OVER NRN ONTARIO. BACK EDGE OF DEEPER MSTR ASSOCIATED WITH THE TROF IS IN ERN UPR MI WITH LINGERING SCT-BKN MID CLD. TO THE W AND NW...00Z INL/YPL RAOBS ARE QUITE DRY/STABLE WITH PWAT JUST A BIT OVER 0.50 INCH/WELL DEFINED CAP ARND H7 ABV WELL MIXED PBL. AFTN DIURNAL CU IN THESE AREAS YDAY GAVE WAY TO MOCLR SKIES DURING THE EVNG. MAIN FCST CONCERNS INTO THU REVOLVE ARND TEMPS WITH ONTARIO HI PRES/ DRY AIRMASS FCST TO DOMINATE. FOCUS FOR THU NGT THRU FRI NGT SHIFTS TO TIMING/IMPACT OF TROF NOW IN THE PAC NW TO THE W OF UPR RDG IN THE PLAINS. FOR TDAY/TNGT...DRY HI PRES FCST TO BLD OVER THE UPR GRT LKS AND TO NR MNM BY 12Z THU. ALTHOUGH THERE WL BE SCT DIURNAL CU OVER THE INTERIOR CWA THIS AFTN AWAY FM THE STABILIZING INFLUENCE OF THE GRT LKS...EXPECT MOCLR SKIES OTRW. THE ONLY OTHER EXCEPTION MAY BE OVER THE FAR ERN CWA TNGT...WHERE ANOTHER SHRTWV ROTATING ARND NRLY STNRY CLOSED LO THE E MAY BRING SOME CLD IN TNGT. DRY AIRMASS SUGS A WIDE DIURNAL VARIATION IN TEMP BTWN THIS AFTN/TNGT. WITH H85 TEMPS FCST ARND 12C BY 00Z THU...EXPECT HI TEMPS TO APRCH 80 AWAY FM LK COOLING MOST PRONOUNCED DOWNWIND OF LK SUP AND THE BAY OF GREEN BAY S OF ESC WITH NLY H925 FLOW MINIMIZING LK MI INFLUENCE AT AREAS E OF ESC. MIXING TO H75-8 TDAY WOULD SUG SFC DWPTS WL FALL INTO THE MID 40S PER 00Z INL RAOB/GFS FCST SDNGS...RESULTING IN MIN RH FALLING AOB 30 PCT OVER THE INTERIOR. ALTHOUGH DVLPG RETURN SSW FLOW LATE TNGT MAY TEND TO BRAKE FALL OF TEMP OVER THE FAR W AT IWD- ONTONAGON...WL GO BLO MOS GUIDANCE OVER MOST OF THE INTERIOR TO THE E WITH PROMISE OF LGT WINDS/CLR SKIES. STUBBORN UPR LO IN ONTARIO IS PROGGED TO LIFT SLOWLY TO THE NE ON THU...BUT LARGER SCALE ACYC FLOW IS PROGGED TO LINGER UNDER RDG AXIS JUST TO THE NW THAT WL BE WEAKENING AS PAC NW TROF PRESSES INTO SCNTRL CAN. ANTECEDENT DRY AIRMASS...PERSISTENCE OF RDGING/ACYC FLOW UPSTREAM OF STUBBORN BLOCK TO THE E...AND INTERCEPTION OF RETURNING DEEPER MSTR CLOSER TO WARM FNT WELL TO THE S WOULD SUG DRY...CAPPED NAM IS ON THE RIGHT TRACK AND GFS IS TOO AGGRESSIVE AT GENERATING PCPN OVER THE WRN ZNS IN THE AFTN. BUT WL RETAIN GOING LO CHC POPS TO ACCOUNT FOR GFS FCST AND RATHER HI ETA MOS POP AS WELL FOR IWD. DESPITE SOME INCRS IN CLD COVER...TEMPS WL BE AOA EXPECTED MAX TEMPS FOR TDAY WITH H85 TEMPS A DEGREE OR TWO WARMER AND RETURN SW FLOW MINIMIZING LK SUP COOLING. THE EXCEPTION WL BE ALONG/DOWNWIND OF THE LK MI SHORE. AS INCOMING UPR TROF ACRS SRN CAN BREAKS DOWN RDG A BIT MORE THU NGT...ASSOCIATED SFC COLD FNT IS PROGGED TO ARPCH WRN LK SUP BY 12Z FRI...GFS A BIT FASTER THAN NAM. PER NCEP GUIDANCE...FOLLOWED COMPROMISE 00Z UKMET/12Z ECMWF FOR TIMING...WHICH SHOW THE BNDRY REACHING THE MN/LK SUP AT 12Z FRI. SINCE SHARP WARM FNT REMAINS WELL TO THE SW...MSTR INFLOW WL BE LIMITED...AND MODEL QPFS ARE RATHER MODEST. 12Z ECMWF IS A BIT MORE AGGRESSIVE THAN THE 00Z UKMET WITH HGT FALLS/DPVA/DEEP LYR QVECTOR CNVGC ASSOCIATED WITH INCOMING TROF...ESPECIALLY OVER WRN UPR MI. WL THUS CARRY A 30 POP OVER THE NW BUT KEEP THE ERN ZNS DRY SO FAR E OF THE INCOMING BNDRY AT DIURNAL MIN HTG TIME. ECMWF/UKMET SHOW SSI ARND +4C AT ERY THRU THE NGT...AND NAM FCST SDNGS ARE QUITE DRY IN THE MID LVLS. BULK OF NUMERICAL GUIDANCE SHOWS COLD FNT REACHING THE SCNTRL AND E LATE IN THE DAY ON FRI. PCPN CHCS ON FRI WL BE LIMITED BY WEAK LLVL CNVGC ALG THE FNT...LIMITED MSTR INFLOW...AND QUITE A BIT OF DRY MID LVL AIR. ON THE OTHER HAND...LACK OF CLD COVER WOULD SUG A GOOD DEAL OF INSOLATION/DESTABILIZATION. PLACEMENT OF FA IN LEFT EXIT OF JET MAX SUPPORTING INCOMING TROF SHOWN MOST BY 12Z ECMWF ALG WITH SOME FAIRLY SHARP DVPA/DEEP LYR QVECTOR CNVGC WOULD ADD LARGER SCALE LIFT. BUT THE 00Z GFS/UKMET SHY AWAY FM THIS STRONGER JET SCENARIO... SO OPTED TO REDUCE POPS A BIT TO NO MORE THAN 30 EXCEPT OVER THE FAR SCNTRL AND E WHERE LATER ARRIVAL OF FNT WL BE MOST IN SYNC WITH DIURNAL HTG CYCLE AND SOME LK BREEZE CNVGC. GOING 40 POP SEEMS APPROPRIATE THERE. TENDED TOWARD THE HI END OF MOS GUIDANCE FOR MAX TEMPS EXCEPT OVER THE W DOWNWIND OF LK SUP/NEAR LK MI WITH DOWNSLOPING WNW FLOW/EXPECTED DECENT AMT OF SUNSHINE. INCRSG UNIDIRECTIONAL WINDS IN THE LO/MID TROP (0-6KM BULK SHEAR FCST TO INCRS TO 40 KTS) AND PRESENCE OF DRY MID LVL AIR WOULD SUG A RISK FOR SOME SVR STORMS. MODIFIED GFS FCST SDNG FOR MNM FOR SFC T/TD 83/60 AND SOMEWHAT COOLER MID LVL TEMPS TO ACCOUNT FOR POTENTIAL OF STRONGER JET DYNAMICS THAN EXPLICITLY FCST BY 00Z GFS YIELDS SB CAPE ARND 930 J/KG. BUT LAPSE RATES...EVEN WITH A DEGREE OR SO OF MID LVL COOLING...DO NOT APPEAR PARTICULARLY STEEP. SINCE SPC DOES NOT HAVE UPR GRT LKS OUTLOOKED FOR MENTION OF SVR STORMS...WL LEAVE OUT MENTION FOR NOW. WITH LOSS OF DIURNAL HTG FRI NGT AND FAIRLY STRONG MID LVL DRYING IN WAKE OF COLD FROPA...TENDED TO END POPS FASTER W-E THAN PREVIOUS FCST. BUT MAINTAINED LO CHC POPS OVER LK SUP THRU THE NGT AND INTO SAT CLOSER TO DIGGING SHRTWV THRU ONTARIO AND SOMEWHAT DEEPER MSTR. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... SURFACE HIGH PRESSURE WILL BE OVERHEAD TODAY...AND MOVE TO THE OHIO VALLEY BY THURSDAY MORNING. EXPECT VFR CIGS AND VIS THROUGH THE PERIOD WITH TRADITIONAL DIURNAL WINDS...LIGHT AND VARIABLE DURING THE OVERNIGHT HOURS. THE ONLY FLY IN THE OINTMENT SHOULD BE WITH CLOUDS LATE IN THE PERIOD AND SHORTLY AFTER...ASSOCIATED WITH AN APPROACHING COLD FRONT. THESE TOO SHOULD REMAIN VFR AT LEAST THROUGH 18Z. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... THE HIGH PRESSURE OVER THE UPPER GREAT LAKES WILL KEEP WINDS LESS THAN 15 KNOTS THROUGH THURSDAY. AS THIS HIGH DRIFTS EAST ON FRIDAY...A LOW PRESSURE TROUGH WILL MOVE INTO THE UPPER GREAT LAKES CAUSING SOUTHERLY WINDS TO INCREASE AND VEER TO THE WEST. AS THIS TROUGH DRIFTS INTO THE CENTRAL GREAT LAKES ON SATURDAY...THE WINDS WILL SHIFT NORTHWEST AGAIN. OTHERWISE...WINDS WILL BE NO GREATER THAN 20 KNOTS THIS WEEK END. WAVES WILL STILL REMAIN 3 FEET OR LESS THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...KF/MRC MARINE...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 728 AM EDT WED JUL 23 2008 .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SLOWLY DEPARTING UPR TROF OVER SE ONTARIO DOWNSTREAM OF HI AMPLITUDE RDG EXTENDING FM THE PLAINS INTO SCNTRL CAN. AT THE SFC/H85...SPRAWLING HI PRES CENTERED OVER NRN ONTARIO. BACK EDGE OF DEEPER MSTR ASSOCIATED WITH THE TROF IS IN ERN UPR MI WITH LINGERING SCT-BKN MID CLD. TO THE W AND NW...00Z INL/YPL RAOBS ARE QUITE DRY/STABLE WITH PWAT JUST A BIT OVER 0.50 INCH/WELL DEFINED CAP ARND H7 ABV WELL MIXED PBL. AFTN DIURNAL CU IN THESE AREAS YDAY GAVE WAY TO MOCLR SKIES DURING THE EVNG. MAIN FCST CONCERNS INTO THU REVOLVE ARND TEMPS WITH ONTARIO HI PRES/ DRY AIRMASS FCST TO DOMINATE. FOCUS FOR THU NGT THRU FRI NGT SHIFTS TO TIMING/IMPACT OF TROF NOW IN THE PAC NW TO THE W OF UPR RDG IN THE PLAINS. FOR TDAY/TNGT...DRY HI PRES FCST TO BLD OVER THE UPR GRT LKS AND TO NR MNM BY 12Z THU. ALTHOUGH THERE WL BE SCT DIURNAL CU OVER THE INTERIOR CWA THIS AFTN AWAY FM THE STABILIZING INFLUENCE OF THE GRT LKS...EXPECT MOCLR SKIES OTRW. THE ONLY OTHER EXCEPTION MAY BE OVER THE FAR ERN CWA TNGT...WHERE ANOTHER SHRTWV ROTATING ARND NRLY STNRY CLOSED LO THE E MAY BRING SOME CLD IN TNGT. DRY AIRMASS SUGS A WIDE DIURNAL VARIATION IN TEMP BTWN THIS AFTN/TNGT. WITH H85 TEMPS FCST ARND 12C BY 00Z THU...EXPECT HI TEMPS TO APRCH 80 AWAY FM LK COOLING MOST PRONOUNCED DOWNWIND OF LK SUP AND THE BAY OF GREEN BAY S OF ESC WITH NLY H925 FLOW MINIMIZING LK MI INFLUENCE AT AREAS E OF ESC. MIXING TO H75-8 TDAY WOULD SUG SFC DWPTS WL FALL INTO THE MID 40S PER 00Z INL RAOB/GFS FCST SDNGS...RESULTING IN MIN RH FALLING AOB 30 PCT OVER THE INTERIOR. ALTHOUGH DVLPG RETURN SSW FLOW LATE TNGT MAY TEND TO BRAKE FALL OF TEMP OVER THE FAR W AT IWD- ONTONAGON...WL GO BLO MOS GUIDANCE OVER MOST OF THE INTERIOR TO THE E WITH PROMISE OF LGT WINDS/CLR SKIES. STUBBORN UPR LO IN ONTARIO IS PROGGED TO LIFT SLOWLY TO THE NE ON THU...BUT LARGER SCALE ACYC FLOW IS PROGGED TO LINGER UNDER RDG AXIS JUST TO THE NW THAT WL BE WEAKENING AS PAC NW TROF PRESSES INTO SCNTRL CAN. ANTECEDENT DRY AIRMASS...PERSISTENCE OF RDGING/ACYC FLOW UPSTREAM OF STUBBORN BLOCK TO THE E...AND INTERCEPTION OF RETURNING DEEPER MSTR CLOSER TO WARM FNT WELL TO THE S WOULD SUG DRY...CAPPED NAM IS ON THE RIGHT TRACK AND GFS IS TOO AGGRESSIVE AT GENERATING PCPN OVER THE WRN ZNS IN THE AFTN. BUT WL RETAIN GOING LO CHC POPS TO ACCOUNT FOR GFS FCST AND RATHER HI ETA MOS POP AS WELL FOR IWD. DESPITE SOME INCRS IN CLD COVER...TEMPS WL BE AOA EXPECTED MAX TEMPS FOR TDAY WITH H85 TEMPS A DEGREE OR TWO WARMER AND RETURN SW FLOW MINIMIZING LK SUP COOLING. THE EXCEPTION WL BE ALONG/DOWNWIND OF THE LK MI SHORE. AS INCOMING UPR TROF ACRS SRN CAN BREAKS DOWN RDG A BIT MORE THU NGT...ASSOCIATED SFC COLD FNT IS PROGGED TO ARPCH WRN LK SUP BY 12Z FRI...GFS A BIT FASTER THAN NAM. PER NCEP GUIDANCE...FOLLOWED COMPROMISE 00Z UKMET/12Z ECMWF FOR TIMING...WHICH SHOW THE BNDRY REACHING THE MN/LK SUP AT 12Z FRI. SINCE SHARP WARM FNT REMAINS WELL TO THE SW...MSTR INFLOW WL BE LIMITED...AND MODEL QPFS ARE RATHER MODEST. 12Z ECMWF IS A BIT MORE AGGRESSIVE THAN THE 00Z UKMET WITH HGT FALLS/DPVA/DEEP LYR QVECTOR CNVGC ASSOCIATED WITH INCOMING TROF...ESPECIALLY OVER WRN UPR MI. WL THUS CARRY A 30 POP OVER THE NW BUT KEEP THE ERN ZNS DRY SO FAR E OF THE INCOMING BNDRY AT DIURNAL MIN HTG TIME. ECMWF/UKMET SHOW SSI ARND +4C AT ERY THRU THE NGT...AND NAM FCST SDNGS ARE QUITE DRY IN THE MID LVLS. BULK OF NUMERICAL GUIDANCE SHOWS COLD FNT REACHING THE SCNTRL AND E LATE IN THE DAY ON FRI. PCPN CHCS ON FRI WL BE LIMITED BY WEAK LLVL CNVGC ALG THE FNT...LIMITED MSTR INFLOW...AND QUITE A BIT OF DRY MID LVL AIR. ON THE OTHER HAND...LACK OF CLD COVER WOULD SUG A GOOD DEAL OF INSOLATION/DESTABILIZATION. PLACEMENT OF FA IN LEFT EXIT OF JET MAX SUPPORTING INCOMING TROF SHOWN MOST BY 12Z ECMWF ALG WITH SOME FAIRLY SHARP DVPA/DEEP LYR QVECTOR CNVGC WOULD ADD LARGER SCALE LIFT. BUT THE 00Z GFS/UKMET SHY AWAY FM THIS STRONGER JET SCENARIO... SO OPTED TO REDUCE POPS A BIT TO NO MORE THAN 30 EXCEPT OVER THE FAR SCNTRL AND E WHERE LATER ARRIVAL OF FNT WL BE MOST IN SYNC WITH DIURNAL HTG CYCLE AND SOME LK BREEZE CNVGC. GOING 40 POP SEEMS APPROPRIATE THERE. TENDED TOWARD THE HI END OF MOS GUIDANCE FOR MAX TEMPS EXCEPT OVER THE W DOWNWIND OF LK SUP/NEAR LK MI WITH DOWNSLOPING WNW FLOW/EXPECTED DECENT AMT OF SUNSHINE. INCRSG UNIDIRECTIONAL WINDS IN THE LO/MID TROP (0-6KM BULK SHEAR FCST TO INCRS TO 40 KTS) AND PRESENCE OF DRY MID LVL AIR WOULD SUG A RISK FOR SOME SVR STORMS. MODIFIED GFS FCST SDNG FOR MNM FOR SFC T/TD 83/60 AND SOMEWHAT COOLER MID LVL TEMPS TO ACCOUNT FOR POTENTIAL OF STRONGER JET DYNAMICS THAN EXPLICITLY FCST BY 00Z GFS YIELDS SB CAPE ARND 930 J/KG. BUT LAPSE RATES...EVEN WITH A DEGREE OR SO OF MID LVL COOLING...DO NOT APPEAR PARTICULARLY STEEP. SINCE SPC DOES NOT HAVE UPR GRT LKS OUTLOOKED FOR MENTION OF SVR STORMS...WL LEAVE OUT MENTION FOR NOW. WITH LOSS OF DIURNAL HTG FRI NGT AND FAIRLY STRONG MID LVL DRYING IN WAKE OF COLD FROPA...TENDED TO END POPS FASTER W-E THAN PREVIOUS FCST. BUT MAINTAINED LO CHC POPS OVER LK SUP THRU THE NGT AND INTO SAT CLOSER TO DIGGING SHRTWV THRU ONTARIO AND SOMEWHAT DEEPER MSTR. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... VFR CONDITIONS WILL PREVAIL THROUGH THIS FORECAST PERIOD WITH DRY HIGH PRESSURE BUILDING OVER THE AREA. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... THE HIGH PRESSURE OVER THE UPPER GREAT LAKES WILL KEEP WINDS LESS THAN 15 KNOTS THROUGH THURSDAY. AS THIS HIGH DRIFTS EAST ON FRIDAY...A LOW PRESSURE TROUGH WILL MOVE INTO THE UPPER GREAT LAKES CAUSING SOUTHERLY WINDS TO INCREASE AND VEER TO THE WEST. AS THIS TROUGH DRIFTS INTO THE CENTRAL GREAT LAKES ON SATURDAY...THE WINDS WILL SHIFT NORTHWEST AGAIN. OTHERWISE...WINDS WILL BE NO GREATER THAN 20 KNOTS THIS WEEK END. WAVES WILL STILL REMAIN 3 FEET OR LESS THROUGH THE PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...DLG MARINE...DLG mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 122 AM EDT WED JUL 23 2008 .SYNOPSIS... WV IMAGERY AND RUC ANALYSIS INDICATED A MID/UPPER LEVEL TROUGH INTO THE CENTRAL GREAT LAKES AND A RIDGE FROM THE SRN ROCKIES TO MANITOBA AND HUDSON BAY RESULTING INT NRLY FLOW THROUGH THE UPPER GREAT LAKES. AT THE SFC...HIGH PRES EXTENDED FROM HUDSON BAY AND NRN ONTARIO INTO WITH ACYC NNE FLOW ACROSS UPPER MICHIGAN. SOME ISOLD SHRA/TSRA HAVE DEVELOPED OVER W AND SRN UPPER MI...WELL DOWNSTREAM FROM STABILIZING INFLUENCE OF LAKE SUPERIOR WHERE CAPE VALUES CAPE VALUES HAD CLIMBED TO AROUND 500 J/KG. .SHORT TERM...(TONIGHT AND WEDNESDAY) AFTER THE SHAR/TSRA FADE WITH DIURNAL COOLING AND INFLUX OF DRIER AIR FROM THE NORTH...EXPECT MOSTLY CLEAR SKIES TONIGHT. WINDS OVER THE WEST HALF SHOULD BE LIGHT ENOUGH...AOB 5 KT...FOR RADIATIONAL COOLING TO ALLOW TEMPS TO DROP INTO THE UPPER 40S. 11C TO 12C 850 MB TEMPS SUPPORT MAX READINGS INTO THE MID AND UPPER 70S INLAND WITH COOLER READINGS ALONG LAKE SUPERIOR. DRY AIR OVER THE REGION ALONG WITH MID LEVEL SUBSIDENCE/WARMING WILL KEEP AREA DRY WITH ONLY FEW/SCT CU DEVELOPING. .LONG TERM (WEDNESDAY NIGHT THROUGH NEXT TUESDAY)... BASED ON HPC CONFIDENCE AND GOOD AGREEMENT IN GFS ENS AND ECMWF...WENT WITH A BLEND OF THOSE TWO MODELS FOR MOST OF THE EXTENDED PART OF THE FORECAST...BUT DID USE A BLEND OF THE NAM DURING THE EARLY PERIODS. UPPER TROUGH CENTERED OVER THE ONTARIO AND QUEBEC BORDER...WILL CONTINUE TO SLOWLY DRIFT TO THE NORTHEAST DURING THE FIRST PART OF THE EXTENDED PERIOD. WITH UPPER MI BEING ON THE WRN SIDE OF THE TROUGH AND UNDER A WEAK RIDGE...HIGH PRESSURE WILL BE OVER THE REGION FOR THE WED NIGHT AND FIRST PART OF THURS. MOSTLY CLEAR SKIES SHOULD ALLOW LOWS TO BE BELOW NORMAL. STAYED TOWARDS THE MOS GUIDANCE...BUT THEY COULD BE TWEAKED DOWN A BIT IN SOME OF THE COOLER SPOTS. WEAK UPPER WAVE AND SFC LOW COMING OUR OF THE NRN ROCKIES ON WED...EJECTING FROM CURRENT TROUGH OVER THE PACIFIC NW...WILL APPROACH THE REGION ON THURS. THIS WILL BRING THE BEST CHANCE FOR RAIN DURING THE THURS NIGHT THROUGH FRI NIGHT TIMEFRAME. GFS AND ECMWF IN GOOD AGREEMENT WITH THE POSITION OF THE WEAK LOW...AROUND 1004MB...OVER THE LAKE WINNIPEG REGION AT 12Z ON THURS. THIS LOW WITH THEN SLOWLY SHIFT NE TOWARDS SRN HUDSON BAY BY 12Z SAT...WHILE DRAGGING A COLD FRONT EASTWARD ACROSS UPPER MI ON FRIDAY. DIDN`T MAKE ANY MAJOR CHANGES TO THE PCPN CHANCES FOR THURS...AS EXISTING CHANCE OVER THE FAR WRN PART OF LK SUPERIOR LOOKED GOOD. NAM IS A LITTLE SLOWER WITH THE START OF THE PCPN ON THURS...DUE TO DRIER AIR HOLDING ON A LONGER...BUT FELT THE EXISTING CHANCE POPS MATCHED UP WELL. INTO THURS NIGHT...ONLY EXPECT A FEW SHOWERS...AND POSSIBLY SOME RUMBLES OF THUNDER. EXPECT THE PCPN TO BE OVER THE WRN HALF OF THE CWA...AS ELEVATED H850 CAPE IS AROUND 500-800 J/KG AND SHOWALTER AROUND -2C...MOVES E INTO THE AREA ALONG THE H850 FRONT. WITH THE LIMITED INSTABILITY AND LACK OF SHEAR...ONLY ABOUT 25-30KT 0-6KM BULK SHEAR...DON`T REALLY EXPECT TO SEE ANYTHING SEVERE. FRIDAY LOOKS LIKE A LITTLE BETTER CHANCE OF SEEING SEVERE THUNDERSTORMS...WITH THE BEST CHANCES S AND W OF A LINE FROM IWD TO MQT TO ISQ. IN THIS AREA...BULK SHEAR VALUES ARE SLIGHTLY IMPROVED...30-35KTS...AND MLCAPE VALUES ARE IN THE 500-1000 J/KG RANGE. WITH THE FRONTAL PASSAGE DURING THE AFTN...DO EXPECT TO SEE SOME THUNDERSTORMS DEVELOPING...BUT BELIEVE THERE WILL ONLY BE ISOLATED STRONG TO SEVERE STORMS. WAVE WITH THE LOW WILL MERGE AND STRENGTHEN THE UPPER TROUGH OVER SWRN QUEBEC ON FRIDAY NIGHT...WITH UPPER TROUGH ALSO OFF THE W COAST OF NOTAM. THIS WILL BRING NW FLOW TO THE REGION FOR THE REST OF THE WEEKEND AND FIRST PART OF NEXT WEEK...AS RIDGE BUILDS OVER CNTL NOTAM. LINGERING MOISTURE WILL ROTATE AROUND THE UPPER LOW FOR THE FIRST PART OF THE WEEKEND. WOULD NOT BE SURPRISED TO SEE SOME VERY LIGHT RAIN OR DRIZZLE BEHIND THE COLD FRONT ON SAT AND SAT NIGHT...ESPECIALLY OVER THE ERN TWO THIRDS OF LK SUPERIOR AND LAND LOCATIONS NEAR THERE...AS MODELS HINT AT A WEAK SHORTWAVE ROTATING THROUGH. CONTEMPLATED ADDING POPS IN OVER THE NRN PORTION OF UPPER MI...BUT SINCE THE COVERAGE WOULD BE PRETTY LIMITED AND THE PCPN WILL BE LIGHT...ONLY ADDED A SLIGHT CHANCE FOR LK SUPERIOR LOCATIONS. ALSO BUMPED UP THE CLOUD COVER FOR THAT TIME PERIOD. WITH THE UPPER LOW FINALLY SHIFTING TO THE E ON SUN...HIGH PRESSURE WILL MOVE OVER THE REGION FOR THE REST OF THE EXTENDED PERIOD. THEREFORE...DIMINISHED CLOUD COVER ACROSS THE AREA AND WENT WITH NEAR NORMAL TEMPS. .AVIATION (FOR THE 06 TAF ISSUANCE)... VFR CONDITIONS WILL PREVAIL THROUGH THIS FORECAST PERIOD WITH DRY HIGH PRESSURE BUILDING OVER THE AREA. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... A HIGH PRESSURE RIDGE FROM HUDSON BAY INTO THE UPPER GREAT LAKES WILL BUILD SOUTH OVER LAKE SUPERIOR ON WEDNESDAY AND THEN INTO THE LOWER GREAT LAKES ON THURSDAY. AS THIS HIGH DRIFTS INTO THE MID ATLANTIC STATES ON FRIDAY...A LOW PRESSURE TROUGH WILL MOVE INTO THE UPPER GREAT LAKES. LOOK FOR THIS TROUGH TO DRIFT INTO THE CENTRAL GREAT LAKES ON SATURDAY IN ADVANCE OF HIGH PRESSURE BUILDING TOWARD THE NORTHERN PLAINS. OTHERWISE...WINDS WILL BE NO GREATER THAN 20 KNOTS THROUGH THE END OF THE WEEK. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JLB LONG TERM...SRF AVIATION...JV MARINE...JLB mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 800 PM EDT TUE JUL 22 2008 LATEST UPDATE...AVIATION... .SYNOPSIS...(215 PM EDT TUE JUL 22 2008) SHOWERS AND SCATTERED THUNDERSTORMS THIS AFTERNOON WILL DISSIPATE EARLY THIS EVENING. THE STRONGEST STORMS COULD CONTAIN SMALL HAIL AND GUSTY WINDS. HIGH PRESSURE BUILDING SOUTH FROM CANADA WILL BRING DRY WEATHER THROUGH FRIDAY. DAYTIME TEMPERATURES WILL BE NEAR NORMAL WITH OVERNIGHT TEMPERATURES A BIT BELOW NORMAL. && .SHORT TERM...(215 PM EDT TUE JUL 22 2008) (TODAY THROUGH THURSDAY MORNING) SFC TROF AND H5 SHORT WAVE TOUCHING OFF SHOWERS AND A FEW THUNDERSTORMS ACROSS THE NORTHERN HALF OF THE CWA ATTM. EXPECT THIS AREA TO CONTINUE TO EXPAND UNTIL ABOUT 22Z AND THEN DECAY AS IT MOVES SOUTHWARD. LATEST RUC DEVELOPS 500-1000 J/KG OF MIXED LAYER CAPE ACROSS CENTRAL ZONES BY 21Z. SHEAR VALUES ARE VERY WEAK SO NOT EXPECTING VERY MUCH ORGANIZATION. SO...NOT EXPECTING SEVERE ATTM...BUT SMALL HAIL...WIND GUSTS TO 40 MPH AND A QUICK INCH OF RAIN IS POSSIBLE WITH THE STRONGEST STORMS. HIGH PRESSURE BUILDS SOUTH FOR WED WITH GRADUALLY FALLING DEWPOINTS...EXPECT NOTHING MORE THAN SCT/BKN FAIR WEATHER CUMULUS WED AFTN. SOME POTENTIAL FOR VALLEY/RIVER FOG THU AM WITH LIGHT WINDS. && .LONG TERM...(310 PM EDT TUE JUL 22 2008) (THURSDAY THROUGH TUESDAY) UPPER LOW IS EXPECTED TO BE EAST OF THE CWFA BY THE BEGINNING OF THE LONG TERM ON THU MORNING. SHORT WAVE RIDGING WILL BE UPSTREAM OF THE AREA AND SLOWLY BUILDING OVER THE CWFA THROUGH THU NIGHT. THIS SETUP WILL BRING MILD TEMPS AND DRY WEATHER THROUGH THU NIGHT. THE GFS DOES BRING AN AREA OF RAIN THROUGH THE CWFA THU NIGHT. THIS LOOKS TO BE THE RESULT OF CONVECTIVE FEEDBACK IN THE MODEL...AND HAS BEEN IGNORED FOR NOW. A SHORT WAVE TROUGH THAT IS EXPECTED TO MOVE ONSHORE OVER THE PACIFIC NW TOMORROW MORNING WILL TRAVERSE THE U.S./CANADIAN BORDER TO LAKE SUPERIOR BY FRI. THIS SHORT WAVE ALONG WITH ADDITIONAL SHORT WAVE ENERGY DIVING SOUTH OUT OF CANADA WILL HELP BRING A COLD FRONT ON FRI NIGHT. AHEAD OF THIS FRONT...WARMER AND MORE MOIST AIR WILL ADVECT INTO THE AREA...AND ALLOW FOR SOME INSTABILITY TO BUILD. A FEW SHOWERS AND STORMS WILL BE POSSIBLE ON FRI WITH THE BETTER CHC LIKELY COMING ON FRI EVENING WITH THE FRONT. THE THREAT OF PCPN WITH THIS FRONT IS NOT IMPRESSIVE AS MOST OF THE UPPER ENERGY REMAINS NORTH OF THE CWFA. MOST OF THE PCPN THREAT WILL END AS THE FRONT MOVES THROUGH FRI NIGHT. SOME LINGERING SHOWERS COULD BE FOUND EARLY SAT. MODELS ARE IN FAIRLY GOOD AGREEMENT IN KEEPING THE UPPER JET AND CYCLONIC FLOW JUST NORTH OF THE CWFA THROUGH THE WEEKEND. WITH THIS IN MIND...WE WILL MAINTAIN THE GOING DRY FCST. IF THIS JET SINKS SOUTH JUST A LITTLE MORE...WE WOULD BE LOOKING AT THE POTENTIAL FOR SOME DIURNALLY DRIVEN SHOWERS/STORMS FOR SUN. THE UPPER LOW SHOULD MOVE OUT...AND UPPER RIDGING WILL MOVE IN FOR EARLY NEXT WEEK BRINGING DRY AND MILD CONDITIONS TO THE AREA. && .MARINE...(1200 PM EDT TUE JUL 22 2008) WEAK LOW PRESSURE TROF LOCATED NEAR PENTWATER WILL SINK SOUTH OF LAKE MICHIGAN BY LATE AFTERNOON. WINDS ARE GENERALLY ONSHORE SOUTH AND NORTH BEHIND THE TROF. GLERL WAVE MODEL CONSISTENT IN SHOWING AREA OF 4-6 FOOT WAVES DEVELOPING OVER CENTRAL LAKE WITH NORTH WINDS BEHIND TROF. THE WAVES MOVE ONSHORE EXTREME SE PORTION THIS EVENING. A SMALL CRAFT ADVISORY MAY BE NEEDED ON WED SOUTH OF WHITEHALL AGAIN WITH GOOD FETCH OF N-NW WINDS OF 15 KTS CONTINUING TO DEVELOP WAVES APPROACHING 5 FEET IN THE AFTERNOON. && .AVIATION...(800 PM EDT TUE JUL 22 2008) UPPER TROUGH IS LOCATED OVERHEAD THIS EVENING...WITH A SHORTWAVE CURRENTLY SWINGING THROUGH THE FORECAST AREA. SHORTWAVE TOUCHED OFF SHOWERS AND THUNDERSTORMS EARLIER THIS AFTERNOON...WHICH HAVE FOR THE MOST PART COME TO AND END. THERE ARE SOME LINGERING SHOWERS ACROSS SOUTHWEST LOWER MICHIGAN...BUT SUSPECT THIS ACTIVITY WILL CONTINUE TO FADE THROUGH THE COURSE OF THE EVENING. MAIN FORECAST ISSUE IS THE LOWER CLOUDS THAT HAVE DEVELOPED IN THE WAKE OF THE AFTERNOON SHOWERS AND STORMS. MVFR CEILINGS BETWEEN 1000 AND 3000 FT EXIST FROM KGRR TO KLAN AND POINTS SOUTH. FEEL THESE CEILINGS WILL PUSH SOUTH AND DISSIPATE THROUGH THE COURSE OF THE NEXT FEW HOURS. LOOKING FOR A VFR NIGHT FOR THE MOST PART WITH A LIGHT NORTH WIND. EXPECT ANY FOG TO BE HELD AT BAY TONIGHT WITH FAIRLY STIFF NORTH WINDS JUST OFF THE DECK (15-25 KTS AT 1000 FT). ON WEDNESDAY... EXPECTING SCT-BKN CUMULUS TO DEVELOP WITH BASES AROUND 5000 FT. && .HYDROLOGY...(200 PM EDT TUE JUL 22 2008) SLIGHT CHANCE OF SOME LOCALIZED FLOODING WITH MAX T-STORM AMOUNTS OF 1.5 INCHES. MOST LOCATIONS WILL SEE 0.25 INCHES OR LESS THROUGH THIS EVENING. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY ST. JOSEPH TO WHITEHALL FROM 18Z THIS AFTN THROUGH 07Z TONIGHT. && $$ SYNOPSIS: COBB SHORT TERM: COBB LONG TERM: NJJ MARINE: COBB AVIATION: DUKE HYDROLOGY: COBB mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 215 PM EDT TUE JUL 22 2008 LATEST UPDATE...AVIATION...HYDROLOGY...SYNOPSIS...SHORT TERM... .SYNOPSIS...(215 PM EDT TUE JUL 22 2008) SHOWERS AND SCATTERED THUNDERSTORMS THIS AFTERNOON WILL DISSIPATE EARLY THIS EVENING. THE STRONGEST STORMS COULD CONTAIN SMALL HAIL AND GUSTY WINDS. HIGH PRESSURE BUILDING SOUTH FROM CANADA WILL BRING DRY WEATHER THROUGH FRIDAY. DAYTIME TEMPERATURES WILL BE NEAR NORMAL WITH OVERNIGHT TEMPERATURES A BIT BELOW NORMAL. && .SHORT TERM...(215 PM EDT TUE JUL 22 2008) (TODAY THROUGH THURSDAY MORNING) SFC TROF AND H5 SHORT WAVE TOUCHING OFF SHOWERS AND A FEW THUNDERSTORMS ACROSS THE NORTHERN HALF OF THE CWA ATTM. EXPECT THIS AREA TO CONTINUE TO EXPAND UNTIL ABOUT 22Z AND THEN DECAY AS IT MOVES SOUTHWARD. LATEST RUC DEVELOPS 500-1000 J/KG OF MIXED LAYER CAPE ACROSS CENTRAL ZONES BY 21Z. SHEAR VALUES ARE VERY WEAK SO NOT EXPECTING VERY MUCH ORGANIZATION. SO...NOT EXPECTING SEVERE ATTM...BUT SMALL HAIL...WIND GUSTS TO 40 MPH AND A QUICK INCH OF RAIN IS POSSIBLE WITH THE STRONGEST STORMS. HIGH PRESSURE BUILDS SOUTH FOR WED WITH GRADUALLY FALLING DEWPOINTS...EXPECT NOTHING MORE THAN SCT/BKN FAIR WEATHER CUMULUS WED AFTN. SOME POTENTIAL FOR VALLEY/RIVER FOG THU AM WITH LIGHT WINDS. && .LONG TERM...(400 AM EDT TUE JUL 22 2008) (THURSDAY NIGHT THROUGH MONDAY) THE MAIN FEATURE IN THE EXTENDED PERIOD WILL BE A SFC COLD FRONT ASSOCIATED WITH THE NEXT UPR LOW MOVING EAST ACROSS SRN CANADA. MODELS ARE IN FAIR AGREEMENT WITH THE TIMING OF THIS FRONT... AND ARE CURRENTLY PROGGING IT TO COME THROUGH THE GRTLKS REGION ON FRIDAY NIGHT AND SATURDAY. HAVE MAINTAINED CHC POPS FOR SHOWERS AND TSTMS ON FRIDAY AND FRIDAY NIGHT IN SW FLOW WAA PATTERN PRECEDING THE FRONT... AND HAVE ADDED POPS FROM GRR SOUTH AND EAST FOR 12Z-18Z SATURDAY. NW FLOW AFTER FROPA SATURDAY SHOULD DRY THINGS OUT FROM WEST TO EAST. THE WX PATTERN FOR SUNDAY AND MONDAY WILL FEATURE NW FLOW ALOFT (UPR LOW OVER QUEBEC)... WITH SURFACE RIDING BUILDING SE FROM THE NRN PLAINS. THIS SHOULD BE A PLEASANT/DRY PERIOD FOR SW MI WITH TEMPS AT OR JUST A TAD BELOW NORMAL. && .MARINE...(1200 PM EDT TUE JUL 22 2008) WEAK LOW PRESSURE TROF LOCATED NEAR PENTWATER WILL SINK SOUTH OF LAKE MICHIGAN BY LATE AFTERNOON. WINDS ARE GENERALLY ONSHORE SOUTH AND NORTH BEHIND THE TROF. GLERL WAVE MODEL CONSISTENT IN SHOWING AREA OF 4-6 FOOT WAVES DEVELOPING OVER CENTRAL LAKE WITH NORTH WINDS BEHIND TROF. THE WAVES MOVE ONSHORE EXTREME SE PORTION THIS EVENING. A SMALL CRAFT ADVISORY MAY BE NEEDED ON WED SOUTH OF WHITEHALL AGAIN WITH GOOD FETCH OF N-NW WINDS OF 15 KTS CONTINUING TO DEVELOP WAVES APPROACHING 5 FEET IN THE AFTERNOON. && .AVIATION...(200 PM EDT TUE JUL 22 2008) SHOWERS AND SCATTERED THUNDERSTORMS THROUGH THE AFTERNOON. SMALL HAIL AND NORTHERLY WIND GUSTS TO 40 KTS ARE POSSIBILITIES WITH STRONGEST STORMS. TOPS WILL GENERALLY STAY BELOW 30 KFT. OUTLOOK FOR VFR ON WED WITH SOME SFC WIND GUST TO 20 KTS. && .HYDROLOGY...(200 PM EDT TUE JUL 22 2008) SLIGHT CHANCE OF SOME LOCALIZED FLOODING WITH MAX T-STORM AMOUNTS OF 1.5 INCHES. MOST LOCATIONS WILL SEE 0.25 INCHES OR LESS THROUGH THIS EVENING. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY ST. JOSEPH TO WHITEHALL FROM 18Z THIS AFTN THROUGH 07Z TONIGHT. && $$ SYNOPSIS: COBB SHORT TERM: COBB LONG TERM: MEADE MARINE: COBB AVIATION: COBB HYDROLOGY: COBB mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 145 PM EDT TUE JUL 22 2008 UPDATED FOR 18Z AVIATION DISCUSSION .UPDATE... MAIN FCST CONCERN IS POTENTIAL FOR SHRA/TSRA SOUTH THIS AFTERNOON. THE -SHRA OVER WRN UPPER MI SUPPORTED BY A WEAK SHORTWAVE TROUGH HAVE DIMINISHED AND SLID S OF THE CWA. HOWEVER...FCST AND MODIFIED OBSERVED SOUNDINGS SUGGEST THAT AFTERNOON HEATING WITH TEMPS INTO THE MID 70S AND DEWPOINTS IN THE MID 50S WOULD GIVE MLCAPE VALUES NEAR 500 J/KG. WITH RELATIVELY STEEP 700-500 MB LAPSE RATES NEAR 7 C/KM...SOME ISOLD SHRA/TSRA ARE STILL POSSIBLE OVER THE SOUTH...AWAY FROM STABILIZING INFLUENCE OF FLOW OFF OF LAKE SUPERIOR. WITH ONLY MARGINAL INSTABILITY...FREEZING LEVEL AROUND 11K FT...AND WEAK SHEAR...ONLY SMALL HAIL WOULD BE EXPECTED WITH ANY STRONGER TSRA. .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE ARE THE TEMPERATURES TODAY AND TONIGHT. WATER VAPOR AND RUC SHOWING A CLOSED LOW OVER QUEBEC WITH WEAK SHORTWAVE WRAPPING THROUGH ITS BASES. THESE ARE OVER EASTERN LAKE SUPERIOR AND NORTHERN ONTARIO. A LARGE RIDGE IS BUILDING OVER THE HIGH PLAINS AND EXTENDING NORTHEAST INTO THE CANADIAN PRAIRIE. ANOTHER LONGWAVE TROUGH DIGGING OVER THE PACIFIC NORTHWEST. SURFACE ANALYSIS DEPICTS A HIGH OVER HUDSON BAY AND ONTARIO. A LOW DEEPENING OVER THE SOUTHWEST SASKATCHEWAN. A STATIONARY FRONT STRETCHES FROM THE CENTRAL PLAINS ACROSS THE OHIO RIVER VALLEY TO NEW ENGLAND. THIS ESSENTIALLY CUTS OFF MOISTURE FROM THE GULF AND OCEAN. THE MID LEVEL RIDGE WILL SHIFT INTO THE NORTHERN PLAINS AND MANITOBA TODAY...WHILE THE LOW CONTINUES TO SPIN OVER QUEBEC AND EASTERN ONTARIO. THE LAKE SUPERIOR SHORTWAVE WILL SHIFT EAST...WHILE THE ONTARIO SHORTWAVE SWEEPS THROUGH WISCONSIN. THE SURFACE HIGH WILL CONTINUE OVER HUDSON BAY AND BLANKETING NORTHERN ONTARIO AND MUCH OF THE UPPER GREAT LAKES. DRY AIR ACCOMPANYING THE SURFACE RIDGE WILL KEEP THE AIR MASS DRY OVER THE AREA. THE MID LEVEL QUEBEC LOW WILL BACK INTO EASTERN ONTARIO WHILE DEEPENING TONIGHT. SHORTWAVES WILL SWEEP AROUND THE BASE OF THIS LOW AND INTO LOWER MICHIGAN AND THE LOWER GREAT LAKES. THE NORTHERN PLAINS RIDGE WILL EDGE INTO EASTERN DAKOTAS. SHORTWAVES WILL BE APPROACHING THE APEX OF THIS RIDGE. THE SURFACE RIDGE WILL EXPAND AND BLANKET THE UPPER GREAT LAKES...UPPER MISSISSIPPI RIVER VALLEY AND ONTARIO...AND MUCH OF HUDSON BAY. CLOUD COVER DUE TO THE WEAK SHORTWAVE AND A NORTHERLY FLOW WILL LIMIT HEATING TODAY. WILL GO WITH TEMPERATURES IN THE MID 70S WHICH WILL BE A LITTLE WARM THAN YESTERDAY. THE MID LEVEL LOW WILL BACK INTO LAKE HURON AS THE RIDGE PUSHES INTO WESTERN ONTARIO AND THE UPPER MISSISSIPPI RIVER VALLEY WEDNESDAY AND WEDNESDAY NIGHT. SHORTWAVES WILL CONTINUE TO PUSH INTO THE RIDGE BUT WILL REMAIN OVER THE DAKOTAS AND MANITOBA. THE SURFACE RIDGE WILL REMAIN OVER ONTARIO AND THE UPPER GREAT LAKES. MEANWHILE THE SURFACE LOW OVER SASKATCHEWAN WILL SHIFT INTO CENTRAL MANITOBA. FRONTOGENESIS WITH THIS LOW WILL PRODUCE A FRONT OVER THE DAKOTAS AND MANITOBA. THE MID LEVEL LOW WILL EDGE INTO WESTERN QUEBEC ON THURSDAY WHILE THE RIDGE CONTINUES OVER CENTRAL ONTARIO WHILE WEAKENING. A WEAK SHORTWAVE MOVING THROUGH THE RIDGE WILL SHIFT INTO THE WESTERN U.P. ANOTHER MID LEVEL WILL DEVELOP OVER NORTHERN MANITOBA. THE SURFACE LOW WILL MOVE TO JUST NORTHEAST OF LAKE WINNIPEG DRAGGING THE COLD FRONT INTO WESTERN MINNESOTA. WEAK SHORTWAVE ENERGY AND ISENTROPIC ASCENT AHEAD OF THE APPROACHING COLD FRONT WILL GENERATE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE FAR WESTERN U.P. LATE ON THURSDAY. THE MID LEVEL CLOSED LOW WILL REMAIN JUST EAST OF HUDSON BAY THURSDAY NIGHT. THE MID LEVEL LOW OVER MANITOBA WILL EDGE INTO WESTERN ONTARIO. THE RIDGE SEPARATING THESE WILL WEAKEN EVEN MORE AS IT SHIFT OVER THE FORECAST AREA. THE COLD FRONT AND ACCOMPANYING LOW WILL EDGE INTO THE UPPER MISSISSIPPI RIVER VALLEY. ISENTROPIC ASCENT AHEAD OF THE FRONT WILL LEAD TO A CHANCE OF SOME SHOWERS AND THUNDERSTORMS DEVELOPING OVER THE AREA. THE LOW OVER MANITOBA WILL MOVE INTO NORTHWEST ONTARIO ON FRIDAY. SHORTWAVES WRAPPING THROUGH THE BASE OF THIS LOW ALONG WITH THE COLD FRONT WHICH WILL MOVE INTO WESTERN LAKE SUPERIOR WILL CONTRIBUTE TO THE CHANCE OF SHOWERS AND THUNDERSTORMS CONTINUING ACROSS THE FORECAST AREA. THE COLD FRONT AND THE SHORTWAVE ENERGY WILL REACH KANJ BY SUNRISE SATURDAY MORNING. DRY AIR WILL MOVE OVER THE AREA BRINGING FAIR WEATHER TO THE AREA FOR WEEK END. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... EXPECT VFR CONDITIONS THIS FCST PD WITH DRY HI PRES BLDG TOWARD LK SUP. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... EXPECT HIGH PRESSURE OVER HUDSON BAY TO BUILD SOUTH OVER LAKE SUPERIOR ON WEDNESDAY AND THEN INTO THE LOWER GREAT LAKES ON THURSDAY. LINGERING FOG OVER LAKE SUPERIOR WILL DISSIPATE THIS MORNING AS DRY AIR ASSOCIATED WITH THE HIGH CONTINUES TO ADVECT OVER THE LAKE. AS THIS HIGH DRIFTS INTO THE MID ATLANTIC STATES ON FRIDAY...A LOW PRESSURE TROUGH WILL MOVE INTO THE UPPER GREAT LAKES. LOOK FOR THIS TROUGH TO DRIFT INTO THE CENTRAL GREAT LAKES ON SATURDAY IN ADVANCE OF HIGH PRESSURE BUILDING TOWARD THE NORTHERN PLAINS. OTHERWISE...WINDS WILL BE NO GREATER THAN 20 KNOTS THROUGH THE END OF THE WEEK. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...JLB DISCUSSION...DLG AVIATION...JLB MARINE...KC mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1140 AM EDT TUE JUL 22 2008 .UPDATE... MAIN FCST CONCERN IS POTENTIAL FOR SHRA/TSRA SOUTH THIS AFTERNOON. THE -SHRA OVER WRN UPPER MI SUPPORTED BY A WEAK SHORTWAVE TROUGH HAVE DIMINISHED AND SLID S OF THE CWA. HOWEVER...FCST AND MODIFIED OBSERVED SOUNDINGS SUGGEST THAT AFTERNOON HEATING WITH TEMPS INTO THE MID 70S AND DEWPOINTS IN THE MID 50S WOULD GIVE MLCAPE VALUES NEAR 500 J/KG. WITH RELATIVELY STEEP 700-500 MB LAPSE RATES NEAR 7 C/KM...SOME ISOLD SHRA/TSRA ARE STILL POSSIBLE OVER THE SOUTH...AWAY FROM STABILIZING INFLUENCE OF FLOW OFF OF LAKE SUPERIOR. WITH ONLY MARGINAL INSTABILITY...FREEZING LEVEL AROUND 11K FT...AND WEAK SHEAR...ONLY SMALL HAIL WOULD BE EXPECTED WITH ANY STRONGER TSRA. .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE ARE THE TEMPERATURES TODAY AND TONIGHT. WATER VAPOR AND RUC SHOWING A CLOSED LOW OVER QUEBEC WITH WEAK SHORTWAVE WRAPPING THROUGH ITS BASES. THESE ARE OVER EASTERN LAKE SUPERIOR AND NORTHERN ONTARIO. A LARGE RIDGE IS BUILDING OVER THE HIGH PLAINS AND EXTENDING NORTHEAST INTO THE CANADIAN PRAIRIE. ANOTHER LONGWAVE TROUGH DIGGING OVER THE PACIFIC NORTHWEST. SURFACE ANALYSIS DEPICTS A HIGH OVER HUDSON BAY AND ONTARIO. A LOW DEEPENING OVER THE SOUTHWEST SASKATCHEWAN. A STATIONARY FRONT STRETCHES FROM THE CENTRAL PLAINS ACROSS THE OHIO RIVER VALLEY TO NEW ENGLAND. THIS ESSENTIALLY CUTS OFF MOISTURE FROM THE GULF AND OCEAN. THE MID LEVEL RIDGE WILL SHIFT INTO THE NORTHERN PLAINS AND MANITOBA TODAY...WHILE THE LOW CONTINUES TO SPIN OVER QUEBEC AND EASTERN ONTARIO. THE LAKE SUPERIOR SHORTWAVE WILL SHIFT EAST...WHILE THE ONTARIO SHORTWAVE SWEEPS THROUGH WISCONSIN. THE SURFACE HIGH WILL CONTINUE OVER HUDSON BAY AND BLANKETING NORTHERN ONTARIO AND MUCH OF THE UPPER GREAT LAKES. DRY AIR ACCOMPANYING THE SURFACE RIDGE WILL KEEP THE AIR MASS DRY OVER THE AREA. THE MID LEVEL QUEBEC LOW WILL BACK INTO EASTERN ONTARIO WHILE DEEPENING TONIGHT. SHORTWAVES WILL SWEEP AROUND THE BASE OF THIS LOW AND INTO LOWER MICHIGAN AND THE LOWER GREAT LAKES. THE NORTHERN PLAINS RIDGE WILL EDGE INTO EASTERN DAKOTAS. SHORTWAVES WILL BE APPROACHING THE APEX OF THIS RIDGE. THE SURFACE RIDGE WILL EXPAND AND BLANKET THE UPPER GREAT LAKES...UPPER MISSISSIPPI RIVER VALLEY AND ONTARIO...AND MUCH OF HUDSON BAY. CLOUD COVER DUE TO THE WEAK SHORTWAVE AND A NORTHERLY FLOW WILL LIMIT HEATING TODAY. WILL GO WITH TEMPERATURES IN THE MID 70S WHICH WILL BE A LITTLE WARM THAN YESTERDAY. THE MID LEVEL LOW WILL BACK INTO LAKE HURON AS THE RIDGE PUSHES INTO WESTERN ONTARIO AND THE UPPER MISSISSIPPI RIVER VALLEY WEDNESDAY AND WEDNESDAY NIGHT. SHORTWAVES WILL CONTINUE TO PUSH INTO THE RIDGE BUT WILL REMAIN OVER THE DAKOTAS AND MANITOBA. THE SURFACE RIDGE WILL REMAIN OVER ONTARIO AND THE UPPER GREAT LAKES. MEANWHILE THE SURFACE LOW OVER SASKATCHEWAN WILL SHIFT INTO CENTRAL MANITOBA. FRONTOGENESIS WITH THIS LOW WILL PRODUCE A FRONT OVER THE DAKOTAS AND MANITOBA. THE MID LEVEL LOW WILL EDGE INTO WESTERN QUEBEC ON THURSDAY WHILE THE RIDGE CONTINUES OVER CENTRAL ONTARIO WHILE WEAKENING. A WEAK SHORTWAVE MOVING THROUGH THE RIDGE WILL SHIFT INTO THE WESTERN U.P. ANOTHER MID LEVEL WILL DEVELOP OVER NORTHERN MANITOBA. THE SURFACE LOW WILL MOVE TO JUST NORTHEAST OF LAKE WINNIPEG DRAGGING THE COLD FRONT INTO WESTERN MINNESOTA. WEAK SHORTWAVE ENERGY AND ISENTROPIC ASCENT AHEAD OF THE APPROACHING COLD FRONT WILL GENERATE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE FAR WESTERN U.P. LATE ON THURSDAY. THE MID LEVEL CLOSED LOW WILL REMAIN JUST EAST OF HUDSON BAY THURSDAY NIGHT. THE MID LEVEL LOW OVER MANITOBA WILL EDGE INTO WESTERN ONTARIO. THE RIDGE SEPARATING THESE WILL WEAKEN EVEN MORE AS IT SHIFT OVER THE FORECAST AREA. THE COLD FRONT AND ACCOMPANYING LOW WILL EDGE INTO THE UPPER MISSISSIPPI RIVER VALLEY. ISENTROPIC ASCENT AHEAD OF THE FRONT WILL LEAD TO A CHANCE OF SOME SHOWERS AND THUNDERSTORMS DEVELOPING OVER THE AREA. THE LOW OVER MANITOBA WILL MOVE INTO NORTHWEST ONTARIO ON FRIDAY. SHORTWAVES WRAPPING THROUGH THE BASE OF THIS LOW ALONG WITH THE COLD FRONT WHICH WILL MOVE INTO WESTERN LAKE SUPERIOR WILL CONTRIBUTE TO THE CHANCE OF SHOWERS AND THUNDERSTORMS CONTINUING ACROSS THE FORECAST AREA. THE COLD FRONT AND THE SHORTWAVE ENERGY WILL REACH KANJ BY SUNRISE SATURDAY MORNING. DRY AIR WILL MOVE OVER THE AREA BRINGING FAIR WEATHER TO THE AREA FOR WEEK END. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... ALTHOUGH THERE WL BE SOME MID CLDS ARND THIS MRNG AND SOME DIURNAL CU THIS AFTN...EXPECT VFR CONDITIONS THIS FCST PD WITH DRY HI PRES BLDG TOWARD LK SUP. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... EXPECT HIGH PRESSURE OVER HUDSON BAY TO BUILD SOUTH OVER LAKE SUPERIOR ON WEDNESDAY AND THEN INTO THE LOWER GREAT LAKES ON THURSDAY. LINGERING FOG OVER LAKE SUPERIOR WILL DISSIPATE THIS MORNING AS DRY AIR ASSOCIATED WITH THE HIGH CONTINUES TO ADVECT OVER THE LAKE. AS THIS HIGH DRIFTS INTO THE MID ATLANTIC STATES ON FRIDAY...A LOW PRESSURE TROUGH WILL MOVE INTO THE UPPER GREAT LAKES. LOOK FOR THIS TROUGH TO DRIFT INTO THE CENTRAL GREAT LAKES ON SATURDAY IN ADVANCE OF HIGH PRESSURE BUILDING TOWARD THE NORTHERN PLAINS. OTHERWISE...WINDS WILL BE NO GREATER THAN 20 KNOTS THROUGH THE END OF THE WEEK. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...DLG AVIATION...KC MARINE...KC mi AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE MARQUETTE MI 720 AM EDT TUE JUL 22 2008 UPDATED FOR 12Z TAF ISSUANCE .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE ARE THE TEMPERATURES TODAY AND TONIGHT. WATER VAPOR AND RUC SHOWING A CLOSED LOW OVER QUEBEC WITH WEAK SHORTWAVE WRAPPING THROUGH ITS BASES. THESE ARE OVER EASTERN LAKE SUPERIOR AND NORTHERN ONTARIO. A LARGE RIDGE IS BUILDING OVER THE HIGH PLAINS AND EXTENDING NORTHEAST INTO THE CANADIAN PRAIRIE. ANOTHER LONGWAVE TROUGH DIGGING OVER THE PACIFIC NORTHWEST. SURFACE ANALYSIS DEPICTS A HIGH OVER HUDSON BAY AND ONTARIO. A LOW DEEPENING OVER THE SOUTHWEST SASKATCHEWAN. A STATIONARY FRONT STRETCHES FROM THE CENTRAL PLAINS ACROSS THE OHIO RIVER VALLEY TO NEW ENGLAND. THIS ESSENTIALLY CUTS OFF MOISTURE FROM THE GULF AND OCEAN. THE MID LEVEL RIDGE WILL SHIFT INTO THE NORTHERN PLAINS AND MANITOBA TODAY...WHILE THE LOW CONTINUES TO SPIN OVER QUEBEC AND EASTERN ONTARIO. THE LAKE SUPERIOR SHORTWAVE WILL SHIFT EAST...WHILE THE ONTARIO SHORTWAVE SWEEPS THROUGH WISCONSIN. THE SURFACE HIGH WILL CONTINUE OVER HUDSON BAY AND BLANKETING NORTHERN ONTARIO AND MUCH OF THE UPPER GREAT LAKES. DRY AIR ACCOMPANYING THE SURFACE RIDGE WILL KEEP THE AIR MASS DRY OVER THE AREA. THE MID LEVEL QUEBEC LOW WILL BACK INTO EASTERN ONTARIO WHILE DEEPENING TONIGHT. SHORTWAVES WILL SWEEP AROUND THE BASE OF THIS LOW AND INTO LOWER MICHIGAN AND THE LOWER GREAT LAKES. THE NORTHERN PLAINS RIDGE WILL EDGE INTO EASTERN DAKOTAS. SHORTWAVES WILL BE APPROACHING THE APEX OF THIS RIDGE. THE SURFACE RIDGE WILL EXPAND AND BLANKET THE UPPER GREAT LAKES...UPPER MISSISSIPPI RIVER VALLEY AND ONTARIO...AND MUCH OF HUDSON BAY. CLOUD COVER DUE TO THE WEAK SHORTWAVE AND A NORTHERLY FLOW WILL LIMIT HEATING TODAY. WILL GO WITH TEMPERATURES IN THE MID 70S WHICH WILL BE A LITTLE WARM THAN YESTERDAY. THE MID LEVEL LOW WILL BACK INTO LAKE HURON AS THE RIDGE PUSHES INTO WESTERN ONTARIO AND THE UPPER MISSISSIPPI RIVER VALLEY WEDNESDAY AND WEDNESDAY NIGHT. SHORTWAVES WILL CONTINUE TO PUSH INTO THE RIDGE BUT WILL REMAIN OVER THE DAKOTAS AND MANITOBA. THE SURFACE RIDGE WILL REMAIN OVER ONTARIO AND THE UPPER GREAT LAKES. MEANWHILE THE SURFACE LOW OVER SASKATCHEWAN WILL SHIFT INTO CENTRAL MANITOBA. FRONTOGENESIS WITH THIS LOW WILL PRODUCE A FRONT OVER THE DAKOTAS AND MANITOBA. THE MID LEVEL LOW WILL EDGE INTO WESTERN QUEBEC ON THURSDAY WHILE THE RIDGE CONTINUES OVER CENTRAL ONTARIO WHILE WEAKENING. A WEAK SHORTWAVE MOVING THROUGH THE RIDGE WILL SHIFT INTO THE WESTERN U.P. ANOTHER MID LEVEL WILL DEVELOP OVER NORTHERN MANITOBA. THE SURFACE LOW WILL MOVE TO JUST NORTHEAST OF LAKE WINNIPEG DRAGGING THE COLD FRONT INTO WESTERN MINNESOTA. WEAK SHORTWAVE ENERGY AND ISENTROPIC ASCENT AHEAD OF THE APPROACHING COLD FRONT WILL GENERATE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE FAR WESTERN U.P. LATE ON THURSDAY. THE MID LEVEL CLOSED LOW WILL REMAIN JUST EAST OF HUDSON BAY THURSDAY NIGHT. THE MID LEVEL LOW OVER MANITOBA WILL EDGE INTO WESTERN ONTARIO. THE RIDGE SEPARATING THESE WILL WEAKEN EVEN MORE AS IT SHIFT OVER THE FORECAST AREA. THE COLD FRONT AND ACCOMPANYING LOW WILL EDGE INTO THE UPPER MISSISSIPPI RIVER VALLEY. ISENTROPIC ASCENT AHEAD OF THE FRONT WILL LEAD TO A CHANCE OF SOME SHOWERS AND THUNDERSTORMS DEVELOPING OVER THE AREA. THE LOW OVER MANITOBA WILL MOVE INTO NORTHWEST ONTARIO ON FRIDAY. SHORTWAVES WRAPPING THROUGH THE BASE OF THIS LOW ALONG WITH THE COLD FRONT WHICH WILL MOVE INTO WESTERN LAKE SUPERIOR WILL CONTRIBUTE TO THE CHANCE OF SHOWERS AND THUNDERSTORMS CONTINUING ACROSS THE FORECAST AREA. THE COLD FRONT AND THE SHORTWAVE ENERGY WILL REACH KANJ BY SUNRISE SATURDAY MORNING. DRY AIR WILL MOVE OVER THE AREA BRINGING FAIR WEATHER TO THE AREA FOR WEEK END. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... ALTHOUGH THERE WL BE SOME MID CLDS ARND THIS MRNG AND SOME DIURNAL CU THIS AFTN...EXPECT VFR CONDITIONS THIS FCST PD WITH DRY HI PRES BLDG TOWARD LK SUP. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... EXPECT HIGH PRESSURE OVER HUDSON BAY TO BUILD SOUTH OVER LAKE SUPERIOR ON WEDNESDAY AND THEN INTO THE LOWER GREAT LAKES ON THURSDAY. LINGERING FOG OVER LAKE SUPERIOR WILL DISSIPATE THIS MORNING AS DRY AIR ASSOCIATED WITH THE HIGH CONTINUES TO ADVECT OVER THE LAKE. AS THIS HIGH DRIFTS INTO THE MID ATLANTIC STATES ON FRIDAY...A LOW PRESSURE TROUGH WILL MOVE INTO THE UPPER GREAT LAKES. LOOK FOR THIS TROUGH TO DRIFT INTO THE CENTRAL GREAT LAKES ON SATURDAY IN ADVANCE OF HIGH PRESSURE BUILDING TOWARD THE NORTHERN PLAINS. OTHERWISE...WINDS WILL BE NO GREATER THAN 20 KNOTS THROUGH THE END OF THE WEEK. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...DLG AVIATION...KC MARINE...KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 345 AM EDT TUE JUL 22 2008 .DISCUSSION... THE MAIN CONCERN WITH THIS FORECAST PACKAGE ARE THE TEMPERATURES TODAY AND TONIGHT. WATER VAPOR AND RUC SHOWING A CLOSED LOW OVER QUEBEC WITH WEAK SHORTWAVE WRAPPING THROUGH ITS BASES. THESE ARE OVER EASTERN LAKE SUPERIOR AND NORTHERN ONTARIO. A LARGE RIDGE IS BUILDING OVER THE HIGH PLAINS AND EXTENDING NORTHEAST INTO THE CANADIAN PRAIRIE. ANOTHER LONGWAVE TROUGH DIGGING OVER THE PACIFIC NORTHWEST. SURFACE ANALYSIS DEPICTS A HIGH OVER HUDSON BAY AND ONTARIO. A LOW DEEPENING OVER THE SOUTHWEST SASKATCHEWAN. A STATIONARY FRONT STRETCHES FROM THE CENTRAL PLAINS ACROSS THE OHIO RIVER VALLEY TO NEW ENGLAND. THIS ESSENTIALLY CUTS OFF MOISTURE FROM THE GULF AND OCEAN. THE MID LEVEL RIDGE WILL SHIFT INTO THE NORTHERN PLAINS AND MANITOBA TODAY...WHILE THE LOW CONTINUES TO SPIN OVER QUEBEC AND EASTERN ONTARIO. THE LAKE SUPERIOR SHORTWAVE WILL SHIFT EAST...WHILE THE ONTARIO SHORTWAVE SWEEPS THROUGH WISCONSIN. THE SURFACE HIGH WILL CONTINUE OVER HUDSON BAY AND BLANKETING NORTHERN ONTARIO AND MUCH OF THE UPPER GREAT LAKES. DRY AIR ACCOMPANYING THE SURFACE RIDGE WILL KEEP THE AIR MASS DRY OVER THE AREA. THE MID LEVEL QUEBEC LOW WILL BACK INTO EASTERN ONTARIO WHILE DEEPENING TONIGHT. SHORTWAVES WILL SWEEP AROUND THE BASE OF THIS LOW AND INTO LOWER MICHIGAN AND THE LOWER GREAT LAKES. THE NORTHERN PLAINS RIDGE WILL EDGE INTO EASTERN DAKOTAS. SHORTWAVES WILL BE APPROACHING THE APEX OF THIS RIDGE. THE SURFACE RIDGE WILL EXPAND AND BLANKET THE UPPER GREAT LAKES...UPPER MISSISSIPPI RIVER VALLEY AND ONTARIO...AND MUCH OF HUDSON BAY. CLOUD COVER DUE TO THE WEAK SHORTWAVE AND A NORTHERLY FLOW WILL LIMIT HEATING TODAY. WILL GO WITH TEMPERATURES IN THE MID 70S WHICH WILL BE A LITTLE WARM THAN YESTERDAY. THE MID LEVEL LOW WILL BACK INTO LAKE HURON AS THE RIDGE PUSHES INTO WESTERN ONTARIO AND THE UPPER MISSISSIPPI RIVER VALLEY WEDNESDAY AND WEDNESDAY NIGHT. SHORTWAVES WILL CONTINUE TO PUSH INTO THE RIDGE BUT WILL REMAIN OVER THE DAKOTAS AND MANITOBA. THE SURFACE RIDGE WILL REMAIN OVER ONTARIO AND THE UPPER GREAT LAKES. MEANWHILE THE SURFACE LOW OVER SASKATCHEWAN WILL SHIFT INTO CENTRAL MANITOBA. FRONTOGENESIS WITH THIS LOW WILL PRODUCE A FRONT OVER THE DAKOTAS AND MANITOBA. THE MID LEVEL LOW WILL EDGE INTO WESTERN QUEBEC ON THURSDAY WHILE THE RIDGE CONTINUES OVER CENTRAL ONTARIO WHILE WEAKENING. A WEAK SHORTWAVE MOVING THROUGH THE RIDGE WILL SHIFT INTO THE WESTERN U.P. ANOTHER MID LEVEL WILL DEVELOP OVER NORTHERN MANITOBA. THE SURFACE LOW WILL MOVE TO JUST NORTHEAST OF LAKE WINNIPEG DRAGGING THE COLD FRONT INTO WESTERN MINNESOTA. WEAK SHORTWAVE ENERGY AND ISENTROPIC ASCENT AHEAD OF THE APPROACHING COLD FRONT WILL GENERATE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE FAR WESTERN U.P. LATE ON THURSDAY. THE MID LEVEL CLOSED LOW WILL REMAIN JUST EAST OF HUDSON BAY THURSDAY NIGHT. THE MID LEVEL LOW OVER MANITOBA WILL EDGE INTO WESTERN ONTARIO. THE RIDGE SEPARATING THESE WILL WEAKEN EVEN MORE AS IT SHIFT OVER THE FORECAST AREA. THE COLD FRONT AND ACCOMPANYING LOW WILL EDGE INTO THE UPPER MISSISSIPPI RIVER VALLEY. ISENTROPIC ASCENT AHEAD OF THE FRONT WILL LEAD TO A CHANCE OF SOME SHOWERS AND THUNDERSTORMS DEVELOPING OVER THE AREA. THE LOW OVER MANITOBA WILL MOVE INTO NORTHWEST ONTARIO ON FRIDAY. SHORTWAVES WRAPPING THROUGH THE BASE OF THIS LOW ALONG WITH THE COLD FRONT WHICH WILL MOVE INTO WESTERN LAKE SUPERIOR WILL CONTRIBUTE TO THE CHANCE OF SHOWERS AND THUNDERSTORMS CONTINUING ACROSS THE FORECAST AREA. THE COLD FRONT AND THE SHORTWAVE ENERGY WILL REACH KANJ BY SUNRISE SATURDAY MORNING. DRY AIR WILL MOVE OVER THE AREA BRINGING FAIR WEATHER TO THE AREA FOR WEEK END. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT THE COMBINATION OF SOME LLVL DRY ADVCTN AND MID CLD TO REDUCE THE CHCS FOR SGNFT RADIATION FOG TNGT...BUT SOME FOG/ST MAY FORM OVERNGT...ESPECIALLY AT SAW WITH MORE FVRBL UPSLOPE NLY WIND COMPONENT AND MORE RECENT RA. ANY FOG/ST WL BURN OFF BY MID MRNG... WITH VFR CONDITIONS PREDOMINATING TDAY AS DRY HI PRES BLDS TOWARD LK SUP. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... EXPECT HIGH PRESSURE OVER HUDSON BAY TO BUILD SOUTH OVER LAKE SUPERIOR ON WEDNESDAY AND THEN INTO THE LOWER GREAT LAKES ON THURSDAY. LINGERING FOG OVER LAKE SUPERIOR WILL DISSIPATE THIS MORNING AS DRY AIR ASSOCIATED WITH THE HIGH CONTINUES TO ADVECT OVER THE LAKE. AS THIS HIGH DRIFTS INTO THE MID ATLANTIC STATES ON FRIDAY...A LOW PRESSURE TROUGH WILL MOVE INTO THE UPPER GREAT LAKES. LOOK FOR THIS TROUGH TO DRIFT INTO THE CENTRAL GREAT LAKES ON SATURDAY IN ADVANCE OF HIGH PRESSURE BUILDING TOWARD THE NORTHERN PLAINS. OTHERWISE...WINDS WILL BE NO GREATER THAN 20 KNOTS THROUGH THE END OF THE WEEK. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...DLG AVIATION...KC MARINE...KC mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DULUTH MN 932 PM CDT WED JUL 23 2008 .UPDATE... FORECAST GENERALLY PROGRESSING AS EXPECTED. DID MAKE SOME SLIGHT TWEAKS AND ADJUSTMENTS...MOST NOTABLY TO THE OVERNIGHT POPS. IT APPEARS THE NAM AND RUC HAVE PERFORMED THE BEST WITH THE SHOWERS AND THUNDERSTORMS OVER WESTERN MINNESOTA AND THE EASTERN DAKOTAS THIS EVENING. LIGHT RAIN WAS REPORTED AS FAR EAST AS KBRD AT 02Z. FOR THE REST OF TONIGHT...THE BEST CHANCE FOR POPS WILL BE CONFINED TO OUR NORTHWEST ZONES...CLOSEST TO THE SHORTWAVE...WHERE THE LOW LEVEL JET IS STRONGEST AND THE 850MB MOISTURE ADVECTION IS GREATEST. PLENTY OF LOW AND MID LEVEL DRY AIR SHOULD ALSO LIMIT PROGRESSION EASTWARD OVERNIGHT...ALTHOUGH DID LEAVE SLIGHT POPS IN FOR LATE TONIGHT AS FAR EAST AS THE TWIN PORTS VICINITY. UPDATED PRODUCTS TO BE SENT SHORTLY AFTER 10PM. && .PREV DISCUSSION... /ISSUED 307 PM CDT WED JUL 23 2008/ .DISCUSSION...CURRENT SURFACE ANALYSIS DEPICTS 1024 MB SURFACE HIGH SHIFTING EAST...AND IS CURRENTLY NORTH AND EAST OF THE ARROWHEAD. RETURN SOUTHEASTERLY FLOW HAS DEVELOPED OVER THE WEST AND CENTRAL CWA. WAA HAS NOT PICKED UP IN EARNEST YET. ALOFT...A 300H 85 KT PLUS JET IS DIVING SOUTH THROUGH CENTRAL AND EASTERN WISCONSIN. CURRENT WATER VAPOR IMAGERY DEPICTS A SERIES OF SHORTWAVES RIDING NORTHEAST ALONG THE RIDGE AXIS INTO MANITOBA...AND ANOTHER STRONGER WAVE BACK NORTHWEST MONTANA. ANOTHER WAVE IS MOVING EAST THROUGH SOUTH DAKOTA. FORECAST FOCUS ON CONVECTIVE ACTIVITY OVERNIGHT AND INTO THURSDAY...AND AGAIN ON FRIDAY. MODELS HANDLING PIECES OF ENERGY DIFFERENTLY...WITH A LARGE RIDGE IN PLACE OVER THE AREA. TIMING AND PLACEMENT ISSUES ARE A CONCERN. THE GFS IS STILL A BIT QUICKER THAN THE NAM/ECMWF/SREF. THE NAM/GFS BOTH DEPICT THE SHORTWAVE IN MONTANA MOVING NORTH INTO CANADA ALONG WITH THE OTHER SMALLER SHORTWAVES OUT AHEAD OF IT. THE GFS PUSHES THE WAVE IN SOUTH DAKOTA SOUTHEAST INTO IOWA. THE NAM PUSHES THIS WAVE ACROSS THE WESTERN CWA...BEFORE PUSHING THE WAVE SOUTHEAST. MODELS INDICATING A 30-35KT 850H LLJ WILL SHIFT WEST TONIGHT AND VEER TO THE SW AND THEN WEAKEN DURING THE DAY AS IT MOVES EAST...IMPINGING ON THE 850H THERMAL BOUNDARY. THE NAM PAINTS THIS AXIS OF CONVERGENCE JUST TO THE WEST OF THE CWA BY 6Z. WITH THE LLJ VEERING...A DECENT AREA OF WAA AND 850H 2-D FGEN WILL SETUP. THE NAM THEN SHIFTS THIS AXIS TO THE SOUTHEAST ALONG WITH THE 500H VORT MAX...BRINGING THE BEST FORCING WITH IT. AREAS SOUTH AND EAST OF THE TWIN PORTS WILL STILL BE UNDER AN AREA OF DECENT WAA DURING THE DAY. THE 0Z NAM 4KM WRF REFLECTIVITY DOES NOT BRING ANY PRECIPITATION INTO THE CWA BEFORE 6Z...AND THEN DRAGS THE BULK OF THE ACTIVITY SOUTH. THE REST OF THE ACTIVITY ASSOCIATED WITH THE NORTHERN BRANCH OF THE SYSTEM...THE WAVE EMANATING OUT OF MONTANA RIDING THE TOP OF THE RIDGE...MOSTLY HEADS NORTH OF THE BORDER. THERE IS DECENT FORCING WITH THIS WAVE...BUT THE NAM HAS THIS PRECIPITATION BREAKING UP IN THE IRON RANGE/ARROWHEAD. THE GFS 0Z/6Z/12Z GFS AS WELL AS THE 12Z ECMWF...ON THE OTHER HAND... BREAK DOWN THE 500H RIDGE QUICKER...AND DRIVE A VORT MAX RIGHT THROUGH THE TWIN PORTS. CONFIDENCE IS HIGHEST IN THE SOUTHERN AND WESTERN CWA...AND DEPICTED IN THE POP GRIDS...WITH MORE UNCERTAINTY ON THE NORTHERN TRACK. MUCAPE IS MARGINAL ON THURSDAY...BULK SHEAR IS DECENT...AROUND 35 TO 40 KT IN THE SOUTH AND EAST. MOISTURE IS DECENT AS WELL..PARTICULARLY SOUTH AND WEST...ALTHOUGH LAPSE RATES ARE A BIT WEAKER. ON FRIDAY...HPC FAVORS A THE NAM...GIVEN SUPPORT FROM THE 0Z ECMWF AND GEM GLOBAL. WITH THE GFS BEING A BIT MORE AMPLIFIED. IN GENERAL...WEST TO NORTHWEST FLOW ALOFT...WITH A CLOSED UPPER LEVEL LOW AS PER THE 12Z GFS...AND 500H TEMPS OF -10 TO -13C...WILL BRING THE CHANCE FOR STRONG TO SEVERE THUNDERSTORMS ON FRIDAY. ADDITIONALLY...SURFACE-850 CONVERGENCE WILL BE MORE IMPRESSIVE...WITH A COLD FRONT PUSHING SOUTHEAST THROUGH THE CWA..COLD 700H TEMPS AROUND 0 TO -2C ELIMINATING ANY CIN IN THE AFTERNOON...AND IMPRESSIVE LO LEVEL LAPSE RATES. A FEW STATIONS...AS PER NAM BUFR SOUNDINGS...ARE SHOWING A WEAK 600H CAP...BUT BULK SHEAR OF 45-50KT...A DECENT TONGUE OF MUCAPE...SURFACE MIXING RATIOS OF 14-15 G/KG...SHOULD SUPPORT THE POTENTIAL FOR STRONG THUNDERSTORMS. LONG TERM...A QUIET WEEKEND IS SHAPING UP...WITH HIGH PRESSURE IN CONTROL. A DISTURBANCE WILL PUSH ALONG THE BORDERLAND ON SATURDAY...BRINGING THE CHANCE OF SHRA/TSRA...AND THEN HIGH PRESSURE WILL BE IN CONTROL THROUGH MONDAY/EARLY TUESDAY. TEMPERATURES WILL REMAIN NEAR NORMAL...WITH UPPER 70S AND LOW 80S FOR DAYTIME HIGHS. ANOTHER DISTURBANCE MOVES THROUGH ON TUESDAY/WEDNESDAY. AVIATION...HIGH PRESSURE WILL BRING VFR CONDITIONS FOR THE EVENING HOURS...BUT AN AREA OF LOW PRESSURE IN THE DAKOTAS WILL CONTINUE TO ADVANCE EASTWARD OVERNIGHT. THIS SYSTEM WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS INTO THE TAF SITES AS THE NIGHT WEARS ON. THE FIRST PLACES TO HAVE THE PRECIPITATION POTENTIAL WILL BE KINL AND KBRD...STARTING AROUND 06Z. THE SHOWERS AND THUNDERSTORMS MAY CAUSE VISIBILITIES AND CIGS TO DROP TO THE MVFR CATEGORY AT TIMES FOR THE LAST HALF OF THE NIGHT AND THURSDAY MORNING. && POINT TEMPS/POPS... DLH 55 73 61 80 / 20 30 20 30 INL 57 77 58 78 / 40 30 20 20 BRD 61 82 63 83 / 40 30 20 20 HYR 54 77 61 83 / 10 30 20 30 ASX 53 72 60 81 / 10 20 20 30 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ BETTWY mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 1007 AM CDT WED JUL 23 2008 .UPDATE... INCREASED SKY COVER MAINLY IN THE WESTERN CWA. REST OF THE FORECAST MOSTLY UNCHANGED. && .DISCUSSION... CIRRUS BLOWOFF FROM THUNDERSTORMS IN THE DAKOTAS WILL FIGHT AGAINST STRONG RIDGE OVER THE CWA TODAY. LATEST IR IMAGERY SHOWS CLOUD TOP TEMPERATURES WARMING IN THE DAKOTAS...AND LIGHTNING ACTIVITY IS DIMINISHING...INDICATING THESE STORMS ARE WEAKENING. VISIBLE SATELLITE IMAGERY DEPICTS SOME OF THE CIRRUS IS INVADING THE WESTERN CWA. LATEST NAM/RUC GUIDANCE INDICATES THIS CLOUD COVER WILL MAKE SOME EASTERN PROGRESSION THIS AFTERNOON FROM WESTERN MN...BUT MUCH OF THE CLOUD COVER WILL BREAK UP AS IT HITS THE RIDGE. CLOUD COVER WILL INCREASE OVERNIGHT AS THE RIDGE SLIDES EAST. FORECAST ATTENTION WILL SHIFT TO POTENTIAL CONVECTIVE ACTIVITY OVERNIGHT. && .PREV DISCUSSION... /ISSUED 315 AM CDT WED JUL 23 2008/ DISCUSSION...MAIN FORECAST FOCUS IS CONVECTIVE CHANCES FOR LATE TONIGHT THROUGH THURSDAY NIGHT. EARLY MORNING SURFACE ANALYSIS SHOWS HIGH PRESSURE CENTERED OVER NW ONTARIO...WITH AXIS STRETCHING ACROSS EASTERN DLH FA. QUIET DAY ON TAP FOR THE NORTHLAND...WITH LARGE SCALE SUBSIDENCE AS UPPER RIDGE NUDGES OVERHEAD. WILL ALSO SEE SOME WEAK WAA TODAY...AS SOUTHERLY WINDS INCREASE BEHIND DEPARTING HIGH PRESSURE. FORECAST SOUNDINGS SHOW DRY AIRMASS IN PLACE FOR TODAY...WITH JUST SOME CIRRUS MOVING OVERHEAD THIS AFTERNOON FROM THE STORM SYSTEM TO THE WEST. HIGH TEMPERATURES WILL BE SEASONABLE TODAY...EXCEPT FOR EXPECTED LAKE BREEZE...KEEPING COOLER TEMPS LAKESIDE. TONIGHT...RETURN FLOW WILL INCREASE AS SHORT WAVE APPROACHES FROM THE WEST. SOME TIMING DIFFERENCES IN THE MODELS WITH THIS WAVE...BUT LOOKS LIKE SCT CONV SHOULD PUSH INTO THE WESTERN ZONES LATE TONIGHT AS 30KT LLJ VEERS. LIMITED MOISTURE RETURN AND WEAK INSTABILITY SHOULD HINDER WIDESPREAD STRONG CONVECTION WITH THIS WAVE AS IT PUSHES SLOWLY EAST THROUGH THURSDAY. THEREFORE MAINTAINED LOW CHANCE POPS ATTM. THURSDAY NIGHT AND FRIDAY...WILL SEE ANOTHER SHORT WAVE DIVE SOUTHEAST AS UPPER FLOW PATTERN BECOMES MORE NORTHWESTERLY...AND SECONDARY COLD FRONT PUSHES THROUGH THE FA. NARROW AXIS OF INSTABILITY AND SUFFICIENT DEEP LAYER SHEAR SHOULD RESULT IN ISOLD TO SCT CONVECTION WITH THIS SHORT WAVE AS WELL. FOR THIS WEEKEND...DRIER CONDITIONS WILL PREVAIL WITH NORTHWEST FLOW ALOFT. DRY HIGH PRESSURE WILL BUILD INTO THE REGION FRIDAY NIGHT AND CONTINUE TO INFLUENCE THE NORTHLAND WEATHER THROUGH MONDAY. TEMPERATURES LOOK TO REMAIN SEASONABLE THROUGH EARLY NEXT WEEK. AVIATION...AREAS OF RADIATIONAL FOG AND LOCAL MVFR/IFR CONDITIONS CAN BE EXPECTED THROUGH 12Z TODAY...OTHERWISE HIGH PRESSURE WILL BEGIN PUSHING EAST OF THE AREA TODAY...WITH VFR CONDITIONS PREVAILING THROUGH THIS EVENING. WHILE A FEW CUMULUS MAY DEVELOP...THE ENTIRE AREA WILL EXPERIENCE A GRADUAL INCREASE IN HIGH AND MID LEVEL CLOUDS WITH A RETURN FLOW AND MODEST WARM AIR ADVECTION IN ADVANCE OF AN APPROACHING SHORTWAVE. PRECIPITATION CHANCES WILL REMAIN WEST OF OUR REGION UNTIL AFTER 6Z THURSDAY. && POINT TEMPS/POPS... DLH 74 54 72 56 / 0 20 30 20 INL 80 56 79 58 / 10 30 30 20 BRD 81 61 80 62 / 10 30 30 20 HYR 80 48 79 61 / 0 10 30 20 ASX 77 49 74 59 / 0 10 30 20 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ KD/DAP mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 255 AM CDT TUE JUL 22 2008 .DISCUSSION... STATIONARY SURFACE BOUNDARY WAS LOCATED JUST SOUTH OF THE NEBRASKA BORDER INTO NORTHERN MISSOURI THIS MORNING. MAIN AREA OF CONVECTION WAS LOCATED OVER NORTHEAST MISSOURI BUT ISOLATED CELLS HAVE BEEN DEVELOPING UPSTREAM JUST EAST OF KICL. SATELLITE SHOWING INCREASING MID CLOUDS FROM NEAR KICL TO NW OF KOMA AT 07Z. THIS AREA LINES UP WITH 00Z GFS QPF AT 12Z AND WITH 06Z RUC 850-700MB THETA-E AXIS WHICH GRADUALLY GETS PUSHED SOUTH THROUGH 18Z. WILL CARRY SOME LOW POPS THIS MORNING FOR SOUTHEASTERN PARTS OF THE CWA IN ASSOCIATION WITH THE THETA-E AXIS. AFTER THIS MORNING LOOKS LIKE AREA STAYS NORTH AND EAST OF THE MOISTURE AXIS FOR THE AFTERNOON AND TONIGHT AS SURFACE HIGH OVER THE UPPER GREAT LAKES BUILDS INTO THE MID MISSISSIPPI VALLEY. HIGH SHIFTS EAST ON WEDNESDAY WITH CHANCE POPS RETURNING TO THE AREA WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. BOTH NAM AND GFS FOCUS AN MCS NEAR THE NEBRASKA SOUTH DAKOTA BORDER LATE WEDNESDAY NIGHT INTO THURSDAY MORNING WITH NAM FASTER IN MOVING IT EAST OF THE AREA. GENERALLY BROADBRUSHED POPS DUE TO UNCERTAINTY IN TIMING. TEMPERATURES NOT AS HOT FOR MOST OF THE AREA TODAY AND WEDNESDAY BUT DO RETURN THURSDAY THROUGH SATURDAY AS UPPER RIDGE REBUILDS OVER THE WEST. NO CHANGE TO THE EXTENDED PERIOD AT THIS TIME. && .AVIATION... FOR TAF SITES KOMA/KLNK/KOFK THRU 23/12Z FRONTAL BOUNDARY SUPPORTING CONVECTION HAS SHIFTED SOUTH OF EASTERN NEBRASKA TAF SITES...HOWEVER A BAND OF MID LEVEL MOISTURE AND RESIDUAL INSTABILITY MAY SPARK SCATTERED SHOWERS OR STORMS THROUGH 15Z IN EASTERN NEBRASKA. THESE SHOULD REMAIN ISOLATED AND NOT LIKELY TO DIRECTLY AFFECT TAF SITES. LOW LEVEL MOISTURE WILL BE SLOW TO LEAVE THE AREA...SO AREAS OF MVFR FOG ARE POSSIBLE IN THE FEW HOURS JUST BEFORE AND AFTER SUNRISE BOTH TUESDAY MORNING AND WEDNESDAY MORNING. OTHERWISE VFR CONDITIONS WITH ONLY SCATTERED AFTERNOON CUMULUS AND PASSING MID/HIGH CLOUDS EXPECTED. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ FOBERT/DERGAN ne AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE ALBUQUERQUE NM 315 PM MDT TUE JUL 22 2008 .DISCUSSION... LATEST RUC80 UPPER AIR ANALYSIS INDICATES TWO HIGH CENTROIDS OVER THE SOUTHWESTERN UNITED STATES. ONE CENTER IS POSITIONED AT THE CA/ AZ/BAJA OF CA TRIPLE POINT...WHILE THE OTHER IS CENTERED JUST EAST OF THE OK/TX PANHANDLES. THIS HAS ALLOWED FOR AN UPR LEVEL WEAKNESS ACROSS THE STATE OF NEW MEXICO. SHOWERS AND THUNDERSTORMS WILL BE MOST NUMEROUS OVER THE CENTRAL AND WRN ZONES...PARTICULARLY WITHIN THE 850-700MB THETA-E RIDGE AXIS. AS MENTIONED IN THE PREVIOUS AFD... A FEW THUNDERSTORMS WILL DEVELOP IN THE HIGH PLAINS...BUT STEERING FLOW WILL CURTAIL ITS EASTWARD PROGRESSION. AS TYPICAL THIS TIME OF YEAR...LOCALIZED FLOODING IS POSSIBLE WITH SLOW MOVING STORMS. MOST OF THE ACTIVITY WILL DIMINISH BEFORE THE MIDNIGHT HOUR...HOWEVER A FEW LINGERING STORMS COULD SURVIVE INTO THE EARLY MORNING. SIMILAR SITUATION IS EXPECTED FOR WEDNESDAY...WITH THE BEST THREAT FOR PCPN TO OCCUR OVER THE CENTRAL AND WRN ZONES. SOME ACTIVITY MAY TRY TO SQUEAK INTO THE NE PLAINS AS THE THETA-E RIDGE AXIS TILTS A BIT. TEMPERATURES WILL BE WARMEST OVER THE ERN PLAINS AS PCPN/CLOUD COVER LIMITS THE AMOUNT OF INCOMING SOLAR IN THE WEST. ALL EYES SHIFT TO THE GULF OF MEXICO FOR THE LATTER PORTION OF THE WEEK AS TROPICAL STORM...SOON TO BE HURRICANE...DOLLY APPROACHES SRN TEXAS. THE NAM80 HAS BEEN CONSISTENTLY ONE OF THE MORE NRN SOLUTIONS AND PROVIDES SOME IMPACT IN THE FORM OF INCREASED QPF ACROSS SRN NM. OF INTEREST...THREE OUT OF 13 HURRICANE MODELS TRACK THE REMAINS OF THE TROPICAL SYSTEM UP THE RIO GRANDE INTO SE NM. THOUGH UNLIKELY... IT BEARS WATCHING WHETHER THIS FEATURE WILL IMPACT THE CWA. ATTM... IT APPEARS THE GFDI MODEL AND TPC TRACK LOOK THE MOST PLAUSIBLE. IN GENERAL...THE BIGGEST PLAYER WILL BE THE POSITION OF THE UPPER HIGH. IN CONTRAST...THE GFS PLACES THE HIGH ON FRI OVER ERN NM/WRN TX... BLOCKING THE STATE FROM AN INTRUSION OF DEEP MOISTURE. MEANWHILE... THE ECMWF PLACES THE HIGH NEAR THE DALLAS AREA...ALLOWING FOR A S/SE COMPONENT ACROSS SRN NM. BY THE WEEKEND...THE GFS SHIFTS THE UPPER HIGH TO CENTRAL NM...SHUNTING THE REMAINS INTO THE EASTERN PACIFIC. THE ECMWF IS LESS AGGRESSIVE AND SHIFTS THE UPR HIGH ONLY TO CENTRAL TX...OPENING THE DOOR FOR TROPICAL MOISTURE TO MIGRATE INTO CENTRAL AZ. BASED ON THE AFOREMENTIONED UNCERTAINTY...WILL NOT MAKE SWEEPING CHANGES TO THE INHERITED MID/LONG RANGE FORECAST. DPORTER && .AVIATION... SCATTERED SHOWERS AND THUNDERSTORMS WILL MAINLY AFFECT THE WESTERN TWO THIRDS OF THE FORECAST AREA THROUGH THE NEXT 24 HOURS. THIS INCLUDES AFFECTS TO TERMINAL SITES SUCH AS GUP...FMN...ABQ AND SAF. MVFR AND SHORT DURATION IFR CONDITIONS WILL BE ASSOCIATED WITH THE STRONGER STORMS. CELL MOVEMENT WILL BE SLOW THUS MAKING THE POTENTIAL FOR LONGER MVFR CONDITIONS NEAR AIRPORTS. STRONG WIND GUSTS WILL ALSO BE ASSOCIATED WITH THE HEAVIEST RAIN ACTIVITY. GUSTS UP TO 40 KTS WILL BE POSSIBLE. NEXT AVIATION DISCUSSION SCHEDULED FOR 09Z. 50 && .FIRE WEATHER... UPPER HIGH WILL REMAIN CENTERED OVER A PORTION OF NEW MEXICO THROUGH AT LEAST THE WORK WEEK. ABUNDANT MOISTURE TRAPPED UNDERNEATH THIS UPPER HIGH WILL RECYCLE OUT IN THE FORM OF WETTING RAIN. THE FAVORED AREA FOR THIS WETTING RAIN WILL BE ACROSS WESTERN AND CENTRAL AREAS. THE EASTERN THIRD WILL SEE THE LEAST AMOUNT OF THUNDERSTORM ACTIVITY...IF ANYTHING AT ALL. TROPICAL STORM DOLLY WILL BE A FEATURE TO WATCH FOR LATE IN THE WEEK AND OVER THE WEEKEND. SOME OF HER MOISTURE COULD GET TRANSPORTED UP INTO NM BUT AT THIS TIME...A LITTLE LESS LIKELY FOR ANY SIGNIFICANT IMPACTS. WILL HAVE TO KEEP AN EYE ON IT. HUMIDITY IS EXPECTED TO REMAIN ABOVE 20 PCT THROUGH FRIDAY. 50 && .PRELIMINARY POINT TEMPS/POPS... FARMINGTON...................... 64 89 62 94 / 60 40 30 20 GALLUP.......................... 59 82 56 87 / 60 50 30 30 GRANTS.......................... 57 82 54 88 / 50 40 30 30 GLENWOOD........................ 64 88 62 92 / 40 50 30 30 CHAMA........................... 49 77 49 81 / 60 50 40 30 LOS ALAMOS...................... 55 83 55 86 / 30 30 30 20 RED RIVER....................... 45 73 45 74 / 30 30 30 30 TAOS............................ 53 85 49 88 / 30 30 30 20 SANTA FE........................ 57 85 59 88 / 40 30 30 20 SANTA FE AIRPORT................ 59 87 59 91 / 40 20 20 20 ESPANOLA........................ 60 89 58 94 / 30 30 30 20 ALBUQUERQUE HEIGHTS............. 67 90 68 92 / 40 20 20 20 ALBUQUERQUE VALLEY.............. 65 92 65 94 / 30 20 20 20 ALBUQUERQUE FOOTHILLS........... 63 88 64 91 / 40 20 20 20 ALBUQUERQUE WEST MESA........... 66 91 66 93 / 40 20 20 20 SOCORRO......................... 64 92 64 92 / 30 20 20 20 SANDIA PARK/CEDAR CREST......... 54 84 54 87 / 40 30 20 20 MORIARTY/ESTANCIA............... 57 87 58 89 / 30 20 20 20 CARRIZOZO....................... 60 90 62 92 / 30 20 20 20 RUIDOSO......................... 55 81 54 81 / 30 20 10 20 RATON........................... 56 90 56 91 / 10 10 10 10 LAS VEGAS....................... 56 86 56 86 / 20 20 20 20 ROY............................. 62 89 63 89 / 10 10 10 10 CLAYTON......................... 64 94 65 93 / 5 5 5 10 SANTA ROSA...................... 63 94 63 94 / 10 10 10 10 TUCUMCARI....................... 66 96 68 97 / 0 5 5 5 FORT SUMNER..................... 67 95 67 95 / 10 5 5 5 CLOVIS.......................... 66 94 68 93 / 0 5 5 5 PORTALES........................ 66 95 68 94 / 5 5 5 5 ROSWELL......................... 69 96 69 96 / 5 5 5 5 && .ABQ WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 46/50 nm AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 126 AM EDT WED JUL 23 2008 .SYNOPSIS... UPPER LEVEL LOW PRESSURE WILL CONTINUE TO DEVELOP ACROSS THE NORTHERN GREAT LAKES TONIGHT. AS THIS SYSTEM DEEPENS WEDNESDAY INTO THURSDAY...DEEP SUBTROPICAL MOISTURE TRANSPORTED NORTHWARD WILL BRING INCREASING CHANCES FOR HEAVY RAINFALL TO THE REGION. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... AS OF 940 PM EDT TUESDAY...LOCALIZED HEAVY RAINFALL HAS OCCURRED ONCE AGAIN THIS EVENING ASSOCIATED WITH SLOW MOVING CONVECTIVE CELLS WITH WARM RAIN PROCESSES DOMINATING. PER RADAR ESTIMATES...THE HEAVIEST RAINFALL AMTS HAVE BEEN IN WASHINGTON COUNTY JUST NORTH OF MPV...WITH ESTIMATES OF 1.5 TO 2 INCHES. ALSO...SEPARATE CONVECTIVE CELL ACROSS FAR SERN ORLEANS COUNTY PRODUCED 1.5 TO 2 INCHES OF RAINFALL BETWEEN WESTMORE AND SUTTON VERMONT. LOCALIZED POOR DRAINAGE FLOODING IS POSSIBLE IN THESE AREAS DURING THE NEXT 1-3 HOURS. ALTHOUGH 01Z LAPS CAPE ANALYSIS STILL INDICATES VALUES AROUND 500 J/KG ACROSS CENTRAL/NRN PORTIONS OF THE NORTH COUNTRY...POTENTIAL FOR LTG IN ISOLD/SCATTERED SHOWER ACTIVITY IS LIMITED BY RELATIVELY HIGH FREEZING LEVELS /13.2 KFT AT KALB PER 00Z RAOB/ AND NARROW NATURE OF CAPE PROFILE. FEEL CONFIDENT THAT REMAINING CONVECTIVE CELLS OVERNIGHT WILL BE FREE OF LIGHTNING AND WE WILL DROP THE LAKE THUNDERSTORM ADVISORY ON LAKE CHAMPLAIN AT THIS TIME. THE 850MB RUC ANALYSIS CONTINUES TO SHOW WEAK WAA ON SWLY FLOW AROUND 10 KTS EAST OF 850MB TROUGH AXIS ACROSS THE ERN GREAT LAKES. THIS COMBINED WITH MODERATELY HIGH PW VALUES AROUND 1.25 INCHES WILL MAINTAIN ISOLD/SCT CELLS OVERNIGHT...LARGELY LINKED TO OROGRAPHIC FORCING. AS SUCH...GREATEST COVERAGE SHOULD CONTINUE TO BE ACROSS THE NRN ADIRONDACKS AND N-CENTRAL/NERN VT. BRIEF PERIODS OF HEAVY RAINFALL REMAIN POSSIBLE WITH STRONGER CELLS. OTHERWISE...2-M WINDS WILL REMAIN NEARLY CALM WITH WEAK P-GRADIENT IN PLACE. SMALL PBL DEWPOINT DEPRESSIONS AND BREAKS IN OVERCAST WILL ALLOW FOR PATCHY FOG DEVELOPING AFTER MIDNIGHT. FOG WILL BE LOCALLY DENSE IN FAVORED VALLEY LOCATIONS...ESPECIALLY AREAS SEEING RAIN SHOWER ACTIVITY THIS EVENING. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/... AS OF 409 PM EDT TUESDAY...LATEST MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT INDICATING AN INCREASING THREAT OF EXCESSIVE RAINFALL ACROSS MUCH OF OUR FORECAST AREA WEDNESDAY INTO THURSDAY. UPPER LOW WILL CONTINUE TO DEEPEN OVER THE GRTLKS TONIGHT/WED...AND WILL TAKE ON A NEUTRAL TO SLIGHTLY NEGATIVE TILT BY THURS. THIS WILL ALLOW A DEEP SUBTROPICAL MOISTURE PLUME TO DEVELOP ACROSS ERN NY AND NEW ENGLAND WED INTO THURS. COUPLED GULF OF MEXICO/WRN ATLC PLUMES TO CONVERGE ACROSS THE AREA DURING THIS PERIOD...WITH PWATS IN EXCESS OF 2 INCHES LIFTING SOUTH TO NORTH INTO FA. HEAVIEST RAIN EXPECTED LATER WED INTO THURS MORNING AS RATHER VIGOROUS SHRTWV ROUNDS BASE OF UPPER LOW AND INTERACTS WITH N-S SFC BOUNDARY APRCHG SLOWLY FROM THE WEST. DESPITE SOME DIFFERENCES IN NAM/GFS REGARDING DURATION OF THE EVENT...THEY ARE REMARKABLY SIMILAR AS TO WHERE THEY INDICATE MAX PCPN...SHOWING A WIDESPREAD 2 TO 4 INCHES OF QPF OVER ERN NY AND WRN/CNTRL VT BTWN MIDDAY WED AND THURS PM...WITH NAM INDICATING SOME LOCALIZED 6"+ TOTALS. ANTECEDENT CONDITIONS (3 TO 6 INCHES OF RAINFALL OVER PAST SEVERAL DAYS ACRS MUCH OF AREA) SUGGEST THIS AMOUNT OF EXPECTED RAIN WILL BE ENOUGH TO PRODUCE FLOODING ACROSS PORTIONS OF FA. HAVE THEREFORE ISSUED A FLOOD WATCH FOR ALL OF OUR CWA EXCEPT FOR ST LWR CTY AND NRN FRANKLIN CTY NY WHERE THREAT OF HVY RAIN IS LOWEST. NAM ALSO INDICATES THERE MAY BE A POTENTIAL WIND PROBLEM FOR WED NITE...MAINLY FOR HIR TRRN/WRN SLOPES OF VT. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 2 PM TUESDAY...OTHER THAN A BREAK IN THE PRECIPITATION ON FRIDAY IT LOOKS LIKE A WET PATTERN WILL CONTINUE WITH TEMPERATURES NEAR OR SLIGHTLY BELOW SEASONAL AVERAGES THROUGH THE PERIOD. MODELS CONTINUE TO BE IN AGREEMENT WITH THE LARGE SCALE LEADING TO DECENT FORECASTER CONFIDENCE THOUGH DETAILS AND TIMING VARY. UPPER TROF MOVES EAST OF THE REGION ON FRIDAY WITH VERY LITTLE CHANCE OF SHOWERS AND NEAR NORMAL TEMPERATURES. THINK MOS MAX TEMPS A BIT OVERDONE AS BEEN THE CASE LATELY. THINK THE WET PATTERN AND DAILY EVAPOTRANSPIRATION KEEPING BOUNDARY LAYER A BIT COOLER THAN WOULD ORDINARILY BE EXPECTED. ON SATURDAY UPPER TROF RELOADS AND A RETRIGGERING OF CONVECTION THAT COULD TURN INTO MORE HEAVY RAIN BY SATURDAY NIGHT INTO EARLY SUNDAY BUT JUST TOO SOON TO TELL. THE FRONT DOES LOOK A LITTLE MORE PROGRESSIVE SO PRECIP TAPERS TO POST FRONTAL CHANCES OF SHOWERS. COULD BE THUNDER BUT LEFT OUT FOR NOW AS COLD CORE ALOFT STAYS MAINLY NORTH. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... THROUGH 06Z THURSDAY....CONDITIONS SHOULD REMAIN VFR THROUGH MOST OF THE FIRST 18 HOURS. FOG SHOULD SET IN AT ALL SITES...GENERALLY 07Z-11Z. KBTV/KPBG/KRUT WILL REMAIN MVFR WITH OCCASIONAL FOG. KMPV/KSLK WILL BOTH SEE IFR VISIBILITY AND CEILINGS AFTER 07Z...THEN LIFR/VLIFR AFTER 09Z. FOG SHOULD LIFT AT ALL SITES BY 12 OR 13Z. THEREAFTER...LOW CEILINGS AS UPPER LOW PRESSURE DEEPENS AND MOISTURE ADVECTS INTO THE AREA. GENERALLY EXPECT CEILINGS 2000-4000 FT 12Z-15Z...THEN MVFR AT ALL SITES AFTER 15Z AT ONSET OF RAIN SHOWERS. HEAVIER PRECIPITATION SHOULD MOVE IN AFTER 21Z...DROPPING VISIBILITY TO 4SM AND CEILINGS TO BELOW 2000 FT. WINDS WILL BE 10 KNOTS OR LESS FROM THE SOUTH TO SOUTHEAST. DONT EXPECT VISBYS AND CEILINGS TO IMPROVE AT ALL OVERNIGHT AS SHRA CONTINUES ACROSS THE AREA THROUGH THE END OF THE TAF FORECAST PERIOD. 06Z THURSDAY THROUGH SUNDAY...UNSETTLED WEATHER TO CONTINUE FOR MUCH OF THE EXTENDED AVIATION. HEAVY RAIN WILL PERSIST INTO THURSDAY MORNING...WITH WIDESPREAD MVFR AND SCATTERED IFR EXPECTED. LINGERING SHOWERS THURSDAY AFTERNOON SHOULD DISSIPATE OVERNIGHT...WITH FRIDAY DRY AND VFR. MORE RAIN EXPECTED FOR SATURDAY AND SUNDAY ESPECIALLY IN THE AFTERNOON. VFR CONDITIONS WITH OCCASIONAL MVFR IN SHOWERS AND THUNDERSTORMS OVER THE WEEKEND. && .HYDROLOGY... THE POTENTIAL FOR VERY HEAVY RAIN AND SERIOUS FLOODING EXISTS WED- THU. THIS EVENINGS SLOW MOVING SHOWERS AND EMBEDDED THUNDERSTORMS HAVE DROPPED NEARLY 2"/HR VIA GAGE AND MATCHING RADAR ESTIMATES JUST A SIGN OF THINGS TO COME. GFS/SREF/NAM MODELS CONSISTENTLY HIGHLIGHTING HEAVY RAIN THREAT SOMEWHERE OVER OUR FORECAST AREA FROM THE ADIRONDACKS/ESSEX EAST. INCREASING CONFIDENCE THAT A POTENTIALLY SIGNIFICANT AND EXCESSIVE RAINFALL EVENT IS ON TAP FOR OUR REGION BEGINNING WED MORNING AND CONTINUING INTO THURSDAY AFTERNOON. WITH HEAVY ANTECEDENT RAINFALL OF 3-6 INCHES AND POINT TOTALS NEARING 8 INCHES ACROSS CENTRAL AND NORTHERN AREAS OVER THE PAST 4 DAYS...HEADWATER 1/3/6 HR FFG VALUES ARE QUITE LOW AND IT WON/T TAKE MUCH TO PUSH STREAMS AND RIVERS INTO FLOOD SHOULD ADDL HEAVY RAFL OCCUR. CONSERVATIVE ESTIMATES WOULD BRING WIDESPREAD 1-3 INCH AND SCT 4 INCH TOTALS TO MUCH OF OUR REGION DURING THE WED/THU PERIOD AS SEMI-STATIONARY DEEP SUBTROPICAL MOISTURE PLUME RIDES NORTH ACROSS OUR AREA. HIGH END ESTIMATES WOULD GIVE SOME AREAS UP TO 7 INCHES DURING THESE PERIODS...WHICH MAY SOMEWHAT OVERDONE AREALLY BUT CERTAINLY POSSIBLE SHOULD THE MOISTURE PLUME SHOW MORE STATIONARITY. IF THESE TOTALS INDEED OCCURRED FLOODING WOULD BE QUITE SERIOUS. && .EQUIPMENT... THE MASSENA ASOS UNDERGOING SERVICE TODAY AFTER THE SITE HAS BEEN REBUILT AND MAY BE AVAILABLE IN THE NEXT DAY OR SO. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...FLOOD WATCH FROM NOON EDT TODAY THROUGH THURSDAY AFTERNOON FOR VTZ001>012-016>019. NY...FLOOD WATCH FROM NOON EDT TODAY THROUGH THURSDAY AFTERNOON FOR NYZ028-030-031-034-035. && $$ SYNOPSIS...JMG NEAR TERM...BANACOS SHORT TERM...RJS LONG TERM...SISSON AVIATION...JAN/MB HYDROLOGY...SISSON/GOFF EQUIPMENT...BTV ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 650 PM EDT TUE JUL 22 2008 .SYNOPSIS...A WEAK SURFACE BOUNDARY OVER THE AREA AND A WARM HUMID AIR MASS WILL RESULT IN MUGGY CONDITIONS TONIGHT WITH A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM...MAINLY EAST OF HIGHWAY 1 AFTER MIDNIGHT. THE THREAT FOR THUNDERSTORMS WILL INCREASE WEDNESDAY AFTERNOON AS AN AREA OF LOW PRESSURE APPROACHES FROM THE WEST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 650 PM TUESDAY... THE HEAT ADVISORY WILL EXPIRE AT 700 PM. SHOWERS AND THUNDERSTORMS CONTINUE ACROSS THE AREA IN RESPONSE TO WARM MOIST CONDITIONS AND SEVERAL BOUNDARIES ACROSS THE REGION. -RHJ PREVIOUS DISCUSSION... SFC ANALYSIS THIS AFTERNOON SHOWS A TROUGH AXIS STRETCHING FROM NJ SOUTHWEST THROUGH THE CENTRAL CAROLINAS INTO GA. WEAK HIGH PRESSURE WAS LOCATED JUST WEST OF THE MOUNTAINS OVER EASTERN TN/KY AND WV. A WEAK COLD FRONT WAS LOCATED FURTHER NORTHWEST ACROSS IA/IL/IN/OH. A LARGE OUTFLOW BOUNDARY ASSOC/W AN MCS THAT BARRELED THROUGH THE OHIO VALLEY INTO WV DURING THE OVERNIGHT HOURS MADE ITS WAY INTO CENTRAL NC DURING THE MORNING...STALLING OUT IN VICINITY OF THE US 1 CORRIDOR (NOTICE THE PROMINENT WIND SHIFT IN THAT AREA). ALOFT...12Z RAOB ANALYSIS SHOWED AN UPPER LOW WELL NORTH OF THE GREAT LAKES IN QUEBEC...WITH A LONGWAVE TROUGH AXIS STRETCHING SOUTHWEST THROUGH THE GREAT LAKES INTO MO/AR. THE BEST DYNAMICS ALOFT WERE ASSOC/W 30-40 METER 12-HR HEIGHT FALLS AND A 75-100 KNOT JET ENTRANCE REGION OVER THE EASTERN OHIO VALLEY INTO NORTHERN WV/VA AND PA. A WEAK SHORTWAVE TROUGH WAS NOTED AT 250MB JUST WEST OF THE SOUTHERN APPALACHIANS ACROSS EASTERN TN/KY/AL. AT 500MB...THERE WAS WEAK DIFFLUENCE ACROSS THE CAROLINAS. CONVECTION: THE 12Z GSO SOUNDING IS SPORTING SOME PRETTY STEEP LAPSE RATES... NEAR DRY ADIABATIC THROUGH 550MB...WITH A PWAT OF 1.31". FCST SOUNDINGS THIS AFTERNOON CONTINUE TO SHOW VERY STEEP LOW/MID LEVEL LAPSE RATES...WITH SFC DEWPOINTS IN THE MID/UPPER 60S. FCST SOUNDINGS ARE SHOWING QUITE A BIT OF AVAILABLE INSTABILITY THIS AFTERNOON WITH TEMPS EXPECTED TO REACH INTO THE UPPER 90S TO NEAR 100F. THE BIG QUESTION TODAY IS WHETHER OR NOT WE WILL HAVE A SUFFICIENT FOCUS FOR SCATTERED CONVECTION TO DEVELOP. AT PRESENT...THE REMNANT MCS OUTFLOW BOUNDARY STALLED OUT AROUND THE US 1 CORRIDOR IS A GOOD CANDIDATE FOR A LOW LEVEL FOCUS. THE WEAK 250MB SHORTWAVE JUST WEST OF THE MOUNTAINS IS ANOTHER CANDIDATE FOR CONVECTIVE SUPPORT...AT THE UPPER LEVELS. HOWEVER...THE LATEST RUC IS NOT SHOWING MUCH IN THE WAY OF LIFT IN ASSOC/W THIS FEATURE OVER CENTRAL NC...KEEPING THE BEST DPVA (ASSOC/W A 15/S VORTMAX) FURTHER SOUTH OVER GA/SC. ANOTHER POTENTIAL SOURCE OF LOW LEVEL LIFT MAY COME FROM THE SEABREEZE...DEPENDING ON HOW FAR INLAND IT PROPAGATES. GIVEN STRONG DIURNAL HEATING...IT SHOULD BE ABLE TO HEAD RELATIVELY FAR INLAND...AS MUCH AS LIGHT SOUTHWEST (COAST PARALLEL) LOW LEVEL WINDS WILL ALLOW. HAVE DECIDED TO DROP POPS IN THE TRIAD TO 20% GIVEN THAT THEY ARE COOLER/DRIER THAN ANYWHERE ELSE...AND ARE BEHIND THE STALLED OUTFLOW BOUNDARY. HAVE KEPT POPS AT LOW CHANCE (30%) CLOSER TO THE TRIANGLE AND SANDHILLS WHERE TEMPS/MOISTURE ARE HIGHER...AND UPPED POPS TO 40% IN THE COASTAL PLAIN WHERE THE STALLED MCS OUTFLOW BOUNDARY MAY MEET WITH OUTFLOW BOUNDARIES FROM DEEP CONVECTION CURRENTLY OVER FAR EASTERN NC AND/OR THE SEABREEZE...SHOULD IT PROPAGATE FAR ENOUGH INLAND THIS AFTERNOON. ANY STORMS THAT DO DEVELOP THIS AFTERNOON COULD EASILY BECOME SEVERE GIVEN THE VERY STEEP LOW/MID LEVEL LAPSE RATES...WITH A PRIMARY THREAT OF DAMAGING WINDS IN EXCESS OF 60 MPH AND HAIL UP TO THE SIZE OF NICKELS. TONIGHT...LOW TEMPERATURES EXPECTED TO BE VERY MILD IN THE LOWER/MID 70S. WILL INTRODUCE A SLIGHT CHANCE OF SHOWERS/STORMS OVERNIGHT TO TAKE INTO ACCOUNT ANY ACTIVITY THAT MAY PERSIST WELL PAST SUNSET AND/OR PROPAGATE INTO CENTRAL NC FROM THE NORTH OR WEST...BASED ON THE LATEST GFS/NAM RUNS WHICH SHOW A POTENTIAL FOR THIS TO OCCUR...IN ADDITION TO THE LATEST RADAR IMAGERY SHOWING CONVECTION DEVELOPING UPSTREAM OVER CENTRAL/EASTERN TN...WITH FCST SOUNDINGS SHOWING ENOUGH ELEVATED INSTABILITY TO SUPPORT CONVECTION THROUGHOUT THE OVERNIGHT HOURS. -VINCENT && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 300 PM TUESDAY... WEDNESDAY/WEDNESDAY NIGHT...VERY MOIST (PRECIP WATER VALUES AROUND 2 INCHES)...APPROACH OF A MID/UPPER LEVEL TROUGH...AND INCREASING DIVERGENCE ALOFT (ESPECIALLY AFTER 18Z) SUGGEST A LIKELIHOOD OF SCATTERED TO NUMEROUS THUNDERSTORMS. NAM/WRF IS A LITTLE FASTER THAN SLOWER GFS WHILE 00Z ECMWF APPEARS TO BE A GOOD COMPROMISE. NAM/WRF DOES APPEAR TO BE VERIFYING BETTER AT MID DAY WITH THE PLACEMENT/DYNAMICS FOR CONVECTION OCCURRING OVER THE MID MS VALLEY INTO THE WESTERN TN VALLEY (GFS LOOKS TOO SLOW AND TOO WEAK OVER THE MO BOOTHEEL INTO WESTERN KY/TN). WHILE LOW/MID LEVEL KINEMATICS RATHER WEAK...PRECIP LOADING IN THE STRONG UPDRAFTS MAY LEAD TO DAMAGING WET MICROBURSTS. IN ADDITION...CONVECTIVE INSTABILITY PARAMETERS SUGGEST THAT STORMS MAY PRODUCE CONTINUOUS TO EXCESSIVE AMOUNT OF LIGHTNING (K INDICES NEAR 40 DEG C; LOW LEVEL THETA-E AXIS OVER CWA; MUCAPE BETWEEN 2000-2500 J/KG ALONG AND EAST OF HIGHWAY 1). INITIATION OF CONVECTION WILL DETERMINE MAX TEMPS. IF TIMING OF GFS IS MORE CORRECT...CONVECTION WILL START MUCH LATER ALLOWING TEMPS TO WARM AT LEAST INTO THE MID 90S. SINCE FAVOR THE NAM TIMING...LEANED TOWARD THE COOLER ETA MOS GUIDANCE. WITH APPROACH OF MID LEVEL TROUGH WEDNESDAY NIGHT...EXPECT CONVECTION TO CONTINUE THROUGH THE EVENING AND INTO THE OVERNIGHT HOURS. THURSDAY...NAM/WRF MORE AGGRESSIVE WITH THE EWD PASSAGE OF MID LEVEL TROUGH THAN GFS/ECMWF. FAVOR THE SLOWER GFS AS DIFFICULT TO GET A "CLEAN" TROUGH PASSAGE THIS TIME OF YEAR. BEST POTENTIAL FOR CONVECTION WILL BE EAST OF HIGHWAY 1 WHERE DEEPER MOISTURE AND BEST INSTABILITY WILL RESIDE. FRIDAY...AIR MASS WILL BE CONDITIONALLY UNSTABLE (PER GFS). MID LEVEL LAPSE RATES UNIMPRESSIVE BUT PRECIP WATER VALUES WILL BE FAIRLY CLOSE TO NORMAL (1.3-1.5 INCHES) AND BOUNDARY LAYER LIFTED INDICES MINUS 2 TO MINUS 3. WILL CARRY A SLIGHT CHANCE POPS DURING THE HEAT OF THE DAY. THICKNESSES SUPPORT TEMPS CLOSE TO NORMAL (NEAR 90/LOWER 90S). && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... AS OF 210 PM TUESDAY... WEAK UPPER LEVEL TROUGH AND ATTENDANT SURFACE TROUGH WILL RESIDE OVER THE FORECAST AREA THROUGH THE PERIOD WITH THE POTENTIAL FOR SOME AMPLIFICATION OF THE UPPER TROUGH BY EARLY NEXT WEEK. THIS TYPE OF PATTERN USUALLY SUPPORTS A SLIGHT TO SMALL CHANCE OF DIURNAL CONVECTION WITH TEMPS HOVERING NEAR NORMAL. CAVEAT TO THIS IS THAT WITH NW MID/UPPER LEVEL FLOW...POTENTIAL FOR DECAYING MCS OR MCS INDUCED VORT MAX TO AFFECT THE REGION FROM ANY CONVECTION THAT DEVELOPS IN THE MID/UPPER MS VALLEY OR THE LOWER GREAT LAKES. THIS IS DIFFICULT TO FORECAST THIS FAR OUT...SO WILL KEEP POPS AOB 30% FOR NOW. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 200 PM TUESDAY... BRIEF IFR/MVFR CONDITIONS IN ISOLATED SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...THEN MVFR FOG AND HAZE WEDNESDAY MORNING. A TRICKY FORECAST REGARDING THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING. AT THIS TIME...THE BEST CHANCE FOR SHOWER/STORM ACTIVITY IS EXPECTED AT THE RWI/FAY TAF SITES...WITH A LESSER CHANCE AT RDU AND THE LEAST CHANCE AT INT/GSO. SEE NEAR TERM DISCUSSION FOR MORE DETAIL ON THE CONVECTIVE CHANCES. AT THIS TIME WILL COVER THE POTENTIAL FOR CONVECTION BY ADDING A SCT060CB TO ALL TAF SITES BETWEEN 20Z AND 02Z THIS AFTERNOON/EVENING. ISOLD SHOWERS/STORMS WILL BE POSSIBLE THROUGHOUT THE OVERNIGHT PERIOD...HOWEVER...CHANCES ARE TOO LOW TO INCLUDE MENTION IN THE TAFS AT THIS TIME. THE SAME AIR MASS OVERHEAD WILL RESULT IN AREAS OF MVFR HAZE AND FOG AGAIN ON WEDNESDAY MORNING. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED WEDNESDAY AFTERNOON AND EVENING AS A COLD FRONT MOVES INTO OUR REGION FROM THE NORTHWEST. LINGERING LOW LEVEL MOISTURE IN THE COASTAL PLAIN MAY ALSO PROMOTE MVFR/IFR FOG DEVELOPMENT AT KRWI AND KFAY EACH MORNING THURSDAY THROUGH SATURDAY. -VINCENT/MWS && .RAH WATCHES/WARNINGS/ADVISORIES... HEAT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR NCZ009>011- 024>028-040>043-073>078-083>086-088-089. && $$ SYNOPSIS...WSS/RHJ NEAR TERM...VINCENT/RHJ SHORT TERM...WSS LONG TERM...WSS AVIATION...VINCENT nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 211 PM EDT TUE JUL 22 2008 .SYNOPSIS... AFTERNOON HIGH TEMPERATURES IN THE UPPER 90S TO NEAR 100 ARE FORECAST FOR TODAY. CHANCES FOR THUNDERSTORMS TODAY WILL INCREASE WEDNESDAY AS A LOW PRESSURE TROUGH SLOWLY MOVED THROUGH THE AREA. && .NEAR TERM /THROUGH TONIGHT/... AS OF 200 PM TUESDAY... ...HEAT ADVISORY IN EFFECT THROUGH 7 PM IN PORTIONS OF CENTRAL NC...SEE TEMPERATURE DISCUSSION BELOW FOR MORE DETAILS... SFC ANALYSIS THIS AFTERNOON SHOWS A TROUGH AXIS STRETCHING FROM NJ SOUTHWEST THROUGH THE CENTRAL CAROLINAS INTO GA. WEAK HIGH PRESSURE WAS LOCATED JUST WEST OF THE MOUNTAINS OVER EASTERN TN/KY AND WV. A WEAK COLD FRONT WAS LOCATED FURTHER NORTHWEST ACROSS IA/IL/IN/OH. A LARGE OUTFLOW BOUNDARY ASSOC/W AN MCS THAT BARRELED THROUGH THE OHIO VALLEY INTO WV DURING THE OVERNIGHT HOURS MADE ITS WAY INTO CENTRAL NC DURING THE MORNING...STALLING OUT IN VICINITY OF THE US 1 CORRIDOR (NOTICE THE PROMINENT WIND SHIFT IN THAT AREA). ALOFT...12Z RAOB ANALYSIS SHOWED AN UPPER LOW WELL NORTH OF THE GREAT LAKES IN QUEBEC...WITH A LONGWAVE TROUGH AXIS STRETCHING SOUTHWEST THROUGH THE GREAT LAKES INTO MO/AR. THE BEST DYNAMICS ALOFT WERE ASSOC/W 30-40 METER 12-HR HEIGHT FALLS AND A 75-100 KNOT JET ENTRANCE REGION OVER THE EASTERN OHIO VALLEY INTO NORTHERN WV/VA AND PA. A WEAK SHORTWAVE TROUGH WAS NOTED AT 250MB JUST WEST OF THE SOUTHERN APPALACHIANS ACROSS EASTERN TN/KY/AL. AT 500MB...THERE WAS WEAK DIFFLUENCE ACROSS THE CAROLINAS. TODAY: THE TEMPERATURE AND CONVECTIVE FORECAST THIS AFTERNOON IS PRETTY CHALLENGING...DUE PRIMARILY TO THE LARGE MCS THAT PROPAGATED INTO THE MOUNTAINS DURING THE OVERNIGHT HOURS. THE OUTFLOW BOUNDARY FROM THE REMNANT MCS STALLED OUT ACROSS CENTRAL NC THIS MORNING. THE FORECAST IS AS FOLLOWS: CONVECTION: THE 12Z GSO SOUNDING IS SPORTING SOME PRETTY STEEP LAPSE RATES... NEAR DRY ADIABATIC THROUGH 550MB...WITH A PWAT OF 1.31". FCST SOUNDINGS THIS AFTERNOON CONTINUE TO SHOW VERY STEEP LOW/MID LEVEL LAPSE RATES...WITH SFC DEWPOINTS IN THE MID/UPPER 60S. FCST SOUNDINGS ARE SHOWING QUITE A BIT OF AVAILABLE INSTABILITY THIS AFTERNOON WITH TEMPS EXPECTED TO REACH INTO THE UPPER 90S TO NEAR 100F. THE BIG QUESTION TODAY IS WHETHER OR NOT WE WILL HAVE A SUFFICIENT FOCUS FOR SCATTERED CONVECTION TO DEVELOP. AT PRESENT...THE REMNANT MCS OUTFLOW BOUNDARY STALLED OUT AROUND THE US 1 CORRIDOR IS A GOOD CANDIDATE FOR A LOW LEVEL FOCUS. THE WEAK 250MB SHORTWAVE JUST WEST OF THE MOUNTAINS IS ANOTHER CANDIDATE FOR CONVECTIVE SUPPORT...AT THE UPPER LEVELS. HOWEVER...THE LATEST RUC IS NOT SHOWING MUCH IN THE WAY OF LIFT IN ASSOC/W THIS FEATURE OVER CENTRAL NC...KEEPING THE BEST DPVA (ASSOC/W A 15/S VORTMAX) FURTHER SOUTH OVER GA/SC. ANOTHER POTENTIAL SOURCE OF LOW LEVEL LIFT MAY COME FROM THE SEABREEZE...DEPENDING ON HOW FAR INLAND IT PROPAGATES. GIVEN STRONG DIURNAL HEATING...IT SHOULD BE ABLE TO HEAD RELATIVELY FAR INLAND...AS MUCH AS LIGHT SOUTHWEST (COAST PARALLEL) LOW LEVEL WINDS WILL ALLOW. HAVE DECIDED TO DROP POPS IN THE TRIAD TO 20% GIVEN THAT THEY ARE COOLER/DRIER THAN ANYWHERE ELSE...AND ARE BEHIND THE STALLED OUTFLOW BOUNDARY. HAVE KEPT POPS AT LOW CHANCE (30%) CLOSER TO THE TRIANGLE AND SANDHILLS WHERE TEMPS/MOISTURE ARE HIGHER...AND UPPED POPS TO 40% IN THE COASTAL PLAIN WHERE THE STALLED MCS OUTFLOW BOUNDARY MAY MEET WITH OUTFLOW BOUNDARIES FROM DEEP CONVECTION CURRENTLY OVER FAR EASTERN NC AND/OR THE SEABREEZE...SHOULD IT PROPAGATE FAR ENOUGH INLAND THIS AFTERNOON. ANY STORMS THAT DO DEVELOP THIS AFTERNOON COULD EASILY BECOME SEVERE GIVEN THE VERY STEEP LOW/MID LEVEL LAPSE RATES...WITH A PRIMARY THREAT OF DAMAGING WINDS IN EXCESS OF 60 MPH AND HAIL UP TO THE SIZE OF NICKELS. TEMPERATURES: TEMPS THIS AFTERNOON WILL DEPEND ON HOW MUCH CLOUD COVER/CONVECTION DEVELOPS ACROSS THE AREA THIS AFTERNOON. CURRENT INDICATIONS ARE THAT AREAS FROM THE TRIANGLE SOUTH/EAST SHOULD HAVE NO PROBLEM MAKING IT INTO THE UPPER 90S TO NEAR 100F THIS AFTERNOON BASED ON THICKNESSES AND MOS GUIDANCE...WHILE THE TRIAD AREA MAY TOP OUT IN THE MID 90S...DEPENDING HOW MUCH AIRMASS MODIFICATION OCCURRED IN ASSOC/W THE MCS OUTFLOW BOUNDARY PASSAGE. DEWPOINTS REMAIN IN THE UPPER 60S TO LOWER 70S ACROSS THE HEAT ADVISORY AREA AS OF 17Z... WITH HEAT INDEX VALUES ALREADY BETWEEN 100-104F. THE HEAT ADVISORY WILL REMAIN IN EFFECT UNTIL 700 PM THIS EVENING. TONIGHT...LOW TEMPERATURES EXPECTED TO BE VERY MILD IN THE LOWER/MID 70S. WILL INTRODUCE A SLIGHT CHANCE OF SHOWERS/STORMS OVERNIGHT TO TAKE INTO ACCOUNT ANY ACTIVITY THAT MAY PERSIST WELL PAST SUNSET AND/OR PROPAGATE INTO CENTRAL NC FROM THE NORTH OR WEST...BASED ON THE LATEST GFS/NAM RUNS WHICH SHOW A POTENTIAL FOR THIS TO OCCUR...IN ADDITION TO THE LATEST RADAR IMAGERY SHOWING CONVECTION DEVELOPING UPSTREAM OVER CENTRAL/EASTERN TN...WITH FCST SOUNDINGS SHOWING ENOUGH ELEVATED INSTABILITY TO SUPPORT CONVECTION THROUGHOUT THE OVERNIGHT HOURS. -VINCENT && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY... MID AND UPPER LEVEL TROUGHS DROP THROUGH THE OHIO VALLEY LATE TONIGHT AND WEDNESDAY...WITH WEST TO SOUTHWEST MID LEVEL WINDS OVER NORTH CAROLINA INCREASING TO 15 TO 30 KNOTS BY LATE AFTERNOON WEDNESDAY. LIKELY RAIN CHANCES BY WEDNESDAY AFTERNOON WITH HEAVIER RAINFALL AMOUNTS MORE LIKELY NEAR AND NORTH OF HIGHWAY 64. CHANCES FOR SHOWERS OR THUNDERSTORMS WILL CONTINUE INTO WEDNESDAY NIGHT. THE LATEST NAM...ECMWF AND GFS MODEL RUNS HAVE SIGNIFICANTLY ADVANCED THE MID LEVEL TROUGH POSITION THURSDAY MORNING... TO WHERE THURSDAY COULD TURN OUT ENTIRELY DRY. THE CANADIAN AND NAVY NOGAPS CONTINUE SLOWER WITH THIS TROUGH AND LINGER RAIN CHANCES OVER CENTRAL NORTH CAROLINA...AT LEAST IN THE EAST HALF. CONFIDENT ENOUGH TO REMOVE RAIN FROM THE WEST FOR THURSDAY...BUT WILL DELAY DRYING OUT THE EAST UNTIL NEAR SUNSET. IF THE MORNING MODELS CONFIRM THE DRYING TREND...THE EAST MAY END UP BEING DRY THURSDAY AS WELL. CURRENT FORECAST TEMPERATURES ARE ACCEPTED. MORNING LOWS 68 TO 73. AFTERNOON HIGHS 88 TO 93. -RLH && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 410 AM TUESDAY... INITIALLY WEST NORTHWEST FLOW ALOFT FRIDAY THROUGH SATURDAY WILL BACK TO WEST SOUTHWESTERLY IN RESPONSE TO A DEEPENING VORTEX OVER SOUTHERN ONTARIO AND QUEBEC SUNDAY INTO THE FIRST OF NEXT WEEK. THIS SHOULD RESULT IN A BROAD LOW LEVEL WARM MOIST ADVECTION AND MCS BEARING REGIME FROM THE MID MS VALLEY TO THE MID ATLANTIC STATES THROUGH SATURDAY... IN THE CONFLUENT FLOW TO THE WEST OF THE LONGWAVE TROUGH ATTENDANT THE SOUTHERN CANADA VORTEX. THEN AS THE TROUGH ALOFT SHARPENS... ADDED LIFT FROM THE UPPER JET MAY CREEP CLOSE ENOUGH TO ENHANCE PRECIPITATION CHANCES SUNDAY THROUGH MONDAY. THUS...INITIALLY DRY AND SUBSIDENT AIR ON FRIDAY -- IN THE WAKE OF THE TROUGH FROM THE SHORT TERM -- MAY MOISTEN RATHER QUICKLY FROM THE WEST FRIDAY EVENING/NIGHT... AS THE AFOREMENTIONED THETA-E ADVECTION AND LOW AMPLITUDE IMPULSES ALOFT (PERHAPS IN THE FORM OF AN MCV) PROVIDE FOR LARGE SCALE ASCENT OVER OUR REGION. WILL ACCORDINGLY DELAY POPS FOR MOST OF THE DAY FRIDAY WHEN THE SUBSIDENCE INVERSION LINGERS... THEN CARRY A CHANCE POP INTO THE LATE EVENING HOURS TO ACCOUNT FOR THE POSSIBLE ARRIVAL OF MCS RESIDUALS FROM THE TN VALLEY. THIS TREND OF RESIDUAL MCS ACTIVITY OR RENEWED DEEP CONVECTIVE DEVELOPMENT OVER OUR REGION FROM UPSTREAM MCV`S OR DIFFICULT TO TIME LOW AMPLITUDE BAROCLINIC WAVES/SHORTWAVE TROUGHS ALOFT WILL THEN CONTINUE THROUGH THE PERIOD... AS WE REMAIN IN A RELATIVELY MOIST AND CONDITIONALLY UNSTABLE AIR MASS. TEMPERATURES THROUGH THE PERIOD SHOULD RANGE FROM THE UPPER 80S TO LOWER 90S FOR HIGHS AND WITHIN A FEW DEGREES EITHER SIDE OF 70 DEGREES FOR LOWS. -MWS && .AVIATION /18Z TUESDAY THROUGH SATURDAY/... AS OF 200 PM TUESDAY... BRIEF IFR/MVFR CONDITIONS IN ISOLATED SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...THEN MVFR FOG AND HAZE WEDNESDAY MORNING. A TRICKY FORECAST REGARDING THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING. AT THIS TIME...THE BEST CHANCE FOR SHOWER/STORM ACTIVITY IS EXPECTED AT THE RWI/FAY TAF SITES...WITH A LESSER CHANCE AT RDU AND THE LEAST CHANCE AT INT/GSO. SEE NEAR TERM DISCUSSION FOR MORE DETAIL ON THE CONVECTIVE CHANCES. AT THIS TIME WILL COVER THE POTENTIAL FOR CONVECTION BY ADDING A SCT060CB TO ALL TAF SITES BETWEEN 20Z AND 02Z THIS AFTERNOON/EVENING. ISOLD SHOWERS/STORMS WILL BE POSSIBLE THROUGHOUT THE OVERNIGHT PERIOD...HOWEVER...CHANCES ARE TOO LOW TO INCLUDE MENTION IN THE TAFS AT THIS TIME. THE SAME AIR MASS OVERHEAD WILL RESULT IN AREAS OF MVFR HAZE AND FOG AGAIN ON WEDNESDAY MORNING. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED WEDNESDAY AFTERNOON AND EVENING AS A COLD FRONT MOVES INTO OUR REGION FROM THE NORTHWEST. LINGERING LOW LEVEL MOISTURE IN THE COASTAL PLAIN MAY ALSO PROMOTE MVFR/IFR FOG DEVELOPMENT AT KRWI AND KFAY EACH MORNING THURSDAY THROUGH SATURDAY. -VINCENT/MWS && .RAH WATCHES/WARNINGS/ADVISORIES... HEAT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR NCZ009>011- 024>028-040>043-073>078-083>086-088-089. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...RLH LONG TERM...MWS AVIATION...VINCENT/MWS nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1035 AM EDT TUE JUL 22 2008 .SYNOPSIS... HOT CONDITIONS EXPECTED THIS AFTERNOON WITH TEMPERATURES APPROACHING THE CENTURY MARK. A LOW CHANCE OF SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON THROUGH THIS EVENING. && .NEAR TERM /THIS AFTERNOON THROUGH TONIGHT/... AS OF 1030 AM TUESDAY... SFC ANALYSIS THIS MORNING SHOWS A TROUGH AXIS STRETCHING FROM NJ SOUTHWEST THROUGH THE CENTRAL CAROLINAS INTO GA. WEAK HIGH PRESSURE WAS LOCATED JUST WEST OF THE MOUNTAINS OVER EASTERN TN/KY AND WV. A WEAK COLD FRONT WAS LOCATED FURTHER NORTHWEST ACROSS IA/IL/IN/OH. A LARGE OUTFLOW BOUNDARY ASSOC/W AN MCS THAT BARRELED THROUGH THE OHIO VALLEY INTO WV DURING THE OVERNIGHT HOURS WAS LOCATED OVER THE SOUTHWEST VA MOUNTAINS...HEADED SOUTHEAST DIRECTLY TOWARD CENTRAL NC. DEWPOINTS ACROSS CENTRAL NC RANGED FROM THE MID 60S TO LOWER 70S. ALOFT...12Z RAOB ANALYSIS SHOWED AN UPPER LOW WELL NORTH OF THE GREAT LAKES IN QUEBEC...WITH A LONGWAVE TROUGH AXIS STRETCHING SOUTHWEST THROUGH THE GREAT LAKES INTO MO/AR. THE BEST DYNAMICS ALOFT WERE ASSOC/W 30-40 METER 12-HR HEIGHT FALLS AND A 75-100 KNOT JET ENTRANCE REGION OVER THE EASTERN OHIO VALLEY INTO NORTHERN WV/VA AND PA. A WEAK SHORTWAVE TROUGH WAS NOTED AT 250MB JUST WEST OF THE SOUTHERN APPALACHIANS ACROSS EASTERN TN/KY/AL. AT 500MB...THERE WAS WEAK DIFFLUENCE ACROSS THE CAROLINAS. AT 850MB...THERE WAS DECENT SPEED CONVERGENCE ACROSS NORTHERN/WESTERN NC (RNK 30KT NORTHWEST WIND...GSO 10KT WESTERLY WIND). TODAY: THE TEMPERATURE AND CONVECTIVE FORECAST THIS AFTERNOON IS PRETTY CHALLENGING...DUE PRIMARILY TO THE LARGE MCS THAT PROPAGATED INTO THE MOUNTAINS DURING THE OVERNIGHT HOURS. THE REMNANT OUTFLOW BOUNDARY CONTINUES TOWARD CENTRAL NC AS OF 14Z...AND WAS LOCATED SOMEWHERE NEAR THE INTERFACE OF THE MOUNTAINS/FOOTHILLS OF SOUTHWEST VA AND NORTHWEST NC. THE FORECAST IS AS FOLLOWS: CONVECTION: THE 12Z GSO SOUNDING IS SPORTING SOME PRETTY STEEP LAPSE RATES... NEAR DRY ADIABATIC THROUGH 550MB...WITH A PWAT OF 1.31". FCST SOUNDINGS THIS AFTERNOON CONTINUE TO SHOW VERY STEEP LOW/MID LEVEL LAPSE RATES...WITH SFC DEWPOINTS MIXING OUT INTO THE LOWER/MID 60S. EVEN WITH SFC DEWPOINTS DROPPING FROM THEIR PRESENT VALUES IN THE UPPER 60S TO LOWER 70S INTO THE LOWER/MID 60S...FCST SOUNDINGS ARE SHOWING QUITE A BIT OF AVAILABLE INSTABILITY THIS AFTERNOON WITH TEMPS EXPECTED TO REACH INTO THE UPPER 90S TO NEAR 100F. THE BIG QUESTION TODAY IS WHETHER OR NOT WE WILL HAVE A SUFFICIENT FOCUS FOR SCATTERED CONVECTION TO DEVELOP. AT PRESENT...THE REMNANT MCS OUTFLOW BOUNDARY HEADED THIS WAY IS A GOOD CANDIDATE FOR A LOW LEVEL FOCUS...HOWEVER...THE BOUNDARY MAY MIX OUT/WEAKEN AND SLOW DOWN ONCE IT SPILLS OFF THE MOUNTAINS INTO THE FOOTHILLS AND WESTERN PIEDMONT OF NC...AND IT IS DIFFICULT TO ANTICIPATE HOW MUCH LIFT WILL BE ASSOC/W THIS FEATURE. THE OUTFLOW BOUNDARY IS ALREADY INITIATING CONVECTION IN SOUTH CENTRAL VA. THE WEAK 250MB SHORTWAVE JUST WEST OF THE MOUNTAINS IS ANOTHER CANDIDATE FOR CONVECTIVE SUPPORT...AT THE UPPER LEVELS. HOWEVER...THE LATEST RUC IS NOT SHOWING MUCH IN THE WAY OF LIFT IN ASSOC/W THIS FEATURE OVER CENTRAL NC...KEEPING THE BEST DPVA (ASSOC/W A 15/S VORTMAX) FURTHER SOUTH OVER GA/SC. ANOTHER POTENTIAL SOURCE OF LOW LEVEL LIFT MAY COME FROM THE SEABREEZE...DEPENDING ON HOW FAR INLAND IT PROPAGATES. GIVEN STRONG DIURNAL HEATING...IT SHOULD BE ABLE TO HEAD RELATIVELY FAR INLAND...AS MUCH AS LIGHT SOUTHWEST (COAST PARALLEL) LOW LEVEL WINDS WILL ALLOW. AT THIS TIME WILL SHOW LOW CHANCE (30%) POPS ACROSS THE ENTIRE CWA THIS AFTERNOON DUE TO THE PRESENCE OF STRONG INSTABILITY AND A FEW POSSIBLE SOURCES FOR LIFT...WHICH MAKE IT DIFFICULT TO PINPOINT ONE AREA OVER ANOTHER FOR A `HIGHER` CHANCE. WILL NEED TO WATCH THE SE COASTAL PLAIN...HOWEVER...AS THERE ARE INDICATIONS THAT THE SEABREEZE MAY INDEED PUNCH INLAND FAR ENOUGH TO ENHANCE CHANCES IN THAT AREA. ANY STORMS THAT DO DEVELOP THIS AFTERNOON COULD EASILY BECOME SEVERE GIVEN THE VERY STEEP LOW/MID LEVEL LAPSE RATES...WITH A PRIMARY THREAT OF DAMAGING WINDS IN EXCESS OF 60 MPH. TEMPERATURES: TEMPS THIS AFTERNOON WILL DEPEND ON HOW FAR INTO THE AREA THE REMNANT MCS OUTFLOW BOUNDARY WILL PENETRATE...AND HOW MUCH CLOUD COVER / CONVECTION DEVELOPS ACROSS THE AREA THIS AFTERNOON. CURRENT INDICATIONS ARE THAT AREAS FROM THE TRIANGLE SOUTH/EAST SHOULD HAVE NO PROBLEM MAKING IT INTO THE UPPER 90S TO NEAR 100F THIS AFTERNOON BASED ON THICKNESSES AND MOS GUIDANCE...WHILE THE TRIAD AREA MAY TOP OUT IN THE MID/UPPER 90S...DEPENDING HOW MUCH (IF ANY) AIRMASS MODIFICATION OCCURRED IN ASSOC/W THE OUTFLOW BOUNDARY PASSAGE. ALTHOUGH DEWPOINTS ARE CURRENTLY IN THE UPPER 60S TO LOWER 70S... THEY ARE EXPECTED TO DROP INTO THE LOWER/MID 60S THIS AFTERNOON IN RESPONSE TO STRONG DIURNAL MIXING. IF THIS OCCURS AS EXPECTED... HEAT INDEX VALUES WILL REMAIN AT OR BELOW 104F THIS AFTERNOON. HOWEVER...IF THEY SOMEHOW MANAGE TO STAY IN THE UPPER 60S TO NEAR 70F...THEN HEAT INDEX VALUES COULD EXCEED 105F FOR A FEW HOURS IN SOME LOCATIONS IN THE SANDHILLS...COASTAL PLAIN AND POTENTIALLY THE TRIANGLE AREA AS WELL. IF THIS OCCURRED...WE WOULD TECHNICALLY BE AT HEAT ADVISORY CRITERIA. GIVEN THAT THERE IS TOO MUCH UNCERTAINTY WITH TEMPS/DEWPOINTS THIS AFTERNOON...PREFER TO NOT ISSUE A HEAT ADVISORY...AND WILL MAKE SURE THERE IS ENHANCED WORDING FOR HEAT IN THE HWO. TONIGHT...LOW TEMPERATURES EXPECTED TO BE VERY MILD IN THE LOWER/MID 70S. WILL INTRODUCE A SLIGHT CHANCE OF SHOWERS/STORMS OVERNIGHT TO TAKE INTO ACCOUNT ANY ACTIVITY THAT MAY PERSIST WELL PAST SUNSET AND/OR PROPAGATE INTO CENTRAL NC FROM THE NORTH OR WEST...BASED ON THE LATEST GFS/NAM RUNS WHICH SHOW A POTENTIAL FOR THIS TO OCCUR...WITH FCST SOUNDINGS SHOWING ENOUGH ELEVATED INSTABILITY TO SUPPORT CONVECTION. -VINCENT && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 300 AM TUESDAY... MID AND UPPER LEVEL TROUGHS DROP THROUGH THE OHIO VALLEY LATE TONIGHT AND WEDNESDAY...WITH WEST TO SOUTHWEST MID LEVEL WINDS OVER NORTH CAROLINA INCREASING TO 15 TO 30 KNOTS BY LATE AFTERNOON WEDNESDAY. LIKELY RAIN CHANCES BY WEDNESDAY AFTERNOON WITH HEAVIER RAINFALL AMOUNTS MORE LIKELY NEAR AND NORTH OF HIGHWAY 64. CHANCES FOR SHOWERS OR THUNDERSTORMS WILL CONTINUE INTO WEDNESDAY NIGHT. THE LATEST NAM...ECMWF AND GFS MODEL RUNS HAVE SIGNIFICANTLY ADVANCED THE MID LEVEL TROUGH POSITION THURSDAY MORNING... TO WHERE THURSDAY COULD TURN OUT ENTIRELY DRY. THE CANADIAN AND NAVY NOGAPS CONTINUE SLOWER WITH THIS TROUGH AND LINGER RAIN CHANCES OVER CENTRAL NORTH CAROLINA...AT LEAST IN THE EAST HALF. CONFIDENT ENOUGH TO REMOVE RAIN FROM THE WEST FOR THURSDAY...BUT WILL DELAY DRYING OUT THE EAST UNTIL NEAR SUNSET. IF THE MORNING MODELS CONFIRM THE DRYING TREND...THE EAST MAY END UP BEING DRY THURSDAY AS WELL. CURRENT FORECAST TEMPERATURES ARE ACCEPTED. MORNING LOWS 68 TO 73. AFTERNOON HIGHS 88 TO 93. -RLH && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 410 AM TUESDAY... INITIALLY WEST NORTHWEST FLOW ALOFT FRIDAY THROUGH SATURDAY WILL BACK TO WEST SOUTHWESTERLY IN RESPONSE TO A DEEPENING VORTEX OVER SOUTHERN ONTARIO AND QUEBEC SUNDAY INTO THE FIRST OF NEXT WEEK. THIS SHOULD RESULT IN A BROAD LOW LEVEL WARM MOIST ADVECTION AND MCS BEARING REGIME FROM THE MID MS VALLEY TO THE MID ATLANTIC STATES THROUGH SATURDAY... IN THE CONFLUENT FLOW TO THE WEST OF THE LONGWAVE TROUGH ATTENDANT THE SOUTHERN CANADA VORTEX. THEN AS THE TROUGH ALOFT SHARPENS... ADDED LIFT FROM THE UPPER JET MAY CREEP CLOSE ENOUGH TO ENHANCE PRECIPITATION CHANCES SUNDAY THROUGH MONDAY. THUS...INITIALLY DRY AND SUBSIDENT AIR ON FRIDAY -- IN THE WAKE OF THE TROUGH FROM THE SHORT TERM -- MAY MOISTEN RATHER QUICKLY FROM THE WEST FRIDAY EVENING/NIGHT... AS THE AFOREMENTIONED THETA-E ADVECTION AND LOW AMPLITUDE IMPULSES ALOFT (PERHAPS IN THE FORM OF AN MCV) PROVIDE FOR LARGE SCALE ASCENT OVER OUR REGION. WILL ACCORDINGLY DELAY POPS FOR MOST OF THE DAY FRIDAY WHEN THE SUBSIDENCE INVERSION LINGERS... THEN CARRY A CHANCE POP INTO THE LATE EVENING HOURS TO ACCOUNT FOR THE POSSIBLE ARRIVAL OF MCS RESIDUALS FROM THE TN VALLEY. THIS TREND OF RESIDUAL MCS ACTIVITY OR RENEWED DEEP CONVECTIVE DEVELOPMENT OVER OUR REGION FROM UPSTREAM MCV`S OR DIFFICULT TO TIME LOW AMPLITUDE BAROCLINIC WAVES/SHORTWAVE TROUGHS ALOFT WILL THEN CONTINUE THROUGH THE PERIOD... AS WE REMAIN IN A RELATIVELY MOIST AND CONDITIONALLY UNSTABLE AIR MASS. TEMPERATURES THROUGH THE PERIOD SHOULD RANGE FROM THE UPPER 80S TO LOWER 90S FOR HIGHS AND WITHIN A FEW DEGREES EITHER SIDE OF 70 DEGREES FOR LOWS. -MWS && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... AS OF 720 AM TUESDAY... BRIEF IFR/MVFR CONDITIONS IN SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING... THEN MVFR FOG AND HAZE WEDNESDAY MORNING. A TRICKY FORECAST REGARDING THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING. A LARGE OUTFLOW BOUNDARY AND ASSOCIATED PRONOUNCED RAIN-COOLED MESO-HIGH... GENERATED BY AN OVERNIGHT THUNDERSTORM COMPLEX OVER THE OHIO VALLEY... WAS SITUATED ALONG THE WEST SLOPES OF THE CENTRAL APPALACHIANS AT SUNRISE THIS MORNING. PURE EXTRAPOLATION OF THIS FEATURE HAS IT ON THE DOORSTEP OF THE WESTERN TERMINALS AROUND 15Z... THEN SOUTHEASTWARD TO KFAY BY 18Z. IT IS UNLIKELY THAT SURFACE HEATING WILL HAVE SUFFICIENTLY DESTABILIZED THE ATMOSPHERE BY 15Z... SO ASIDE FROM A BRIEF WIND SHIFT TO NORTHWEST... THE BOUNDARY MAY PASS WITH LITTLE FANFARE AT WESTERN TERMINALS. HOWEVER... IT MAY TRIGGER RENEWED SHOWERS AND THUNDERSTORMS BY THE TIME IT ARRIVES AT KRDU... AND ESPECIALLY KFAY AND KRWI... WHERE TEMPERATURES ARE APT TO BE AROUND 90 DEGREES BY THAT TIME. ADDITIONAL SHOWERS AND THUNDERSTORMS WILL THEN LIKELY DEVELOP TO THE WEST... ALONG THE EAST SLOPES OF APPALACHIANS AND IN THE FOOTHILLS. THESE STORMS COULD PROPAGATE EASTWARD INTO THE KGSO AND KINT VICINITY LATER THIS AFTERNOON OR THIS EVENING. HAVE INCLUDED ONLY A CB CLOUD GROUP IN THE TAFS GIVEN THE STILL SOMEWHAT UNCERTAIN TIMING AND COVERAGE OF CONVECTION. THE MAGNITUDE OF THE FORECAST INSTABILITY COMBINED WITH STEEP LAPSE RATES FROM THE SURFACE TO THE MID LEVELS WILL PROVIDE AMPLE ENERGY FOR STRONG (POTENTIALLY DAMAGING) WIND GUSTS IN ANY STORMS THAT DEVELOP. LOOKING BEYOND TUESDAY EVENING... THE SAME AIR MASS OVERHEAD WILL RESULT IN MVFR HAZE AND FOG AGAIN WEDNESDAY MORNING. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED WEDNESDAY AFTERNOON AND EVENING... AS A COLD FRONT MOVES INTO OUR REGION FROM THE NORTHWEST. LINGERING LOW LEVEL MOISTURE IN THE COASTAL PLAIN MAY ALSO PROMOTE MVFR/IFR FOG DEVELOPMENT AT KRWI AND KFAY EACH MORNING THURSDAY THROUGH SATURDAY. -MWS && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...RLH LONG TERM...MWS AVIATION...MWS nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 415 AM CDT TUE JUL 22 2008 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT... SOME OF THE RICHEST BOUNDARY LAYER MOISTURE OF THE SUMMER IS ON OUR DOORSTEP AND SHOULD BE WELL IN PLACE BY LATE WED...WHEN 00Z MODELS ARE QUITE AGREEABLE TO LOCAL MID/UPPER 60S F DEWPOINTS. THIS MAKES FOR AN INCREASING RISK OF THUNDER AND SEVERE POTENTIAL AS AN UPPER RIDGE AXIS PEAKS OVER ND TODAY AND IS REPLACED BY SW FLOW ALOFT AND TWO IF NOT THREE S/W`S...EACH GROWING IN STRENGTH UNTIL THE PRIMARY WAVE PASSES ON THU. THE 00Z MODELS ARE IN AGREEMENT ON THE SYNOPTIC SCALE AND AS A RESULT THE FCST DATABASE IS A MIX OF ALL...THOUGH IT IS WORTH NOTHING THAT THE 00Z GFS IS THE DRIEST SOLUTION 06-18Z WED. THE MODEL ALSO INITIALIZED SFC DEWPOINT FIELDS POORLY AND THIS HAS PROPAGATED UNTIL AT LEAST 06Z...THOUGH ITS MOS PRODUCTS RESOLVE THE SITUATION MORE CLEARLY. AS A RESULT...A BIT MORE WEIGHT WAS PUT INTO THE 00Z NAM SOLUTION WITH THIS RELEASE. FIRST...LOW/MID LVL THETA-E ADVECTION IS DRIVING ELEVATED CONVECTION IN THE FAR SW ATTM. RADAR SIGNATURES SUGGEST ENOUGH STRENGTH TO SUPPORT SOME HAIL. THE 06Z RUC KEEPS THIS ACTIVITY AROUND IN THE SW INTO THE MORNING HOURS. MOIST SE FLOW STRENGTHENS THE NEXT 36 HRS...REFLECTED IN SFC WINDS WHICH GET GUSTY IN THE SW LATE TDY AND CENTRAL WED WHEN MODELS MIX TO NEARLY 800 MB WHERE 30KT WINDS RESIDE. THIS IS IN RESPONSE TO HEIGHT FALLS ASSOCIATED WITH S/W ENERGY TO OUR WEST...WHICH ALSO ORGANIZES A SFC COLD FRONT IN EASTERN MT BY 12Z WED...SHIFTING IT TO NEAR A KISN-KDIK CORRIDOR 21-00Z WED AND SHOVING IT THROUGH KJMS THU MORNING. THIS FEATURE WILL BE THE FOCUS FOR THE HIGHEST-IMPACT WX DURING THE SHORT TERM...BUT TWO OTHER RISKS PRESENT THEMSELVES... 1/POTENTIAL SFC-BASED CONVECTION IN WSTRN ND LATE AFTN/EVE TDY AND 2/ NEWLY-DEVELOPED ELEVATED CONVECTION AND/OR A WEAKENING MCS MOVING INTO THE AREA FROM MT AFT 06Z TONIGHT. WHERE 1/ IS CONCERNED...THE MODELS ARE IN DIFFERENT CAMPS WITH A VORT MAX IN NW WY ATTM...WITH THE 00Z GFS SHOVING IT INTO SW ND BY 00Z WED WHILE THE 00Z NAM TAKES IT ON A MORE NRLY COURSE INTO MT. WE DO BECOME UNSTABLE WITH SBCAPE OF 600 J/KG IN THE FAR SW LATE TDY...BUT THE DEEPER BUOYANCY IS FURTHER WEST IN MT. THAT SAID...IF MOISTURE DOES NOT MIX OUT MUCH THEN SBCAPE WILL BE HIGHER. THE MAIN PROBLEM IS WITH THE MOVEMENT OF THE VORT...A GFS SOLUTION PORTENDING SCT TSRA BY 00Z AND THE NAM KEEPING IT DRY. ENOUGH UNCERTAINTY TO KEEP SLGT CHANCE POPS IN THE DATABASE. NUMBER 2/ HAS GREATER CERTAINTY AS A 40-45KT LLJ AND NOTABLE 850 THETA-E ADVECTION DRIVE ELEVATED CONVECTION AFT 06Z TONIGHT. LENGTHENING MOISTURE TRANSPORT VECTORS AND PWATS TO 1.5 INCHES SUPPORT DEEP MOIST CONVECTION...AND A RESERVOIR OF MODERATE INSTABILITY /MUCAPE OF 1000-1500 J/KG/ IS AVAILABLE TO ELEVATED PARCELS. THUS THERE IS SVR POTENTIAL...ESPECIALLY 09-15Z WED OVER CENTRAL ND...WHICH IS TYPICALLY THE MOST ACTIVE TIME FOR ELEVATED HAILERS ON THE LLJ. THE 00Z NAM CLEARLY DEPICTS THIS SCENARIO IN ITS QPF FIELDS. THE THREAT OF AN MCS MOVING INTO THE AREA FROM MT IS ALSO NON-ZERO...AND IT COULD BE THAT THE EVENTUAL CONVECTION IS SOME COMBINATION OF BOTH NEW DEVELOPMENT AND ANY PRE-EXISTING MCS. THE BIGGER STORY WILL BE INITIATION OF SFC-BASED STORMS ALONG THE COLD FRONT LATE WED AFTN. STEEP MID LVL LAPSE RATES AND STRONG DIABATIC HEATING WILL PUSH MLCAPE VALUES TO 2500+ J/KG. MODERATE MID LVL FLOW WILL CONTRIBUTE TO 30-40KTS OF 0-6KM BULK SHEAR... SUFFICIENT FOR ORGANIZED UPDRAFTS AND EVEN SUPERCELLS GIVEN THE INSTABILITY. MODELS SUGGEST ENOUGH LOW LVL CONVERGENCE TO ERODE CAPPING ALONG THE FRONT SO CONFIDENCE ON AN ORGANIZED SVR EVENT IS INCREASING. MODELS ALSO SUGGEST THAT THE LLJ WED NIGHT IS FOCUSED OVER SD/NE AND THAT THE UPPER JET IS NOT PARTICULARLY INTERESTING... SO IT IS NOT YET CLEAR HOW LONG-LIVED OUR EVENT WILL BE. WAVE NUMBER THREE FINALLY SHIFTS OVER THE NRN PLAINS ON THU. THE MAIN FRONTAL ZONE WILL HAVE PASSED THRU THE FA WED NIGHT...WHICH MAKES THE CONVECTIVE SCENARIO MORE DIFFICULT DURING THIS PERIOD. 00Z SFC WIND FIELDS SUGGEST LITTLE RESPONSE TO THE HEIGHT FALLS ALOFT... SOMETHING THAT MAY NOT BE ENTIRELY TRUE. WE COULD WIND UP WITH SOME NEW /ALBEIT WEAK/ CONVERGENCE ZONES OVER THE AREA THU AFTN. IF THIS IS THE CASE THE THUNDER THREAT WOULD BE ENHANCED. REGARDLESS...WE REMAIN UNSTABLE AND HENCE WE HAVE ADDED SLGT CHANCE POPS TO THE FCST DATABASE IN THIS PERIOD. .LONG TERM...FRIDAY THROUGH MONDAY NIGHT... FOR THE MOST PART...FOLLOWED A SOLUTION CLOSE TO THE 00 UTC GFS AND BLENDED WITH THE 00 UTC ECMWF WHEN APPROPRIATE IN GRIDS THIS MORNING. MODELS/ENSEMBLES ARE IN GOOD AGREEMENT WITH THE SOMEWHAT AMPLIFIED POSITIVE PACIFIC NORTH AMERICAN LONGWAVE PATTERN OVER NORTH AMERICA THIS PERIOD. THERE ARE TWO MAIN SHORTWAVES FORECAST TO PASS OVER NORTH DAKOTA. THE FIRST...LINGERING MIDDLE LEVEL ENERGY FROM THURSDAYS SYSTEM SHOULD COOL MIDDLE LEVEL TEMPERATURES AND PROVIDE SUFFICIENT SYNOPTIC SCALE LIFT TO INITIATE AT LEAST SCATTERED CONVECTION. THE SECOND...AN ELONGATED MIDDLE/UPPER LEVEL TROUGH EXTENDING FROM THE NORTHWEST TERRITORIES OF CANADA ALL THE WAY SOUTH INTO THE NORTHERN PLAINS. AGAIN...ASSOCIATED DESTABILIZATION OF THERMAL PROFILES AND DEEP-LAYER ASCENT SUPPORTS MCS FORMATION ON SUNDAY/MONDAY. OF COURSE...TIMING LOW-PREDICTABILITY IMPULSES IS VERY DIFFICULT IN THE EXTENDED PERIOD...AND THEY MAY EJECT OUT AHEAD OF THE MAIN TROUGH AXIS. EXPECT TIMING ISSUES TO RESOLVE THEMSELVES AS THE WEEKEND APPROACHES. OTHERWISE...TEMPERATURES SHOULD REMAIN NEAR OR SLIGHTLY ABOVE CLIMATOLOGY AS THE LONGWAVE RIDGE SITS ALONG THE FRONT RANGE. && .AVIATION... SURFACE HIGH PRESSURE OVER SOUTHERN MANITOBA IS FORECAST TO CONTINUE MOVING EASTWARD AS BROAD LOW PRESSURE OVER THE NORTHERN ROCKIES/HIGH PLAINS DEEPENS AND APPROACHES EASTERN MONTANA/WESTERN NORTH DAKOTA BY WEDNESDAY EVENING. EXPECT VFR CONDITIONS WITH LOW-LEVEL SOUTHEASTERLY WINDS. SOME THUNDERSTORMS ARE EXPECTED TO FORM AHEAD OF THIS LOW PRESSURE...BUT IT APPEARS THAT MOST OF THE ACTIVITY WILL REMAIN WEST OF THE STATE UNTIL AFTER DARK ON TUESDAY NIGHT. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ CJS/NH/SCHECK nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1142 AM EDT WED JUL 23 2008 .SYNOPSIS... AN UNUSUALLY STRONG STORM SYSTEM FOR MID SUMMER WILL MOVE SOUTHEAST FROM THE GREAT LAKES REGION TODAY...DRAGGING A SLOW MOVING COLD FRONT ACROSS THE STATE. SEVERAL WAVES OF LOW PRESSURE RIDING NORTHWARD ALONG THE FRONT WILL BRING HEAVY RAINFALL OF 2 INCHES OR MORE TO PARTS OF EASTERN EASTERN PENNSYLVANIA TODAY AND TONIGHT. SLOW IMPROVEMENT WILL OCCUR THURSDAY AS HIGH PRESSURE BUILDS EAST INTO THE REGION. FRIDAY WILL BE WARM AND DRY. ANOTHER COLD FRONT WILL APPROACH THE REGION THIS WEEKEND WITH ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS ON SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... CONVEYOR BELT OF RAIN CONTINUES TO FEED UP OVER ABOUT THE EASTERN HALF OF MY FCST AREA...WITH ONLY SLOW EASTWARD TRANSLATION TO THE BACK EDGE. FURTHER WEST UNDER THE RELATIVELY COOL CYCLONIC UPPER FLOW...INSTABILITY IS STARTING TO MAKE ITSELF KNOWN WITH A BROKEN LINE OF STORMS FROM WARREN COUNTY SOUTHWARD. ENSEMBLES AND OPERATIONAL MODELS CONTINUE TO PUSH THE IDEA THAT THE FURTHER ONE GOES IN THE STATE THE HIGHER THE THREAT FOR HEAVY RAIN WILL BE. THIS IS WHERE THE BEST PRECIP WATER/LOW LEVEL JET ANOMALIES FOCUS ALONG WITH THE STRONGEST LOW LEVEL MOISTURE FLUX CONVERGENCE. WATER VAPOR SHOWS STRONG DRYING DIVING INTO THE SRN OHIO VALLEY...TESTAMENT TO THE STRENGTH OF THE DIGGING UPPER TROUGH. THE RESULTANT UPPER JET ENTRANCE REGION IS FCST TO SHARPEN AND PIVOT AS IT SLIDES ONLY SLOWLY EASTWARD TODAY...SUPPORTING THE IDEA OF A FRONTOGENTIC REGION...AND SEVERAL WAVES OF LOW PRESSURE RIPPLING ALONG THE BOUNDARY. OPERATIONAL MODELS ARE NOT ANALYZING THE SORT OF FRONTOGENETIC FORCING THAT IS IMPLIED BY THE BANDED RADAR RETURNS AND WOULD BE EXPECTED UNDER THE STRONGLY ANTICYCLONICALLY CURVED UPPER JET ENTRANCE REGION. I IMAGINE EMBEDDED CONVECTION MAY BE TAKING ITS TOLL. REGARDLESS...THE SYSTEM HAS A MORE WINTER- LIKE LOOK AND FEEL TO IT THAN A SYSTEM NORMALLY SEEN AT THE HEIGHT OF SUMMER. FLASH FLOOD GUIDANCE REMAINS HIGH SO NO FLOOD WATCHES PLANNED AT THIS TIME...BUT SMALLER SCALE NUISANCE FLOODING CANNOT BE RULED OUT IN SOME OF THE LOCALLY HEAVY BANDS THAT MANAGE TO TRAIN ALONG FOR ANY AMOUNT OF TIME. WILL HANDLE THOSE WITH ADVISORIES AND STATEMENTS...FOR NOW. IF THINGS DO LOOK LIKE THEY HAVE THE POTENTIAL TO DETERIORATE...WOULD THINK THE HIGHEST THREAT AREA FOR A FLOOD WATCH WOULD BE EAST OF A LINE FROM ABOUT WILLIAMSPORT TO YORK. ALL OF CENTRAL PENN IS ONCE AGAIN IN SPC`S SLIGHT RISK AREA...HOWEVER INSTABILITY IS MEAGER GIVEN THE EXTENSIVE CLOUD COVER AND WIDESPREAD RAIN. RUC SHOWS HIGHEST CAPES OVER SERN AREAS WHERE DEWPOINTS ARE NEAR 70...AND ANOTHER MAX OF CAPE OVER THE FAR WEST WHERE SUNSHINE WAS MOST ABUNDANT EARLIER TODAY. WINDS ALOFT ARE NOT TERRIBLY IMPRESSIVE SO WE WOULD HAVE TO SEE SOME RELATIVELY POTENT CORES DEVELOP IN ORDER TO MANAGE ANY KIND OF SIGNIFICANT WIND GUSTS. THINK THE LIKELIHOOD OF THAT IS LOW. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... 03Z SREF PUSHES FRONTAL BOUNDARY SLOWLY THRU CENTRAL/EASTERN PA THIS AFTERNOON AND TONIGHT...AS AN AMPLIFYING UPPER TROF SWINGS THRU...TAKING ON A NEG TILT BY LATE IN THE DAY/EVENING. STRONG LARGE SCALE FORCING...FAVORABLE RIGHT ENTRANCE OF JET AND ANOMALOUS PWATS ALONG FRONT ALL POINT TOWARD THE POTENTIAL OF LOCALLY HVY CONVECTIVE RAINFALL ACROSS EASTERN PA INTO TONIGHT. CATEGORICAL POPS ACROSS THE SUSQ VALLEY (ALL NIGHT)...AND IN MOST OTHER AREAS AREAS EARLY...WILL BE TRIMMED CHC OR LIKELY ACROSS THE CENTRAL AND WEST AFTER MIDNIGHT. UPPER TROUGH DEEPENS TO -2 TO -3 STD DEVIATIONS OVERNIGHT...BEFORE SLOWLY FILLING AS IT DRIFTS ENE ACROSS PENN THURSDAY. 700 HPA TEMPS COOLING STEADILY TO SLIGHTLY BELOW ZERO ACROSS THE WRN HALF OF THE STATE BY 00Z FRIDAY WILL CREATE STEEP MID LEVEL LAPSE RATES ON THE ORDER OF NEARLY 7C/KM...ABUNDANT CLOUDS OR "SELF DESTRUCT" SUNSHINE...AND AT LEAST SCATTERED SHOWERS. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... DRIER AIR GRADUALLY WORKS INTO THE REGION FROM THE WEST THURSDAY NIGHT...WITH A PARTLY TO MSTLY SUNNY AND WARM FRIDAY IN STORE. COLD FRONT FALLS APART JUST TO THE SE OF C PA...THEN WARM AND HUMID AIR MOVES BACK TO THE NW FRIDAY NIGHT. NEXT FRONT MOVES ACROSS SATURDAY...BUT WEAK SFC TROUGH AND UPPER TROUGH TO LINGER ACROSS THE GREAT LAKES EARLY NEXT WEEK. THUS WENT MAINLY DRY FCST FOR THU AND FRI...THEN CHC FOR SAT... THEN S CHC ON SUNDAY. WENT WITH DRY FCST FOR MONDAY AND TUE. GFS BLOWS UP A SYSTEM OVER SOUTH CENTRAL PA ON MONDAY...BUT THIS NOT CONSISTENT WITH OTHER MODELS AND RUNS...SO THINK IS A CONVECTIVE FEEDBACK PROBLEM. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... QUITE VARIABLE CONDITIONS ACROSS THE CWA THIS MORNING. ONGOING CONVECTION MOVING NE WILL CONTINUE TO AFFECT MSOT TAF SITES FOR NEXT COUPLE OF HOURS BEFORE WINDING DOWN FOR SEVERAL HOURS LATE THIS MORNING. THEN CONVECTION WINDS UP AGAIN LATER THIS AFTERNOON INTO THE EVENING...WITH STRONG TO SEVERE STORMS POSSIBLE IN THE EASTERN HALF. THEN THE SYSTEM EVOLVES INTO A POTENTIAL HEAVY RAIN EVENT IN THE CENTRAL/EAST THIS EVENING. THE MAIN WEATHER FEATURE CAUSING THE AFORMENTIONED WEATHER WILL BE THE PERSISTENT UPPER LEVEL TROUGH...WHICH WILL BECOME NEGATIVELY TILTED OVERHEAD TODAY AS A SERIES OF IMPRESSIVE WAVES WITH GOOD JET DYNAMICS SLIDE THROUGH IT. CONVECTION IN THE WESTERN AREAS SHOULD IMPROVE EARLIEST LATER ON TODAY. FURTHER EAST HEAVY RAIN AND THUNDERSTORMS CAN BE EXPECTED TO CONTINUE THROUGH MUCH OF TONIGHT WITH REDUCTIONS TO MVFR AND IFR VISIBILITY AND CEILING EXPECTED. THE FRONT SHOULD FINALLY BE OFFSHORE BY THURSDAY MORNING BRINGING IN VFR CONDITIONS. HOWEVER WE WILL STILL BE UNDER THE UPPER LEVEL TROUGH WHICH MAY CAUSE A FEW ISOLATED AFTERNOON SHOWERS TO DEVELOP...WHICH MAY BRIEFLY LOWER CEILINGS AND VISIBILITIES TO MVFR. VFR CONDITIONS EXPECTED FRIDAY AND SUNDAY... BUT YET ANOTHER FRONT MAY BRING ANOTHER CHANCE OF THUNDERSTORMS ON SATURDAY. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LACORTE/LAMBERT NEAR TERM...LACORTE/LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...MARTIN AVIATION...GARTNER/RXR pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 307 AM EDT TUE JUL 22 2008 .SYNOPSIS... A SLOW MOVING FRONTAL BOUNDARY OVER THE GREAT LAKES WILL SAG SOUTHWARD INTO PENNSYLVANIA TONIGHT...THEN STALL OUT ACROSS THE SOUTHEAST PART OF THE STATE THROUGH MIDWEEK. HIGH PRESSURE WILL BUILD INTO THE REGION LATE IN THE WEEK...FOLLOWED BY A POSSIBLE COLD FRONT BY NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... IMPRESSIVE BOW ECHO NOW EXITING SRN SOMERSET/BEDFORD CNTYS ATTM. PIT BASE V SIGNATURES WERE IN EXCESS OF 50KTS AT 3-6KFT AGL. RUC ANAL ALONG WITH IR SAT IMAGERY SHOWS THE MCV HAS NOW MOVED INTO WCENT PA...WITH SCT SHRA/TSRA EVIDENT ON RADAR FM THE MID SUSQ VLY NWWD BACK INTO THE NW MTNS. BROADBRUSHED SCHC/CHC POPS AFT 06Z WITH SOME PATCHY FOG TO DEVELOP TWD DAWN. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... THE SHOWERS SHOULD TAPER OFF EARLY IN THE WEST. THE HIGH AMBIENT MOISTURE AND PARTIAL CLEARING SHOULD LEAD TO SOME FOG AND PERHAPS STRATUS AGAIN IN THE MORNING. HAVE MADE CLOUD COVER RATHER DARK/DISMAL IN THE WEST LATE TONIGHT. ANY SHOWERS THAT LAST AFTER MIDNIGHT SHOULD BE OVER THE EAST AND EXITING STAGE RIGHT. SOME FOG POSSIBLE THERE...TOO...BUT MOST LIKELY IN THE WEST/CENTRAL. MINS WILL BE MILD/MUGGY AGAIN. LOOK FOR A SIMILAR DAY TO THE PAST WEEK OR SO WITH HOT TEMPS IN THE SE AND COOLER/NEARER-NORMAL TEMPS IN THE NW. FOCUSING MECHANISMS FOR AFTN CONVECTION STILL IN DOUBT AT THIS POINT...BUT THOSE DEAD MCS/S AND THEIR ASSOCIATED VERTICAL MOTION ARE THE BIG SUSPECTS AT THIS TIME. WILL KEEP POPS IN THE SCT/CHC RANGE FOR NOW...AND MAKE IT MOSTLY IN THE AFTN. LATEST SREF DATA SUGGEST HIGHEST CHC OF RAIN TUES NIGHT WILL BE IN THE WEST - ESP THE SW...AS MODELS WANT TO DROP AN MCS RIGHT THRU SWRN PA OVERNIGHT. FELT A GOOD MOVE WAS TO BUMP POPS INTO LIKELY CATEGORY FOR THE SW...AND KEEP CHCS FOR THE REST AT THIS RANGE. TIMING AND UPSTREAM DEVELOPMENT...OR LACK THEREOF...WILL TELL THIS TALE. KEPT MINS VERY MILD/MUGGY AGAIN. IT IS...AFTER ALL...THE HEIGHT OF SUMMER - WITH THE HOTTEST TEMPS /CLIMATOLOGICALLY/ UPON US FOR ALL OF THE NEXT WEEK. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... YESTERDAY I HELD ONTO THE MENTION OF SHOWERS AND STORMS INTO TUESDAY NIGHT...AND EVEN PUT A CHC INTO THE SE FOR WED AM. YESTERDAY THE GFS SHOWED THE UPPER LEVEL TROUGH SHARPENING UP FOR MID WEEK...BUT I DID NOT WANT TO MAKE THE WHOLE WEEK WET. WITH THIS TREND STILL TODAY...LEFT MEINTON OF SHOWERS AND STORMS IN FOR WED...THAT MID SHIFT ADDED...AND ADDED CHC FOR WED NIGHT. GFS SLIGHTLY LESS GLOOMY AND FASTER THAN NAM WITH SYSTEM WED...BUT COULD STILL SEE A SIGNIFICANT SEVERE WEATHER...EVEN HEAVY RAIN EVENT...WITH SUCH A STRONG UPPER LEVEL FEATURE FOR LATE JULY. ONLY HAVE ISSUED ONE FLASH FLOOD WARNING THIS SEASON...AND THAT WAS THE OTHER EVENING WHEN I WAS WORKING. THIS HAS BEEN A WET SUMMER SO FAR...JUST HAVE NOT HAD THE TYPICAL PATTERN FOR HEAVY RAIN SO FAR THIS SEASON. IF ONE IS LOOKING FOR DRY WEATHER...IT LOOKS LIKE THU AND PERHAPS FRIDAY WILL BE THE DAYS. THE OLD FRONT STALLS JUST OFFSHORE AT BEST...AND STARTS TO WORK BACK TO THE NW BY LATE IN THE WEEK. AT THE SAME TIME...A NEW COLD FRONT WORKS EASTWARD ON SAT. WENT WITH DRY WEATHER AGAIN FOR THE PERIOD SUNDAY INTO TUE. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... IR IMAGERGY INDICATES BREAKS IN THE CLOUDS SLIDING IN BEHIND EVENING CONVECTION. FOG/LOW CLOUDS DEVELOPING EVERWHERE BY 08Z AND PERSISTING THRU SUNRISE. UPPER LEVEL LOW CONTINUES TO PUSH EAST INTO WEDNESDAY AS MID-LVL TROUGH DIGS DEEP INTO THE ATLANTIC SEABOARD. EACH OF THE NEXT SEVERAL DAYS WILL PRESENT LOW CHC FOR SHRA/TSRA...ALTHOUGH IT DOES NOT APPEAR THESE WILL BE LONG LIVED CONVECTIVE PIECES. BY SATURDAY YET ANOTHER TROUGH LOOKS TO MOVE IN BRINGING WITH IT MORE SHOWERS AND THUNDERSTORMS FOR THE WEEKEND. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO/FITZGERALD NEAR TERM...STEINBUGL SHORT TERM...DANGELO LONG TERM...MARTIN AVIATION...BEACHLER/RXR pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 237 PM EDT TUE JUL 22 2008 .SYNOPSIS... A WEAK COLD FRONT WILL CONTINUE TO MOVE TOWARD AND ACROSS THE FORECAST AREA THROUGH LATE WEDNESDAY. THIS SYSTEM SHOULD STALL ACROSS THE CAROLINAS FOR THE LATTER PART OF THE WEEK...WHILE WEAK HIGH PRESSURE TRIES TO BUILD IN FROM THE NORTH. A REINFORCING COLD FRONT WILL APPROACH FROM THE NORTHWEST AND MOVE OVER THE AREA EARLY NEXT WEEK. && .NEAR TERM /THROUGH WEDNESDAY/... FOR THE REMAINDER OF THIS AFTERNOON AND EVENING...THE FOCUS IS ON WHERE CONVECTION WILL DEVELOP. RUC AND NAM ARE TARGETING THE MOUNTAINS...NE GA AND THE WESTERN UPSTATE WITH BEST CHANCES FOR CONVECTION. CURRENT LAPS CAPE AND REGIONAL RADARS SUPPORTS THIS IDEA. ALSO...CONVECTION CURRENTLY DEVELOPING WITHIN THE SPC WATCH OVER TN WILL MAKE A RUN AT THE NC MOUNTAINS..SO WILL HAVE SOLID/HIGH CHANCE POPS FOR SCATTERED THUNDERSTORMS IN THOSE AREAS...TRENDING LOWER ACROSS THE SOUTHERN UPSTATE. WITH CAPES IN THE 1000-2000J RANGE AND DCAPES AROUND 1000J SEVERE DOWNBURSTS ARE AGAIN A POSSIBILITY. 50-55DBZ CORES AROUND 28K FT SHOULD BE SUFFICIENT FOR SVR WIND AND AROUND 33K FR FOR SVR HAIL. STORMS SHOULD DISSIPATE BY MIDNIGHT AND THEN REMAIN QUIET OVERNIGHT. USED A MOS BLEND FOR MIN TEMPS. WILL ALSO GO AHEAD AN CANCEL THE HEAT ADVISORY FOR THE REMAINDER OF THIS AFTERNOON AS HEAT INDEX COMING UP SHY OF THE NEEDED 105 CRITERIA. ON THU...AN APPROACHING COLD FRONT IS EXPECTED TO TRIGGER FAIRLY WIDESPREAD COVERAGE OF THUNDERSTORMS. UPPER DYNAMICS NOT BAD EITHER AS EAST COAST UPPER TROUGH DEEPENS ALLOWING FOR SOME DECENT LAPSE RATES AND PVA. GFS/NAM DIFFER ON TIMING OF FRONT WITH THE NAM THE FASTER OF THE MODELS. WILL USE THE SREF WHICH IS CLOSE TO A COMPROMISE BETWEEN THE GFS/NAM. HENCE...WILL BRING LIKELY POPS INTO THE MOUNTAINS DURING THE MORNING AND ELSEWHERE DURING THE AFTERNOON. MAX TEMPS WILL BE ON THE DECLINE DUE TO CLOUDS/STORMS....BUT OUTSIDE OF THE MOUNTAINS TEMPS ARE STILL EXPECTED TO CLIMB INTO THE LOWER TO MID 90S. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... AS OF 230 PM TUESDAY...OVERNIGHT PERIOD WEDNESDAY WILL BEGIN WITH ONGOING CONVECTION AT SOUTHERN END OF RATHER STRONG SHORT WAVE TROUGH MOVING FROM GREAT LAKES TOWARD NEW ENGLAND. SOME TIMING AND DETAIL DIFFERENCES EXIST AMONG MODELS... BUT GFS... NAM... AND SREF INDICATE UNSTABLE AIR... DIVERGENCE ALOFT... AND CONVERGENT FLOW IN BOUNDARY LAYER WILL BE PROGRESSING EASTWARD BETWEEN 00Z AND 06Z THURSDAY. 500 MB TROUGH WILL MOVE INTO NEW ENGLAND AND EASTERN CANADA BY THURSDAY MORNING... BUT APPEARS THAT WEAKNESS IN HEIGHT FIELD AT SOUTHERN END OF TROUGH WILL NOT PROGRESS RAPIDLY EASTWARD. THUS... SURFACE FRONTAL BOUNDARY WILL MOVE OFF COAST OF NORTHEASTERN STATES BUT EXTEND SOUTHWARD INTO CAROLINAS JUST SOUTH OF OUR CWA. BOUNDARY SUFFICIENTLY CLOSE AND MOISTURE DEEP ENOUGH TO SUPPORT SLIGHT CHANCE POPS DURING DAY THURSDAY... PRIMARILY ACROSS SOUTHEAST. HAVE LEANED TOWARD THE GFS DEPICTION OF MOISTURE AND LOW-LEVEL FLOW ON FRIDAY WHICH INDICATES ENOUGH MOISTURE FOR SCATTERED SHOWERS OR THUNDERSTORMS. HAVE CONTINUED LOW CHANCE POPS THROUGH FRIDAY NIGHT DUE PRIMARILY TO APPROACH OF NEXT TROUGH AND FRONT FROM THE WEST. DAYTIME TEMPERATURES SHOULD BE IN 80S AND LOWER 90S... NOT QUITE AS HOT AS EARLIER IN WEEK. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 145 PM TUESDAY...NO SIGNIFICANT CHANGES WERE MADE TO THE GOING FORECAST FOR THE MEDIUM RANGE. I PRIMARILY USED THE 00Z/22 ECMWF FOR THE DETAILS OF THE FORECAST WHICH STILL FEATURES EAST COAST TROUGHING THROUGH THE PERIOD. DID NUDGE MAX TEMPS UP A BIT ON SAT AND SUN AS IT LOOKS LIKE THE EASTERN EXTENSION OF THE STRONG RIDGE OVER THE SOUTHERN PLAINS WILL BRING IN SOME HIGHER HEIGHTS...BEFORE RETROGRADING BACK TOWARDS THE DESERT SOUTHWEST AS A REINFORCING SHOT OF ENERGY AMPLIFIES THE EASTERN CONUS TROUGH EARLY NEXT WEEK. AT THE SURFACE...THE FA WILL REMAIN UNDER THE INFLUENCE OF A MOIST AND UNSTABLE LLVL AIR MASS THROUGH THE PERIOD AS A COLD FRONT SAGS SOUTHWARD MON AND TUES. OVERALL...HPC AND MODEL GUIDANCE CONTINUES TO SUPPORT AN ACTIVE PERIOD WITH A SOLID CHC OF CONVECTION THROUGH TUES. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... VFR CONDITIONS AT 18Z WILL HOLD THROUGH THE AFTERNOON AND MOST OF THE NIGHT. THE EXCEPTION WOULD BE IF A THUNDERSTORM MOVED OVER AN AIR FIELD LATE THIS AFTERNOON OR EVENING. CURRENT INDICATIONS ARE THAT CONVECTIVE DEVELOPMENT WILL BE MOST WIDESPREAD LATE THIS AFTERNOON OVER THE NC MOUNTAINS. THESE STORMS THEN MAY PROPOGATE INTO THE FOOTHILLS AND PIEDMONT DURING THE EVENING. HAVE CONTINUED WITH THE MENTION OF CB IN THE TAFS FROM ABOUT 21Z-01Z EXCEPT 20Z-01Z AT KAVL. SCATTERED THUNDERSTORMS SHOULD DISSIPATE BY 02Z. MOST GUIDANCE INDICATES SOME MINOR RESTRICTION TO VSBY AROUND SUNRISE...SO HAVE INCLUDED HZ AND VSBYS 5-6SM. A COLD FRONT WILL ENTER THE AREA ON WEDNESDAY WHICH IS EXPECTED TO PRODUCE FAIRLY WIDESPREAD COVERAGE OF THUNDERSTORMS DURING THE AFTERNOON. HAVE INCLUDED A CB GROUP AFTER 16Z AT ALL SITES...THOUGH THIS MAY BE A LITTLE EARLY FOR SITES LIKE KAND. OUTLOOK...THUNDERSTORMS WED EVENING WILL MOVE E AND S OF THE REGION OVERNIGHT ALONG WITH ASSOCIATED COLD FRONT. HIGH PRESSURE WILL BRIEFLY BUILD S PROVIDING GENERALLY VFR CONDITIONS THURSDAY INTO FRIDAY. SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS CAN BE EXPECTED FRIDAY THROUGH SUNDAY. SOME MVFR CEILINGS AND VISIBILITY MAY OCCUR IN THE THUNDERSTORM...WITH MVFR VISIBILITY AT NIGHT IN FOG WHERE RAIN FALLS. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...BSH NEAR TERM...LG SHORT TERM...LGL LONG TERM...BSH AVIATION...LG sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1057 AM EDT TUE JUL 22 2008 .SYNOPSIS... A WEAK COLD FRONT WILL APPROACH FROM THE NORTHWEST TODAY AND SLOWLY CROSS THE AREA THROUGH WEDNESDAY NIGHT. THIS SYSTEM SHOULD STALL OVER CENTRAL SOUTH CAROLINA AND GEORGIA FOR THE LATTER PART OF THE WEEK...WHILE WEAK HIGH PRESSURE TRIES TO BUILD IN FROM THE NORTH. A REINFORCING COLD FRONT WILL APPROACH FROM THE NORTHWEST AND MOVE OVER THE AREA EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... TEMPS NOT RISING QUITE AS FAST TODAY AS OPPOSED TO YESTERDAY OUTSIDE OF THE MOUNTAINS DUE TO SOME DEBRIS CI AND PROBABLY SOME EVAPORATIVE EFFECTS WHERE THUNDERSTORMS OCCURRED YESTERDAY EVENING. HAVE TWEAKED THE MAX TEMP GRID DOWNWARD A DEGREE OR TWO AS A RESULT. SFC DEWPOINTS SHOULD ACTUALLY INCREASE SOME AS DAY PROGRESSES DUE TO EVAPORATION AND ADVECTION AS WINDS SWING TO THE S THIS AFTERNOON. THEREFORE...HEAT INDEX VALUES WILL STILL BE IN THE VICINITY OF 105...SO SEE NO REASON TO CANCEL THE ADVISORY OUTSIDE OF THE MOUNTAINS. IN REGARD TO CONVECTIVE EXPECTATIONS...THE ATMOSPHERE WILL CERTAINLY BE POTENTIALLY UNSTABLE WITH CAPES INCREASING INTO THE 1000-2000J RANGE. RUC AND 12Z NAM TARGETING MOUNTAINS FOR MOST WIDESPREAD COVERAGE BEGINNING AFTER 18Z AS WEAK SHORT WAVE ARRIVES WITH SOME OF THIS ACTIVITY PROBABLY MOVING INTO THE FOOTHILLS/PIEDMONT AREAS THIS EVENING. ESSENTIALLY JUST MADE SOME MINOR ADJUSTMENTS TO TIMING IN THE POP FIELD. SOME SEVERE STORMS AGAIN POSSIBLE LATE THIS AFTERNOON AND EVENING. DCAPE`S AGAIN LOOK TO BE AROUND 1000J...SO SVR DOWNBURSTS ARE A THREAT AGAIN. INITIAL EVALUATION LOOKS LIKE 50-55DBZ CORES AROUND 28K FT FOR SVR DOWNBURSTS AND AROUND 33K FT FOR SVR HAIL. WARM AND MUGGY CONDITIONS ARE EXPECTED TONIGHT...WITH CONVECTION CHANCES DECREASING THROUGH THE NIGHT. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... AS OF 230 AM TUESDAY...GFS CONTINUES HAVING CONVECTIVE FEEDBACK ISSUES SO LEANED A BIT MORE TOWARD A NAM/ECMWF BLEND. CLOSED H5 LOW OVER E GREAT LAKES AND ASSOC E US TROF CONTINUE TO DEEPEN WED. AT THE SAME TIME...A WEAK COLD FRONT SINKS S OVER THE FORECAST AREA. ADD DEEP MOISTURE WITH CAPES AROUND 2000J/KG IN THE AFTN AND ALL THE INGREDIENTS ARE THERE FOR LIKELY SHWRS/TSTMS. EVEN THO H5 HEIGHTS DECREASE AND MORE CLOUDS ARE EXPECTED...1000-850MB THICKNESS STAYS FAIRLY HIGH. SO ALTHO GUIDANCE IS COOLER THAN TUE...A MODEL BLEND YIELDS TEMPS STILL ABOVE AVG... RANGING FROM L-M90S TO U80S FOOTHILLS AND PIEDMONT...WITH U70S TO M80S MTNS. NAM/GFS FASTER THAN ECMWF PUSHING FRONT S WED NIGHT-THU AND AM LEANING TOWARD SLOWER ECMWF. UPPER SUPPORT WANES AS H5 TROF BEGINS TO PULL AWAY TO THE NE THU AND SFC FRONT CONTINUES SLOWLY S...SO HAVE POPS TAPERING OFF FROM THE NW DURING THE DAY TO SLIGHT CHANCE. EXPECT HIGHS THU AROUND 90 S CWA...U80S N...WITH U70S-M80S MTNS. && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 230 AM TUESDAY...MODELS IN FAIR AGREEMENT PUSHING WEAK SFC BOUNDARY S AND STALLING IT OUT JUST S OF CWA FRI...AS WEAK HIGH PRESSURE TRIES TO BUILD IN FROM THE N. WITH NO SIG AIRMASS CHANGE DIURNALLY DRIVEN SHWRS/TSTMS ARE EXPECTED INTO THE WEEKEND WITH TEMPS WITHIN A DEG OR TWO OF AVG. E COAST TROF DEEPENS AGAIN LATE THIS WEEKEND WHILE A REINFORCING COLD FRONT APPROACHES FROM THE NW. WITH AN H5 SHORTWAVE AND SFC COLD FRONT EXPECTED TO MOVE INTO THE CWA AT THE BEGINNING OF THE WEEK...A CHANCE OF RAIN CONTINUES. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... WINDS HAVE STAYED UP OVERNIGHT...KEEPING THE LOWER ATMOSPHERE MIXED AND PREVENTING FOG FORMATION. HIGH CEILINGS FROM THE ANVILS OF PREVIOUS THUNDERSTORMS PERSIST AT THE SC TAF SITES. BY MID MORNING WINDS BACK TO THE SOUTHWEST AT 5 KTS...WHILE CUMULUS FORMS WITH DAYTIME HEATING. WINDS BACK FURTHER TO THE SOUTH SOUTHWEST AT MIDDAY...AND THUNDERSTORMS BEGIN TO DEVELOP IN ERNEST. COVERAGE WILL ONLY BE SUFFICIENT TO BE CARRIED IN THE VICINITY OF KAVL...HOWEVER CUMULONIMBUS WILL BE CARRIED AT EACH TAF SITE. BY EARLY EVENING CONVECTION WILL HAVE DIMINISHED...WHILE WINDS BECOME GENERALLY LIGHT AND VARIABLE. ANVIL DEBRIS FORM THUNDERSTORMS WILL BE THE CEILING OVERNIGHT...AS THE MODEL TIME HEIGHTS HAVE BACKED OFF ON LOW CLOUD COVER. MODEL GUIDANCE ONLY CARRIES MVFR FOG AT KAVL...AND ONLY FOR A COUPLE OF HOURS AROUND DAWN ON WEDNESDAY. OUTLOOK...THUNDERSTORM COVERAGE WILL INCREASE AGAIN ON WED AS A COLD FRONT APPROACHES AND MOVES ACROSS THE REGION. BEHIND THE FRONT...GENERALLY VFR CONDITIONS ARE EXPECTED DURING THE DAY ON THU AND CONTINUING ON FRI. ANOTHER FRONT APPROACHES ON SATURDAY...AND CONVECTION ASSOCIATED WITH THIS FEATURE COULD PRODUCE MVFR CEILINGS AND VISIBILITY IN AFTERNOON AND EVENING THUNDER...WITH MVFR VISIBILITY AT NIGHT IN FOG WHERE RAIN FALLS. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...HEAT ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR GAZ026-028-029. NC...HEAT ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR NCZ070-071-082. SC...HEAT ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR SCZ004>014-019. && $$ SYNOPSIS...RB NEAR TERM...LG SHORT TERM...RB LONG TERM...RB AVIATION...LG sc AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE ABERDEEN SD 1130 AM CDT WED JUL 23 2008 .UPDATE...REST OF TODAY AREA OF ISO/SCT SHOWERS CONTINUES TO MOVE EASTWARD ACROSS CENTRAL SOUTH DAKOTA LATE THIS MORNING AND WILL APPROACH THE JAMES RIVER VALLEY DURING THE NEXT FEW HOURS. RATHER COMPLEX CONVECTIVE SITUATION TODAY WITH PLENTY OF CLOUD COVER KEEPING INSTABILITY AT BAY TODAY ACROSS THE EAST...ALTHOUGH PRESENCE OF LLJ TODAY SHOULD PROMOTE AN INCREASE IN ELEVATED SHOWERS/STORMS LATER THIS AFTERNOON. FARTHER WEST...SFC BOUNDARY LOCATED ACROSS WESTERN SD WITH IMPULSE MOVING NORTHEAST THROUGH WYOMING. CLEARING LINE APPROACHING WESTERN MOST COUNTIES AND STILL EXPECT SOME DEVELOPMENT OF STORMS ACROSS THIS AREA LATER THIS AFTERNOON AS INSTABILITY INCREASES AND WYOMING IMPULSE NEARS THE AREA. ALSO INCREASED WINDS TODAY INTO THE BREEZY CATEGORY. DID SOME TWEAKS TO ALL OTHER WX ELEMENTS TO BETTER MATCH OBS AND RADAR TRENDS. && .PREV DISCUSSION... .SHORT TERM...TODAY THROUGH FRIDAY MAIN FCST CHALLENGE IN THE SHORT TERM DEALS WITH PCPN CHANCES THROUGH THE PERIOD. CURRENTLY ONGOING MCS LOCATED ACROSS ERN MT/WRN ND...WITH MORE ACCAS TYPE TSRA DEVELOPING IN LLJ REGION OF WRN SD...WITH IR TOPS INDICATING SOME COOLING TAKING PLACE ACROSS SWRN SD. RUC HAS THIS PCPN HANDLED FAIRLY WELL...WITH PCPN ADVECTION MOVING EAST/JUST NORTH OF EAST THROUGH THE REMAINDER OF THE MORNING. HAVE INCLUDED SOME LIKELY POPS FOR THE MORNING HOURS ACROSS SECTIONS OF THE NW CWA TO HANDLE CONVECTION THAT IS CURRENTLY ON GOING/EXPECTED TO DEVELOP. ATTENTION THEN TURNS TOWARD LATER THIS AFTERNOON/THIS EVENING FOR CONVECTIVE CHANCES. MODELS AGREE ON 7H TROF/WAVE COMBO TO IMPACT CWA LATER THIS AFTERNOON...WITH VERY SLOW MOVT EXPECTED WITH 7H TROF. BY 00Z THURSDAY...BOTH GFS/NAM SHOW SHOW QUITE A BIT OF 85H- 7H FRONTOGENESIS TAKING PLACE ACROSS THE MO RIVER REGION...ALONG WITH SPEC HUMIDITIES AOA 10G/KG. 7H TEMPS MAY BE JUST HIGH ENOUGH TO KEEP ATMOS CAPPED THROUGH 21/22Z BEFORE ALLOWING RAPID CONVECTIVE DEVELOPMENT. THE MAIN UNCERTAINITY IN THIS IS THE SKY COVER. CURRENT MCS SHIELD OVERSPREADING CWA...AND THIS MAY BE ENOUGH TO HELP INHIBIT SOME DEVELOPMENT. THINK THAT THE WRN PART OF THE CWA WILL CLEAR OUT ENOUGH LATER THIS AFTN FOR RAPID DESTABILIZATION TO TAKE PLACE. ALSO...NOTICED THAT LOW LEVEL TRAJECTORIES TURN MORE SOUTHERLY AHEAD OF EXPECTED SFC TROF...WHICH SHOULD ALSO ALLOW MORE LOLEVEL MOISTURE TO STREAM NORTHWARD. NOTICED THAT DWPTS ACROSS SC NEB AT 08Z WERE IN THE LOWER 70S. GFS HAS PWATS APPROACHING 2 INCHES BY 00Z TONIGHT. STEERING FLOW LOOKS TO BE SUFFICENT TO PREVENT A LARGE RESIDENCE TIME...SO NO PLANS ON ANY HEAVY RAIN HEADLINES ATTM...BUT LOCALLY HEAVY RAIN IS GOING TO BE POSSIBLE...SO WILL COVER IN THE HWO. WITH WRN PART OF THE CWA ALSO EXPECTED TO CLEAR...WILL COVER PSBL SEVERE IN THE HWO. 7H TROF IS SLOW TO MOVE EAST...SO MECHANISM WILL RESET A BIT FOR THURSDAY...ALTHO HIGHER AXIS OF PWATS DO SHIFT A BIT MORE SOUTH AND EAST. CONCERN IS THAT BOTH NAM/GFS HIGHLIGHT SFC LOW MOVING SLOWLY THROUGH DURING THE DAY. OVERNIGHT CONVECTION LEAVES ERN CWA THURSDAY MORNING...WITH ANOTHER ROUND OF CONVECTION DEVELOPING IN POST FROPA INSTABILITY AXIS WITH NEXT 7H WAVE IMPACTING SLOW MOVING FEATURE. HAVE ADDED IN SOME SLIGHT CHC POPS FOR THURSDAY AFTN...AND THESE WILL NEED TO BE REVISITED DURING LATER SHIFTS TO SEE IF THURSDAY AFTN INSTABILITY DOES INDEED DEVELOP. TEMP WISE...HAVE STUCK PRETTY CLOSE TO INHERITED GRIDS AS TEMPS WILL BE HIGHLY DEPENDANT UPON THE AMOUNT OF CLEARING THAT TAKES PLACE COUPLED WITH HOW MUCH MOISTURE DOES ADVECT NORTHWARD. .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY THE BEST CHANCES FOR THUNDER STILL RESIDE ACROSS THE WESTERN HALF OF FORECAST ZONES...SATURDAY NIGHT AND THEN AGAIN MONDAY AND MONDAY NIGHT...PER THE LATEST 12Z/00Z GFS/EC OPERATIONAL SOLUTIONS. BOTH OF THESE MODELS ARE IN FAIR AGREEMENT ALOFT THROUGH APPX 96 HOURS...BEFORE BEGINNING TO DIVERGE ON TIMING/AMPLITUDE OF MID/UPPER LEVEL TROF/RIDGE AXES OVER THE LOWER 48. BOTH MODELS HINT AT SHORTWAVE TROFPAS SATURDAY NIGHT AND AGAIN SOMEWHERE IN THAT MONDAY/MONDAY NIGHT TIMEFRAME. NO NOTABLE CHANGES MADE TO FRIDAY NIGHT THROUGH SUNDAY AFTERNOON PORTION OF THE EXTENDED WITH THE MORNING FORECAST PACKAGE. && .AVIATION... RATHER COMPLEX AVIATION FORECAST FOR THE NEXT 24 HOURS WITH CONVECTION SCATTERED ACROSS THE CWA. THIS WILL CONTINUE THROUGH THE LATE MORNING AND EARLY AFTERNOON WITH AN ISOLD CB...BUT MORE GENERALLY 8-10KFT BASED SHRA ACTIVITY. ONE CAVEAT IS THAT FROM KMBG TO KBIS THERE IS AN AREA OF MVFR CIGS...BUT EXPECT THIS WILL LIFT OUT AS CLEARING LINE MOVES EAST DURING THE LATE MORNING HOURS. CB ACTIVITY IS EXPECTED TO BECOME MORE WIDESPREAD DURING THE MID TO LATE AFTERNOON...WITH STRONG TO SEVERE STORMS POSSIBLE THIS EVENING MOVING IN A LINE FROM KPIR/KMBG...BUT WILL LIKELY SEE A DECREASE IN ACTIVITY AS THIS LINE MOVES TOWARD THE ATY/KABR TERMINALS LATE THIS EVENING. SYSTEM WILL EVOLVE INTO A HEAVY RAIN PRODUCER WITH BRIEF MVFR/IFR CIGS/VISBY POSSIBLE AS IT MOVES THROUGH KABR/KATY AND POINTS EAST. AS ALWAYS DURING THE SUMMER CONVECTIVE SEASON...AREAS THAT SEE HEAVY RAINFALL TODAY COULD EXPERIENCE FOG DEVELOPMENT OVERNIGHT. WE WILL ALSO SEE A SECOND FRONTAL FEATURE MOVE INTO THE REGION THURSDAY...AND WITH PLENTY OF MOISTURE AROUND...MORE THUNDERSTORM DEVELOPMENT FOR MUCH OF THE AFTERNOON. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...TMT SHORT TERM...HINTZ LONG TERM...DORN AVIATION...CONNELLY WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 410 AM CDT WED JUL 23 2008 .SHORT TERM...TODAY THROUGH FRIDAY MAIN FCST CHALLENGE IN THE SHORT TERM DEALS WITH PCPN CHANCES THROUGH THE PERIOD. CURRENTLY ONGOING MCS LOCATED ACROSS ERN MT/WRN ND...WITH MORE ACCAS TYPE TSRA DEVELOPING IN LLJ REGION OF WRN SD...WITH IR TOPS INDICATING SOME COOLING TAKING PLACE ACROSS SWRN SD. RUC HAS THIS PCPN HANDLED FAIRLY WELL...WITH PCPN ADVECTION MOVING EAST/JUST NORTH OF EAST THROUGH THE REMAINDER OF THE MORNING. HAVE INCLUDED SOME LIKELY POPS FOR THE MORNING HOURS ACROSS SECTIONS OF THE NW CWA TO HANDLE CONVECTION THAT IS CURRENTLY ON GOING/EXPECTED TO DEVELOP. ATTENTION THEN TURNS TOWARD LATER THIS AFTERNOON/THIS EVENING FOR CONVECTIVE CHANCES. MODELS AGREE ON 7H TROF/WAVE COMBO TO IMPACT CWA LATER THIS AFTERNOON...WITH VERY SLOW MOVT EXPECTED WITH 7H TROF. BY 00Z THURSDAY...BOTH GFS/NAM SHOW SHOW QUITE A BIT OF 85H- 7H FRONTOGENESIS TAKING PLACE ACROSS THE MO RIVER REGION...ALONG WITH SPEC HUMIDITIES AOA 10G/KG. 7H TEMPS MAY BE JUST HIGH ENOUGH TO KEEP ATMOS CAPPED THROUGH 21/22Z BEFORE ALLOWING RAPID CONVECTIVE DEVELOPMENT. THE MAIN UNCERTAINITY IN THIS IS THE SKY COVER. CURRENT MCS SHIELD OVERSPREADING CWA...AND THIS MAY BE ENOUGH TO HELP INHIBIT SOME DEVELOPMENT. THINK THAT THE WRN PART OF THE CWA WILL CLEAR OUT ENOUGH LATER THIS AFTN FOR RAPID DESTABILIZATION TO TAKE PLACE. ALSO...NOTICED THAT LOW LEVEL TRAJECTORIES TURN MORE SOUTHERLY AHEAD OF EXPECTED SFC TROF...WHICH SHOULD ALSO ALLOW MORE LOLEVEL MOISTURE TO STREAM NORTHWARD. NOTICED THAT DWPTS ACROSS SC NEB AT 08Z WERE IN THE LOWER 70S. GFS HAS PWATS APPROACHING 2 INCHES BY 00Z TONIGHT. STEERING FLOW LOOKS TO BE SUFFICIENT TO PREVENT A LARGE RESIDENCE TIME...SO NO PLANS ON ANY HEAVY RAIN HEADLINES ATTM...BUT LOCALLY HEAVY RAIN IS GOING TO BE POSSIBLE...SO WILL COVER IN THE HWO. WITH WRN PART OF THE CWA ALSO EXPECTED TO CLEAR...WILL COVER PSBL SEVERE IN THE HWO. 7H TROF IS SLOW TO MOVE EAST...SO MECHANISM WILL RESET A BIT FOR THURSDAY...ALTHO HIGHER AXIS OF PWATS DO SHIFT A BIT MORE SOUTH AND EAST. CONCERN IS THAT BOTH NAM/GFS HIGHLIGHT SFC LOW MOVING SLOWLY THROUGH DURING THE DAY. OVERNIGHT CONVECTION LEAVES ERN CWA THURSDAY MORNING...WITH ANOTHER ROUND OF CONVECTION DEVELOPING IN POST FROPA INSTABILITY AXIS WITH NEXT 7H WAVE IMPACTING SLOW MOVING FEATURE. HAVE ADDED IN SOME SLIGHT CHC POPS FOR THURSDAY AFTN...AND THESE WILL NEED TO BE REVISITED DURING LATER SHIFTS TO SEE IF THURSDAY AFTN INSTABILITY DOES INDEED DEVELOP. TEMP WISE...HAVE STUCK PRETTY CLOSE TO INHERITED GRIDS AS TEMPS WILL BE HIGHLY DEPENDANT UPON THE AMOUNT OF CLEARING THAT TAKES PLACE COUPLED WITH HOW MUCH MOISTURE DOES ADVECT NORTHWARD. .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY THE BEST CHANCES FOR THUNDER STILL RESIDE ACROSS THE WESTERN HALF OF FORECAST ZONES...SATURDAY NIGHT AND THEN AGAIN MONDAY AND MONDAY NIGHT...PER THE LATEST 12Z/00Z GFS/EC OPERATIONAL SOLUTIONS. BOTH OF THESE MODELS ARE IN FAIR AGREEMENT ALOFT THROUGH APPX 96 HOURS...BEFORE BEGINNING TO DIVERGE ON TIMING/AMPLITUDE OF MID/UPPER LEVEL TROF/RIDGE AXES OVER THE LOWER 48. BOTH MODELS HINT AT SHORTWAVE TROFPAS SATURDAY NIGHT AND AGAIN SOMEWHERE IN THAT MONDAY/MONDAY NIGHT TIMEFRAME. NO NOTABLE CHANGES MADE TO FRIDAY NIGHT THROUGH SUNDAY AFTERNOON PORTION OF THE EXTENDED WITH THE MORNING FORECAST PACKAGE. && .AVIATION... 06Z TAFS FOR KABR...KATY...KPIR AND KMBG VFR PARTLY TO MOSTLY CLOUDY SKIES WITH UNRESTRICTED VISBYS PREVAIL THROUGH TODAY. CIGS WILL REMAIN MAINLY AT OR ABOVE 5000FT AGL THROUGHOUT THE TAF VALID PERIOD. AN AREA OF LOW PRESSURE WILL MOVE THROUGH THE REGION FROM THE WEST TODAY AND TONIGHT RESULTING IN SCATTERED SHOWERS AND THUNDERSTORMS THIS MORNING MOVING ACROSS THE KPIR AND KMBG TERMINALS. BETWEEN 15Z AND 21Z TODAY...THE MAIN THREAT FOR THUNDER IS SHIFTING EAST TO IMPACT THE KABR AND KATY TERMINALS. THESE SHOWERS AND STORMS WILL BE RATHER EFFICIENT AT PRODUCING HEAVY RAIN...SO ANTICIPATE IFR CIG/VISBY REDUCTIONS UNDERNEATH THESE STORMS THIS AFTERNOON. THEN...FROM 00Z TO 06Z TONIGHT...THE FOCUS FOR POTENTIAL THUNDERSTORM REDEVELOPMENT WILL BACK-PEDDLE TO THE WEST...AGAIN WITH THE KPIR AND KMBG TERMINALS MAINTAINING THE GREATEST POTENTIAL TO SEE THUNDERSTORMS RUMBLE THROUGH TERMINAL AIRSPACE DURING THE EVENING HOURS. THESE EVENING THUNDERSTORMS WILL BE CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING THUNDERSTORM WIND GUSTS. WILL WHITTLE DOWN TSRA MENTION IN THE TAFS AS THUNDERSTORM EVENT TIMES GROW CLOSER...STARTING OUT THIS MORNING MAINLY WITH CB MENTION AND/OR VCTS AS WARRANTED...UPDATING WITH TSRA MENTION IN THE NEARER TERM AS APPROPRIATE. SURFACE WINDS SHOULD MAINTAIN A SOUTH-SOUTHEASTERLY DIRECTION AND BREEZY FOR MUCH OF THE TAF VALID PERIOD. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ SHORT TERM...HINTZ LONG TERM...DORN AVIATION...DORN WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 1035 PM CDT WED JUL 23 2008 .UPDATE... CONVECTION HAVING A HARD TIME HOLDING TOGETHER AND THE TRAJECTORY OF A FEEDER BAND OVER THE GULF IS HEADING MORE TOWARD THE CRP CWA. STILL FEEL SHRA/TSRA WILL REDEVELOP OVERNIGHT BUT TORNADO THREAT IS SMALL. HAVE COORDINATED WITH SPC AND CANCELED THE TORNADO WATCH. OTHER THAN THE HEADLINES...NO CHANGES. 43 && .PREV DISCUSSION... /ISSUED 917 PM CDT WED JUL 23 2008/ UPDATE... MOISTURE WRAPPING AROUND DOLLY CONTINUES TO ADVECT INTO SOUTHEAST TEXAS. PW`S ARE AROUND 2.3 INCHES ALONG THE UPPER COAST. THERE SHOULD BE A GAP IN PRECIP THROUGH ABOUT 2 AM BEFORE ANOTHER SURGE IN MOISTURE APPROACHES THE COAST. INITIAL THOUGHTS WERE THAT THE PRECIP WOULD CONTRACT TOWARD THE CENTER OF DOLLY BUT RADAR RETURNS SUGGEST OTHERWISE. WILL LEAN TOWARD A 00Z NAM 12/RUC 40 SOLUTION OVERNIGHT INTO THURSDAY MORNING. TORNADO THREAT IS MINIMAL BUT PREFER TO LET THE WATCH GO TO AT LEAST 04Z. LOWERED POPS OVER THE NORTH SIGNIFICANTLY OVERNIGHT. TEMP FORECAST LOOKS OK. NEW NAM AND FWC GUIDANCE SUPPORT HIGH RAIN CHANCES AGAIN ON THURSDAY. 43 PREV DISCUSSION... /ISSUED 717 PM CDT WED JUL 23 2008/ UPDATE... SPC HAS ISSUED A NEW TORNADO WATCH 741 TO REPLACE THE EXPIRED WATCH. THE ONLY COUNTIES LEFT IN THE WATCH ARE JACKSON AND MATAGORDA. THE FEEDER BAND ROLLING INTO MATAGORDA COUNTY DID PRODUCE SEVERAL REPORTS OF A FUNNEL CLOUD. THINK THE THREAT WILL DIMINISH AFTER 04Z AS THE PRECIP SHIELD CONTRACTS AROUND THE CENTER OF DOLLY. NO OTHER CHANGES AT THIS TIME. 43 PREV DISCUSSION... /ISSUED 657 PM CDT WED JUL 23 2008/ DISCUSSION... ISSUING THE EARLY EVENING AVIATION DISCUSSION. AVIATION... RAIN BANDS CAUGHT UP IN THE OUTER CIRCULATION AROUND DOLLY WILL AFFECT MOST OF THE TERMINAL SITES THIS EVENING...AT LEAST UNTIL AROUND 03Z. EXPECT THE ACTIVITY TO DIMINISH DURING THE LATE EVENING AND OVERNIGHT AS A CORE TROPICAL CYCLONE EVENT SETS UP DOWN SOUTH. THAT BEING SAID...THE CONFIDENCE FACTOR IS NOT HIGH ENOUGH TO TAKE OUT ALL MENTION OF RAIN. BECAUSE OF THE RAIN TODAY...MVFR CEILINGS ARE POSSIBLE TONIGHT INTO THURSDAY MORNING. THURSDAY AFTERNOON THE BEST THUNDERSTORM CHANCES WILL BE FROM THE BIG AIRPORTS SOUTH TO THE COAST. WIND SPEEDS SHOULD DIMINISH LATER THIS EVENING. THROUGH THE EARLY EVENING...STRONGER WINDS OF UP TO 30 KNOTS WILL BE PRESENT JUST ABOVE THE SURFACE AND COULD BE MIXED DOWN TO THE SURFACE IN ANY SHOWERS OR THUNDERSTORMS THAT DO AFFECT A TERMINAL SITE. 40 PREV DISCUSSION... /ISSUED 256 PM CDT WED JUL 23 2008/ DISCUSSION... RAIN BANDS ASSOCIATED WITH DOLLY WILL CONTINUE TO MOVE ACROSS SOUTHEAST TEXAS ESPECIALLY THE SOUTHERN HALF OF CWFA THIS AFTERNOON. RADAR RAINFALL TOTALS INDICATE HEAVIEST ACCUMULATIONS JUST WEST OF BAY CITY AND NEAR PALACIOS ABOUT 2.4 INCHES. REST OF CWFA (MAINLY SOUTHERN HALF INDICATE RAINFALL AMOUNTS OF 1/8 TO NEAR AN INCH). RAIN CHANCES SHOULD BE LOWER TONIGHT EXCEPT LIKELY FOR SW ZONES WHERE RAIN BANDS WILL BE MORE FREQUENT (COMING FROM THE EAST AND SOUTHEAST). MODELS DO INDICATE A CONTINUED GOOD CHANGE OF RAIN TOMORROW WITH PW VALUES REMAINING HIGH. HOWEVER THE NORTHEAST ZONES PROBABLY WILL HAVE LOWER POPS AND TO A LESSER EXTENT THE REST OF THE NORTHERN ZONES DUE TO THE INFLUENCE OF THE SOUTHERN PERIPHERY OF UPPER RIDGE. UPPER HIGH WILL START TO RIDGE OVER OUR CWFA THE END OF THE WEEK AND INTO THE WEEKEND SQUELCHING RAIN CHANCES WITH INCREASING MID/UPPER LEVEL SUBSIDENCE. WARMER TEMPERATURES WILL BE IN STORE FOR US DURING THIS PERIOD. UPPER RIDGE OF HIGH PRESSURE WILL WEAKEN BY TUESDAY NEXT WEEK AS AN INVERTED UPPER TROUGH APPROACH OUR REGION FROM THE EAST. GFS INDICATE PW VALUES STARTING TO INCREASE MID TO LATTER PERIOD OF NEXT WEEK. 37 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 76 89 75 94 74 / 20 50 20 20 10 HOUSTON (IAH) 76 88 76 93 75 / 40 50 20 20 20 GALVESTON (GLS) 79 86 79 90 81 / 60 50 20 20 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT ADVISORY UNTIL 7 PM CDT THURSDAY FOR THE FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY...WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL 20 NM TO 60 NM...WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM. && $$ DISCUSSION...43 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 917 PM CDT WED JUL 23 2008 .UPDATE... MOISTURE WRAPPING AROUND DOLLY CONTINUES TO ADVECT INTO SOUTHEAST TEXAS. PW`S ARE AROUND 2.3 INCHES ALONG THE UPPER COAST. THERE SHOULD BE A GAP IN PRECIP THROUGH ABOUT 2 AM BEFORE ANOTHER SURGE IN MOISTURE APPROACHES THE COAST. INITIAL THOUGHTS WERE THAT THE PRECIP WOULD CONTRACT TOWARD THE CENTER OF DOLLY BUT RADAR RETURNS SUGGEST OTHERWISE. WILL LEAN TOWARD A 00Z NAM 12/RUC 40 SOLUTION OVERNIGHT INTO THURSDAY MORNING. TORNADO THREAT IS MINIMAL BUT PREFER TO LET THE WATCH GO TO AT LEAST 04Z. LOWERED POPS OVER THE NORTH SIGNIFICANTLY OVERNIGHT. TEMP FORECAST LOOKS OK. NEW NAM AND FWC GUIDANCE SUPPORT HIGH RAIN CHANCES AGAIN ON THURSDAY. 43 && .PREV DISCUSSION... /ISSUED 717 PM CDT WED JUL 23 2008/ UPDATE... SPC HAS ISSUED A NEW TORNADO WATCH 741 TO REPLACE THE EXPIRED WATCH. THE ONLY COUNTIES LEFT IN THE WATCH ARE JACKSON AND MATAGORDA. THE FEEDER BAND ROLLING INTO MATAGORDA COUNTY DID PRODUCE SEVERAL REPORTS OF A FUNNEL CLOUD. THINK THE THREAT WILL DIMINISH AFTER 04Z AS THE PRECIP SHIELD CONTRACTS AROUND THE CENTER OF DOLLY. NO OTHER CHANGES AT THIS TIME. 43 PREV DISCUSSION... /ISSUED 657 PM CDT WED JUL 23 2008/ DISCUSSION... ISSUING THE EARLY EVENING AVIATION DISCUSSION. AVIATION... RAIN BANDS CAUGHT UP IN THE OUTER CIRCULATION AROUND DOLLY WILL AFFECT MOST OF THE TERMINAL SITES THIS EVENING...AT LEAST UNTIL AROUND 03Z. EXPECT THE ACTIVITY TO DIMINISH DURING THE LATE EVENING AND OVERNIGHT AS A CORE TROPICAL CYCLONE EVENT SETS UP DOWN SOUTH. THAT BEING SAID...THE CONFIDENCE FACTOR IS NOT HIGH ENOUGH TO TAKE OUT ALL MENTION OF RAIN. BECAUSE OF THE RAIN TODAY...MVFR CEILINGS ARE POSSIBLE TONIGHT INTO THURSDAY MORNING. THURSDAY AFTERNOON THE BEST THUNDERSTORM CHANCES WILL BE FROM THE BIG AIRPORTS SOUTH TO THE COAST. WIND SPEEDS SHOULD DIMINISH LATER THIS EVENING. THROUGH THE EARLY EVENING...STRONGER WINDS OF UP TO 30 KNOTS WILL BE PRESENT JUST ABOVE THE SURFACE AND COULD BE MIXED DOWN TO THE SURFACE IN ANY SHOWERS OR THUNDERSTORMS THAT DO AFFECT A TERMINAL SITE. 40 PREV DISCUSSION... /ISSUED 256 PM CDT WED JUL 23 2008/ DISCUSSION... RAIN BANDS ASSOCIATED WITH DOLLY WILL CONTINUE TO MOVE ACROSS SOUTHEAST TEXAS ESPECIALLY THE SOUTHERN HALF OF CWFA THIS AFTERNOON. RADAR RAINFALL TOTALS INDICATE HEAVIEST ACCUMULATIONS JUST WEST OF BAY CITY AND NEAR PALACIOS ABOUT 2.4 INCHES. REST OF CWFA (MAINLY SOUTHERN HALF INDICATE RAINFALL AMOUNTS OF 1/8 TO NEAR AN INCH). RAIN CHANCES SHOULD BE LOWER TONIGHT EXCEPT LIKELY FOR SW ZONES WHERE RAIN BANDS WILL BE MORE FREQUENT (COMING FROM THE EAST AND SOUTHEAST). MODELS DO INDICATE A CONTINUED GOOD CHANGE OF RAIN TOMORROW WITH PW VALUES REMAINING HIGH. HOWEVER THE NORTHEAST ZONES PROBABLY WILL HAVE LOWER POPS AND TO A LESSER EXTENT THE REST OF THE NORTHERN ZONES DUE TO THE INFLUENCE OF THE SOUTHERN PERIPHERY OF UPPER RIDGE. UPPER HIGH WILL START TO RIDGE OVER OUR CWFA THE END OF THE WEEK AND INTO THE WEEKEND SQUELCHING RAIN CHANCES WITH INCREASING MID/UPPER LEVEL SUBSIDENCE. WARMER TEMPERATURES WILL BE IN STORE FOR US DURING THIS PERIOD. UPPER RIDGE OF HIGH PRESSURE WILL WEAKEN BY TUESDAY NEXT WEEK AS AN INVERTED UPPER TROUGH APPROACH OUR REGION FROM THE EAST. GFS INDICATE PW VALUES STARTING TO INCREASE MID TO LATTER PERIOD OF NEXT WEEK. 37 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 76 89 75 94 74 / 40 50 20 20 10 HOUSTON (IAH) 76 88 76 93 75 / 40 60 20 20 20 GALVESTON (GLS) 79 86 79 90 81 / 60 60 20 20 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT ADVISORY UNTIL 7 PM CDT THURSDAY FOR THE FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY...WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL 20 NM TO 60 NM...WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM. && $$ DISCUSSION...43 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 310 PM CDT WED JUL 23 2008 .SHORT TERM...TONIGHT THROUGH SATURDAY FORECAST CONCERNS THROUGH THE PERIOD WILL FOCUS ON PRECIPITATION CHANCES LATER TONIGHT THROUGH FRIDAY EVENING. SURFACE MAP THIS AFTERNOON HAD A RIDGE OF HIGH PRESSURE CENTERED OVER WI/UPPER MICHIGAN WHILE A TROUGH OF LOW PRESSURE WAS LOCATED FROM WESTERN SD THROUGH EASTERN CO. FAIRLY NARROW CORRIDOR OF LOW LEVEL MOISTURE TRANSPORT/CONVERGENCE AHEAD OF THE TROUGH WAS MAINTAINING CLUSTERS OF SHRA/OCNL THUNDER ACROSS THE EASTERN DAKOTAS. THIS HAS BEEN ONGOING ALL DAY. OTHERWISE...TEMPERATURES CURRENTLY IN THE MID AND UPPER 70 AND DEW POINTS IN THE 50S TO LOWER 60S ACROSS THE LOCAL FORECAST AREA FAIRLY ATYPICAL FOR LATTER JULY. 23.12Z GFS/NAM SHORT TERM MODELS IN FAIRLY GOOD AGREEMENT WITH NO GLARING DIFFERENCES NOTED. THE RIDGE OF HIGH PRESSURE WILL DRIFT SLOWLY EAST INTO THE GREAT LAKES REGION TONIGHT AS THE TROUGH OVER THE NORTHERN PLAINS BUDGES INTO WESTERN MN THROUGH EASTERN NEB BY 12Z. EASTERN PERIPHERY OF 925-700MB MOISTURE TRANSPORT AHEAD OF THE TROUGH WILL EDGE INTO WESTERN SECTIONS OF THE FORECAST AREA AFTER MIDNIGHT...THICKENING CLOUD COVER AND BRINGING A CHANCE OF PRECIPITATION TO AREAS ALONG AND WEST OF THE MISSISSIPPI RIVER. MUCAPE NOT ALL THAT IMPRESSIVE ...SO CARRIED SHRA/ISOLATED THUNDER MENTION FOR AREAS WEST OF THE MISSISSIPPI AFTER MIDNIGHT. THE TROUGH WILL REMAIN FAIRLY STATIONARY ACROSS WESTERN MN/EASTERN NEB THROUGH THURSDAY WITH THE MAIN SLUG OF LOW LEVEL MOISTURE TRANSPORT STAYING ALONG AND SOUTH OF I-80 ACROSS IA THROUGH THE DAY. THIS WILL FUEL A CLUSTER OF THUNDERSTORMS ACROSS EASTERN IA/NORTHWEST IL BY TOMORROW MORNING WITH NORTHERN PERIPHERY OF THIS STRONGER TRANSPORT SIGNAL EDGING INTO SOUTHEAST MN/NORTHEAST IA COUNTIES. BASED ON THIS SIGNAL...CARRIED LIKELY SHRA/T CHANCES ACROSS THAT AREA IN THE 12-18Z TIME FRAME. MODELS STILL SHOWING A SECONDARY LIGHTER MOISTURE TRANSPORT SIGNAL FURTHER NORTH ACROSS THE AREA FOR A SMALLER CHANCE OF SHRA/T. AGAIN...MUCAPE IS NOT THAT IMPRESSIVE...SO WOULD EXPECT MAINLY SHRA WITH PERHAPS A RUMPLE OR TWO OF THUNDER. WITH CLOUD COVER AND SCATTERED CONVECTION IN THE AREA THURSDAY...TEMPERATURES WILL BE BE WELL BELOW NORMAL TOPPING OFF IN THE MID 70S TO UPPER 70S. WEAK LOW-LEVEL MOISTURE TRANSPORT AHEAD OF THE TROUGH WILL CONTINUE SHRA/ISOLD T CHANCES ACROSS THE AREA THURSDAY NIGHT. ON FRIDAY...A STRONGER MID-LEVEL SHORTWAVE TROUGH COMING ACROSS THE NORTHERN PLAINS WILL TRANSITION THE SURFACE TROUGH INTO A COLD FRONT AND PUSH IT INTO THE AREA BY AFTERNOON. MOISTURE TRANSPORT NOT PARTICULARLY STRONG AHEAD OF THIS WAVE...BUT BUILDING CAPE INTO THE 1000-2000J/KG RANGE WITH SURFACE HEATING AHEAD OF THE FRONT SHOULD BE AMPLE FOR SCATTERED SHRA/TS ACTIVITY. BUMPED POPS INTO TE 30-40 PERCENT RANGE BASED ON THIS FOR THE AFTERNOON HOURS ON FRIDAY. THE FRONT WILL DROP SLOWLY SOUTHEAST ACROSS THE AREA THROUGH THE EVENING HOURS FRIDAY WITH LINGERING SHRA/TS CHANCES...THEN EXIT THE AREA AROUND MIDNIGHT. SLIGHTLY COOLER AND DRIER CANADIAN AIRMASS WILL SETTLE INTO THE AREA ON SATURDAY FOR PLEASANT CONDITIONS. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY 23.00Z/06Z MEDIUM RANGE MODELS SHOWING FRONTAL BOUNDARY SETTLING WELL SOUTH OF THE AREA SATURDAY NIGHT/SUNDAY TIME FRAME. MODELS HAVE A WEAK MID-LEVEL SHORTWAVE TROUGH RIPPLING ALONG THE FRONTAL BOUNDARY WITH PERHAPS THE NORTHERN EDGE OF RESULTANT SHRA/TS ACTIVITY TOUCHING FAR SOUTHERN SECTIONS OF THE FORECAST AREA. GFS ENSEMBLE OF PRECIPITATION PROBABILITIES KEEP EVERYTHING SOUTH...SO HAVE OPTED TO GO WITH A DRY FORECAST FOR NOW. WILL BUMP UP CLOUD COVER SOMEWHAT AS ALMOST CERTAIN THAT SOME CONVECTIVE DEBRIS CLOUDS WILL AT LEAST AFFECT SOUTHERN PORTIONS OF THE AREA. THEN FOR MONDAY THROUGH WEDNESDAY...THE GEM/DGEX/GFS ENSEMBLES AMPLIFY RIDGING ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST REGION. THE DETERMINISTIC GFS/ECMWF WANT TO BLOW A COLD FRONT THROUGH THE RIDGE IN THE TUESDAY/WEDNESDAY TIME FRAME...BUT THIS SEEMS LIKE AN OUTLIER SOLUTION GIVEN THE STRENGTH OF THE RIDGE. WILL GO WITH A DRY FORECAST FOR NOW. GFS AND ECMWF KEEP 850MB TEMPERATURES IN CHECK THROUGH THE PERIOD WITH THE GFS STARTING OUT IN THE 10-13C RANGE ON SUNDAY...WARMING TO AROUND 16-17C BY WEDNESDAY. THE ECMWF IS SLIGHT COOLER. BOTTOM LINE...IT WILL BE DRY WITH TEMPERATURES JUST A FEW DEGREES BELOW SEASONAL NORMALS. && .AVIATION...TONIGHT THROUGH THURSDAY MORNING 12Z MODELS IN GOOD AGREEMENT OF DEVELOPING A CONVECTIVE COMPLEX OVER WESTERN MINNESOTA THIS EVENING AND BRINGING THIS EAST/SOUTHEAST THROUGH THURSDAY MORNING. BY LATE TONIGHT INTO THURSDAY MORNING...THE LOW LEVEL JET AND MOISTURE TRANSPORT REALLY STARTS TO TAKE A TURN TO THE SOUTHWEST AND BECOMES MORE FOCUSED OVER SOUTHEAST IOWA. THIS WOULD SUGGEST THAT THE COMPLEX SHOULD BE ON A DIMINISHING TREND AS IT APPROACHES THE AREA. THE CONCERN BECOMES WHETHER THIS WILL HOLD TOGETHER LONG ENOUGH TO BRING ANY RAIN TO THE TAF SITES. PREVIOUS TAFS INTRODUCED VCSH FOR KRST AND HAVE CONTINUED THIS TREND BUT PUSHED THE TIMING BACK A LITTLE FOR A SLOWER ARRIVAL. THE NAM HAS BEEN CONSISTENT FOR A COUPLE RUNS OF SHOWING THE RAIN REACHING KLSE AS WELL. THE 23.09Z SREFS DO BRING IN PROBABILITIES OF 30-40 FOR KLSE AND BOTH THE 23.00Z ARW WRF AND 23.09Z RUC WRF SUGGEST THE RAIN WILL REACH KLSE SO HAVE INTRODUCED A VCSH THERE AS WELL. NO CAPE IS FORECAST TO BE PRESENT THROUGH 18Z THURSDAY SO NO MENTION OF THUNDER OR INCLUSION OF CB. CEILINGS EXPECTED TO STAY ABOVE 5K FEET FOR THE MOST PART. THE 23.12Z NAM BUFKIT SOUNDINGS SUGGEST KRST MAY GO DOWN TO 3K FEET OR LOWER BY MID TO LATE MORNING. OBSERVATIONS OVER SOUTH DAKOTA WITH THE RAIN THIS MORNING DID INDICATE MVFR CEILINGS SO HAVE TRENDED TOWARD THIS POSSIBILITY. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...DAS AVIATION..........04 wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 227 PM CDT TUE JUL 22 2008 .SHORT TERM...TONIGHT THROUGH FRIDAY MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES WEDNESDAY NIGHT INTO THURSDAY NIGHT. LATEST WATER VAPOR SATELLITE IMAGERY INDICATING UPPER LEVEL TROUGH OVER NORTHEASTERN U.S. AND UPPER LEVEL RIDGE OVER THE NORTHERN PLAINS AND HIGH PLAINS. LATEST WATER VAPOR IMAGERY ALSO INDICATING WEAK SHORTWAVE TROUGH EMBEDDED IN NORTHERLY FLOW ALOFT OVER NORTHEAST WISCONSIN. WITH DAYTIME HEATING AND STEEP LAPSE RATES PER 22.15Z RUC OVER THE REGION...ISOLATED SHOWERS AND THUNDERSTORMS HAVE DEVELOPED OVER NORTHEAST WISCONSIN THIS AFTERNOON. 22.12Z GFS AND NAM INITIALIZE UPPER LEVEL PATTERN AND ASSOCIATED SHORTWAVE TROUGHS PER WATER VAPOR SATELLITE IMAGERY. NO REAL SIGNIFICANT DIFFERENCES NOTED...THOUGH 22.12Z GFS SLIGHTLY FARTHER NORTH WITH MOISTURE TRANSPORT AND CONVERGENCE ASSOCIATED WITH SHORTWAVE TROUGH THURSDAY. THIS WILL HAVE AN IMPACT...AS FAR AS HOW FAR NORTH PRECIPITATION WILL BE THURSDAY ACROSS FORECAST AREA. BOTH MODELS AND 22.09Z SREF FOCUS MESO COMPLEX SYSTEM ACROSS SOUTHERN FORECAST AREA WEDNESDAY NIGHT INTO THURSDAY. CONFIDENCE IN FORECAST WEDNESDAY NIGHT INTO THURSDAY IS LOW...BASED ON EXACT PLACEMENT OF THE MESO COMPLEX SYSTEM. TONIGHT INTO WEDNESDAY...SURFACE RIDGE OVER SOUTHERN ONTARIO CANADA BUILDS SOUTHWARD ACROSS FORECAST AREA 18Z WEDNESDAY. ISOLATED SHOWERS AND THUNDERSTORMS ASSOCIATED WITH SHORTWAVE TROUGH OVER NORTHEAST WISCONSIN WILL BEGIN TO DIMINISH BY SUNSET...AS LOSS OF DAYTIME INSTABILITY AND SUBSIDENCE UNDER SURFACE RIDGE MOVES OVER THE REGION AFTER 03Z. HAVE INTRODUCED ISOLATED SHOWERS AND THUNDERSTORMS THROUGH 03Z WEDNESDAY ACROSS THE NORTHEAST FORECAST AREA. SURFACE RIDGE BUILDS EAST OF FORECAST AREA WEDNESDAY NIGHT INTO THURSDAY AND NEXT SHORTWAVE TROUGH EJECTS OUT OF THE UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST AND FLATTENS UPPER LEVEL RIDGE. THIS WILL RESULT IN RETURN OF SOUTHERLY FLOW AND MOISTURE INTO THE FORECAST AREA AFTER 06Z THURSDAY. BOTH THE 22.12Z GFS AND NAM IN GOOD AGREEMENT WITH MOVING SHORTWAVE TROUGH INTO THE NORTHERN PLAINS AND UPPER MIDWEST WEDNESDAY NIGHT INTO THURSDAY...AND FOCUS MOISTURE TRANSPORT AND CONVERGENCE INTO THE SOUTHERN PORTIONS OF THE FORECAST AREA AFTER 12Z THURSDAY. BOTH MODELS DO INDICATE BEST INSTABILITY AND SHEAR ASSOCIATED WITH SHORTWAVE TROUGH TO BE SOUTH AND WEST OF FORECAST AREA. AT THIS TIME...NOT EXPECTING ANY SEVERE POTENTIAL WITH THUNDERSTORMS. WITH BOTH MODELS INDICATING DECENT LIFT AND CONVERGENCE WITH SHORTWAVE TROUGH...HAVE INCREASED PRECIPITATION CHANCES ACROSS THE SOUTHERN FORECAST AREA 12Z THURSDAY TO 00Z FRIDAY. BOTH MODELS INDICATE SURFACE COLD FRONT TO TRACK ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION AND UPPER LEVEL TROUGH TO BEGIN DIGGING OVER THE UPPER GREAT LAKES REGION THURSDAY NIGHT INTO FRIDAY. BOTH THE MODELS INDICATING WEAK MOISTURE CONVERGENCE ALONG SURFACE FRONT. HAVE KEPT SMALL PRECIPITATION CHANCES ACROSS FORECAST AREA THURSDAY NIGHT INTO FRIDAY. .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES FRIDAY NIGHT INTO SATURDAY...THEN TEMPERATURES THE REST OF THE PERIOD. THE 22.00Z GFS AND ECMWF ARE IN GOOD AGREEMENT IN DIGGING UPPER LEVEL TROUGH OVER THE GREAT LAKES REGION AND SOUTHERN ONTARIO THROUGH PERIOD. THE BIGGEST DIFFERENCE BETWEEN THE MODELS IS THE GFS MUCH STRONGER AND SLOWER MOVEMENT THAN THE ECMWF WITH THE SHORTWAVE TROUGH EMBEDDED IN NORTHWEST FLOW ON BACKSIDE OF UPPER LEVEL TROUGH FRIDAY NIGHT AND SATURDAY. THIS WOULD ALLOW FOR DEEPER MOISTURE AND STRONGER LIFT OVER MUCH OF THE FORECAST AREA FRIDAY NIGHT AND INTO SATURDAY. ENSEMBLES INDICATE HIGH VARIABILITY IN THE STRENGTH OF THE SHORTWAVE TROUGH AND INDICATES THE AXIS OF MEASURABLE PRECIPITATION PROBABILISTIC WILL BE JUST SOUTH AND EAST OF FORECAST AREA FRIDAY NIGHT AND SATURDAY. AT THIS TIME...WILL CONTINUE WITH DRY FORECAST ACROSS FORECAST AREA. THEN...BOTH MODELS ARE IN MUCH BETTER AGREEMENT IN BUILDING SURFACE/UPPER LEVEL RIDGE INTO THE UPPER MIDWEST AND GREAT LAKES REGION SUNDAY INTO EARLY NEXT WEEK. COLDER AIR FILTERS IN BEHIND SHORTWAVE TROUGH/SURFACE COLD FRONT SUNDAY ACROSS THE UPPER GREAT LAKES AND UPPER MIDWEST REGION. BOTH THE 22.00Z GFS AND ECMWF INDICATING 850MB TEMPERATURES FROM PLUS 10 DEGREES CELSIUS TO PLUS 15 DEGREES CELSIUS ACROSS FORECAST AREA. GOOD SUBSIDENCE AND COOLER AIR MASS OVER FORECAST AREA...WILL CONTINUE WITH TREND OF UNSEASONABLY COOLER TEMPERATURES AND DRIER WEATHER INTO EARLY NEXT WEEK. && .AVIATION... GENERALLY VFR CONDITIONS EXPECTED ACROSS THE TAF SITES THROUGH WEDNESDAY. ONLY ITEM WE ARE MONITORING IS THE VALLEY FOG POSSIBILITY FOR THE MISSISSIPPI RIVER AND WISCONSIN RIVER VALLEYS FOR WEDNESDAY MORNING. HAVE INTRODUCED AN MVFR TEMPO PERIOD AT KLSE FOR THIS CHANCE. THE DRYING NORTHEAST WIND WILL WORK AGAINST THE FOG FORMATION...BUT HIGHER SOIL MOISTURE AND PLANT EVAPOTRANSPIRATION WILL WORK TOWARD BETTER FOG CHANCES. OVERALL WIND FIELD IS ABOUT 5 KTS THROUGH THE LOWEST 2KFT UNDER CLEAR SKIES. FOG MAY BE LOCALIZED TO THE MAIN CHANNEL OF THE MISS RIVER AND OFF OF THE KLSE FIELD PROPER. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...DTJ AVIATION..........DAB wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 403 AM CDT TUE JUL 22 2008 FORECAST FOCUS ON PRECIPITATION CHANCES TODAY...COOLER AND LESS HUMID AIRMASS NEXT FEW DAYS. LATEST WATER VAPOR IMAGERY INDICATED AN ELONGATED UPPER LEVEL TROUGH OVER THE WESTERN GREAT LAKES REGION...WITH AN UPSTREAM RIDGE OVER THE WESTERN HIGH PLAINS. RUC ANALYSIS INDICATED A VORTICITY MAXIMUM WITHIN THE TROUGH...CENTERED OVER NORTHEAST MINNESOTA. AT THE SURFACE...CANADIAN HIGH PRESSURE WAS LOCATED ACROSS NORTHERN ONTARIO CANADA...MOVING SLOWLY SOUTH. A LOW CLOUD DECK WITH EMBEDDED RAIN SHOWERS WAS MOVING SOUTHWEST FROM THE DOOR COUNTY AREA. .SHORT TERM...TODAY THROUGH THURSDAY... PATCHY FOG SEEN OVER PORTIONS OF THE FORECAST AREA...WITH LIGHT WINDS AND MAINLY CLEAR SKIES. WILL CARRY EARLY MORNING FOG WORDING UNTIL DAYTIME HEATING PICKS UP. MORNING SHIFT WILL HAVE TO WATCH FOR LOW STRATUS DECK AND ASSOCIATED SHOWERS FROM NORTHEAST WISCONSIN MOVING INTO THE AREA. THINK THAT DAYTIME HEATING LATER THIS MORNING COMBINED WITH SLOW MOVEMENT OF DECK SHOULD PREVENT THIS AREA FROM MAKING IT THIS FAR SOUTH. AFOREMENTIONED VORTICITY MAXIMUM IS EXPECTED TO DROP SOUTHEAST ACROSS SOUTHERN WISCONSIN THIS AFTERNOON. THIS FEATURE SHOULD COMBINE WITH MEAN LAYER CAPE VALUES OF AROUND 500 J/KG TO BRING CHANCES FOR SHOWERS AND THUNDERSTORMS. WILL GO SHOWERS THIS MORNING...AND HOLD OFF ON THE THUNDER UNTIL THE AFTERNOON. CORE OF CANADIAN HIGH PRESSURE THEN DROPS THROUGH THE REGION TONIGHT THROUGH WEDNESDAY NIGHT. THIS FEATURE SHOULD BRING DRY CONDITIONS...A COOLER AND DRIER AIRMASS AND LIGHT WINDS. WEAK COLD AIR ADVECTION...WITH 1000/500MB THICKNESSES DROPPING INTO THE UPPER 550S TO MID 560S DKM RANGE TODAY...SHOULD BRING COOLER TEMPERATURES TO THE AREA. DEW POINTS SHOULD ALSO DROP INTO THE UPPER 50S TO AROUND 60 FAHRENHEIT...WHICH SHOULD MAKE FOR A LESS HUMID DAY. THE PASSING HIGH SHOULD ALLOW FOR NORTH TO NORTHEAST WINDS TO OCCUR NEAR THE LAKE TODAY AND WEDNESDAY...KEEPING HIGHS THERE IN THE UPPER 60S TO LOWER 70S. 1000/500MB THICKNESSES THEN RISE BACK INTO THE MID TO UPPER 560S DKM RANGE TONIGHT AND WEDNESDAY...WITH A SLOW MODERATION IN TEMPERATURES THROUGH THURSDAY AWAY FROM THE LAKE. LIGHT WINDS AND RADIATIONAL COOLING CONDITIONS SHOULD ALLOW FOR AT LEAST PATCHY FOG TO FORM TONIGHT AND WEDNESDAY NIGHT...ESPECIALLY IN THE RIVER VALLEYS AND LOW LYING AREAS. IF DEW POINTS STAY HIGHER THAN EXPECTED...COULD SEE SOME DENSE FOG IN SPOTS. NEXT CHANCE OF PRECIPITATION COMES LATE THURSDAY IN THE WESTERN COUNTIES...AS FOCUSED WARM AIR ADVECTION IN THE LOW LEVELS APPROACHES. .LONG TERM...THURSDAY NIGHT THROUGH MONDAY... POPS CONTINUE THURSDAY NIGHT WITH THE WARM AIR ADVECTION...AND FRIDAY AS A VORTICITY MAXIMUM PASSES JUST NORTH OF THE AREA. AFTER THAT...THE UPCOMING WEEKEND APPEARS DRY FOR NOW...WITH ANOTHER CANADIAN HIGH PRESSURE SYSTEM WORKING INTO THE AREA. && .AVIATION... AREAS OF IFR AND PATCHY LIFR IN FOG THIS MORNING UNTIL JUST AFTER 14Z. MID LEVEL TROF AXIS WILL SWING ACROSS THE FORECAST AREA TODAY. ENOUGH MOISTURE BELOW 15 THSD FT...SO EXPECT SOME CU/SC WITH A SCATTERED SHOWERS/ISOLATED THUNDERSTORMS MAINLY IN THE AFTERNOON. SOME MVFR CIGS EXPECTED. && .MARINE... SOME MORNING FOG. THEN NORTH TO NORTHEAST WINDS WILL INCREASE. WAVES MAY APPROACH SMALL CRAFT CRITERIA THIS AFTERNOON AND TONIGHT. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...NONE. && $$ SHORT/LONG TERM...08/WOOD AVIATION/MARINE...06/HENTZ wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 518 AM EDT THU JUL 24 2008 .DISCUSSION... CONVECTION THAT DEVELOPED ALONG SOUTHEASTWARD MOVING OUTFLOW OVER THE MAINLAND LATE YESTERDAY EVENING CONTINUES TO DISSIPATE THIS MORNING...WITH SHOWERS/STORMS NOW BECOMING CONCENTRATED OVER THE ATLANTIC WATERS. LATEST WATER VAPOR ANIMATION ALONG WITH RUC ANALYSES INDICATE THAT THE FLORIDA PENINSULA REMAINS LOCATED BENEATH A WEAKNESS IN THE UPPER-LEVEL RIDGE...WITH AN AMPLIFYING MID-LEVEL TROUGH LOCATED OVER THE EASTERN GREAT LAKES REGION...AND A WEAKER INVERTED TROUGH CENTERED OVER THE FLORIDA STRAITS JUST OFF THE SOUTHEAST COAST OF THE PENINSULA. GUIDANCE FROM THE NGM/NAM/GFS IS IN GOOD AGREEMENT WITH SOLUTIONS FROM THE UKMET/ECMWF IN ADVERTISING THIS STAGNANT PATTERN TO PERSIST FOR MUCH OF THE SHORT TERM. SIMILAR TO YESTERDAY...LIGHT EASTERLY FLOW IN THE BOUNDARY LAYER WILL ALLOW THE ATLANTIC COAST SEA BREEZE TO SLOWLY MOVE INLAND LATER THIS MORNING...WITH THUNDERSTORMS EXPECTED TO DEVELOP ALONG THIS BOUNDARY BY LATE MORNING/EARLY AFTERNOON. GIVEN POTENTIAL FOR ADDITIONAL CONVECTIVE DEVELOPMENT ALONG NUMEROUS MESOSCALE BOUNDARIES...AND LIGHT NORTHERLY FLOW ALOFT...WILL SIDE WITH HIGHER FWC/MET POP NUMBERS BOTH TODAY AS WELL AS TONIGHT...TO ACCOUNT FOR LINGERING EVENING CONVECTION MAINLY ALONG THE EAST COAST. BY FRIDAY...THERE ARE SOME INDICATIONS THAT A STRONGER AND DEEPER EASTERLY FLOW REGIME MAY BECOME ESTABLISHED OVER THE AREA...AS CENTRAL PLAINS UPPER RIDGE STRENGTHENS AND SHIFTS SOUTHEASTWARD IN RESPONSE TO THE DEVELOPMENT OF A STRONGER UPPER LOW OVER ONTARIO/QUEBEC. DESPITE THIS...AN AXIS OF LOWER HEIGHTS ALOFT WILL REMAIN OVER THE FLORIDA PENINSULA...PROVIDING A FAVORABLE THERMAL ENVIRONMENT FOR AT LEAST SCATTERED AFTERNOON CONVECTION ALONG SEA BREEZE BOUNDARIES. WILL PLACE HIGHEST POPS ALONG THE GULF COAST TO REFLECT INCREASING -- ALTHOUGH STILL VERY WEAK -- EASTERLY FLOW. BOUNDARY LAYER EASTERLIES APPEAR TO STEADILY INCREASE FROM FRIDAY NIGHT INTO SATURDAY MORNING...WITH CORRESPONDINGLY HIGHER POPS WARRANTED FOR THE ATLANTIC WATERS AND SOUTHEAST COAST OF THE MAINLAND. EXPECT CONDITIONS SIMILAR TO FRIDAY ONCE AGAIN ON SATURDAY...WITH WEAK EASTERLY STEERING FLOW FOCUSING HIGHEST COVERAGE OF AFTERNOON SHOWERS/STORMS OVER WESTERN PORTION OF THE FORECAST AREA. MEDIUM RANGE GUIDANCE FROM THE GFS/ECMWF/CMC NOW SUGGESTS THAT THIS PERSISTENT WEAKNESS IN THE UPPER-LEVEL RIDGE MAY LINGER OVER THE PENINSULA THROUGH THE BEGINNING OF NEXT WEEK...AND WILL REFLECT THIS IN THE EXTENDED FORECAST WITH NEAR CLIMO VALUES FOR POPS...EXCEPT SLIGHTLY HIGHER THAN CLIMO ALONG THE GULF COAST. CONDITIONS MAY BEGIN TO CHANGE...HOWEVER...BY THE MIDDLE OF THE WEEK...AS UPPER LOW OVER SOUTHEASTERN CANADA IS EVENTUALLY FORCED EASTWARD...ALLOWING CENTRAL ATLANTIC BRANCH OF THE SUBTROPICAL UPPER RIDGE TO FINALLY BUILD OVER THE AREA. THIS...IN COMBINATION WITH SOUTHWEST FLOW...COULD LEAD TO WARMER THAN NORMAL TEMPERATURES LATE NEXT WEEK...ALONG WITH LOWER CHANCES FOR RAIN. && .MARINE... CONDITIONS WILL REMAIN FAVORABLE FOR THE FORMATION OF WATERSPOUTS THIS MORNING...ESPECIALLY OVER THE LOCAL ATLANTIC WATERS AND BISCAYNE BAY. OTHERWISE...THERE ARE NO SIGNIFICANT WEATHER-RELATED CONCERNS TO MARINERS THROUGHOUT THIS FORECAST PERIOD...WITH CONDITIONS OUTSIDE OF SHOWERS/THUNDERSTORMS EXPECTED TO INCLUDE PREVAILING EAST TO SOUTHEAST WINDS IN THE 5-10 KNOT RANGE. THIS WIND FLOW WILL MAINTAIN SEAS IN THE 1-3 FOOT RANGE ACROSS ALL OF THE LOCAL COASTAL WATERS. && .FIRE WEATHER... THERE ARE NO FIRE WEATHER CONCERNS THROUGHOUT THIS FORECAST PERIOD...WITH MINIMUM AFTERNOON RH VALUES EXPECTED TO RANGE FROM 45-55 PERCENT ACROSS THE NORTHWEST ZONES...TO 55-60 PERCENT ELSEWHERE. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 89 74 89 76 / 50 40 40 20 FORT LAUDERDALE 91 76 90 78 / 50 40 40 30 MIAMI 91 76 90 77 / 50 40 40 30 NAPLES 90 73 90 75 / 40 30 50 30 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. GM...NONE. && $$ LONG TERM...70/DD SHORT TERM/AVIATION...15/JR fl AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE JACKSONVILLE FL 355 AM EDT THU JUL 24 2008 .SYNOPSIS...WATER VAPOR IMAGERY AND RUC 400 MB ANALYSIS SHOW A WELL-DEFINED TROUGH EXTENDING FROM VA TO S CENTRAL GA TO THE WRN FL PANHANDLE. MUCH DRIER AIR IS FILTERING IN ON THE BACK SIDE OF THIS TROUGH AND ENTERING OUR GA ZONES. DEEPER MOISTURE RESIDES OVER THE SRN ZONES WITH RECENT GPS-MET DATA AND RUC INDICATING PWATS OF 1.9 INCHES NEAR GAINESVILLE. AT SFC...TROUGHING IS N OF THE AREA FROM NC TO S CENTRAL GA TO NEAR ERN AL. SYNOPTIC FLOW FROM SFC TO 10 KFT IS BECOMING NW AS SEEN IN LATEST VWP AND MODEL OUTPUT GUIDANCE. SO FAR RADAR IS QUIET BUT ANTICIPATE SOME CONVECTIVE ACTIVITY TO DEVELOP LATER THIS MORNING OVER THE SW ZONES. .SHORT TERM... TODAY AND TONIGHT...MODELS ARE IN GOOD AGREEMENT THAT NW FLOW IN THE 7H-5H LAYER WILL BECOME MORE NLY AS THE TROUGHING OVER THE REGION MOVES EWD AND HEIGHTS RISE. SFC TROUGHING N OF THE AREA WILL DROP SWD AND DEEPER MOISTURE MOVES WELL S AND E WITH SKIES BECOMING MOSTLY CLEAR TO PARTLY CLOUDY. A N TO S POP GRADIENT IS IN ORDER TODAY WITH ONLY 20% FOR GA AND 30-40% OVER NE FL. SLIGHTLY HIGHER POP IS ANTICIPATED FROM MARION COUNTY TO FLAGLER COUNTY IN AREA OF DEEPEST MOISTURE. SHOWERS AND STORMS SHOULD FIRST BEGIN OVER THE INTERIOR NE FL ZONES WHERE LOW LEVEL MOISTURE CONVERGENCE AND HIGHER THETA-E AIR WILL RESIDE THROUGH MID MORNING. DUE TO DRYING ALOFT AND TEMPS PUSHING THE LOWER 90S...ANY STORMS THAT GET GOING WILL BE CAPABLE OF PRODUCING DAMAGING DOWNBURST WINDS AND MARGINALLY SEVERE HAIL. MODIFIED CAPE FROM GFS AND NAM IS ABOUT 2300-2600 AND LI OF -6. DIFFERENTIAL THETA VALUES ARE ESTIMATED AROUND 20-25 BUT HIGHER IN SE GA. MAX TEMPS HIGHER TODAY THAN WED DUE TO LESS CLOUD COVER. TONIGHT...ISOLD THUNDERSTORMS IN THE EVENING WITH PATCHY FOG OCCURRING LATE. FRIDAY...SFC TROUGHING OVER THE AREA AND A RELATIVELY DRY AIRMASS WILL AGAIN YIELD LOWER POPS THAN PREVIOUS DAYS. PWATS OF 1.4 TO 1.7 INCHES ARE ANTICIPATED AND DRIEST AIR WILL BE FROM ABOUT 750-450 MB. E COAST SEA BREEZE WILL HAVE AN EASIER TIME MOVING INLAND AND BEST LOW LEVEL FORCING WILL BE OVER INLAND ZONES. WILL CONT WITH THE N TO S POPS WITH 20% IN SE GA AND 30-40% OVER INLAND NE FL. TEMPS EXPECTED TO PUSH INTO MID 90S OVER SE GA AND INLAND NE FL AND HEAT INDICES JUST OVER 100 DEG AT TIMES. FRIDAY NIGHT...MAINLY EXPECT ISOLATED THUNDERSTORM ACTIVITY OVER INLAND AREAS IN THE EVENING WITH PATCHY FOG POSSIBLE AGAIN. SATURDAY...SFC TROUGH IS NOT AS APPARENT AND RIDGING MAY WORK NWD OVER FL. MOISTURE IS STILL SOMEWHAT LIMITED AND E COAST SEA BREEZE SHOULD HAVE NO PROBLEM MOVING INLAND. WILL KEEP POPS LIMITED TO ABOUT 20-30% FOR MOST AREAS. MAX TEMPS IN THE LOWER TO MID 90S EXPECTED. ISOLATED EVENING SHOWERS AND STORMS ANTICIPATED SATURDAY NIGHT. .LONG TERM...SUNDAY-WEDNESDAY. MODEL GUIDANCE HAS SHOWN INDICATIONS OF ERN CONUS TROUGH TO DEEPEN A BIT DURING THIS TIME FRAME OR AT LEAST KEEPING A WEAKNESS IN THE MID LEVEL RIDGE OVER THE FORECAST AREA. GFS ENSEMBLE IN GENERAL AGREEMENT WITH THIS PATTERN AND KEEPS 500 MB TEMPS IN THE -6 TO -8 C DEG RANGE. AT SFC...RIDGE AXIS WILL REMAIN S OF THE AREA AND WEAK TROUGHING WILL BE OVER THE SE STATES WILL KEEP A SWLY FLOW OVER THE REGION. THIS PATTERN SHOULD FAVOR TYPICAL AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS AND POPS IN THE 30-50% RANGE AT THIS TIME. TEMPS APPEAR TO BE CLOSE TO NORMAL...LOWS IN THE LOWER 70S AND HIGH AROUND 90. && .AVIATION...PREVAILING VFR WITH MID/HIGH CLOUDS AT MOST TERMINALS EARLY THIS MORNING. THE EXCEPTION WILL BE GNV WHERE THERE WILL BE A SCATTERED DECK AT 400 FEET AND POSSIBLY TEMPO MVFR VSBY TIL 12Z. WITH MUCH DRIER AIR ALOFT FILTERING IN TODAY BEHIND SHORT WAVE... EXPECTING MUCH LESS COVERAGE OF STORMS AND PRIMARILY DURING THE AFTERNOON. HOWEVER...WITH WITH LIGHT SYNOPTIC FLOW...WILL PROBABLY HAVE SEABREEZES AND ASSOCIATED OUTFLOWS DEVELOP AND MOVE INLAND DURING THE AFTERNOON WHICH MAY BRING IN ENOUGH MOISTURE TO HELP PRODUCE A FEW STRONG STORMS WITH STRONG WIND GUST POTENTIAL. HAVE GONE WITH PREVIOUS FORECAST OF CB AT JAX...CRG...SSI AFTER 18Z AND VCTS AT GNV AFTER 18Z. SOME OF THESE TERMINALS MAY NEED SOME AMENDMENTS THIS AFTERNOON. && .MARINE...A SURFACE TROUGH MOVES ACROSS THE WATERS THIS MORNING AND THEN WASHES OUT. A RIDGE REMAINS ACROSS CENTRAL FLORIDA. THIS PRODUCES A WEAK PRESSURE PATTERN WITH WINDS MAINLY SOUTH OR SOUTHWEST 10 KNOTS OR LESS EXCEPT SOUTHEAST ALONG THE COAST IN THE AFTERNOONS. SEAS 1 TO 3 FEET. SCATTERED AFTERNOON AND EVENING STORMS. STRONG WIND GUST POTENTIAL WITH SOME OF THE STORMS NEAR SHORE. && .PRELIMINARY POINT TEMPS/POPS... AMG 94 70 96 71 / 20 20 20 10 SSI 90 75 89 76 / 20 20 10 10 JAX 91 71 93 72 / 30 20 20 10 SGJ 89 72 88 73 / 40 20 20 10 GNV 90 70 93 70 / 40 20 40 20 OCF 89 70 92 70 / 40 20 40 20 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...NONE. && $$ SHASHY/PETERSON fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 1251 AM CDT THU JUL 24 2008 .DISCUSSION... 234 PM CDT MAIN FORECAST ISSUES WILL CENTER AROUND CHANCES OF PRECIPITATION NEXT FEW DAYS. GENERALLY TRANQUIL WEATHER PATTERN WITH NO TEMPERATURE EXTREMES AND LITTLE THREAT OF ANY SIGNIFICANT SEVERE WEATHER THROUGH THE MIDDLE OF NEXT WEEK. LARGE CLOSED LOW OVER EASTER GREAT LAKES WILL SLOWLY LIFT E WHILE SHARP RIDGE PUSHES INTO WESTERN LAKES TONIGHT. A SERIES OF MINOR SHORT WAVES WILL EVENTUALLY FLATTEN OUT HIGH AMPLITUDE PATTERN THU AND FRI. GFS SEEMS TO HAVE INITIALIZED WELL. CLUSTER OF CONVECTION AT NE/SD/MN/IA FOUR CORNERS AREA DEPICTED WELL. AS THIS CUTS THROUGH UPPER RIDGE TONIGHT IT SHOULD DROP SE ALONG THICKNESS LINES. THE LOW LEVEL MOISTURE AXIS ALSO EXTENDS FROM LOWER OH VALLEY BACK INTO CENTRAL PLAINS. THUS EXPECT CONVECTION TO SKIRT SOUTH OF FORECAST AREA INTO CENTRAL AND SOUTHERN ILLINOIS THURSDAY. ANOTHER WEAK PERTURBATION IS PRODUCING ANOTHER CLUSTER OF SHOWERS AND THUNDERSTORMS EASTERN ND. THIS WILL MOVE E INTO MN AND WI TONIGHT AND THU AND SHOULD WEAKEN AS IT MOVES INTO MORE STABLE/DRY AIR MASS AND AWAY FROM BETTER LOW LEVEL INFLOW. THUS EXPECT INCREASE IN CLOUD COVER OVER NORTHERN IL AND NORTHWEST IN THU BUT ONLY SLIGHT CHANCE OF PRECIP...MAINLY SOUTH PORTIONS OF FORECAST AREA WELL SOUTH OF I-80. THERE MAY BE A SERIES OF THUNDERSTORM CLUSTERS THAT TRAVERSE THIS BAROCLINIC BOUNDARY FROM THE CENTRAL PLAINS INTO CENTRAL AND SOUTHERN IL THU NIGHT AND FRI. AS HEIGHTS GRADUALLY BUILD SLIGHTLY THE BOUNDARY MAY CREEP NORTH CLOSER TO NORTHERN IL AND DEWPOINTS WILL GRADUALLY CREEP UP. THEREFORE WILL CONTINUE WITH SMALL 30 PCT POPS FOR MUST OF THE AREA INTO FRIDAY...BUT HIGHEST POPS WILL BE SOUTH OF 1-80. MEANWHILE MORE SIGNIFICANT SHORT WAVE IN NORTHERN STREAM WILL EVENTUALLY CAUSE BIG UPPER LOW TO REDEVELOP/RETROGRADE INTO UPPER GREAT LAKES THIS WEEKEND...PUTTING NORTHERN IL INTO NWLY FLOW AGAIN AND SUPPRESS BOUNDARY FURTHER SOUTH AGAIN. WILL INCLUDE SLIGHT CHANCE OF THUNDER FOR FRIDAY NIGHT AS GFS HINTING AT A WEAK SURFACE BOUNDARY DROPPING DOWN THROUGH THE WESTERN GREAT LAKES. MAY BE A A CHANCE OF PRECIP IN SOUTHERN PART OF AREA INTO SAT BUT WILL MAINTAIN DRY FORECAST FOR NOW. GFS BRINGS ANOTHER SHORT WAVE THROUGH WESTERLIES INTO GREAT LAKES ABOUT TUESDAY BUT NOT MUCH CONSISTENCY WITH ECMWF...SO WILL MAINTAIN DRY FORECAST THROUGH MID WEEK WHICH MATCHES WELL WITH SURROUNDING OFFICES. VERY PLEASANT NIGHT TONIGHT WITH CLEAR SKIES AND LOW DEWPOINTS. DEWPOINTS WILL EVENTUALLY CREEP BACK INTO LOW TO MID 60S BY FRI AND SAT BUT THAT IS CERTAINLY TOLERABLE IN LATE JULY. THEN WARM DAYS AND PLEASANT NIGHTS EARLY NEXT WEEK. LIGHT SOUTH TO SOUTHEAST WINDS THU WILL ALLOW A JUST A WEAK LAKE BREEZE TO MOVE INLAND...MAINLY NORTH SHORE. LITTLE BETTER SOUTHWESTERLY FLOW FRIDAY AND THEN WESTERLY SAT...SO NOT MUCH LAKE COOLING. WEAK NORTH FLOW SUNDAY INTO EARLY WEEK SHOULD ALLOW LAKE BREEZES TO RETURN. BUT THIS TIME OF YEAR NOT A WHOLE LOT OF COOLING AND INLAND TEMPS ONLY EXPECTED IN LOW TO MID 80S. OVERALL VERY PLEASANT FOR LATE JULY. ALLSOPP && .AVIATION... 1251 AM CDT FOR 06Z TAFS...MAIN CONCERN TODAY IS WITH WEAK LAKE BREEZE POTENTIAL FOR KORD/KMDW. OTHERWISE JUST VRF MID/HIGH CLOUD COVER AND HIGH LEVEL CONVECTIVE DEBRIS CLOUDINESS THROUGH NEXT 18-24 HOURS AS PAIR OF SHORT WAVES MOVE INTO UPPER RIDGE AND DROP SOUTHEAST ACROSS MO/SOUTHERN IL. SURFACE RIDGE AXIS ACROSS NORTHEAST IL AT 05Z...WITH LIGHT PRESSURE GRADIENT ALLOWING CALM OR LGT/VARIABLE WIND CONDITIONS ACROSS FORECAST AREA THIS MORNING. SURFACE HIGH PROGGED TO SLOWLY SHIFT SOUTH ACROSS CENTRAL/SOUTHERN IL AND OHIO VALLEY BY MIDDAY... RESULTING IN LIGHT SOUTH/SOUTHWEST SURFACE WINDS BY AFTERNOON. VARIOUS MOS GUIDANCE DO NOT INDICATE LAKE BREEZE TODAY...THOUGH WITH WEAK GRADIENT THIS MORNING...HIGH RESOLUTION NAM/RUC AND LOCALLY RUN WRF ALL SUGGEST SOUTHEAST LAKE BREEZE TO DEVELOP BY MIDDAY...MOVING THROUGH KMDW AND JUST MAKING IT TO KORD BEFORE SLIGHTLY STRONGER SOUTH WINDS PUSH IT NORTH/EAST OF THESE TERMINALS LATER IN THE AFTERNOON. WITH THIS IN MIND HAVE INTRODUCED SOUTHEAST WINDS AT KORD/KMDW 16-17Z...WITH A MORE SOUTHERLY SHIFT BY MID AFTERNOON. RETURN FLOW EXPECTED TO BE RATHER WEAK...THOUGH MID/HIGH CLOUD COVER EXPECTED TO HELP LIMIT LAND/LAKE TEMP DIFFERENTIAL AND KEEP LAKE BREEZE PUSH LIGHTER THAN IT OTHERWISE WOULD BE. GRADIENT WIND BECOMES LIGHT SOUTH/SOUTHWEST TONIGHT AS HIGH WEAKENS AND CONTINUES TO DRIFT OFF ACROSS OHIO VALLEY. CLOUD WISE...CIRRUS ALREADY STREAMING ACROSS REGION...AND AS LOW LEVEL WARM ADVECTION BECOMES BETTER ESTABLISHED INTO THE MISSISSIPPI VALLEY TODAY FORECAST SOUNDINGS FROM BOTH NAM/GFS INDICATE MOISTENING OF MID/UPPER LEVELS TO CONTINUE...AIDED BY CONVECTIVE BLOW OFF FROM STORMS IN NEB/IA AND EVENTUALLY MO. SOUNDINGS/TIME SECTIONS INDICATE SOME HIGH BASED CU OR MID CLOUD IN 6-7 KFT RANGE BY AFTERNOON... THOUGH VFR CONDITIONS TO PREVAIL WITH RELATIVELY DRY AIR BELOW THAT LEVEL. APPEARS ANY REAL THREAT OF PRECIP/THUNDERSTORMS TO HOLD OFF UNTIL FRIDAY MORNING WITH BETTER LOW LEVEL JET FORCING STAYING OFF TO THE WEST OF FORECAST AREA UNTIL THEN. RATZER && .MARINE... 215 PM...LARGE HIGH PRESSURE EXTENDS FROM ONTARIO SOUTH ACROSS THE WESTERN LAKES. THIS HIGH WILL MOVE SOUTHEAST TONIGHT AS IT SLOWLY WEAKENS...REACHING THE OHIO VALLEY THURSDAY. LOW PRESSURE NEAR THE U.S. AND CANADIAN BORDER WILL MOVE NORTHEAST ACROSS NORTHERN ONTARIO THURSDAY NIGHT AND FRIDAY. SOUTHERLY FLOW WILL DEVELOP BETWEEN THIS LOW AND THE HIGH PRESSURE WHICH WILL CONTINUE TO SLIDE SOUTHEAST OFF THE ATLANTIC COAST FRIDAY. A WEAK TRAILING COLD FRONT WILL TURN WINDS WESTERLY OR NORTHWESTERLY FRIDAY NIGHT INTO SATURDAY ACROSS THE WESTERN LAKES. CMS && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 240 AM CDT THU JUL 24 2008 .SHORT TERM...TODAY EVOLUTION OF CURRENT MCS IS OBVIOUSLY PRIMARY FORECAST CONCERN THIS MORNING WHICH LINES UP QUITE WELL WITH DECENT MOISTURE CONVERGENCE ASSOCIATED WITH 30-40KT LLJ NOTED ON 305/310K ISENT SFCS. THIS CONVERGENCE REACHES S CENTRAL/SE SECTIONS BY 12Z-15Z SO HAVE BOOSTED POPS TO CATEGORICAL IN THOSE LOCATIONS AND DIMINISHED NRN PORTIONS. CONVECTION SHOULD HAVE NO PROBLEM SUSTAINING ITSELF AND WILL LIKELY INCREASE SOMEWHAT. LIFTING PARCELS FROM VARIOUS ELEVATED LEVELS ON THE RUC DEPICT STEADY 1500-2000 J/KG CAPES WITH DECREASING CIN AND CONVECTION BEING ROOTED LOWER. EFFECTIVE SRH AND ESPECIALLY EFFECTIVE SHEAR SUFFICIENT FOR ORGANIZATION AS WELL...ESPECIALLY IF STORMS BECOME ROOTED LOWER AS CINS SUGGEST SO MAY SEE A GRADUAL INCREASE IN SVR THREAT TOWARD DAYBREAK. HEAVY RAINS WILL BE A CONCERN AS WELL WITH PWS AROUND TWO INCHES...13KFT WCDS...AND CELLS TRACKING OVER SAME LOCATIONS. AIRMASS SHOULD STABILIZE SOMEWHAT DURING THE AFTERNOON WITH NO REAL FORCING MECHANISM NOTED SO HAVE SLIGHTS/CHANCES LINGERING BY THEN...MAINLY SRN PORTIONS. SREF AND ESPECIALLY NAM RAW TEMPS ARE NOT TOO BULLISH ON TEMPS WITH NAM SUGGESTING AREAS OF POST-PCPN STRATUS SO WENT AT OR JUST BELOW GUIDANCE...LOWER END NE. .LONG TERM...TONIGHT THROUGH WEDNESDAY FRONTAL BOUNDARY TO BE IN PLACE FROM NORTHEAST TO SOUTHWEST ACROSS THE CWA BY THIS EVENING...WITH MUCH OF CWA IN THE WARM SECTOR. FAIR AMOUNT OF INSTABILITY WITH BEST SFC BASED CAPE SITUATED ACROSS THE SOUTHWESTERN CWA. MAY SEE SOME ISOLATED STORMS INITIALLY WITH DAYTIME HEATING...BUT EXPECT MAJORITY OF CONVECTION WITH APPROACHING SHORTWAVE THROUGH INTO THE LATER EVENING/OVERNIGHT HOURS AS LLJ STRENGTHENS. MOISTURE EXPECTED TO POOL AHEAD OF APPROACHING WEAK COOL FRONT SITUATED ACROSS ERN NE/WC IOWA...WITH PWATS APPROACHING TWO INCHES. MAIN ACTIVITY STILL EXPECTED ALONG THE FRONTAL BOUNDARY THROUGH THE EARLY EVENING...WITH EVERYTHING PUSHING EASTWARD OVERNIGHT. FRIDAY INTO SATURDAY...MAIN FRONTAL BOUNDARY TO BE SOMEWHAT WASHED OUT...BUT IN VICINITY OF THE SRN CWA. NORTHWEST FLOW PATTERN CONTINUES...WITH MAIN WEAK DISTURBANCES DROPPING SOUTHEAST OUT OF THE NORTHERN ROCKIES INTO THE AREA. HARD TO NAIL DOWN TIMING AND PLACEMENT...BUT INSTABILITY TO REMAIN GREATEST ACROSS THE SOUTHERN HALF OF THE CWA INTO FRIDAY NIGHT AND SATURDAY...AS SFC HIGH PRESSURE/DRIER AIR BEGINS TO BUILD SOUTHEASTWARD INTO NORTHERN IOWA. LITTLE CHANGES MADE INTO THE EXTENDED RANGE...AS WESTERN/CENTRAL US UPPER RIDGING FLATTENS SOME. HOWEVER STILL LOOKS LIKE TREND FOR WEAK WAVES TO TRAVERSE THE RIDGE...AND IMPACT THE AREA ALLOWING FOR UNSETTLED CONDITIONS TO CONTINUE THROUGH THE WEEKEND INTO THE MIDDLE OF NEXT WEEK. && .AVIATION...24/06Z LIGHT SHOWERS CONTINUE MOVE OVER CENTRAL IOWA THOUGH IS FALLING WITH VFR CONDITIONS. THUNDERSTORMS DEVELOPING WEST OF THE MISSOURI RIVER AND WILL MOVE INTO WRN IA LATER TONIGHT. MAIN SITES AFFECTED WILL BE DSM THEN LATER OTM. MVFR CEILINGS EXPECTED FOR A PERIOD ALL SITES AS THIS SYSTEM PASSES. ADDITIONAL MVFR CEILINGS MAINLY NORTH EXPECTED AFTER 00Z. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...BSS LONG TERM...MJA AVIATION...DONAVON ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 311 AM CDT THU JUL 24 2008 .DISCUSSION... 08Z WATER VAPOR SHOWS A CLOSED LOW OVER THE GREAT LAKES...A SHORTWAVE TROUGH PROPAGATING EAST OVER THE NORTHERN ROCKIES...AND A BROAD RIDGE FROM THE SOUTHERN PLAINS BACK WEST OVER SOUTHERN CA. HEIGHT FALLS ACROSS THE NORTHERN ROCKIES AND PLAINS HAVE FLATTENED THE UPPER RIDGE OVER THE CENTRAL PLAINS. AT THE SFC A TROUGH WAS FOUND ACROSS WESTERN KS STRETCHING NORTH. A MOIST AND WARM AIRMASS WAS FOUND EAST OF THIS TROUGH...AND ELEVATED CONVECTION HAS ONCE AGAIN DEVELOPED ALONG THE PERIPHERY OF THE UPPER RIDGE. FOR THIS MORNING...THE RUC AND NAM 310K ISENTROPIC SFC KEEPS THE BETTER MOISTURE AXIS JUST TO THE NORTHEAST OF THE FORECAST AREA. THIS IS SUPPORTED BY LATEST RADAR TRENDS WITH THUNDERSTORMS MOVING SOUTHEAST INTO NORTHERN MO. A FEW ELEVATED STORMS DEVELOPED OVER SOUTH CENTRAL NEB BUT HAVE SINCE FALLEN APART. SO EXPECT THE MAJORITY OF THE AREA TO REMAIN DRY THIS MORNING. HAVE KEPT SLIGHT CHANCE POPS ACROSS THE NORTHEAST THIS MORNING AND THEN ACROSS THE NORTH FOR THE AFTERNOON AS MODELS STILL SHOW A WEAK WIND SHIFT SLIDING INTO NORTHERN KS. MODELS SHOW THE BOUNDARY LAYER MIXING TO BETWEEN 850 AND 800MB. THEREFORE WOULD EXPECT HIGHS TO AGAIN REACH THE LOWER TO MID 90S FOR MOST AREAS. COOLEST SPOT SHOULD BE NORTHEAST WHERE THERE IS LIKELY TO BE A LITTLE MORE CLOUD COVER...WITH THE WARMEST SPOT ACROSS THE SOUTHWEST. FOR TONIGHT THROUGH SATURDAY...PRECIP CHANCES LOOK TO BE A LITTLE HIGHER. MODELS SHOW THE UPPER LEVEL RIDGE AXIS SHIFTING SOUTH ACROSS THE SOUTHERN PLAINS...WITH WEAK NORTHWEST FLOW SETTING UP OVER THE FORECAST AREA. THINK BECAUSE OF THIS...CONVECTION THAT HAS PASSED JUST NORTHEAST OF THE AREA THE PAST COUPLE NIGHTS WILL BE MORE LIKELY TO MOVE ACROSS NORTHEAST KS. NAM AND GFS SHOW WEAK SHORTWAVES CLIPPING NORTHEAST KS TONIGHT AND AGAIN FRIDAY NIGHT WITH ABUNDANT MOISTURE STILL IN PLACE. THEREFORE HAVE GONE WITH CHANCE POPS ACROSS NORTHEAST KS TONIGHT AND SPREAD CHANCE POPS A LITTLE FURTHER SOUTH FOR FRIDAY NIGHT INTO SATURDAY MORNING. USED PERSISTENCE FOR THE TEMP FORECAST AS AIRMASS APPEARS TO CHANGE LITTLE FROM DAY TO DAY. DO NOT EXPECT PRECIP TO OCCUR LONG ENOUGH DURING ANY GIVEN DAY TO APPRECIABLY HAMPER DAY TIME HEATING. WEAK NORTHWEST FLOW CONTINUES THROUGH SUNDAY WITH ANOTHER POTENTIAL VORT MAX CLIPPING NORTHEAST KS. SO MAINTAINED THE SLIGHT CHANCE POPS FOR SATURDAY NIGHT AND SUNDAY. FORECAST WAS LEFT PRETTY MUCH IN TACT BEYOND SUNDAY. WOLTERS && .AVIATION... CONVECTION DEVELOPING ALONG NW-SE LOW LEVEL MOISTURE GRADIENT AS LOW LEVEL JET IS INCREASING...WITH WEAKER SHOWERS TO THE NORTHWEST IN GENERAL WARM AIR ADVECTION REGIME IN AIRMASS OF PRECIPITABLE WATER VALUES NEAR 2 INCHES. STILL BELIEVE CONVECTION OF ANY AVIATION SIGNIFICANCE WILL REMAIN NORTHEAST OF THE LOCAL TERMINALS TONIGHT AND INTO THURSDAY MORNING. CONVECTIVE CHANCES WILL NEED TO BE MONITORED AS THURSDAY AFTERNOON/EVENING APPROACH WITH GOOD MOISTURE AND POSSIBLE BOUNDARIES AROUND...BUT AGAIN NOTHING SUGGESTING PRECIP INCLUSION AT THIS POINT. CU MAY FORM NEAR 3000 FEET BY MIDDAY...BUT VFR CONDITIONS ARE STILL EXPECTED. 65 && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 400 AM EDT THU JUL 24 2008 .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW HI AMPLITUDE TROF CENTERED OVER SE ONTARIO...WITH SHARP UPR RDG FM MN INTO NW ONTARIO BTWN THE TROF AND FALLING HGTS OVER THE NRN PLAINS/SCNTRL CAN ASSOCIATED WITH A PAIR OF STRONG SHRTWS RIDING ENEWD OUT OF A MEAN TROF IN THE PAC NW/SW CAN. 00Z GRB RAOB DEPICTS A VERY DRY...STABLE AIRMASS (KINX 8...PWAT 0.74 INCH) DOMINATING THE UPR GRT LKS OVER SFC HI PRES CENTERED ACRS LK SUP AT 03Z. THERE ARE SOME MID CLDS MOVING INTO THE ERN CWA ASSOCIATED WITH SHRTWV ROTATING ARND DEEP TROF TO THE E. THE CNTRL CWA IS CLR...BUT THERE ARE SOME HI CLDS TO THE W PUSHING EWD THRU THE UPR RDG AXIS AND OVER VERY DRY...STABLE AIR ALSO SHOWN ON THE 00Z INL RAOB (KINX -13...PWAT 0.55 INCH THERE). LEADING EDGE OF THIS CI IS TENDING TO FADE AS IT PUSHES EWD INTO THE LARGER SCALE SUBSIDENCE OVER UPR MI TO THE W OF TROF TO THE E. A VERY SHAPR GRADIENT IN H85 DWPT IS APRNT FM MN INTO THE NRN PLAINS. WHILE 00Z H85 DWPT AT INL IS ONLY 5C...THE VALUE IS 17C AT BIS IN RETURN SW FLW BTWN RDG OVER THE GRT LKS AND TROFFING IN THE PAC NW. THE INTERACTION BTWN THE RESULTING INSTABILITY SHOWN ON THE 00Z BIS SDNG AND LEAD SHRTWV APRCHG LK WINNIPEG HAS RESULTED IN SOME CNVCTN AS FAR E AS THE MN/ND BORDER. HOWEVER...RATHER DRY NATURE OF THE MID LVLS (00Z H5 DWPT DEPRESSION 28C AT BIS) APPEARS TO BE LIMITING COVG OF SHRA/TSRA IN THAT AREA. MAIN FCST CONCERN TDAY THRU TMRW WL BE TIMING BREAKDOWN OF RDG/DRY AIR NOW IN PLACE AND THEN COVG/STRENGTH OF CNVCTN THAT CAN SPREAD INTO THE UPR GRT LKS ASSOCIATED WITH SHRTWVS TO THE W. FOR TDAY...THE DAY WL START ON THE QUIET SIDE WITH RDG STILL IN CONTROL. THE LLVL FLOW WL GRDLY SHIFT TO THE SW ONCE THE SFC-H85 RDG AXIS SHIFTS TO THE E. 00Z NAM/GFS SHOW ISENTROPIC LIFT ON THE 305K SFC (ARND H75) RESULTING IN INCRSG RH AT THAT LVL OVER THE W IN THE AFTN. 00Z NAM/RUC13 ALSO APPEAR TO GENERATE SOME ISOLD CNVCTN OVER THE INTERIOR W HALF OF THE FA IN THE AFTN. BUT SINCE THE HIER H85 DWPTS ARE TO THE W AND NOT THE SW (23Z TAMDAR SDNG FM MSP SHOWED H85 DWPT ONLY 6.5C THERE IN ABSENCE OF 00Z MPX RAOB)...PREFER THE DRIER 00Z GFS/00Z LOCAL WRF-ARW RUN AND SISTER MODEL RUN WITH KF CONVECTIVE SCHEME THAT GENERATES SCT CNVCTN ONLY OVER WRN LK SUP CLOSER TO THE DEEPER LARGE SCALE H85-3 QVECTOR CNVGC/DPVA ASSOCIATED WITH SHRTWV NOW NEAR LK WINNIPEG THAT IS RIDING INTO THE UPR RDG OVER ONTARIO. HAVE THUS REMOVED POPS OVER THE LAND FA EXCEPT FOR SOME SCHC VALUES OVER THE FAR W AFT 18Z. ELEVATED MSTR (MID CLD) RETURN/ WEAK DESTABILIZATION SHOWN ON FCST SDNGS WARRANTS EXCLUSION OF TS EXCEPT OVER FAR WRN LK SUP. GOING MAX TEMPS FCST NEEDED LTL ADJUSTMENT. SECOND SHRTWV UPSTREAM THAT WAS MOVING THRU THE NRN ROCKIES IS PROGGED TO REACH NEAR LK WINNIPEG BY 12Z FRI...FURTHER WEAKENING THE UPR RDG IN PLACE OVER THE GRT LKS AS ITS ACCOMPANYING SFC COLD FNT APRCHS THE WRN LK SUP SHORE BY 12Z. WITH THE LLVL FLOW FCST TO VEER MORE W OVERNGT...LOOKS LIKE A BETTER OPPORTUNITY FOR THE HIER DWPTS TO THE W TO SPREAD INTO THE FA. IN FACT...00Z GFS/NAM SHOW SOME SHARPER ISENTROPIC LIFT/MOISTENING ON THE 300K SFC SPRDG W-E DURING THE NGT AND SUPPORTING CHC POPS. WL GO WITH THE HIER POPS (40) ACRS THE NRN TIER CLOSER TO SHARPER H85-7 FGEN FCST BY NAM/GFS. ADJUSTED POPS CLOSE TO SHARPER ISENTROPIC LIFT...RESULTING IN REDUCED POPS OVER THE W WITH GUIDANCE SHOWING DRIER AIR INFLUX IN THE MID LVLS/ CAPPING. DID INCRS POPS AGAIN LATE OVER WRN LK SUP WITH APRCH OF COLD FNT AND WHERE 12Z ECMWF PERSISTS IN SHOWING SHARPER DPVA AHD OF INCOMING SHRTWV. MSTR INFLUX/CLDS GUARANTEE A MUCH WARMER OVERNGT THAN EARLY THIS MRNG. ON FRI...00Z GFS HAS TRENDED A BIT TOWARD THE 12Z ECMWF SHOWING SHARPER HGT FALLS WITH A SHRTWV THAT DIGS A BIT MORE AND EXHIBITS A BIT MORE DIFFLUENT UPR FLOW IN THE LEFT EXIT REGION OF A MORE POTENT LOOKING UPR JET. BUT WHILE THE 12Z ECMWF SHOWED LLVL DRY ADVCTN OVERSPREADING THE FA EVEN AHD OF THE COLD FROPA...THE 00Z GFS SLOWS DOWN THE BNDRY AND ALLOWS FOR ADDITIONAL MSTR ADVCTN/MUCH HIER QPF AS THE DYNAMICS INTERACT WITH THE GREATER MSTR FLUX. THE 00Z UKMET APPEARS TO TREND IN THE DIRECTION OF THE GFS...BUT IS NOT AS EXTREME EVEN THOUGH ITS FCST 90KT H3 JET MAX IN SRN MN BY 00Z SAT LOOKS LIKE THE STRONGER 12Z ECMWF. SINCE THE 00Z GFS IS SUCH A DRASTIC CHANGE FM PREVIOUS RUNS...WL TEND MORE TOWARD THE NAM/CNDN/UKMET/LOCAL WRF-ARW WITH KF CONVECTIVE SCHEME SCENARIO...WHICH SUPPORTS THE GOING FCST HIER AFTN POPS OVER THE SCNTRL AND E WHERE LATER ARRIVAL OF COLD FNT WL BE IN BETTER SYNC WITH DAYTIME HTG/PSBL LK BREEZE INTERACTION. DESPITE THE POTENTIAL DESTABILIZATION WITH DRYING ALF... WEAK LLVL CNVGC AND THE DRY ADVCTN WL LIMIT POPS. NEW SPC DAY2 CONVECTIVE OUTLOOK HAS CWA JUST N OF SLGT TSRA RISK AREA... BUT INCRSG UNIDIRECTIONAL MID LVL WINDS/0-6KM BULK SHEAR APRCHG 40 KT/ MODIFIED NAM FCST SDNG FOR MAX TEMPS IN THE LOW 80S AND DWPTS ARND 63 (VS EXPLICIT MODEL FCST TO 68) SBCAPE IN EXCESS OF 1100 J/KG/MID LVL DRYING...SUG A POTENTIAL FOR SVR STORMS. LINGERING EVNG CNVCTN ON FRI OVER THE SCNTRL AND E WL DIMINISH WITH COLD FROPA...INFLUX OF LLVL DRY AIR...LOSS OF DIURNAL HTG AND DEPARTURE OF LEFT EXIT DYNAMICS. BUT WITH TREND TOWARD MORE DIGGING OF SHRTWV/LOWER HGTS...BROUGHT BACKWASH MSTR POPS OVER NRN LK SUP A BIT FARTHER S TO TICKLE THE NRN CWA FRI NGT. BUT WITH BULK OF DEEP MSTR PROGGED TO REMAIN IN ONTARIO CLOSER TO DEEP UPR TROF FOR MID SUMMER...NOTHING MORE THAN SCHC POPS WARRANTED. GFS SEEMS TO BE THE OUTLIER IN MAINTAINING HIER BACKWASH MSTR/RH OVER LK SUP ON SAT... BUT WITH TREND TOWARD DEEPER TROF IN SE CAN...HESITANT TO DISCOUNT ITS FCST SCENARIO. WITH THAT TREND TOWARD LOWER HGTS IN MIND... TENDED TOWARD THE SOMEWHAT COOLER GFS MOS TEMPS FOR FRI NGT/SAT. COORDINATED WITH APX/GRB/DLH. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD WITH HIGH PRESSURE IN CONTROL AND CONVECTION REMAINING TO THE WEST UNTIL THU NIGHT. ONLY THING CONVECTION WILL DO IS CONTINUE TO GIVE OFF SOME MID AND HIGH LEVEL CLOUDS IN THIS FORECAST THROUGH 00Z AND THEN WILL GET CLOSE ENOUGH TO HAVE A PROB GROUP IN KCMX THU NIGHT. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WINDS SHOULD BE AT OR LESS THAN 20 KT THROUGH THE PERIOD. WINDS WILL REMAIN OUT OF THE SOUTH TODAY AS THE HIGH PRESSURE SLOWLY SHIFTS SOUTHEASTWARD. THE WINDS WILL VEER TO THE WEST AS THE COLD FRONT SLIDES ACROSS THE LAKE ON FRIDAY AND FRIDAY NIGHT. THEN WHEN THE HIGH PRESSURE SYSTEM RETURNS...WINDS WILL DIMINISH AND SHIFT SOUTH AGAIN ON MONDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...GM MARINE...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 342 AM CDT THU JUL 24 2008 .DISCUSSION... ANOMALOUS UPPER LOW OVER ERN GT LAKES HAS BLOCKED THE WESTERLIES EARLY THIS MORNING. AN AREA OF UPPER DIFFLUENCE IS DEVELOPING ACROSS CWA. LATEST WV IMAGERY/RUC13 SHOWS INITIAL SHORTWAVE ROTATING NE INTO ONTARIO UNDER INCREASING DIFFLUENT FLOW. 88D RETURNS OVER NORTH COUNTRY MAINLY INDICATIVE OF MID LVL MOISTURE AS 0Z INL SOUNDING WAS VERY DRY. A LINE OF CONVECTION HAS FORMED NEAR ND/MN BORDER WITHIN AN AXIS OF 85H THETAE. RUC13 ALSO INDICATES A NARROW TONGUE OF MID LVL WARMING HAS DEVELOPED BEHIND CONVECTION. TODAY/TONIGHT...INITIAL SHORTWAVE WILL WEAKEN AS IT MOVES ACROSS CWA. TOUGH CLOUD FCST AS THINNING OF DEEP LAYER MOISTURE MAY ALLOW VARYING AMNTS OF SUNSHINE. A FAIRLY WELL DEFINED SFC/85H THETAE AXIS OVER ND WILL TRY TO MOVE EAST. HOWEVER...IT SEEMS THAT MDLS SUGGEST INITIAL THERMAL AXIS MAY ONLY GET SO FAR AND STALL OVER WRN HALF OF CWA....WHILE A SECOND AXIS FORMS IN RESPONSE TO SECONDARY...AND STRONGER... MID LVL DISTURBANCE. OVERALL SYNOPTIC SUPPORT FOR ASCENT IS MEAGER WITH MAIN UPPER JET TRAVERSING WELL SOUTH OF REGION. HAVING SAID THAT...INTERESTING TO NOTE THAT MDLS ARE IN AGREEMENT THAT ATMOSPHERE WILL CONTINUE TO DESTABILIZE TODAY AS FAIRLY HIGH PWS ENTER REGION. BY LATE AFTERNOON...4KM NMM/WRF SIMULATED REFLECTIVITY PRODUCT GENERATES CONVECTION OVER WRN CWA AND PUSHES THE DEVELOPMENT ESE OVERNIGHT. THIS APPEARS REASONABLE CONSIDERING DEVELOPMENT OF NWLY MID LVL FLOW TONIGHT. MDLS FCST SBCAPES INTO 1500/2000 J/KG RANGE LATE AFTERNOON INTO EVENING OVER WRN THIRD OF CWA. GFS SIG SVR PARAMETER VALUES ARE MAXIMIZED OVER CASS LAKE/BRAINERD LAKES VICINITY BY EARLY EVENING. SPC HAS OUTLINED AN AREA WEST OF A CDD-HIB-MALMO LINE FOR SLIGHT RISK OF SVR STORMS. FRIDAY...MDLS DIVERGE ON AMPLITUDE/SPEED OF PRIMARY MID LVL FEATURE...DEEPENING TROF. THIS IMPACTS CONFIDENCE ON CONVECTIVE ASPECT OF FCST. EC WOULD PUSH INSTABILITY QUICKLY ACROSS CWA FRIDAY...MINIMIZING SVRWX THREAT. GFS IS A BIT SLOWER/DEEPER WITH TROF AND ALLOWS SIGNIFICANT INSTABILITY TO DEVELOP ACROSS SE ZONES OF NW WISCONSIN. STEEPENING LAPSE RATES FRIDAY ACROSS ENTIRE CWA AS MID LVL TROF MOVES OVERHEAD. SHOULD SEE SOME HAILERS/GUSTY WINDS. EXTENDED...BRISK NWLY MID LVL FLOW DOMINATES WEEKEND. CURRENT FCST IS DRY BUT WILL NEED TO WATCH FOR ISOLATED CONVECTION WITH VERY STEEP LAPSE RATES. MSTR IS LIMITED SO IF RW/TRW DEVELOP...SHOULD BE OVER ARROWHEAD. VERY PLEASANT TEMPS SAT/SUN. NEXT CHANCE OF PRECIP MON NIGHT/EARLY TUESDAY PER GFS/EC. && .AVIATION... SCATTERED SHOWERS WILL MOVE THROUGH NE MN EARLY THIS MORNING WITH ISOLD CIGS IN THE MVFR RANGE. THE SHOWERS WILL SPREAD INTO NW WI BY MID MORNING. A FEW THUNDERSTORMS ARE ALSO ANTICIPATED ALONG AND AHEAD OF AN APPROACHING WARM FRONT. THE SHOWERS AND THUNDERSTORMS WILL PERSIST INTO THE EVENING AS A WEAK COLD FRONT APPROACHES FROM THE W. MVFR CIGS ARE POSSIBLE IN THE VICINITY OF THE THUNDERSTORMS. && POINT TEMPS/POPS... DLH 73 61 80 54 / 30 30 20 10 INL 77 58 78 53 / 30 20 20 10 BRD 82 63 83 55 / 30 30 20 10 HYR 77 61 83 53 / 30 30 30 10 ASX 72 60 81 55 / 30 30 30 10 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ CANNON/GSF mn AREA FORECAST DISCUSSION...UPDATED AVIATION NATIONAL WEATHER SERVICE ST LOUIS MO 1106 PM CDT WED JUL 23 2008 .UPDATE... /913 PM CDT WED JUL 23 2008/ UPDATED FORECAST TO INCREASE CLOUD COVER OVERNIGHT BASED ON EXTENSIVE AREA OF MID AND HIGH CLOUDS MOVING SE OUT OF IA. ALSO UPPED POPS INTO THE CHANCE CATERGORY IN THE FAR NWRN PART OF THE CWA AS PAST FEW RUNS OF RUC ARE SHOWING DECENT 925-850MB FORCING ON THE EDGE OF 500-1000MB MUCAPES USING 850MB PARCELS. ALSO TRIMMED LOWS A BIT IN THE SERN PART OF THE CWA AS TEMPERATURES ARE FALLING OFF PRETTY QUICKLY AND DEWPOINTS ARE NEAR 60. BRITT && .DISCUSSION... /353 PM CDT WED JUL 23 2008/ SURFACE RIDGE CENTERED OVER THE GREAT LAKES IS PUMPING UNSEASONABLY COOL AND DRY AIR INTO CWFA. TEMPS HAVE ONLY RISEN INTO THE UPPER 70S TO LOW 80S BY 300 PM WITH DEWPOINTS GENERALLY IN THE 50S. HEAT AND HUMIDITY IS NOT THAT FAR AWAY THO WITH JOPLIN READING 91/72 AT 200 PM. AS THE SURFACE RIDGE DRIFTS EAST THROUGH THE END OF THE WEEK WE`LL SEE THE MOISTURE ENCROACH BACK INTO CENTRAL AND EASTERN MISSOURI. NORTHWEST FLOW ALOFT DUE TO THE TROF OVER THE GREAT LAKES AND THE ELONGATED RIDGE OVER THE PLANS AND SOUTHWEST WILL ALLOW SEVERAL SHORTWAVES TO RIPPLE SOUTHEAST ACROSS THE AREA. THESE WAVES COMBINED WITH AN ACTIVE LOW LEVEL JET ARE SETTING UP THE POTENTIAL FOR A WET PATTERN STARTING THURSDAY AND CONTINUING AT LEAST THROUGH FRIDAY...AND POTENTIALLY INTO SATURDAY AS WELL. OPERATIONAL MODELS ARE IN PRETTY GOOD AGREEMENT THAT THERE WILL BE 2 OR 3 MCS`S TO AFFECT MAINLY NORTHERN AND CENTRAL PORTIONS OF THE AREA...BUT NAILING DOWN THE SPECIFICS IS DIFFICULT THIS FAR OUT. IT LOOKS LIKE STARTING THE RAIN TOMORROW WILL BE THE RESULT OF NOCTURNAL CONVECTION TONIGHT OVER EASTERN NEBRASKA AND IOWA THAT WILL ROLL DOWN INTO NORTHEAST MISSOURI AND WESTERN ILLINOIS LATE TONIGHT OR EARLY THURSDAY MORNING. RESULTING MCV WILL CONTINUE TO PROVIDE A FOCUS FOR DAYTIME CONVECTION TO CONTINUE DURING THE DAY. HAVE BUMPED POPS UP TO LIKELY/HIGH CHANCE ACROSS MUCH OF THE NORTHERN AND WESTERN PORTIONS OF THE CWFA. ANOTHER MCS LOOKS LIKELY TO DEVELOP SOMEWHERE OVER SOUTHERN IOWA/NORTHERN MISSOURI THURSDAY NIGHT AND IT SHOULD ROLL EAST/SOUTHEAST AFFECTING PORTIONS OF THE BI-STATE AREA THROUGH FRIDAY MORNING. OF COURSE...OUTFLOW BOUNDARIES WILL LIKELY PROVIDE FOCI FOR ADDITIONAL THUNDERSTORM DEVELOPMENT FRIDAY AFTERNOON. THIS PATTERN COULD CONTINUE THROUGH MUCH OF THE WEEKEND AS THE LOW LEVEL JET CONTINUES TO UNDERCUT PERSISTENT NORTHWEST FLOW ALOFT...THO I THINK THE PRIMARY MCS TRACK WILL STAY NORTH OVER IOWA AND CENTRAL AND NORTHERN ILLINOIS. CARNEY && .AVIATION... /1043 PM CDT WED JUL 23 2008/ FOR THE 06Z TAFS... RIDGE OF HIGH PRESSURE CONTINUED TO DOMINATE AREA WEATHER PATTERN LATE THIS EVENING. HIGHER MOISTURE WILL SPREAD BACK ACROSS THE REGION ON THURSDAY WITH A CHANCE OF SHOWERS AND THUNDERSTORMS. NAM AND LOCAL WRF MODELS FORECAST A COMPLEX OF SHOWERS/THUNDERSTORMS WILL SPREAD ACROSS NORTH MO TOWARD SUNRISE AND THEN DROP DOWN INTO CENTRAL MO LATE MORNING AND THEN DROP APART. TPS && .LSX WATCHES/WARNINGS/ADVISORIES... MO...NONE. IL...NONE. && $$ WFO LSX mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPRINGFIELD MO 1127 PM CDT TUE JUL 22 2008 ...UPDATE TO AVIATION... .UPDATE... SCATTERED CONVECTION WILL CONTINUE TO BE POSSIBLE TONIGHT AS A MODEST LOW LEVEL S-SW FLOW CONTINUES TO PRODUCE SOME MODEST LIFT ALONG AN ELEVATED NW-SE FRONTAL BOUNDARY FROM NW MO INTO THE MO OZARKS. CAPES DEPICTED BY THE RUC STILL PRETTY STOUT OVER KS...WITH MLCAPES 2000+ J/KG. THIS WEAKENS INTO THE MO OZARKS... WITH MLCAPES OF 500-1500 J/KG...BUT MUCAPES STILL 1500-2000 J/KG. STILL HAVE ONE GOOD PERSISTENT UPDRAFT OVER EAST CENTRAL KS...AND A WEAKER CLUSTER OVER WEST CENTRAL MO. BELIEVE WE WILL SEE THIS ELEVATED CONVECTION CONTINUE FOR AWHILE INTO THE OVERNIGHT HOURS. MAY BE A SIMILAR STORY FOR THE COMING DAYS...WITH THE NW-SE BAROCLINIC ZONE STUCK OVER THE AREA. DSA && .AVIATION... FOR THE 0000 UTC KSGF/KJLN TAFS...ISOLATED TO WIDELY SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO BE POSSIBLE OVERNIGHT...MAINLY ALONG A WEAK ELEVATED FRONT FROM THE KC METRO AREA SOUTHEAST INTO THE MO OZARKS. WILL CONTINUE TO CARRY SOME MENTION OF SHOWERS/VICINITY SHOWERS FOR KSGF OVERNIGHT. ANY PRECIP SHOULD BE BRIEF. WILL KEEP TAFS VFR...BUT MAY SEE SOME AFTERNOON/EARLY EVENING THUNDERSTORMS ONCE AGAIN WED...BUT PROBABILITY IS TOO LOW TO CARRY A MENTION IN THE TAFS FOR NOW. WE MAY SEE SOME REDUCTION IN VISIBILITY IN LIGHT FOG/HAZE AGAIN TOWARD DAWN. DSA .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPRINGFIELD MO 920 PM CDT TUE JUL 22 2008 .UPDATE... SCATTERED CONVECTION WILL CONTINUE TO BE POSSIBLE TONIGHT AS A MODEST LOW LEVEL S-SW FLOW CONTINUES TO PRODUCE SOME MODEST LIFT ALONG AN ELEVATED NW-SE FRONTAL BOUNDARY FROM NW MO INTO THE MO OZARKS. CAPES DEPICTED BY THE RUC STILL PRETTY STOUT OVER KS...WITH MLCAPES 2000+ J/KG. THIS WEAKENS INTO THE MO OZARKS... WITH MLCAPES OF 500-1500 J/KG...BUT MUCAPES STILL 1500-2000 J/KG. STILL HAVE ONE GOOD PERSISTENT UPDRAFT OVER EAST CENTRAL KS...AND A WEAKER CLUSTER OVER WEST CENTRAL MO. BELIEVE WE WILL SEE THIS ELEVATED CONVECTION CONTINUE FOR AWHILE INTO THE OVERNIGHT HOURS. MAY BE A SIMILAR STORY FOR THE COMING DAYS...WITH THE NW-SE BAROCLINIC ZONE STUCK OVER THE AREA. DSA && .AVIATION... FOR THE 0000 UTC KSGF/KJLN TAFS...OUTFLOW BOUNDARY HAS PUSHED CONVECTION WEST AND SOUTH OF THE TAFS SITES...BUT ACTUAL WEAK SFC BOUNDARY STILL EXTENDS FROM CENTRAL KS INTO THE MO OZARKS. WILL CONTINUE TO MONITOR FOR POSSIBLE REDEVELOPMENT ALONG AN ELEVATED FRONTAL BOUNDARY LATER TONIGHT FROM THE KC METRO AREA SOUTH INTO CENTRAL MO AND THE MO OZARKS. CAN`T RULE OUT SOME SHALLOW FOG WHERE HEAVIER RAIN FELL TODAY...BUT THE TAF SITES ESCAPED THE HEAVIER RAINFALL SO WILL LEAVE BOTH TAFS VFR THROUGH WED. DSA && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 421 AM CDT THU JUL 24 2008 .SHORT TERM...TODAY THROUGH 00Z SUNDAY MAIN FCST CHALLENGE FACING THE SHORT TERM IS PCPN CHANCES AGAIN TODAY THROUGH FRIDAY MORNING. LATEST MSAS ANLYS SHOWS SFC BOUNDARY DRAPED NW-SE ACROSS WRN PART OF THE CWA...WITH ONLY TELLING DIFFERENCE IS THE L-M50 DWPTS LOCATED ACROSS THE NW PART OF SD. AREAS OF LOW STRATUS/FOG IS SETTING UP UNDER TROF AXIS WHERE MIXING WINDS ARE MINIMAL. HAVE INSERTED SOME PATCHY FOG WORDING FOR THIS MORNING ACROSS ALL THE CWA TO ACCOUNT FOR THIS. ATTENTION THEN TURNS TOWARD THIS AFTERNOON. MODELS ALL AGREE ON 85H/925H BOUNDARY REMAINING PROGRESSIVE ACROSS THE NORTH...WHILE HANGING UP ACROSS SRN SD BY 00Z. 5H WAVE THAT IS CURRENTLY TRACKING ACROSS MT WILL INTERSECT THE SFC/LOW LEVEL BOUNDARIES DURING PEAK HEATING ACROSS THE EAST...AND THERE SHOULDN`T BE THE CONVECTIVE DEBRIS CLOUDS IN PLACE SIMILAR TO YESTERDAY...AND WITH DWPTS ALREADY IN THE MID 60S...AND DWPTS IN THE LOWER 70S IN PLACE ACROSS PARTS OF NERN NEB...THE MECHANISM SHOULD BE RESET FOR CONVECTIVE DEVELOPMENT LATER THIS AFTERNOON. HOWEVER...WILL HAVE TO SEE HOW MUCH OF A ROLE THE LOW CLOUDS/STRATUS PLAY UNDER TROF AXIS...AND WHETHER OR NOT THEY CAN BE MIXED OUT. LATEST RUC SHOWS THAT 7H THETA-E DOWNGLIDE REMAINS IN PLACE THROUGH 18Z FOR MUCH OF THE CWA...WITH WAA RETURNING TO THE WEST LATER IN THE AFTN PER THE 06Z NAM12 SOLN. BY 00Z FRIDAY...NAM12 SHOWS AREA OF BEST LI`S LOCATED ALONG AND JUST AHEAD OF NE-SW DRAPED SFC BOUNDARY...WITH LI`S TO -8...ALONG WITH MOST UNSTABLE CAPES FROM 1500 TO 3000 J/KG. HAVE TRIED TO ORIENT POPS ALONG SFC BOUNDARY FOR LATER THIS AFTERNOON THROUGH THE NIGHT. WITH RESPECT FOR THE OVERNIGHT HOURS...MODELS AGREE ON PRESSURE RISES ON THE 305-315K LAYERS...ALONG WITH SPEC HUMIDIES DECREASING ACROSS MY NW CWA. THETA-E ANLYS POINTS TO DOWNGLIDE AND DRYING NOTED IN THE RH FIELDS. HAVE REMOVED MENTION OF POPS ACROSS THE NW FOR THE OVERNIGHT HOURS ON ACCOUNT OF THIS. OVERALL...VERY DIFFICULT AND COMPLEX CONVECTIVE FCST SETTING UP FOR TODAY...AND WILL BE HIGHLY DEPENDANT UPON LOCATION OF SFC BOUNDARY AND TIMING OF 5H/7H WAVES. THERE IS SOME CONCERN FOR FRIDAY AS THE NAM SHOWS SFC BOUNDARY REMAINING STALLED ACROSS SRN SD...ALLOWING MORE CONVECTIVE DEVELOPMENT TO TAKE PLACE LATER IN THE AFN. THE GFS REMAINS MORE PROGRESSIVE WITH THIS FEATURE...PUSHING IT OUT OF STATE DURING THE DAY FRIDAY...WHICH ALLOWS COOLER/DRY CANADIAN HIGH PRESSURE TO SETTLE IN FOR THE BEGINNING OF THE WEEKEND. GIVEN THE NEARLY ZONAL FLOW SETTING UP ALOFT AND THAT FLOW REMAINS NEARLY CROSSWISE TO SFC FRONTAL POSITION...HAVE OPTED WITH THE GFS SOLN AND KEPT PCPN OUT OF FCST FOR FRIDAY. TEMP WISE...THINK THAT TODAY WILL BE WARMEST DAY OF THE SHORT TERM...WITH DECENT SUNSHINE PROVIDED THAT LOW CLOUDS/STRATUS BURN OFF BY 15Z. DIDN`T GO REALLY WILD WITH HEATING AS AMPLE LOW LEVEL MOISTURE WILL ABSORB SOME OF THE HEATING ENERGY...BUT SHOULD PROVE TO BE A MUGGY DAY...ESPECIALLY ACROSS THE EAST. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY 00Z EC/GFS OPERATIONAL SOLUTIONS STILL SHOWING REASONABLY SIMILAR UPPER LEVEL AND SURFACE SOLUTIONS. OVER THIS CWA...MUCH OF THE EXTENDED FORECAST IS A PERIOD OF WEAK UPPER LEVEL RIDGING WITH STEERING FLOW PREDOMINANTLY FROM THE WNW. IN THE LOW LEVELS...HIGH PRESSURE IS PARKED OVER THE UPPER MISSISSIPPI RIVER VALLEY WITH THE WESTERN HALF OF THE CWA IN SERLY RETURN FLOW WHILE THE EASTERN HALF IS EITHER LIGHT AND VARIABLE WINDS OR WINDS OUT OF THE NORTHEAST. BEST CHANCES FOR MEASURABLE PRECIP OVER THE CWA CONTINUES TO EXIST SATURDAY NIGHT AND AGAIN MONDAY/MONDAY NIGHT...SATURDAY NIGHT IN THE FORM OF AN MCC MEATBALL ORIGINATING OVER EASTERN MONTANA/SWRN NODAK AND PROPAGATING SEWD THROUGH THIS CWA...AND MONDAY/MONDAY NIGHT IN THE FORM OF CONVECTION GOING UP ALONG AND AHEAD OF A SYNOPTIC SCALE COLD FRONTAL BOUNDARY PROGGED TO WORK THROUGH THE NORTHERN PLAINS STATES. NO CHANGES MADE TO MAX/MIN T GRIDS AS...THEY APPEAR SPOT ON WHEN COMPARED WITH 00Z LOW LEVEL THERMAL PROGS OF THE EC AND GFS MODELS. && .AVIATION... LOW LEVEL GULF OF MEXICO MOISTURE ABOUNDS IN THE LOWEST COUPLE THOUSAND FEET OF THE ATMOSPHERE THIS MORNING. COUPLE THAT WITH VACATING MID/HIGH CLOUDS AND LIGHT SOUTHERLY WINDS AT THE SURFACE AND THE RESULT IS FOG AND LOW STRATUS CLOUDS DEVELOPING ACROSS THE FORECAST AREA. BEEN MONITORING THE MOVEMENT OF A SURFACE TROF ACROSS THE WESTERN AND CENTRAL DAKOTAS THIS MORNING. THE TROF AXIS WILL BE POSITIONED OVER KMBG AND CLOSE TO KPIR THIS MORNING AT SUNRISE. WINDS WILL BE LIGHTEST HERE...AND SURFACE OBS ARE RESPONDING WITH IFR VISBIES IN GROUND FOG DEVELOPMENT. THIS IFR VISBY CONDITION IN SHALLOW GROUND FOG ACROSS CENTRAL AND NORTH CENTRAL SOUTH DAKOTA SHOULD BE SHORT-LIVED...DIMINISHING SHORTLY AFTER SUNRISE. FURTHER EAST ACROSS THE KABR AND KATY TERMINALS...SURFACE WINDS OF 5 TO 10 KNOTS SHOULD TRANSLATE TO MVFR VISBIES AND SOME IFR CIGS IN LOW STRATUS THROUGH MID-MORNING. SHOULD NOT TAKE LONG FOR DAYTIME INSOLATION TO MIX OUT THE LOW CLOUDS. AFTER 15Z THIS MORNING...GOOD VFR SHOULD RESUME ACROSS ALL FOUR TERMINALS. LATER THIS AFTERNOON...THIS PREVIOUSLY MENTIONED SURFACE TROF WILL BECOME THE FOCUS FOR AFTERNOON AND EVENING THUNDERSTORM ACTIVITY. THE BOUNDARY WILL BE ORIENTED ROUGHLY FROM KPIR TO KATY...SO EXPECT THESE TWO TERMINALS TO BEGIN CARRYING SOME SORT OF CONVECTION MENTION /EITHER CB OR VCTS/ IN THE LATE AFTERNOON/EARLY EVENING TIMEFRAME. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ SHORT TERM...HINTZ LONG TERM...DORN AVIATION...DORN WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 104 PM EDT TUE JUL 22 2008 .SYNOPSIS... A WEAK COLD FRONT WILL SLIDE SOUTHEAST INTO THE OHIO VALLEY THIS AFTERNOON AND THEN INTO OUR AREA ON WEDNESDAY. SCATTERED STRONG THUNDERSTORMS ARE EXPECTED THIS AFTERNOON WITH MORE NUMEROUS STORMS EXPECTED ON WEDNESDAY. WEAK HIGH PRESSURE SHOULD BUILD IN BEHIND THE FRONT ON THURSDAY BRINGING DRIER WEATHER FOR WEEKS END. && .NEAR TERM /THROUGH TONIGHT/... ALREADY UPDATED TO LOWER POPS WEST THIS MORNING IN WAKE OF OUTFLOW AND INCREASE IN THE PIEDMONT WHERE OLD BOUNDARY OFF THE MCS HAS STALLED. WITH OLD MCS EXITING TO THE NORTH AND FRONT STILL WELL TO THE NW EXACT COVERAGE OF ADDED CONVECTION IFFY THIS AFTERNOON WITH GUIDANCE OFFERING SEVERAL DIFFERING SOLUTIONS. LATEST NAM APPEARS TOO FAR EAST WITH SIG TSRA THIS AFTERNOON WHILE THE GFS TO THE WEST WITH NEXT ROUND OF TSRA CLOSER TO THE FRONT. LOCAL WRF AND LATEST RUC IN BETWEEN WITH MORE DEVELOPMENT WESTERN SLOPES TO THE BLUE RIDGE WHERE BETTER INSTABILITY LOOKS TO TAKE SHAPE. MODIFIED MORNING RAOBS ALSO SHOW QUITE A BIT OF CAPE WEST UNDER DEEPER RH AND LESS EAST. THINK DEEP BUT RATHER WEAK WESTERLY FLOW COMBO WITH PASSING OUTFLOW MAY DELAY NEW DEVELOPMENT BEFORE NEXT S/W APPROACHES ALLOWING THE FLOW TO BACK MORE SW LATER ON. THIS SUPPORTS BETTER COVERAGE ALONG WEST OF THE BLUE RIDGE WHERE WILL KEEP HIGHEST POPS AND LOW CHANCE EASTERN ZONES. OTRW ANOTHER HOT AFTERNOON IN STORE WITH 850 MB TEMPERATURES RUNNING AROUND +22-23C AND SURFACE DEW POINTS IN THE MID 60S TO LOWER 70S. HOWEVER SIMILAR TO MONDAY THINK DEWPOINTS WILL MIX OUT A BIT ALLOWING HEAT INDICES TO REMAIN JUST BELOW ADVISORY CRITERIA ACROSS THE PIEDMONT. 12Z THICKNESS ALSO IN SUPPORT OF PUSHING HIGHS TO AROUND 100 SE WITH MID/UPR 90S ELSW OVER THE EAST...BUT SLIGHTLY LOWER MID/UPR 80S FAR WEST WHERE WILL SEE MORE CLOUDS/TSRA. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... MORE STRONG STORMS CAN BE EXPECTED ON WEDNESDAY AS A COLD FRONT APPROACHES THE REGION DURING THE AFTERNOON. THE AREA...ESPECIALLY IN THE EAST...WILL BE IN THE ENTRANCE REGION OF THE LOW LEVEL JET. THE COMBINATION OF THE FRONT AND JET DYNAMICS WILL BRING ABOUT ANOTHER ROUND OF SEVERE WEATHER AND HEAVY DOWNPOURS TO THE REGION. PROGRESSION OF THE FRONT MAY BE SLOW TO MOVE TO THE EAST COAST SO WILL HANG ON TO SOME POPS IN THE PIEDMONT THURSDAY MORNING. DRIER SLIGHTLY COOLER AIR WILL MOVING INTO THE REGION ON THURSDAY. BY FRIDAY...THETA-E BOUNDARY BUCKLES BACK TO THE NORTH WITH HEAT AND HUMIDITY INCREASING INTO THE WEEKEND. DEPENDING ON THE TIMING OF PRECIPITATION INTO THE AREA...WE COULD SEE A WIDE RANGE IN TEMPERATURES ACROSS THE AREA. TEMPERATURES COULD RANGE FROM THE LOWER TO MID 70S IN THE GREENBRIER VALLEY TO LOWER 90S IN THE PIEDMONT. && .LONG TERM /SATURDAY THROUGH MONDAY/... UPPER TROUGH OVER THE EAST WILL SLOWLY DEEPEN AND STRENGTHEN OVER THE NEXT SEVERAL DAYS...EVENTUALLY DISPLACING THE HEAT AND HUMIDITY AT LEAST FROM THE NW HALF OF THE CWA BY EARLY NEXT WEEK. WHILE THIS OCCURS...SHWS/TSTORMS SHOULD DEVELOP AHEAD OF IT THIS WEEKEND. A PREFRONTAL TROUGH WILL PASS THROUGH ON SATURDAY FIRST...WITH POSSIBLY MORE NUMEROUS SHOWERS AND STORMS ON SUNDAY WHEN THE COLD FRONT CROSSES. ALTHOUGH MANY COLD FRONTS HAVE PERISHED BEFORE CLEARING THE NC/VA BORDER...IF SOME OF THE LR MODELS VERIFY IN REGARDS TO THE AMPLITUDE OF THE UPPER RIDGE THROUGH SOUTH CENTRAL CANADA...THIS FRONT MAY ACTUALLY PASS FAR ENOUGH SOUTH TO BRING A NICE STRING OF NORMAL OR SLIGHTLY BELOW NORMAL TEMPS...AND DRY CONDITIONS FOR MUCH OF NEXT WEEK. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... WEAK SINKING MOTION BEHIND EARLIER MCS CONTINUES TO SLOW CU AND SUBSEQUENT CONVECTION EARLY THIS AFTERNOON. HOWEVER WITH HEATING EXPECT SOME REDEVELOPMENT OF TSRA ESPCLY OVER THE WEST IN ADVANCE OF NEXT WEAK IMPULSE ADVECTING IN FROM THE TN VALLEY. BUFKIT SUGGESTS MUCH OF THIS MAY HOLD OFF UNTIL AFTER 20Z BUT THEN LINGER SE WVA INTO TONIGHT. THUS WILL SLOW DOWN TIMING OF TSRA ONSET AND INCLUDE VICINITY MENTION MOST SPOTS FROM LATE AFTERNOON THRU 00Z. AREAS OF IFR/MVFR FOG ALSO POSSIBLE ESPCLY VALLEYS WHERE EARLIER RAINFALL OCCURRED. OTRW MAINLY VFR INTO TONIGHT OUTSIDE SHRA. COLD FRONT DROPS IN FROM THE NW WED WITH ONGOING SHRA/TSRA BAND OR QUICK REDEVELOPMENT OF CONVECTION LIKELY TAKING PLACE FROM WEST TO EAST. MAY INCLUDE SOME PREVAILING VSBY REDUCTION IN SE WVA IN THE MORNING OTRW RUNNING WITH CB MENTION BY MIDDAY FAR WEST. CONVECTION LIKELY TO LINGER INTO WED EVENING AS THE FRONT MOVES THROUGH WITH DRYING CONDITIONS ON THU UNDER WEAK HIGH PRESSURE. THIS SHOULD ALSO KEEP VFR CONDITIONS ONGOING INTO LATE WEEK BEFORE ANOTHER COLD FRONT ARRIVES WITH ADDITIONAL SHOWERS AND STORMS BY SAT OR SUNDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/RCS NEAR TERM...JH/RCS SHORT TERM...RCS LONG TERM...KM AVIATION...JH/JS va AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 338 AM CDT THU JUL 24 2008 .SHORT TERM...TODAY THROUGH SATURDAY NIGHT FORECAST CONCERNS THIS PACKAGE...PRECIPITATION CHANCES TODAY THROUGH FRIDAY EVENING...TEMPERATURES. DATA ANALYSIS AT 06Z HAD HIGH PRESSURE RIDGING FROM JAMES BAY SOUTH INTO WI AND IL. LOW PRESSURE WAS LIFTING NORTH OF LK WINNIPEG WITH A TRAILING TROUGH/COLD SOUTH THRU THE DAKOTAS TO EASTERN CO. FOG- PRODUCT/IR IMAGERY/SFC OBS SHOWED WIDESPREAD MID/HIGH CLOUDS ACROSS MN/IA/WI AS MOISTURE PUSHED INTO/THRU THE UPPER RIDGE AXIS. WEAK TO MDT 850-700MB MOISTURE TRANSPORT/THETA-E CONVERGENCE RESPONSIBLE FOR BAND OF SCT -SHRA FROM NORTHWEST OF KMSP TO SOUTHEAST IA. STRONGER/ DEEPER CONVECTION WAS IN THE KFSD/KOMA AREAS ON NOSE OF LOW LEVEL JET/STRONGER 850MB MOISTURE TRANSPORT AND INSTABILITY. ALL THE SHRA/TSRA MOVING SOUTHEAST EARLY THIS MORNING...FOLLOWING CORFIDI VECTORS QUITE NICELY. NO LARGE ERRORS NOTED WITH 24.00Z NAM/GFS INITIALIZATIONS...WITH THESE 2 MODELS PRESENTING RATHER SIMILAR SOLUTIONS FOR TODAY THRU SAT NIGHT. DPROG/DT OF 500MB HGTS AT 24.00Z SHOWED NAM/GFS RUNS OF 22.00Z AND 23.00Z VERIFIED QUITE WELL ACROSS NOAM...WITH EDGE AND BETTER RUN-TO-RUN CONSISTENCY TO GFS OVER EASTERN NOAM AND TO NAM WITH THE TROUGHS OVER OR/WA AND SASKAT/ND. THRU 36HRS TREND IS TOWARD MORE PROGRESSIVE WITH THE EASTERN CONUS TROUGH AND A BIT SLOWER/STRONGER WITH THE TROUGHS NEAR LK WINNIPEG AND OFF THE WEST COAST AT 12Z FRI. FOR 36-84HRS TREND IS FURTHER WEST/SLOWER WITH THE UPPER LOW NEAR JAMES BAY AND WITH THE NEXT TROUGH NEARING THE BC COAST. THIS LEAVES THE AREA MORE UNDER THE INFLUENCE OF THE EASTERN CAN UPPER LOW/NORTHWEST FLOW ALOFT FOR THE WEEKEND. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED NAM/GFS WITH REASONABLE DEPICTIONS OF THE SFC MASS FIELDS ACROSS CENTRAL NOAM. PER WV IMAGERY MODELS REASONABLE WITH THE SHORTWAVE DETAILS ACROSS THE CONUS...WITH NO CLEAR FAVORITE ON THE DETAILS. GFS GENERALLY BETTER WITH THE 00Z- 06Z PRECIP ACROSS THE REGION. NO CLEAR DETERMINISTIC MODEL OF CHOICE THIS CYCLE. WITH MODEL SOLUTIONS QUITE SIMILAR...INCLUDING UKMET/ ECMWF AND LCL/RUC WRF MODELS...FAVORING ONE OVER THE OTHER AGAIN LOOKS TO HAVE LITTLE IMPACT ON THE SENSIBLE WEATHER FOR TODAY INTO SAT NIGHT. AGAIN FAVORED A MODEL/ENSEMBLE COMPROMISE THIS CYCLE. SHORT TERM FORECAST CONFIDENCE ON THE GOOD SIDE. FOR THE SHORT TERM...GENERALLY WEAK 850-700MB MOISTURE TRANSPORT/ THETA-E CONVERGENCE PRODUCING THE SCT -SHRA FROM EAST CENTRAL MN TO SOUTHEAST IA WEAKENS OR DROPS SOUTHEAST OF THE FORECAST AREA BY 15Z THIS MORNING. STRONGER THERMODYNAMIC FORCING FOR CONVECTION OVER SOUTHEAST SD/WESTERN IA WEAKENS/DROPS SOUTHEAST ACROSS IA THIS MORNING AS WELL. UPPER RIDGE AXIS IS OVER THE AREA TODAY WITH RELATIVELY WARM MID LEVEL TEMPS AND AN INVERSION REMAINING NEAR 800MB. THIS AND CONSIDERABLE DEBRIS MOISTURE/CLOUDINESS LIMIT CAPE DEVELOPMENT OVER THE AREA TODAY. ALL THIS LEAVES THE AREA WITH LITTLE IN THE WAY OF FORCING/LIFT/INSTABILITY FOR CONVECTION TODAY/TONIGHT AND LOWERED MOST RAIN CHANCES THESE PERIODS TO SLIGHT CHANCE. RESURGENCE OF LOW LEVEL JET/MOISTURE TRANSPORT TONIGHT RE- FIRES CONVECTION ACROSS CENTRAL IA...BUT GOOD MODEL CONSENSUS ON THE DETAILS THAT THIS FORCING WILL REMAIN/PASS SOUTHWEST OF THE FORECAST AREA TONIGHT. DID LEAVE A BIT HIGHER RAIN CHANCE ACROSS NORTHEAST IA TONIGHT WITH THAT AREA CLOSER TO THE CONVECTIVE FORCING/INSTABILITY. MOISTURE/INSTABILITY INCREASE OVER THE AREA FRI...AHEAD OF THE TROUGH/FRONT. MIXED LAYER CAPES INCREASE TO THE 1K-2K J/KG RANGE FOR FRI AFTERNOON. 0-6KM SHEAR INCREASES AS WELL WITH SWODY2 LOOKING REASONABLE. WITH THE TREND TOWARD A SLOWER/STRONGER TROUGH/FRONTAL PASSAGE ON FRI...AND THE MDT/STRONG CAPE/SHEAR...RAISED SHRA/TSRA CHANCES FOR FRI. DUE TO THE SLOWER FRONTAL PASSAGE AND SOME LINGERING INSTABILITY...SHRA/TSRA CHANCES FRI EVENING LOOK WELL TRENDED AND RAISED THESE A BIT AS WELL. HIGH PRESSURE AND A DRIER AIRMASS IN THE WAKE OF THE FRONT SLIDE INTO THE AREA FOR SAT/SAT NIGHT. THE DRY FORECAST FOR THESE PERIODS CONTINUES TO LOOK GOOD. GENERALLY FAVORED A BLEND OF GUIDANCE HIGHS TODAY. SHOULD BE PLENTY OF DEBRIS CLOUDINESS TODAY...BUT ANY HOLES IN THE CLOUDS THIS AFTERNOON WOULD ALLOW TEMPS TO JUMP QUICKLY. GUIDANCE LOWS TONIGHT/ FRI NIGHT SIMILAR AND LOOK GOOD. TRENDED TOWARD WARMER OF GUIDANCE HIGHS FRI...AHEAD OF THE TROUGH/FRONT. GUIDANCE HIGHS SIMILAR AND REASONABLE FOR SAT. WITH THE DRIER HIGH BUILDING IN...TRENDED LOWS DOWN A BIT FOR SAT NIGHT TOWARD THE 24.00Z GFS MEX-MOS GUIDANCE. .LONG TERM...SUNDAY THROUGH WEDNESDAY 24.00Z MEDIUM RANGE MODELS IN GENERALLY GOOD AGREEMENT WITH EACH OTHER FOR THE SUN-WED PERIOD. RUN-TO-RUN CONSISTENCY REMAINS GOOD ON SUN. BY MON/TUE THIS STARTS TO DECREASE AS MODELS TREND TOWARD A STRONGER SHORTWAVE PUSHING THRU THE WESTERN NOAM RIDGE AXIS MON... THEN DROPPING ACROSS THE REGION TUE. THIS TREND TOWARD 23.00Z ECMWF RUN...WHICH LOOKED LIKE AN OUTLIER AT THE TIME. SOME TIMING DIFFERENCES WITH THIS WAVE DROPPING ACROSS THE REGION...BUT BOTTOM LINE LOOKS TO BE THE AREA REMAINS UNDER NORTHWEST FLOW ALOFT THRU THE MIDDLE OF NEXT WEEK. STILL SOME THREAT FOR CONVECTION ON SUN... HOWEVER MODEL CONSENSUS INCREASING FOR THE FORCING FOR THIS TO REMAIN SOUTHWEST OF THE FORECAST AREA. DID ADD A SMALL SHRA/TSRA CHANCE TO TUE WITH THE INCREASING MODEL SIGNAL/CONSENSUS FOR A TROUGH/FRONTAL PASSAGE. WITH THE CONTINUED NORTHWEST FLOW ALOFT... TEMPS LOOK TO REMAIN NEAR TO A BIT BELOW NORMAL. THIS WELL TRENDING IN THE DAY 4-7 GRID-SET AT THIS TIME. && .AVIATION...TODAY AND TONIGHT CONTINUE TO EXPECT VFR CONDITIONS THROUGH AT LEAST MUCH OF THE AFTERNOON...BEFORE TRENDS TO POTENTIAL MVFR CEILINGS AND PERHAPS VSBYS COME INTO THE FORECAST. BANDS OF MAINLY -SHRA TO CONTINUE TO WORK EAST ACROSS THE TAF SITES THIS MORNING...BUT RAINFALL SPOTTY AND LIGHT AND CEILINGS/VSBYS EXPECTED TO REMAIN LARGELY VFR. MAINLY LGT SLY FLOW FOR THE TAF SITES TODAY...WITH THIS BRINGING A HIGHER MOISTURE AIRMASS INTO THE TAF SITES LATER THIS AFTERNOON/EVENING. INDICATIONS IN THE BOTH DETERMINISTIC AND PROBABILISTIC DATASETS FOR AN MVFR STRATOCUMULUS FIELD TO DEVELOP WITH THIS LOW LEVEL THETA-E ADVECTION...AND POTENTIAL FOR HAZE/BR TO BE WIDESPREAD IN THE 4-6SM RANGE OVERNIGHT. THERE/S A MORE SUBTLE INDICATION IN THE ABOVE DATASETS FOR IFR FOG TO DEVELOP AFTER 06Z GIVEN LIGHT FLOW...AND WEAK CONVERGENCE AHEAD OF A COLD FRONT. WOULD BE DEPENDENT ON LOWER MVFR CEILINGS BREAKING UP...WHICH MAY NOT HAPPEN. FOR NOW...WILL CONTINUE TRENDS OF LOWERING VIS INTO MVFR CATEGORIES TONIGHT AND CONTINUE MVFR CEILINGS ALREADY FORECAST. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...RRS AVIATION..........BINAU wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1050 AM EDT THU JUL 24 2008 .SYNOPSIS... 14Z WATER VAPOR AND H4 RUC ANALYSIS SHOWING AN ACTIVE NORTHERN STREAM ACROSS THE NORTHERN TIER OF THE COUNTRY AND SOUTHERN CANADA. FURTHER SOUTH WE FIND AN ELONGATED UPPER RIDGE FROM SOUTHERN CALIFORNIA TO THE LOWER/MIDDLE MISSISSIPPI VALLEY. "THE SUMMER OF THE EAST COAST TROUGH" CONTINUES TO HOLD ITS PATTERN WITH AMPLIFIED TROUGHING FOR LATE JULY COVERING THE EASTERN GREAT LAKES...MID ATLANTIC AND NEW ENGLAND STATES. THE TROUGH IS ANCHORED BY A CLOSED LOW OVER WESTERN NY/SE ONTARIO. FURTHER UPSTREAM WE FIND ANOTHER SHORTWAVE TROUGH MOVING INTO SOUTH-CENTRAL CANADA AND THE NORTHERN PLAINS. AS THE CURRENT EAST COAST TROUGH BEGINS TO LIFT OUT FRIDAY INTO SATURDAY...THIS NEXT PIECE OF ENERGY IN LINE WILL AMPLIFY AND TAKES IT PLACE INTO EARLY NEXT WEEK. OUR FORECAST AREA RESIDES IN A MID/UPPER LEVEL NW/N FLOW PATTERN WEDGED IN BETWEEN THE TROUGHING TO OUR NORTHEAST AND THE RIDGING TO OUR WEST. OVER THE PAST 12 HOURS THIS NW FLOW HAS DELIVERED A SIGNIFICANTLY DRIER UPPER LEVEL AIRMASS INTO THE SOUTHEAST. AT THE SURFACE...MORNING RUC ANALYSIS SHOWING SURFACE RIDGING TO OUR SOUTH OVER THE FL PENINSULA AND EASTERN GULF AND WEAK TROUGHING FURTHER NORTH ACROSS CENTRAL GA/AL. EXPANSIVE AREA OF LOW CLOUDS/FOG ACROSS SOUTHEAST ALABAMA AND MUCH OF SOUTHWEST AND SOUTH-CENTRAL GA FORMED DURING THE OVERNIGHT AND MORNING HOURS AS THE UPPER LEVEL DRIER AIR OVERRODE THE MOIST LOW LEVELS PRECONDITIONED BY RAINFALL ON WEDNESDAY. NOCTURNAL CONVECTION THAT FORMED NEAR THE COAST AND ACROSS THE NEARSHORE MARINE LEGS EARLY THIS MORNING IS SETTLING SOUTHWARD INTO THE OFFSHORE LEGS AND WEAKENING. && .DISCUSSION... LOW CLOUDS ACROSS THE NORTHERN ZONES ARE FINALLY BEGINNING TO SHOW SIGNS OF DISSIPATING AS DIURNAL HEATING BEGINS TO MIX THE LOWER LEVELS. WITH THE DISSIPATION EXPECT A SCT CU FIELD TO DEVELOP REGIONWIDE INTO THE EARLY AFTERNOON HOURS AS LOW LEVEL CONVERGENCE INCREASES WITH DEVELOPING SEA-BREEZES AND ASSOCIATED WITH THE SURFACE TROUGH ACROSS THE NORTH. TEMPERATURE RISES HAVE BEEN SLOWED ACROSS THE NORTH WITH THE LOWER CLOUDS BUT EXPECT THESE AREAS TO CATCH UP QUICKLY INTO THE EARLY AFTERNOON ONCE BETTER INSOLATION DEVELOPS...AND STILL ANTICIPATE WIDESPREAD LOWER TO MIDDLE 90S BY THE MID/LATE AFTERNOON. 12Z KTLH SOUNDING REALLY SHOWS THE ARRIVAL OF THE DRIER AIR ALOFT WITH SIGNIFICANT INCREASES IN DEWPOINT DEPRESSIONS ABOVE AROUND 600MB SINCE LAST EVENING AND A DROP IN PW FROM AROUND 2" DOWN TO AROUND 1.6". ALSO HAVE SEEN MID LEVEL TEMPERATURES RISE AROUND 3 DEGREES IN THE MID-LEVELS FROM YESTERDAY. THIS WAS PREDICTED WELL BY EARLIER MODEL SOUNDINGS AS MENTIONED IN THE PREVIOUS DISCUSSION BELOW. MODIFYING THIS MORNINGS SOUNDING FOR AN AFTERNOON SURFACE PARCEL OF 91/68 YIELDS CAPE VALUES AROUND 2000 J/KG (A BIT BELOW CLIMO). WITH THE WARMER MID-LEVELS TODAY...THE FREEZING LEVEL IS ALSO QUITE HIGH AT JUST UNDER 15KFT. DUE TO THE ATMOSPHERE BEING SLIGHTLY MORE CONVECTIVELY HOSTILE... DO NOT EXPECT THE WIDESPREAD COVERAGE OF STORMS SEEN ON WEDNESDAY AFTERNOON/EVENING. 1000-700MB MEAN FLOW IS N/NW AT AROUND 10 KNOTS. THIS TYPE OF FLOW REGIME TENDS TO PIN THE SEA-BREEZE TOWARD THE COAST WITH SEA-BREEZE CONVECTION GENERALLY CONFINED TO THE SOUTHERN ZONES. OFTEN HOWEVER WITH THE NORTHWEST FLOW WE SEE SYNOPTIC DISTURBANCES WITHIN THE FLOW THAT KEEP AT LEAST SOME POPS FURTHER TO THE NORTH. ALTHOUGH THERE ARE NO CLEAR CUT UPPER DISTURBANCES TODAY...THE SURFACE TROUGH SHOULD PROVIDE ENOUGH FOCUS TO INITIATE WIDELY SCT-SCT STORMS AWAY FROM THE SEA-BREEZE INFLUENCE. CURRENT FORECAST SHOWS CHANCE POPS FOR OUR FLORIDA ZONES UP INTO SOUTHEAST ALABAMA (40-50%) AND SLIGHT CHANCE TO LOW END CHANCE (20-35%) ACROSS OUR GA/ZONES. THIS FORECAST SEEMS ON TRACK AS A BIT BETTER UPPER MOISTURE BEGINS TO WORK BACK INTO OUR WESTERN ZONES LATE IN THE DAY LEAVING THE MOST HOSTILE PROFILE OVER SOUTH-CENTRAL GEORGIA. && .MARINE... WAVE PERIODS AT THE BUOYS HAVE BEEN HOLDING STEADY THIS MORNING...HOWEVER SHOULD BEGIN TO COME DOWN TONIGHT INTO THURSDAY. WILL CONTINUE ONGOING FORECAST OF 2 TO 4 FEET...BUT SHOW A DECREASING TREND TONIGHT. WINDS AND SEAS FRIDAY AND BEYOND WILL REMAIN LOW. MORNING THUNDERSTORMS CONTINUE TO PULLS FURTHER OFFSHORE. && .AVIATION... AFTER YESTERDAY`S WIDESPREAD RAINS...MID LEVEL DRY AIR SURGED SWD PROVIDING A CLASSIC SET UP FOR IFR CONDITIONS THIS MORNING. THE LOW STRATUS WILL PERSIST AT ABY UNTIL ABOUT 16Z. VFR CONDITIONS ARE THEN FORECAST TO PREVAIL FOR THE REMAINDER OF THE DAY OUTSIDE OF THUNDERSTORMS. SCATTERED CONVECTION IS EXPECTED FOR AREAS AROUND PFN...TLH AND DHN WITH MORE ISOLATED COVERAGE FOR THE VLD AND ABY AREAS. WE DO NOT ANTICIPATE A REPEAT OF THE LOW STRATUS TONIGHT, EXCEPT AT ABY. OTHER TERMINALS WILL SEE A BRIEF PERIOD OF MVFR VSBY. AFTER 08Z. && .PREV DISCUSSION... .SHORT TERM...TODAY THROUGH SATURDAY. IT IS NICE TO SEE SOME GENERAL AGREEMENT BETWEEN THE NAM AND GFS THIS MORNING. IN FACT...IT IS THE GFS SOLUTION THIS CYCLE THAT HAS COME AROUND MORE TO THE NAM SOLUTION. VAPOR IMAGERY THIS MORNING CONFIRMS THAT MID AND UPPER LEVEL DRY AIR IS SURGING SOUTHWARD AS THE UPPER TROF AMPLIFIES OVER THE NORTHEAST AND MID ATLANTIC STATES. THIS SURGE OF DRIER MID/UPPER LEVEL AIR WILL HELP TO SUPPRESS AFTERNOON CONVECTION...ESPECIALLY ACROSS OUR NORTHERN ZONES. MOREOVER...MODEL SOUNDINGS INDICATE THAT TEMPERATURES IN THE 700 TO 400 MB LAYER WILL BE AROUND 2 DEGREES C WARMER TODAY THAN YESTERDAY. THE SURFACE BOUNDARY SHOULD REMAIN FAR ENOUGH NORTH THROUGHOUT TODAY TO LIMIT DRIER SURFACE AIR FROM REACHING OUR COUNTIES. WITH A TYPE 8/9 SEA BREEZE REGIME TODAY (1000-700 MB FLOW NW AROUND 10 KNOTS)...THE SEA BREEZE FRONTS WILL BE PINNED NEAR THE COAST...BUT WITH THE BEST DEEP LAYER MOISTURE AVAILABLE IN THESE AREAS...HIGHER POPS ARE INDICATED CLOSER TO THE COAST. WILL GO FOR SLIGHT CHANCE POPS FAR NORTHERN AREAS WHERE MOISTURE AND INSTABILITY WILL BE LOWEST. MODIFIED PARCELS IN THE NORTH (93/67...WHICH MAY BE GENEROUS FOR THE DEWPOINT) YIELDS ABOUT 1500 J/KG OF SBCAPE...BUT A PWAT AROUND 1.5 INCHES. THIS IS EASILY 1 STANDARD DEVIATION BELOW THE MEAN FOR THIS REGIME. FURTHER SOUTH...A MODIFIED PARCEL OF 91/69 WAS USED WHICH PRODUCED AROUND 2000 J/KG OF SBCAPE...BUT THE PWAT WAS AROUND 1.8 INCHES. THESE VALUES ARE CLOSER TO THE MEAN FOR THIS REGIME. TEMPERATURES WILL BE NOTICEABLY WARMER TODAY ACROSS THE NORTH AS LESS CLOUD COVER AND THUNDERSTORM ACTIVITY WILL ALLOW TEMPERATURES TO REACH THE MID 90S. FRIDAY...A MID LEVEL RIDGE WILL BUILD EASTWARD OVER THE WESTERN PARTS OF OUR REGION...HELPING TO SUPPRESS AFTERNOON CONVECTION. THE PRESENCE OF THE DRY AIR WILL MAKE IT DIFFICULT FOR STORMS TO DEVELOP IN THE NORTH AS WELL. THE ONLY POSITIVE FOR DECENT CONVECTION WILL BE THE DECAYING FRONTAL BOUNDARY ACROSS OUR CWA. THIS...ALONG WITH THE SEA BREEZE FRONTS WILL SERVE AS A FOCUS FOR STORMS...BUT MAINLY ALONG AND SOUTH OF THE I-10 CORRIDOR. TEMPERATURES WILL BE QUITE WARM...IN THE UPPER 90S OR BETTER ACROSS OUR NORTHERN TIER COUNTIES WHERE NEAR FULL INSOLATION UNDER THE JULY SUN WILL MAKE FOR A HOT DAY. SATURDAY...MOISTURE GRADUALLY INCREASES AS LOW LEVEL FLOW TURNS SOUTHERLY. THE MID LEVEL RIDGE SHOULD SERVE TO LIMIT THE OVERALL COVERAGE OF STORMS...BUT WITH INCREASING DEEP LAYER MOISTURE...POPS INCREASING INTO THE 30 TO 40 PERCENT RANGE...EVEN IN THE NORTHERN ZONES SEEMS APPROPRIATE. WILL SCALE TEMPERATURES BACK A LITTLE FROM THE HIGH VALUES ON FRIDAY...BUT WILL STILL BE A WARM DAY WITH MOST INLAND AREAS HITTING THE MID 90S. .LONG TERM...SUNDAY THROUGH THURSDAY. LARGE SCALE PATTERN TO REMAIN RELATIVELY UNCHANGED THROUGH THE NEXT SEVEN DAYS. UPPER FLOW WILL BE DOMINATED BY A PERSISTENT EASTERN CONUS TROUGH FLANKED BY RIDGES OVER THE WESTERN ATLANTIC AND SOUTHERN PLAINS. AT THE SFC...TROUGH WILL PERSIST NORTH OF THE CWA WITH RIDGE AXIS OVER THE GULF SOUTH OF THE COASTAL WATERS. THIS WILL KEEP A GENERAL WEST TO SOUTHWEST FLOW IN PLACE THROUGH THE FORECAST PERIOD. OVERALL...EXPECT NEAR CLIMO CONDITIONS THROUGH PERIOD WITH SCATTERED AFTERNOON AND EVENING CONVECTION AND NEAR NORMAL TEMPERATURES. && .FIRE WEATHER...LOW LEVEL FLOW WILL BECOME MORE NORTHERLY TODAY AND FRIDAY WITH SLIGHTLY DRIER AIR MASS FILTERING INTO THE AREA. HOWEVER...RELATIVE HUMIDITY VALUES ARE EXPECTED TO REMAIN WELL ABOVE RED FLAG CRITERIA. NO HEADLINES NEEDED. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 92 72 95 71 93 / 50 30 30 20 40 PANAMA CITY 90 74 91 77 90 / 50 30 40 20 40 DOTHAN 92 71 95 73 93 / 40 20 20 10 40 ALBANY 94 70 97 73 95 / 20 10 20 10 30 VALDOSTA 92 71 95 70 95 / 40 20 20 10 30 CROSS CITY 91 72 93 71 93 / 40 30 40 20 40 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$ AVIATION...WOOL SYNOPSIS/UPDATE...MROCZKA PREVIOUS DISCUSSION...GODSEY/CAMP fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 1005 AM EDT THU JUL 24 2008 .SHORT TERM...UPPER TROF HAS SHIFTED SE AND IS PRESENTLY LOCATED OVER THE SE CORNER OF OUR COUNTY WARNING AREA. 12Z KJAX SOUNDING HAD PRECIP H2O VALUE OF 1.84 IN AND EXPECT THIS TO FURTHER DECREASE THRU THE AFTN AS DRY AIR DEPICTED ON H2O VAPOR LOOP ADVECTS INTO THE AREA. MODIFIED SOUNDING HAS JUST UNDER 3000 J/KG CAPE WITH -7 LI AND 500MB TEMP OF -8C. RUC80 PROGS CAPES BACK TO 2700 BY 21Z AT KJAX WITH PWAT DOWN TO 1.51. SOME STORMS MAY BECOME STRONG TO SEVERE WITH WIND AND SOME HAIL THREAT...BUT COVERAGE SHOULD BE LESS THAN PREVIOUS FEW DAYS...MOSTLY ACROSS THE SE 1/3 OF THE AREA ON RADAR...MUCH LESS CONVECTION OVER THE COASTAL WATERS AND MOST OF IT IS EITHER WELL E OR S OF THE AREA. UPSTREAM DISTURBANCE LOCATED OVER MO AND IA MOVING SE. HOWEVER...THIS SHOULD REMAIN N OF THE AREA THRU THE EVENING. AGREE THAT MOST CONVECTION WILL BE SEABREEZE FORCE TODAY WITH HIGHEST POPS TO S BECAUSE OF DEEPER MOISTURE AND TO THE E BECAUSE OF MORE DOMINANT GULF COAST SEABREEZE. ZFP TEMPS AND CLOUDS APPEAR TO BE ON TRACK. && .AVIATION... SOME LOW CIGS ACROSS SE GA SHOULD GRADUALLY LIFT AND THIN THRU THE REMAINDER OF THE MORNING HOURS. WILL LIKELY ADD AT LEAST VCTS TO KJAX AND KCRG AND TEMPO TSTM TO KGNV. && .MARINE...WILL ADJUST SEAS IN THE NEAR SHORE WATERS. MAY ALSO SCALE BACK 1ST PERIOD POPS TO ISOLD. && .PRELIMINARY POINT TEMPS/POPS... AMG 94 70 96 71 / 20 20 20 10 SSI 90 75 89 76 / 20 20 10 10 JAX 91 71 93 72 / 30 20 20 10 SGJ 89 72 88 73 / 40 20 20 10 GNV 90 70 93 70 / 40 20 40 20 OCF 89 70 92 70 / 40 20 40 20 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...NONE. && $$ CARROLL/KERNS fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 956 AM EDT THU JUL 24 2008 .UPDATE...AFTER PERFORMING CAREFUL ANALYSIS, IT APPEARS THERE ARE SEVERAL BOUNDARIES AROUND THIS MORNING FOR CONVECTION TO INITIATE. IN OTHER WORDS, IT COULD EASILY FORM JUST ABOUT ANYWHERE ACROSS S FLA. IN THE UPPER LEVELS, THE LEFT OVER 50H TROUGH AND ABOVE REMAINS JUST OFF THE SE CST OF THE PENINSULA WHICH EXPLAINS THE CONVECTIVE PATTERN CURRENTLY OVR THE OPEN ATLANTIC WELL OFFSHORE. A WEAK COLD FRONT EXISTS ACROSS SOUTHERN GEORGIA WHICH IS ASSOCIATED WITH THE MAIN MID/UPPER TROUGH MOVING OFF THE MID ATLANTIC SEABOARD WITH A PRE-FRONTAL TROUGH MOVING INTO N FLA WHICH EXPLAINS THE CURRENT CONVECTION ALONG THE GULF COAST JUST NORTH OF TPA. COULD EVEN BE A WEAK VORT MAX ASSOCIATED WITH THIS FEATURE. WATER VAPOR IMAGERY CLEARLY SHOWS THE MAIN MID LEVEL TROUGH CONTINUING TO DIG SOUTHWARD BUT BOTH THE 06Z GFS AND NAM RUNS SHOW THE TROUGH BEGINNING TO LIFT NE THROUGH THE COURSE OF THE DAY. THE 12Z MFL SOUNDING SHOWS SOME DRYING THAT HAS OCCURRED DURING THE PAST 24 HOURS BUT IF THE TROUGH BOUNDARY NORTH OF OUR REGION MOVES FAR ENOUGH TO THE SOUTH, THEN WE COULD MOISTEN UP AGAIN BY AFTERNOON. IT APPEARS THE BEST COURSE OF ACTION WOULD BE JUST TO GO WITH PERSISTENCE CONSIDERING THE WEAK BOUNDARIES THAT REMAIN IN PLACE AND SO HAVE MENTIONED POSSIBILITY OF STRONG WIND GUSTS AND SMALL HAIL WITH THE STRONGEST CELLS THAT DEVELOPMENT MAINLY ACROSS ALL OF S FLA WITH THE EXCEPTION OF ALONG BOTH COASTS. 30/KOB && .PREV DISCUSSION... /ISSUED 745 AM EDT THU JUL 24 2008/ AVIATION... THE WINDS TODAY WILL BE FROM THE NORTHEAST THIS MORNING BEFORE SWINGING TO A SOUTHEAST DIRECTION THIS AFTERNOON ALONG THE EAST COAST TAF SITES. FOR APF TAF SITE...THE WINDS WILL BE NORTHEAST THIS MORNING BEFORE SWINGING TO A WESTERLY DIRECTION BY 17Z THIS AFTERNOON. THE SPEEDS WILL ALSO BE 10 KNOTS OR LESS TODAY AT ALL OF THE TAF SITES. FOR THE WX AT THE TAF SITES TODAY...PLAN ON KEEPING THE TAF SITES DRY UNTIL AROUND 17Z AND THEN PUT IN VCTS ALL OF THE TAF SITES FROM 17Z UNTIL 21Z FOR THE ACTIVITY ALONG BOTH SEA BREEZES. BETWEEN 21Z AND 01Z PLAN ON HAVING ONLY VCSH FOR THE EAST COAST TAF SITES...AS THE EAST COAST SEA BREEZE WILL BE PUSHING FURTHER INLAND...BUT WILL CONTINUE TO HOLD THE VCTS FOR APF TAF SITE DUE TO THE SLOWLY PUSH OF THE WEST COAST SEA BREEZE. THE CEILING AND VIS FOR THE TAF SITES TODAY WILL REMAIN IN THE VFR CONDITIONS DUE TO THE TIMING OF THE ACTIVITY. SO WHEN THE ACTIVITY GETS GOING WILL COVERAGE THE SITES WITH THE ADMINS. AVIATION...54/BNB PREV DISCUSSION... /ISSUED 518 AM EDT THU JUL 24 2008/ DISCUSSION... CONVECTION THAT DEVELOPED ALONG SOUTHEASTWARD MOVING OUTFLOW OVER THE MAINLAND LATE YESTERDAY EVENING CONTINUES TO DISSIPATE THIS MORNING...WITH SHOWERS/STORMS NOW BECOMING CONCENTRATED OVER THE ATLANTIC WATERS. LATEST WATER VAPOR ANIMATION ALONG WITH RUC ANALYSES INDICATE THAT THE FLORIDA PENINSULA REMAINS LOCATED BENEATH A WEAKNESS IN THE UPPER-LEVEL RIDGE...WITH AN AMPLIFYING MID-LEVEL TROUGH LOCATED OVER THE EASTERN GREAT LAKES REGION...AND A WEAKER INVERTED TROUGH CENTERED OVER THE FLORIDA STRAITS JUST OFF THE SOUTHEAST COAST OF THE PENINSULA. GUIDANCE FROM THE NGM/NAM/GFS IS IN GOOD AGREEMENT WITH SOLUTIONS FROM THE UKMET/ECMWF IN ADVERTISING THIS STAGNANT PATTERN TO PERSIST FOR MUCH OF THE SHORT TERM. SIMILAR TO YESTERDAY...LIGHT EASTERLY FLOW IN THE BOUNDARY LAYER WILL ALLOW THE ATLANTIC COAST SEA BREEZE TO SLOWLY MOVE INLAND LATER THIS MORNING...WITH THUNDERSTORMS EXPECTED TO DEVELOP ALONG THIS BOUNDARY BY LATE MORNING/EARLY AFTERNOON. GIVEN POTENTIAL FOR ADDITIONAL CONVECTIVE DEVELOPMENT ALONG NUMEROUS MESOSCALE BOUNDARIES...AND LIGHT NORTHERLY FLOW ALOFT...WILL SIDE WITH HIGHER FWC/MET POP NUMBERS BOTH TODAY AS WELL AS TONIGHT...TO ACCOUNT FOR LINGERING EVENING CONVECTION MAINLY ALONG THE EAST COAST. BY FRIDAY...THERE ARE SOME INDICATIONS THAT A STRONGER AND DEEPER EASTERLY FLOW REGIME MAY BECOME ESTABLISHED OVER THE AREA...AS CENTRAL PLAINS UPPER RIDGE STRENGTHENS AND SHIFTS SOUTHEASTWARD IN RESPONSE TO THE DEVELOPMENT OF A STRONGER UPPER LOW OVER ONTARIO/QUEBEC. DESPITE THIS...AN AXIS OF LOWER HEIGHTS ALOFT WILL REMAIN OVER THE FLORIDA PENINSULA...PROVIDING A FAVORABLE THERMAL ENVIRONMENT FOR AT LEAST SCATTERED AFTERNOON CONVECTION ALONG SEA BREEZE BOUNDARIES. WILL PLACE HIGHEST POPS ALONG THE GULF COAST TO REFLECT INCREASING -- ALTHOUGH STILL VERY WEAK -- EASTERLY FLOW. BOUNDARY LAYER EASTERLIES APPEAR TO STEADILY INCREASE FROM FRIDAY NIGHT INTO SATURDAY MORNING...WITH CORRESPONDINGLY HIGHER POPS WARRANTED FOR THE ATLANTIC WATERS AND SOUTHEAST COAST OF THE MAINLAND. EXPECT CONDITIONS SIMILAR TO FRIDAY ONCE AGAIN ON SATURDAY...WITH WEAK EASTERLY STEERING FLOW FOCUSING HIGHEST COVERAGE OF AFTERNOON SHOWERS/STORMS OVER WESTERN PORTION OF THE FORECAST AREA. MEDIUM RANGE GUIDANCE FROM THE GFS/ECMWF/CMC NOW SUGGESTS THAT THIS PERSISTENT WEAKNESS IN THE UPPER-LEVEL RIDGE MAY LINGER OVER THE PENINSULA THROUGH THE BEGINNING OF NEXT WEEK...AND WILL REFLECT THIS IN THE EXTENDED FORECAST WITH NEAR CLIMO VALUES FOR POPS...EXCEPT SLIGHTLY HIGHER THAN CLIMO ALONG THE GULF COAST. CONDITIONS MAY BEGIN TO CHANGE...HOWEVER...BY THE MIDDLE OF THE WEEK...AS UPPER LOW OVER SOUTHEASTERN CANADA IS EVENTUALLY FORCED EASTWARD...ALLOWING CENTRAL ATLANTIC BRANCH OF THE SUBTROPICAL UPPER RIDGE TO FINALLY BUILD OVER THE AREA. THIS...IN COMBINATION WITH SOUTHWEST FLOW...COULD LEAD TO WARMER THAN NORMAL TEMPERATURES LATE NEXT WEEK...ALONG WITH LOWER CHANCES FOR RAIN. MARINE... CONDITIONS WILL REMAIN FAVORABLE FOR THE FORMATION OF WATERSPOUTS THIS MORNING...ESPECIALLY OVER THE LOCAL ATLANTIC WATERS AND BISCAYNE BAY. OTHERWISE...THERE ARE NO SIGNIFICANT WEATHER-RELATED CONCERNS TO MARINERS THROUGHOUT THIS FORECAST PERIOD...WITH CONDITIONS OUTSIDE OF SHOWERS/THUNDERSTORMS EXPECTED TO INCLUDE PREVAILING EAST TO SOUTHEAST WINDS IN THE 5-10 KNOT RANGE. THIS WIND FLOW WILL MAINTAIN SEAS IN THE 1-3 FOOT RANGE ACROSS ALL OF THE LOCAL COASTAL WATERS. FIRE WEATHER... THERE ARE NO FIRE WEATHER CONCERNS THROUGHOUT THIS FORECAST PERIOD...WITH MINIMUM AFTERNOON RH VALUES EXPECTED TO RANGE FROM 45-55 PERCENT ACROSS THE NORTHWEST ZONES...TO 55-60 PERCENT ELSEWHERE. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 89 74 89 76 / 50 40 40 20 FORT LAUDERDALE 91 76 90 78 / 50 40 40 30 MIAMI 91 76 90 77 / 50 40 40 30 NAPLES 90 73 90 75 / 40 30 50 30 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. GM...NONE. && $$ fl AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MIAMI FL 745 AM EDT THU JUL 24 2008 .AVIATION... THE WINDS TODAY WILL BE FROM THE NORTHEAST THIS MORNING BEFORE SWINGING TO A SOUTHEAST DIRECTION THIS AFTERNOON ALONG THE EAST COAST TAF SITES. FOR APF TAF SITE...THE WINDS WILL BE NORTHEAST THIS MORNING BEFORE SWINGING TO A WESTERLY DIRECTION BY 17Z THIS AFTERNOON. THE SPEEDS WILL ALSO BE 10 KNOTS OR LESS TODAY AT ALL OF THE TAF SITES. FOR THE WX AT THE TAF SITES TODAY...PLAN ON KEEPING THE TAF SITES DRY UNTIL AROUND 17Z AND THEN PUT IN VCTS ALL OF THE TAF SITES FROM 17Z UNTIL 21Z FOR THE ACTIVITY ALONG BOTH SEA BREEZES. BETWEEN 21Z AND 01Z PLAN ON HAVING ONLY VCSH FOR THE EAST COAST TAF SITES...AS THE EAST COAST SEA BREEZE WILL BE PUSHING FURTHER INLAND...BUT WILL CONTINUE TO HOLD THE VCTS FOR APF TAF SITE DUE TO THE SLOWLY PUSH OF THE WEST COAST SEA BREEZE. THE CEILING AND VIS FOR THE TAF SITES TODAY WILL REMAIN IN THE VFR CONDITIONS DUE TO THE TIMING OF THE ACTIVITY. SO WHEN THE ACTIVITY GETS GOING WILL COVERAGE THE SITES WITH THE ADMINS. && .AVIATION...54/BNB .PREV DISCUSSION... /ISSUED 518 AM EDT THU JUL 24 2008/ DISCUSSION... CONVECTION THAT DEVELOPED ALONG SOUTHEASTWARD MOVING OUTFLOW OVER THE MAINLAND LATE YESTERDAY EVENING CONTINUES TO DISSIPATE THIS MORNING...WITH SHOWERS/STORMS NOW BECOMING CONCENTRATED OVER THE ATLANTIC WATERS. LATEST WATER VAPOR ANIMATION ALONG WITH RUC ANALYSES INDICATE THAT THE FLORIDA PENINSULA REMAINS LOCATED BENEATH A WEAKNESS IN THE UPPER-LEVEL RIDGE...WITH AN AMPLIFYING MID-LEVEL TROUGH LOCATED OVER THE EASTERN GREAT LAKES REGION...AND A WEAKER INVERTED TROUGH CENTERED OVER THE FLORIDA STRAITS JUST OFF THE SOUTHEAST COAST OF THE PENINSULA. GUIDANCE FROM THE NGM/NAM/GFS IS IN GOOD AGREEMENT WITH SOLUTIONS FROM THE UKMET/ECMWF IN ADVERTISING THIS STAGNANT PATTERN TO PERSIST FOR MUCH OF THE SHORT TERM. SIMILAR TO YESTERDAY...LIGHT EASTERLY FLOW IN THE BOUNDARY LAYER WILL ALLOW THE ATLANTIC COAST SEA BREEZE TO SLOWLY MOVE INLAND LATER THIS MORNING...WITH THUNDERSTORMS EXPECTED TO DEVELOP ALONG THIS BOUNDARY BY LATE MORNING/EARLY AFTERNOON. GIVEN POTENTIAL FOR ADDITIONAL CONVECTIVE DEVELOPMENT ALONG NUMEROUS MESOSCALE BOUNDARIES...AND LIGHT NORTHERLY FLOW ALOFT...WILL SIDE WITH HIGHER FWC/MET POP NUMBERS BOTH TODAY AS WELL AS TONIGHT...TO ACCOUNT FOR LINGERING EVENING CONVECTION MAINLY ALONG THE EAST COAST. BY FRIDAY...THERE ARE SOME INDICATIONS THAT A STRONGER AND DEEPER EASTERLY FLOW REGIME MAY BECOME ESTABLISHED OVER THE AREA...AS CENTRAL PLAINS UPPER RIDGE STRENGTHENS AND SHIFTS SOUTHEASTWARD IN RESPONSE TO THE DEVELOPMENT OF A STRONGER UPPER LOW OVER ONTARIO/QUEBEC. DESPITE THIS...AN AXIS OF LOWER HEIGHTS ALOFT WILL REMAIN OVER THE FLORIDA PENINSULA...PROVIDING A FAVORABLE THERMAL ENVIRONMENT FOR AT LEAST SCATTERED AFTERNOON CONVECTION ALONG SEA BREEZE BOUNDARIES. WILL PLACE HIGHEST POPS ALONG THE GULF COAST TO REFLECT INCREASING -- ALTHOUGH STILL VERY WEAK -- EASTERLY FLOW. BOUNDARY LAYER EASTERLIES APPEAR TO STEADILY INCREASE FROM FRIDAY NIGHT INTO SATURDAY MORNING...WITH CORRESPONDINGLY HIGHER POPS WARRANTED FOR THE ATLANTIC WATERS AND SOUTHEAST COAST OF THE MAINLAND. EXPECT CONDITIONS SIMILAR TO FRIDAY ONCE AGAIN ON SATURDAY...WITH WEAK EASTERLY STEERING FLOW FOCUSING HIGHEST COVERAGE OF AFTERNOON SHOWERS/STORMS OVER WESTERN PORTION OF THE FORECAST AREA. MEDIUM RANGE GUIDANCE FROM THE GFS/ECMWF/CMC NOW SUGGESTS THAT THIS PERSISTENT WEAKNESS IN THE UPPER-LEVEL RIDGE MAY LINGER OVER THE PENINSULA THROUGH THE BEGINNING OF NEXT WEEK...AND WILL REFLECT THIS IN THE EXTENDED FORECAST WITH NEAR CLIMO VALUES FOR POPS...EXCEPT SLIGHTLY HIGHER THAN CLIMO ALONG THE GULF COAST. CONDITIONS MAY BEGIN TO CHANGE...HOWEVER...BY THE MIDDLE OF THE WEEK...AS UPPER LOW OVER SOUTHEASTERN CANADA IS EVENTUALLY FORCED EASTWARD...ALLOWING CENTRAL ATLANTIC BRANCH OF THE SUBTROPICAL UPPER RIDGE TO FINALLY BUILD OVER THE AREA. THIS...IN COMBINATION WITH SOUTHWEST FLOW...COULD LEAD TO WARMER THAN NORMAL TEMPERATURES LATE NEXT WEEK...ALONG WITH LOWER CHANCES FOR RAIN. MARINE... CONDITIONS WILL REMAIN FAVORABLE FOR THE FORMATION OF WATERSPOUTS THIS MORNING...ESPECIALLY OVER THE LOCAL ATLANTIC WATERS AND BISCAYNE BAY. OTHERWISE...THERE ARE NO SIGNIFICANT WEATHER-RELATED CONCERNS TO MARINERS THROUGHOUT THIS FORECAST PERIOD...WITH CONDITIONS OUTSIDE OF SHOWERS/THUNDERSTORMS EXPECTED TO INCLUDE PREVAILING EAST TO SOUTHEAST WINDS IN THE 5-10 KNOT RANGE. THIS WIND FLOW WILL MAINTAIN SEAS IN THE 1-3 FOOT RANGE ACROSS ALL OF THE LOCAL COASTAL WATERS. FIRE WEATHER... THERE ARE NO FIRE WEATHER CONCERNS THROUGHOUT THIS FORECAST PERIOD...WITH MINIMUM AFTERNOON RH VALUES EXPECTED TO RANGE FROM 45-55 PERCENT ACROSS THE NORTHWEST ZONES...TO 55-60 PERCENT ELSEWHERE. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 89 74 89 76 / 50 40 40 20 FORT LAUDERDALE 91 76 90 78 / 50 40 40 30 MIAMI 91 76 90 77 / 50 40 40 30 NAPLES 90 73 90 75 / 40 30 50 30 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. GM...NONE. && $$ LONG TERM...70/DD SHORT TERM/AVIATION...15/JR fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 1039 AM CDT THU JUL 24 2008 .DISCUSSION... 1039 AM CDT WITH A SLIGHTLY DRIER THAN ADVERTISED ATMOSPHERE IN PLACE WITH SFC DEW POINTS RUNNING IN THE LOW TO MID 50S...AND UPPER 40S IN THE CHICAGOLAND AREA...TO GO ALONG WITH THE SUN ONLY BEING MINIMALLY FILTERED BY THE UPPER LEVEL CLOUD DECK...HAVE BUMPED UP HIGH TEMPERATURES A TAD FOR THIS AFTERNOON MAINLY INTO THE LOWER 80S. ALSO REMOVED THE SLIGHT CHANCE POPS FOR OUR FAR SOUTHWEST THIS AFTERNOON WITH THE FAIRLY DRY AND CAPPED ATMOSPHERE IN PLACE. INITIAL THOUGHTS WERE ALSO TO GO A BIT MORE DRY TONIGHT...BUT WILL TAKE A DEEPER LOOK INTO THAT WITH THIS AFTERNOONS FORECAST PACKAGE. HALBACH && .PREV DISCUSSION... 335 AM CDT PRECIP CHANCES FROM LATER TODAY THROUGH SATURDAY ARE THE MAIN FORECAST ISSUES THIS MORNING. AN UNSEASONABLY LARGE AMPLITUDE UPPER PATTERN CONTINUES ACROSS EASTERN HALF OF CONUS THIS MORNING WITH EASTERN LONGWAVE TROUGH AND BROAD CENTRAL CONUS UPPER RIDGE BEING MAINTAINED. REGIONAL RADAR MOSAICS THIS MORNING INDICATING INCREASING COVERAGE TO SHOWERS AND THUNDERSTORMS ACROSS MUCH OF WESTERN AND SOUTHERN IOWA AT NOSE OF SOUTHWEST LOW LEVEL JET AND FAIRLY IMPRESSIVE LOW LEVEL MOISTURE CONVERGENCE. WITH THIS LARGE AMPLITUDE PATTERN...LOW/MID LEVEL MOISTURE GRADIENT REMAINS JUST OFF TO THE WEST THIS MORNING AS EVIDENT IN 00Z RAOB SAMPLING FROM LAST EVENING WITH KMPX SOUNDING INDICATING PWATS OF AROUND 0.75 INCHES AND KOAX WITH 1.50 INCHES. CURRENT POSITION OF LOW LEVEL RIDGE AXIS APPEARS TO BE A BIT FURTHER WEST THAN MODELS HAVE BEEN ADVERTISING FOR THIS TIME PERIOD THE PAST FEW DAYS...AND GIVEN AMPLITUDE OF LOW LEVEL RIDGE AXIS WOULD EXPECT THAT THIS MOISTURE GRADIENT OFF TO THE WEST WILL NOT REALLY MOVE IN WITH FULL FORCE INTO NORTHERN ILLINOIS UNTIL THIS EVENING. WITH NOT MUCH ADVECTIVE CHANGE IN LOW LEVEL MOISTURE PROFILE TODAY...EXPECTING SFC DEW PTS TO AGAIN BE IN THE MID 50S THIS AFTERNOON AND WITH FAIRLY STRONG MID LEVEL SUBSIDENCE INVERSION SHOWING IN LAST EVENINGS ILX/DVN RAOBS...PRECIPITATION CHANCES LOOK TO BE MINIMAL EVEN ACROSS FAR WESTERN PORTIONS OF THE FORECAST AREA THROUGH THIS AFTERNOON. HAVE TRIMMED BACK POPS TO SLIGHT CHANCE POPS FOR -TSRA ACROSS THE FAR SOUTHWEST THIS AFTERNOON. PROFILER NETWORK DOES SUGGEST PRESENCE OF UPSTREAM MID/UPPER LEVEL SHORT WAVE TROUGH ACROSS EASTERN COLORADO WHICH WILL BE A FEATURE TO WATCH FOR TONIGHT. LOW LEVEL WINDS WILL BACK TO THE WEST IN ADVANCE OF THIS SHORT WAVE TONIGHT AS LOW LEVEL RIDGE AXIS CONTINUES TO TRACK OFF TO THE EAST ALLOWING FOR MORE IMPRESSIVE LOW LEVEL MOISTURE ADVECTION. STILL EXPECTING CONVECTION TO INCREASE ACROSS SOUTHERN IOWA/NORTHERN MISSOURI THIS EVENING IN RESPONSE TO APPROACHING SHORT WAVE AND LOW LEVEL THETA-E ADVECTION FORCING...BUT CORFIDI VECTORS/THICKNESS PATTERN HINTING AT PROPAGATION PERHAPS JUST SOUTH OF THE FORECAST AREA. GIVEN THIS HAVE BACKED OFF A SHADE ON POPS BUT KEPT HIGHEST CHANCE POPS ACROSS THE FAR SOUTH TONIGHT. MAY EVEN END UP BEING MORE RAIN THAN THUNDER GIVEN RATHER LIMITED ELEVATED INSTABILITY/MARGINAL MID LEVEL LAPSE RATES. ALTHOUGH WIDESPREAD SEVERE WEATHER STILL DOES NOT APPEAR TO BE ON THE HORIZON...PERHAPS BEST CHANCE OF ANY ISOLD SEVERE WOULD BE ON FRIDAY AS LARGER SCALE UPPER TROUGH CURRENTLY ACROSS PACIFIC NORTHWEST MOVES INTO THE GREAT LAKES REGION. FORCING WILL BE RATHER WEAK HOWEVER...WITH SFC TROUGH/COOL FRONT NOT APPROACHING NRN IL UNTIL AFTER PEAK HEATING. NONETHELESS...FORECAST SOUNDINGS STILL INDICATE AROUND 1500 J/KG OF MIXED LAYER CAPE AND SOME ENHANCEMENT TO SHEAR PROFILES ACROSS THE FAR NORTH DURING THE AFTERNOON AS AN UPPER JET STREAK MOVES THROUGH THE BASE OF THE APPROACHING UPPER TROUGH. OTHER FOCUS AREA POSSIBLE ACROSS THE FAR SOUTH WITH SLOW MOVING OR STATIONARY BOUNDARY LIKELY DRAPED ACROSS CENTRAL ILLINOIS DURING THIS TIME FRAME. OVERALL SEVERE THREAT LOOKS ON THE LOW SIDE FOR FRIDAY. THE SFC COLD FRONT IS EXPECTED TO STALL OUT SOMEWHERE ACROSS FAR SOUTHERN PORTIONS OF THE CWA ON SATURDAY OR JUST TO THE SOUTH. DID INCLUDE AN ISOLD TSRA MENTION ACROSS SOUTHERN HALF OF THE AREA SATURDAY GIVEN EXPECTED PROXIMITY OF THIS FRONT AND SOME MODERATE AFTERNOON INSTABILITY. ANOTHER SFC HIGH WILL BUILD INTO THE GREAT LAKES LATE SUNDAY INTO MONDAY AND EXPECTING ADDITIONAL PRECIP CHANCES TO BE CONFINED WELL SOUTH OF THE FORECAST AREA WITH MAIN SFC BOUNDARY SINKING TO THE SOUTH. HAVE NOT MADE ANY CHANGES TO EXTENDED FORECAST AT THIS TIME WITH ECMWF/GFS COMPLETELY OUT OF PHASE BY MIDDLE OF NEXT WEEK ACROSS WESTERN CONUS. IN TERMS OF TEMPS...HIGHS TODAY IN THE LOW 80S ARE EXPECTED MOST LOCATIONS ALTHOUGH UPPER 70S STILL LOOK ON TRACK FOR NORTHERN COOK/LAKE COUNTIES IN NORTHEAST ILLINOIS WHERE LAKE BREEZE HAS POTENTIAL OF MAKING SOME INLAND PROGRESS TODAY. TEMPS WARM A BIT FOR THE END OF THE WEEK IN ADVANCE OF NORTHERN TIER UPPER TROUGH...AND THEN GENERALLY LOWER TO MID 80S REMAINDER OF THE PERIOD WITH SOME MINOR LAKESIDE COOLING POSSIBLE ON SAT-MON. MARSILI && .AVIATION... 639 AM CDT FOR 12Z TAFS...NO SIGNIFICANT CHANGES TO THINKING FROM 06Z FORECASTS. WIND DIRECTION WITH WEAK GRADIENT AND LAKE BREEZE REMAIN MAIN FOCUS FOR CHICAGO TERMINALS TODAY...WITH PRECIP/CONVECTION POTENTIAL A SECONDARY FACTOR TOWARD 12Z FRIDAY. SURFACE HIGH REMAINS ACROSS NORTHEAST IL EARLY THIS MORNING WITH WEAK GRADIENT SUPPORTING CALM OR LIGHT/VARIABLE WINDS NEXT FEW HOURS. THIS RIDGE MOVES SLOWLY TO THE SOUTH TODAY...RESULTING IN SYNOPTIC LIGHT SOUTH GRADIENT DEVELOPING. WITH SUCH WEAK GRADIENT ACROSS AREA...EXPECT LAKE BREEZE DEVELOPMENT BY LATE MORNING/MIDDAY WITH 06Z WRF/RUC GUIDANCE CONTINUING DEPICT LAKE BREEZE BOUNDARY MOVING THROUGH BOTH KORD/KMDW WITH WINDS SHIFTING SOUTHEAST BY/BEFORE NOON. WIND LIKELY TO GRADUALLY VEER MORE SSE WITH TIME LATER THIS AFTERNOON. AS FOR PRECIP TONIGHT...LOW LEVEL BAROCLINIC ZONE ACROSS MISSOURI VALLEY HAS BEEN FOCUS FOR OVERNIGHT CONVECTION ON NOSE OF LOW LEVEL JET ACROSS IA/MO. THIS EXPECTED TO SHIFT EASTWARD TOWARD MISSISSIPPI VALLEY TONIGHT...WITH ELEVATED CONVECTION AGAIN SPREADING INTO EASTERN IOWA AND ILLINOIS BY 12Z FRIDAY. AT THIS TIME...MODEL GUIDANCE SUGGESTS CONVECTION MOST LIKELY ACROSS AREAS WEST/SOUTHWEST OF CHI METRO BY EARLY FRIDAY. NAM FORECAST SOUNDINGS INDICATE ELEVATED CAPES OF AROUND 500 J/KG AT KRFD TOWARD MORNING...WHILE LIMITED TO 150 J/KG AT KORD BY 12Z. 850-300 MB THICKNESS PATTERN AND CORFIDI VECTORS INDICATE SOUTHEAST PROPAGATION OF CONVECTIVE ELEMENTS THROUGH TONIGHT. BASED ON THIS HAVE ELECTED TO INTRODUCE A PROB30 MENTION FOR KRFD FOR LAST FEW HOURS OF TAF...THOUGH HAVE KEPT CHI AREA TERMINALS DRY WITH CONFIDENCE OF CONVECTION MOVING THAT FAR EAST TOO LOW FOR NOW. RATZER && .MARINE... 345 AM CDT HIGH PRESSURE OVER THE FAR WESTERN GREAT LAKES WILL CONTINUE TO MOVE SOUTH TODAY...INTO THE OHIO VALLEY TONIGHT. THIS WILL ALLOW LIGHT NORTHERLY WINDS TO BACK TO THE SOUTH BY THIS AFTERNOON... THOUGH THE RELATIVELY WEAK PRESSURE GRADIENT ON THE SOUTH PORTION OF THE LAKE WILL LIKELY RESULT IN LAKE BREEZES WHICH MAY RESULT IN VARIABLE WIND DIRECTIONS FOR A TIME THIS AFTERNOON. THE HIGH WILL CONTINUE TO DRIFT SOUTHEAST ACROSS THE OHIO VALLEY ON FRIDAY... WHILE LOW PRESSURE TRAVERSES NORTHERN MANITOBA AND ONTARIO WITH A SOUTH/SOUTHWESTERLY GRADIENT WIND DEVELOPING ACROSS LAKE MICHIGAN. A WEAK COLD FRONT TRAILING FROM THIS LOW WILL PUSH SOUTHEAST ACROSS THE WESTERN LAKES FRIDAY NIGHT INTO SATURDAY...AS THE LOW CONTINUES TOWARD JAMES BAY. THIS WILL SHIFT WINDS BACK TO THE NORTHWEST...THOUGH A SECONDARY SURFACE TROUGH IS EXPECTED TO MOVE ACROSS THE LAKE EARLY SUNDAY WITH WINDS BRIEFLY BACKING WEST OR SOUTHWEST AHEAD OF IT. WEAK HIGH PRESSURE WILL THEN SPREAD ACROSS THE UPPER MIDWEST AND WESTERN LAKES BY THE END OF THE WEEKEND. RATZER && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 630 AM CDT THU JUL 24 2008 .UPDATE... UPDATED FOR THE 12Z TAFS. && .DISCUSSION... SEE PREVIOUS DISCUSSION. && .AVIATION... VFR CONDITIONS EXPECTED THROUGH 12Z FRIDAY. CONVECTION THIS MORNING WILL REMAIN WELL NORTH AND EAST OF TOP/FOE/MHK...WITH ONLY A FEW MID/UPPER LEVEL DEBRIS CLOUDS TO CONTEND WITH LOCALLY. CU FIELD TO DEVELOP AGAIN TODAY ACROSS THE EASTERN HALF OF THE AREA...ALONG MOST ROBUST MOISTURE AXIS. TONIGHT...UPPER RIDGE BREAKS DOWN A BIT MORE...AND A SHORTWAVE SLIDES ON THROUGH NORTHEAST KANSAS...COINCIDENT WITH A WEAK BOUNDARY OVER THE NORTHEAST PART OF THE STATE DROOPING SOUTHWARD. BEST CHANCE FOR PRECIP LOOKS TO BE CLOSER TO TOP/FOE AFTER 02Z...SO BEGAN TO TREND FORECAST TOWARD TS AFTER 02Z...BY INSERTING A CB GROUP AT EACH SITE. MHK MAY BE A BIT TOO FAR WEST FOR THE TS...AND VCTS OR NO THUNDER AT ALL MAY RESULT LATER ON. FUTURE FORECASTS SHOULD HAVE A BETTER HANDLE ON WHERE/WHEN TO EXPECT TS. KONOP && .PREV DISCUSSION... /ISSUED 311 AM CDT THU JUL 24 2008/ DISCUSSION... 08Z WATER VAPOR SHOWS A CLOSED LOW OVER THE GREAT LAKES...A SHORTWAVE TROUGH PROPAGATING EAST OVER THE NORTHERN ROCKIES...AND A BROAD RIDGE FROM THE SOUTHERN PLAINS BACK WEST OVER SOUTHERN CA. HEIGHT FALLS ACROSS THE NORTHERN ROCKIES AND PLAINS HAVE FLATTENED THE UPPER RIDGE OVER THE CENTRAL PLAINS. AT THE SFC A TROUGH WAS FOUND ACROSS WESTERN KS STRETCHING NORTH. A MOIST AND WARM AIRMASS WAS FOUND EAST OF THIS TROUGH...AND ELEVATED CONVECTION HAS ONCE AGAIN DEVELOPED ALONG THE PERIPHERY OF THE UPPER RIDGE. FOR THIS MORNING...THE RUC AND NAM 310K ISENTROPIC SFC KEEPS THE BETTER MOISTURE AXIS JUST TO THE NORTHEAST OF THE FORECAST AREA. THIS IS SUPPORTED BY LATEST RADAR TRENDS WITH THUNDERSTORMS MOVING SOUTHEAST INTO NORTHERN MO. A FEW ELEVATED STORMS DEVELOPED OVER SOUTH CENTRAL NEB BUT HAVE SINCE FALLEN APART. SO EXPECT THE MAJORITY OF THE AREA TO REMAIN DRY THIS MORNING. HAVE KEPT SLIGHT CHANCE POPS ACROSS THE NORTHEAST THIS MORNING AND THEN ACROSS THE NORTH FOR THE AFTERNOON AS MODELS STILL SHOW A WEAK WIND SHIFT SLIDING INTO NORTHERN KS. MODELS SHOW THE BOUNDARY LAYER MIXING TO BETWEEN 850 AND 800MB. THEREFORE WOULD EXPECT HIGHS TO AGAIN REACH THE LOWER TO MID 90S FOR MOST AREAS. COOLEST SPOT SHOULD BE NORTHEAST WHERE THERE IS LIKELY TO BE A LITTLE MORE CLOUD COVER...WITH THE WARMEST SPOT ACROSS THE SOUTHWEST. FOR TONIGHT THROUGH SATURDAY...PRECIP CHANCES LOOK TO BE A LITTLE HIGHER. MODELS SHOW THE UPPER LEVEL RIDGE AXIS SHIFTING SOUTH ACROSS THE SOUTHERN PLAINS...WITH WEAK NORTHWEST FLOW SETTING UP OVER THE FORECAST AREA. THINK BECAUSE OF THIS...CONVECTION THAT HAS PASSED JUST NORTHEAST OF THE AREA THE PAST COUPLE NIGHTS WILL BE MORE LIKELY TO MOVE ACROSS NORTHEAST KS. NAM AND GFS SHOW WEAK SHORTWAVES CLIPPING NORTHEAST KS TONIGHT AND AGAIN FRIDAY NIGHT WITH ABUNDANT MOISTURE STILL IN PLACE. THEREFORE HAVE GONE WITH CHANCE POPS ACROSS NORTHEAST KS TONIGHT AND SPREAD CHANCE POPS A LITTLE FURTHER SOUTH FOR FRIDAY NIGHT INTO SATURDAY MORNING. USED PERSISTENCE FOR THE TEMP FORECAST AS AIRMASS APPEARS TO CHANGE LITTLE FROM DAY TO DAY. DO NOT EXPECT PRECIP TO OCCUR LONG ENOUGH DURING ANY GIVEN DAY TO APPRECIABLY HAMPER DAY TIME HEATING. WEAK NORTHWEST FLOW CONTINUES THROUGH SUNDAY WITH ANOTHER POTENTIAL VORT MAX CLIPPING NORTHEAST KS. SO MAINTAINED THE SLIGHT CHANCE POPS FOR SATURDAY NIGHT AND SUNDAY. FORECAST WAS LEFT PRETTY MUCH IN TACT BEYOND SUNDAY. WOLTERS && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 937 AM EDT THU JUL 24 2008 .SYNOPSIS... HIGH PRESSURE COMING FROM MICHIGAN WILL BRING DRY AND PLEASANT WEATHER INTO FRIDAY. A COLD FRONT COMING FROM THE DAKOTAS WILL WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS THIS WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... JUDGING FROM RECENT SATELLITE AND RADAR DATA THE LAST OF THE SHOWERS WILL HAVE EXITED THE DUBOIS PA AREA BY 10 AM. WITH THE RECENT RUC MODEL RUN SHOWING THE UPPER TROUGH THAT CONTRIBUTED TO THE DEVELOPMENT OF THESE SHOWERS CONTINUING TO MOVE EAST. SO HAVE FORECASTED DRY CONDITIONS THE REST OF TODAY. EXPECT DAYTIME CUMULUS CLOUDS TO BARELY REACH BROKEN COVERAGE...SO SHOULD BE MAINLY SUNNY THE REST OF THE DAY WITH FORECASTED TEMPERATURES CLOSE TO BLEND OF NAM AND GFS MOS. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... HIGH PRESSURE CONTINUES TO DOMINATE FRIDAY AS THE RIDGE MOVES TO THE EAST COAST. DRY WEATHER AND SLOWLY WARMING TEMPERATURES CAN BE EXPECTED. AS WARMER AND MORE HUMID AIR MOVES BACK INTO THE DISTRICT FOR FRIDAY NIGHT A RISK OF SHOWERS AND THUNDERSTORMS IS POSSIBLE. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... A COLD FRONT WILL PUSH ACROSS THE DISTRICT SATURDAY BRINGING A THREAT OF SHOWERS AND THUNDERSTORMS FOR SATURDAY AND SATURDAY NIGHT. AS THE FRONT MOVES EAST OF THE DISTRICT SUNDAY THE UPPER TROF BEHIND THE FRONT WILL KEEP A RISK OF SHOWERS FOR SUNDAY. HIGH PRESSURE BUILDING INTO THE DISTRICT FOR THE FIRST OF THE WEEK WILL BRING A PERIOD OF DRY WEATHER AND SEASONABLE TEMPERATURES THROUGH WEDNESDAY. && .AVIATION /13Z THURSDAY THROUGH MONDAY/... JUDGING FROM RECENT SURFACE AND SATELLITE DATA IN CONJUNCTION WITH RECENT NAM MODEL PROFILES...EXPECT ANY RESIDUAL MVFR STRATOCUMULUS CEILINGS TO GIVE WAY BY 15Z TO SCATTERED TO BROKEN CUMULUS WITH BASES IN THE VFR RANGE. WITH UPPER TROUGH HAVING EXITED EAST OF THE UPPER OHIO VALLEY...DO NOT EXPECT ENOUGH INSTABILITY FOR THE CUMULUS TO SUFFICIENTLY VERTICALLY DEVELOP TO CAUSE ANY MORE SHOWERS. WINDS WILL BE FROM THE WEST TO NORTHWEST NEAR 10 KTS BY AFTERNOON AND THEN DECREASE TO UNDER 5 KTS TONIGHT. AT THIS TIME NOT FORECASTING FOG DEVELOPMENT AT ANY TAF SITES FOR EARLY FRIDAY ALTHOUGH WOULD NOT RULE OUT ISOLATED FOG PATCHES IN RIVER VALLEYS THEN. SO VFR WILL CONTINUE TO BE DOMINANT INTO FRIDAY NIGHT. RECENT BLEND OF SREF AND GEFS MODEL RUNS SHOW A DAKOTAS COLD FRONT IMPACTING THE UPPER OHIO VALLEY WITH SCATTERED SHOWERS AND THUNDERSTORMS AND HENCE POTENTIAL MVFR CONDITIONS SATURDAY AND SUNDAY. HIGH PRESSURE AND PREVALENT VFR SHOULD RETURN FOR MONDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$ md AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1056 AM CDT THU JUL 24 2008 .DISCUSSION... LATEST VISIBLE IMAGERY SHOWS FAIRLY EXTENSIVE CLOUD COVER ACROSS THE CWFA AT THIS TIME...WITH ACTUALLY SOME FILLING IN OF LOW TO MID CLOUDS OVER THE PAST FEW HOURS OVER MINNESOTA. THINGS ARE CLEARER TO THE EAST WHERE 925-700MB WARM ADVECTION AND BETTER RH VALUES HAVE NOT YET ARRIVES...ALTHOUGH THERE SHOULD BE SOME INCREASE IN MID CLOUDS IN THAT AREA AS THE DAY PROGRESSES. RADAR IMAGERY SHOWS SOME SHRA EXITING INTO FAR NORTHEAST MINNESOTA AT THE CURRENT TIME. THESE WERE FORCED BY THE WARM ADVECTION AND A WEATHER SHORTWAVE THAT IS NOW PUSHING EAST OF THE AREA...AND WERE INITIALLY MORE ROBUST WHILE THEY TAPPED INTO THE ELEVATED INSTABILITY THAT WAS PRESENT OVER WESTERN MINNESOTA. THE MAIN FORECAST ISSUE FOR TODAY AND THIS EVENING IS THE CHANCES FOR CONVECTION ACROSS THE AREA. LATEST OBSERVED DATA AND 12Z NAM AND LATEST RUC SUGGEST LESSER CHANCES FOR PCPN OVER THE AREA...AND HAVE TRIMMED BACK POPS...WHICH WERE ALREADY FAIRLY LOW...TO ACCOUNT FOR THIS. INSTABILITY WILL INCREASE THROUGH THE DAY DUE TO DIURNAL HEATING...ALTHOUGH THAT IS BEING MITIGATED BY THE LOW-MID CLOUDS PRESENT AHEAD OF THE COLD FRONT WHICH STRETCHES FROM THE FAR NORTHWEST CORNER OF THE STATE THROUGH CENTRAL SOUTH DAKOTA. IT APPEARS CLEARING SHOULD BECOME A BIT MORE PREVALENT JUST AHEAD OF THE FRONT DURING THE AFTERNOON...WITH MLCAPES GETTING AOA 1500 J/KG...ALONG WITH 30-35KT OR SO OF DEEP LAYER SHEAR. BY LATE AFTERNOON...THE MLCIN IS EXPECTED TO DIMINISH SUFFICIENTLY FOR SOME STORMS TO INITIATE NEAR THE FRONTAL BOUNDARY...ALTHOUGH THE 12Z NAM AND LOCAL LAPSWRF MODEL RUNS ARE NOT VERY AMBITIOUS IN DEVELOPING MUCH. THE RUC IS A BIT MORE BULLISH...BUT IN ALL CASES IT APPEARS THE BEST CHANCES OF SEEING ANYTHING WILL BE OVER THE WESTERN AND NORTHWESTERN PORTION OF THE FORECAST AREA...WHERE THE BEST COMBINATION OF FORCING AND INSTABILITY WILL BE PRESENT. IN ADDITION...A WEAK SHORTWAVE CAN BE SEEN IN THE WATER VAPOR IMAGERY MOVING THROUGH WESTERN SOUTH DAKOTA...AND IT IS HELPING TO GET SOME WEAK CONVECTION GOING THERE AT THE CURRENT TIME. THIS FEATURE LOOKS LIKE IT WILL WORK INTO THE WESTERN PART OF THE CWFA BY LATE AFTERNOON...WHICH SHOULD FURTHER HELP TO GET A FEW STORMS GOING. ANY STORMS WHICH MANAGE TO DEVELOP COULD PRODUCE MARGINALLY SEVERE HAIL GIVEN THE DECENT MLCAPE VALUES AND SUFFICIENT DEEP LAYER SHEAR FOR SOME MULTI-CELL ORGANIZATION. WILL KEEP SOME LOW POPS INTO THE CENTRAL PART OF THE AREA BY LATE AFTERNOON AND EARLY EVENING...BUT CHANCES LOOK FAIRLY LIMITED EAST OF A LINE FROM REDWOOD FALLS TO SAINT CLOUD. THE SOUTHERN PART OF THE AREA WILL HAVE A TOUGH TIME AS WELL SINCE THE SOUTH PART OF THE FRONT WILL BE SLOWER TO MOVE EAST...AND IT LOOKS LIKE LOW LEVEL RIDGING WILL PREDOMINATE IN THAT AREA THROUGH THE AFTERNOON. && .AVIATION.../12Z TAF ISSUANCE/ ISOLD SHRA/TSRA ARE PSBL OVER MOST OF THE TAF SITES MAINLY THIS MORNING. CLOUDS/CEILING HEIGHTS WILL BE GENERALLY AT OR ABOVE 4K FEET AGL EXCEPT LOWERING TO AROUND 2-3K FEET AGL IN TSRA IN THE VCNTY OF THE AFORMENTIONED FRONT IN THE DISCUSSION ABOVE. WEATHER CONDS IMPROVING AFTER FRONTAL PASSAGE...BASICALLY SCATTERED CLOUDS AT OR ABOVE 6K FEET AGL. && .PREV DISCUSSION... /ISSUED 630 AM CDT THU JUL 24 2008/ THE CHALLENGE WITH THE FORECAST IS CONVECTIVE CHANCES LATER TODAY AS WELL AS FRIDAY. GOES WV LOOP SHOWING A SERIES OF WAVES APPROACHING UPPER MISSISSIPPI VALLEY AROUND A CENTRAL ONE MOVING EAST INTO SRN MANITOBA. UPSTREAM MID AND UPPER LEVEL RIDGING CURRENTLY RESIDE OVER THE FORECAST AREA...THOUGH DEAMPLIFICATION IS EXPECTED TODAY. THIS IS NOT NECESSARILY DUE TO THE IMPINGEMENT OF THESE SHORTWAVES BUT THE SLIGHT RETROGRADING OF THE ERN GREAT LAKES LONG WAVE TROUGH. THIS WILL LEAD TO AN ALMOST SQUISHING/WEAKENING OF THESE SHORTWAVES AS THEY NEAR MN THIS AFTN AND EVE. SO THIS SHOULD BE A MAJOR CAVEAT TO SUSTAINED SEVERE WEATHER LATER TODAY. FOR THIS MORNING...CONTINUED 5K-10KFT WARM AIR ADVECTION /WAA/ WILL LEAD TO LIGHT SHOWERS WITH MAYBE A FEW LIGHTNING STRIKES. CONVECTIVE CHANCES SEEM NIL FOR ERN MN AND WRN WI THROUGH AT LEAST THROUGH MID AFTN IF NOT THROUGHOUT THE DAYLIGHT HOURS...AS CONVECTIVE INDICIES ARE WEAK AND ACTUALLY WEAKEN FURTHER AFTER INITIAL WAA PUSH THIS MORNING. THEY THEN BEGIN TO CREEP UP AGAIN IN THE LATE AFTN. SO THROUGH MID AFTN FOR MUCH OF THE CWA THINK THUNDER WILL BE FEW AND FAR BETWEEN WITH ANY SHOWERS. SFC COLD FRONT WILL BE ENTERING MN LATE THIS AFTN INTO EARLY THIS EVE. AHEAD OF THIS...PRIMARILY IN WRN AND CTRL MN...A FAIR AMOUNT OF SUN IS EXPECTED TODAY. THIS COMBINED WITH THE AFOREMENTIONED GRADUAL HEIGHT FALLS WILL HELP DESTABILIZATION. SFC TDS ARE EXPECTED TO BE IN THE 66 TO 70 DEGREE RANGE AHEAD OF THE FRONT. THIS CREATES SFC BASED CAPE BETWEEN 1500 AND 2500 J/KG IN A TONGUE INTO WRN AND CTRL MN BY LATE AFTN. MARGINAL UPPER LEVEL DIVERGENCE IS PRESENT AT THAT TIME WITH INCOMING 80-90 KT 250MB JET IN THE WRN PLAINS. ASSOCIATED THICKNESS DIFLUENCE ALSO SEEN ON MODEL SOLUTIONS. SO ISOLD TO SCT CONVECTION IS EXPECTED IN AT LEAST WRN MN LATE THIS AFTN INTO EARLY THIS EVE. THESE SHOULD BE PULSY-TYPE STORMS...POSSIBLY WITH SOME CLUSTERING IN A FAIRLY UNIDIRECTIONAL LOWER TROP PROFILE. MID-LEVEL LAPSE RATES ARE MARGINAL FOR STRONG UPDRAFTS. PREDICTED DCAPE VALUES ARE 600-1000 J/KG...THOUGH FURTHER EXAMINATION OF MODEL SOUNDINGS SHOWS DELTA THETA-E TO BE SLIGHT IN THE VERTICAL...SO WIND THREAT THOUGHT TO BE MARGINAL TOO. SOME THOUGHT TOO OF CONVECTION GETTING ACTIVE IN NEB/WRN IA ABSORBING SOME OF OUR BUOYANCY AND LOW LEVEL WINDS. THIS SHOULD COME TO FRUITION LATER IN THE EVE AS NOCTURNAL LLJ WILL BE FOCUSED IN IA WITH EXPECTED ONGOING CONVECTION. SO ALL IN ALL...POPS FAIRLY SMALL TODAY AND TONIGHT AND SEVERE WEATHER POTENTIAL AND POSSIBLE AREAL COVERAGE SEEM SMALL AS WELL. FRONT WILL GRADUALLY WORK SE OVERNIGHT INTO FRI MORNING BEFORE GETTING A KICK FRI AFTN FROM A DIVING H5 WAVE IN SASKATCHEWAN. INSTABILITY EXPECTED TO BUILD AHEAD OF THE FRONT IN SRN MN AND WRN WI WITH TDS IN THE UPPER 60S TO LOWER 70S. DYNAMICS SHOULD BE MORE IMPRESSIVE THAN TODAY WITH A DIGGING WAVE AND AN ASSOCIATED STRONGER JET. SO SVR POTENTIAL DOES EXIST IN SE MN AND MORESO IN WRN WI ON FRI AFTN AND VERY EARLY EVE. AFTER THAT POINT...FRONT SHOULD BE EAST OF THE FORECAST AREA. DESPITE THESE DAYS BEING ARE WARMEST CLIMATOLOGICALLY...WE ARE NOT EXPECTING ANY MARKED HEAT. IN FACT...TEMPERATURES SHOULD BE SLIGHTLY BELOW NORMAL MOST DAYS. FRIDAY MAY SEE MID TO UPPER 80S...AS H8 THERMAL RIDGE GRADUALLY WORKS SE ACROSS THE AREA WITH AFOREMENTIONED FRONT. DRY AND COOL AIR ADVECTION THEN WILL PREVAIL FRI NIGHT AND SAT. THE WEEKEND LOOKS DRY WITH MAINLY LOWER 80S. ELEVATED MOIST ADVECTION SHOULD REMAIN TO OUR SOUTH AND WEST DURING THAT TIME. NEXT WEEK MAY BE SLIGHTLY MORE ACTIVE AS THIS ADVECTION APPROACHES...BUT PRIMARY LOW LEVEL BAROCLINIC AND TD GRADIENT ALONG WITH ANY REMNANT MOISTURE FROM ONCE HURRICANE DOLLY LOOKS TO BE TO OUR SOUTH. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ TRH/JVM/MTF mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 300 AM CDT THU JUL 24 2008 .DISCUSSION... SCATTERED THUNDERSTORMS ONGOING THIS MORNING FROM NORTHEAST NEBRASKA INTO SOUTHWEST IOWA. LATEST RUC DATA INDICATES STRONG THETA-E ADVECTION ASSOCIATED WITH THE ELEVATED CONVECTION THIS MORNING WEAKENS AFTER 12Z THEN REDEVELOPS DURING THE AFTERNOON OVER WESTERN AND CENTRAL NEBRASKA. LITTLE CHANGE TO CURRENT FORECAST WITH SOME POPS THROUGH MUCH OF THE SHORT TERM PERIOD AS AREA REMAINS ON THE SOUTHERN EDGE OF FASTER FLOW ACROSS THE NORTHERN PLAINS. MAIN UNCERTAINTY REMAINS TIMING OF SHORT WAVES IN THE FLOW WITH PLENTY OF MOISTURE AVAILABLE IN BOTH THE MID AND LOWER LEVELS. WEAK SURFACE BOUNDARY ALSO INDICATED TO LINGER ACROSS THE REGION THROUGH THE WEEKEND AND HELP FOCUS ACTIVITY. CLOUDS AND PRECIP EXPECTED TO LIMIT HEATING SO AGAIN HAVE TRENDED TOWARD THE COOLER GUIDANCE VALUES. NO CHANGE TO THE EXTENDED PERIOD AT THIS TIME. 00Z MODELS AMPLIFY UPPER RIDGE OVER THE WESTERN CONUS NEXT WEEK WITH FLOW REMAINING ACTIVE ACROSS THE PLAINS REGION. && .AVIATION... FOR TAF SITES KOMA/KLNK/KOFK. MVFR CIGS WILL PERSIST THROUGH MID MORNING AS MOIST SOUTHEAST FLOW CONTINUES TO INVADE EASTERN NEBRASKA. SCATTERED THUNDERSTORMS MAY AFFECT KOMA AND KOFK THROUGH 15Z. VFR CIGS ARE EXPECTED THROUGH THE DAY WITH MORE THUNDERSTORMS POPPING UP IN THE LATE AFTERNOON...LIKELY AFTER 21Z...AND COULD OCCUR ACROSS ALL OF EASTERN NEBRASKA. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ FOBERT/DERGAN ne AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE ABERDEEN SD 751 AM CDT THU JUL 24 2008 .UPDATE... JUST A QUICK UPDATE TO ADJUST SKYCOVER MENTION TO MOSTLY CLOUDY THIS MORNING AS LOW STRATUS HAS JUST ABOUT SOCKED IN THE ENTIRE CWA THIS MORNING /AS OF 12Z/. ALSO RETWEAKED WX GRIDS THROUGH 15Z THIS MORNING TO BEEF UP THE FOG WORDING ACROSS THE WESTERN HALF OF ZONES WHERE SURFACE OBS AND MORNING COOP REPORTS TRICKLING IN ARE INDICATING SOME AREAL COVERAGE OF DENSE FOG. && .PREV DISCUSSION... .SHORT TERM...TODAY THROUGH 00Z SUNDAY MAIN FCST CHALLENGE FACING THE SHORT TERM IS PCPN CHANCES AGAIN TODAY THROUGH FRIDAY MORNING. LATEST MSAS ANLYS SHOWS SFC BOUNDARY DRAPED NW-SE ACROSS WRN PART OF THE CWA...WITH ONLY TELLING DIFFERENCE IS THE L-M50 DWPTS LOCATED ACROSS THE NW PART OF SD. AREAS OF LOW STRATUS/FOG IS SETTING UP UNDER TROF AXIS WHERE MIXING WINDS ARE MINIMAL. HAVE INSERTED SOME PATCHY FOG WORDING FOR THIS MORNING ACROSS ALL THE CWA TO ACCOUNT FOR THIS. ATTENTION THEN TURNS TOWARD THIS AFTERNOON. MODELS ALL AGREE ON 85H/925H BOUNDARY REMAINING PROGRESSIVE ACROSS THE NORTH...WHILE HANGING UP ACROSS SRN SD BY 00Z. 5H WAVE THAT IS CURRENTLY TRACKING ACROSS MT WILL INTERSECT THE SFC/LOW LEVEL BOUNDARIES DURING PEAK HEATING ACROSS THE EAST...AND THERE SHOULDN`T BE THE CONVECTIVE DEBRIS CLOUDS IN PLACE SIMILAR TO YESTERDAY...AND WITH DWPTS ALREADY IN THE MID 60S...AND DWPTS IN THE LOWER 70S IN PLACE ACROSS PARTS OF NERN NEB...THE MECHANISM SHOULD BE RESET FOR CONVECTIVE DEVELOPMENT LATER THIS AFTERNOON. HOWEVER...WILL HAVE TO SEE HOW MUCH OF A ROLE THE LOW CLOUDS/STRATUS PLAY UNDER TROF AXIS...AND WHETHER OR NOT THEY CAN BE MIXED OUT. LATEST RUC SHOWS THAT 7H THETA-E DOWNGLIDE REMAINS IN PLACE THROUGH 18Z FOR MUCH OF THE CWA...WITH WAA RETURNING TO THE WEST LATER IN THE AFTN PER THE 06Z NAM12 SOLN. BY 00Z FRIDAY...NAM12 SHOWS AREA OF BEST LI`S LOCATED ALONG AND JUST AHEAD OF NE-SW DRAPED SFC BOUNDARY...WITH LI`S TO -8...ALONG WITH MOST UNSTABLE CAPES FROM 1500 TO 3000 J/KG. HAVE TRIED TO ORIENT POPS ALONG SFC BOUNDARY FOR LATER THIS AFTERNOON THROUGH THE NIGHT. WITH RESPECT FOR THE OVERNIGHT HOURS...MODELS AGREE ON PRESSURE RISES ON THE 305-315K LAYERS...ALONG WITH SPEC HUMIDIES DECREASING ACROSS MY NW CWA. THETA-E ANLYS POINTS TO DOWNGLIDE AND DRYING NOTED IN THE RH FIELDS. HAVE REMOVED MENTION OF POPS ACROSS THE NW FOR THE OVERNIGHT HOURS ON ACCOUNT OF THIS. OVERALL...VERY DIFFICULT AND COMPLEX CONVECTIVE FCST SETTING UP FOR TODAY...AND WILL BE HIGHLY DEPENDANT UPON LOCATION OF SFC BOUNDARY AND TIMING OF 5H/7H WAVES. THERE IS SOME CONCERN FOR FRIDAY AS THE NAM SHOWS SFC BOUNDARY REMAINING STALLED ACROSS SRN SD...ALLOWING MORE CONVECTIVE DEVELOPMENT TO TAKE PLACE LATER IN THE AFN. THE GFS REMAINS MORE PROGRESSIVE WITH THIS FEATURE...PUSHING IT OUT OF STATE DURING THE DAY FRIDAY...WHICH ALLOWS COOLER/DRY CANADIAN HIGH PRESSURE TO SETTLE IN FOR THE BEGINNING OF THE WEEKEND. GIVEN THE NEARLY ZONAL FLOW SETTING UP ALOFT AND THAT FLOW REMAINS NEARLY CROSSWISE TO SFC FRONTAL POSITION...HAVE OPTED WITH THE GFS SOLN AND KEPT PCPN OUT OF FCST FOR FRIDAY. TEMP WISE...THINK THAT TODAY WILL BE WARMEST DAY OF THE SHORT TERM...WITH DECENT SUNSHINE PROVIDED THAT LOW CLOUDS/STRATUS BURN OFF BY 15Z. DIDN`T GO REALLY WILD WITH HEATING AS AMPLE LOW LEVEL MOISTURE WILL ABSORB SOME OF THE HEATING ENERGY...BUT SHOULD PROVE TO BE A MUGGY DAY...ESPECIALLY ACROSS THE EAST. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY 00Z EC/GFS OPERATIONAL SOLUTIONS STILL SHOWING REASONABLY SIMILAR UPPER LEVEL AND SURFACE SOLUTIONS. OVER THIS CWA...MUCH OF THE EXTENDED FORECAST IS A PERIOD OF WEAK UPPER LEVEL RIDGING WITH STEERING FLOW PREDOMINANTLY FROM THE WNW. IN THE LOW LEVELS...HIGH PRESSURE IS PARKED OVER THE UPPER MISSISSIPPI RIVER VALLEY WITH THE WESTERN HALF OF THE CWA IN SERLY RETURN FLOW WHILE THE EASTERN HALF IS EITHER LIGHT AND VARIABLE WINDS OR WINDS OUT OF THE NORTHEAST. BEST CHANCES FOR MEASURABLE PRECIP OVER THE CWA CONTINUES TO EXIST SATURDAY NIGHT AND AGAIN MONDAY/MONDAY NIGHT...SATURDAY NIGHT IN THE FORM OF AN MCC MEATBALL ORIGINATING OVER EASTERN MONTANA/SWRN NODAK AND PROPAGATING SEWD THROUGH THIS CWA...AND MONDAY/MONDAY NIGHT IN THE FORM OF CONVECTION GOING UP ALONG AND AHEAD OF A SYNOPTIC SCALE COLD FRONTAL BOUNDARY PROGGED TO WORK THROUGH THE NORTHERN PLAINS STATES. NO CHANGES MADE TO MAX/MIN T GRIDS AS...THEY APPEAR SPOT ON WHEN COMPARED WITH 00Z LOW LEVEL THERMAL PROGS OF THE EC AND GFS MODELS. && .AVIATION... LOW LEVEL GULF OF MEXICO MOISTURE ABOUNDS IN THE LOWEST COUPLE THOUSAND FEET OF THE ATMOSPHERE THIS MORNING. COUPLE THAT WITH VACATING MID/HIGH CLOUDS AND LIGHT SOUTHERLY WINDS AT THE SURFACE AND THE RESULT IS FOG AND LOW STRATUS CLOUDS DEVELOPING ACROSS THE FORECAST AREA. BEEN MONITORING THE MOVEMENT OF A SURFACE TROF ACROSS THE WESTERN AND CENTRAL DAKOTAS THIS MORNING. THE TROF AXIS WILL BE POSITIONED OVER KMBG AND CLOSE TO KPIR THIS MORNING AT SUNRISE. WINDS WILL BE LIGHTEST HERE...AND SURFACE OBS ARE RESPONDING WITH IFR VISBIES IN GROUND FOG DEVELOPMENT. THIS IFR VISBY CONDITION IN SHALLOW GROUND FOG ACROSS CENTRAL AND NORTH CENTRAL SOUTH DAKOTA SHOULD BE SHORT-LIVED...DIMINISHING SHORTLY AFTER SUNRISE. FURTHER EAST ACROSS THE KABR AND KATY TERMINALS...SURFACE WINDS OF 5 TO 10 KNOTS SHOULD TRANSLATE TO MVFR VISBIES AND SOME IFR CIGS IN LOW STRATUS THROUGH MID-MORNING. SHOULD NOT TAKE LONG FOR DAYTIME INSOLATION TO MIX OUT THE LOW CLOUDS. AFTER 15Z THIS MORNING...GOOD VFR SHOULD RESUME ACROSS ALL FOUR TERMINALS. LATER THIS AFTERNOON...THIS PREVIOUSLY MENTIONED SURFACE TROF WILL BECOME THE FOCUS FOR AFTERNOON AND EVENING THUNDERSTORM ACTIVITY. THE BOUNDARY WILL BE ORIENTED ROUGHLY FROM KPIR TO KATY...SO EXPECT THESE TWO TERMINALS TO BEGIN CARRYING SOME SORT OF CONVECTION MENTION /EITHER CB OR VCTS/ IN THE LATE AFTERNOON/EARLY EVENING TIMEFRAME. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...DORN SHORT TERM...HINTZ LONG TERM...DORN AVIATION...DORN WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 330 PM MDT THU JUL 24 2008 .SHORT TERM...UPPER LEVEL HIGH PRESSURE RIDGE OVER COLORADO WITH A STRONGLY CAPPED MID-TROP PRETTY MUCH SUPPRESSING STORM DVLPMNT ON THE PLAINS UNTIL ABOUT AN HOUR OR SO AGO. HOWEVER SINCE 20Z A FEW LOW-TOP STORMS HAVE MANAGED TO FORM ALONG A DEWPT DISCONTINUITY AXIS ALIGNED SW-NE ACROSS NRN BOULDER-NERN WELD COUNTIES. OTHER STORMS HAVE ALSO POPPED OVER PARK COUNTY AND THE SRN FRONT RANGE FOOTHILLS. CORE REFLECTIVITIES FM THE KFTG RADAR HAVE NOT BEEN ALL THAT HIGH YET. HOWEVER WITH RUC BASED SFC CAPE VALUES CURRENTLY UP AROUND 1800 J/KG IN WELD COUNTY AND UP AGAINST THE NRN FOOTHILLS...WOULD EXPECT TO SE FURTHER DEVELOPMENT IN THESE AREAS IN THE NEXT COUPLE OF HOURS. MAY ALSO SEE NEW STORM DEVELOPMENT UP ALONG THE COLORADO/ WYOMING BORDER THIS EVENING WITH PASSAGE OF A WEAK THERMAL/ INSTABILITY TROF PASSING OVER THE AREA. AT THIS TIME MAIN THREAT FM THESE SLOW MOVING STORMS ACCORDING TO INVERTED-V FCST SOUNDINGS WILL BE STRONG/ DAMAGING DOWNBURST WINDS AND BRIEF MODERATE/HEAVY RAINFALL. RAIN AMOUNTS LOCALLY UP A HALF INCH ARE POSSIBLE WITH PRECIPITABLE WATER VALUES UP AROUND INCH. HAVE SEEN A SLIGHT INCREASE IN PW VALUES IN THE PAST FEW HOURS AS THE SUBTROPICAL MOISTURE PLUME BEGINS ITS SLOW NWRN SHIFT ACROSS THE STATE. LATER TONIGHT...STRONG CONVECTION UP ACROSS NEBRASKA MAY SEND A FAIR AMT OF LOW-LEVEL MOISTURE BACK INTO THE NERN COUNTIES TOWARDS MORNING. LATEST RUC SHOWS THIS OCCURRING. NAM AND GFS ALSO SHOW PW VALUES/HUMIDITIES INCREASING ON FRIDAY AS THE SUBTROPICAL MOISTURE PLUME ALIGNS SW-NE ACROSS THE CWFA IN THE AFTERNOON. AT THIS TIME... SUSPECT CONVECTION ON THE PLAINS WILL HOLD OFF UNTIL ERLY/ MID-AFTERNOON. WHEREAS COULD SEE AN EARLY START TO STORM GROWTH IN MTN AND HIGH VALLEY AREAS SOUTH OF I-70. SHOULD CLOUD COVER DVLP EARLIER THAN EXPECTED MAY NOT SEE TEMPERATURES CLIMB ABOVE THE 90 DEG MARK ON THE PLAINS. HOWEVER...STRONG HEATING DURING THE MORNING/ EARLY AFTERNOON SHOULD STILL SEND THE MERCURY INTO THE LOWER 90S AT MOST PLAINS LOCALES. AFTER 21Z...THE THREAT FOR LOCALLY HEAVY RAINFALL FM SLOW MOVING STORMS WILL INCREASE...ESPLY OVER AND NEAR THE HIGHER ELEVATIONS. SHOULD SEE SCATTERED STORM COVERAGE BY LATE AFTERNOON ACROSS THE ENTIRE CWFA. .LONG TERM...ONLY SUBTLE DIFFERENCES BETWEEN THE MODELS...AND MODULATION OF CONVECTION IN A WARM AND FAIRLY MOIST ENVIRONMENT WILL BE HARD TO FORECAST MUCH IN ADVANCE. IN THE BIG PICTURE...UPPER RIDGE OVER US DEVELOPS A WEAKNESS TO OUR SOUTH OR SOUTHWEST BY MONDAY...ALLOWING SOME MOISTURE TO SEEP NORTHWARD...THEN THE RIDGE WILL REBUILD WHICH SHOULD SHUT OFF THE DEEP MOISTURE. LOW LEVEL FEATURES RATHER BENIGN BUT WILL PROBABLY DETERMINE WHICH DAYS WILL BE THE MOST ACTIVE. MODELS STILL SHOWING CONVECTIVE BLOBS ALONG THE EAST SLOPES FRIDAY EVENING AND SATURDAY EVENING...BUT PLACEMENT IS NOT CONSISTENT. THE LOW LEVEL MOISTURE SEEMS TO BE MAXIMIZED FRIDAY EVENING...THOUGH THERE COULD BE SOME HELP FROM A WEAK FRONT ON SATURDAY EVENING. THIS LOOKS TO BE IN AN ENVIRONMENT WHICH IS WARMING AND DRYING ALOFT HOWEVER. OVERALL SOME THREAT FOR LOCALIZED SIGNIFICANT RAIN BUT NOT LOOKING LIKE A WIDESPREAD EVENT AS SUBSTANTIAL FORCING IS ABSENT AND ENVIRONMENT IS MARGINAL. SUNDAY LOOKS LIKE A TRANSITION DAY IN A SLIGHTLY DRIER ENVIRONMENT OVER THE PLAINS...BUT MOISTURE MAY BE CREEPING IN FROM THE SOUTHWEST AS THE DAY GOES ON. MONDAY LOOKING LIKE AN UP DAY AGAIN WITH POSSIBLE INTERACTION OF INCREASED MOISTURE FROM THE SOUTHWEST AND THE TAIL END OF A NORTHERN PLAINS SHORTWAVE...OF COURSE THE TIMING OF THIS COULD BE OFF BY A DAY AT THAT RANGE. ANALOG PRECIPITATION PROBABILITY MAPS FROM NOAA/ESRL/PSD WERE INTERESTING TODAY...GIVING PROBABILITIES OF .10 INCH OF RAINFALL FROM 20 TO 50 PERCENT EACH DAY SAT THROUGH MONDAY...THEN BACK TO A CLIMATOLOGICAL 10-20 PERCENT FROM TUESDAY ON. EACH DAY HAD A BULLSEYE OF 50 PERCENT OVER DOUGLAS AND JEFFERSON COUNTIES. SO WHILE THE DETAILS ARE EPHEMERAL...THE ENVIRONMENT SEEMS TO JUSTIFY SOME INCREASE TO ABOVE CLIMATOLOGICAL POPS...ESPECIALLY FOR THE EVENING HOURS. AS FOR OUR STREAK OF 90 DEGREE READINGS...LITTLE CHANGE TO THE ENVIRONMENT BEYOND THE CONVECTIVE UPS AND DOWNS. SATURDAY AND SUNDAY SHOULD HAVE ENOUGH SUN TO GET INTO THE 90S EVEN IF IT DOES CLOUD UP LATE...MONDAY AND TUESDAY COULD BE A LITTLE COOLER DUE TO THE INCREASED MOISTURE. && .AVIATION...ISOLATED THUNDERSTORMS CAPABLE OF STRONG DOWNBURST WINDS MAY PRODUCE GUSTY AND ERRATIC OUTFLOW WINDS AT DENVER AREA AIRPORTS THRU MID-EVENING. PASSING HIGH BASED STORMS MAY ALSO PRODUCE A BRIEF LIGHT TO MODERATE RAIN SHOWER. CLEARING SKIES ARE EXPECTED AFTER 03Z THIS EVENING. THE CHANCE FOR THUNDERSTORMS WILL INCREASE ON FRIDAY WITH THE BEST CHANCE FOR T-STORMS AFTER 21Z/FRIDAY. .BOU WATCHES/WARNINGS/ADVISORIES...NONE. && BAKER/GIMMESTAD co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 400 PM EDT THU JUL 24 2008 .SYNOPSIS... 19Z WATER VAPOR AND H4 RUC ANALYSIS SHOWING AN ACTIVE NORTHERN STREAM ACROSS THE NORTHERN TIER OF THE COUNTRY AND SOUTHERN CANADA. FURTHER SOUTH WE FIND AN ELONGATED UPPER RIDGE FROM SOUTHERN CALIFORNIA TO THE LOWER/MIDDLE MISSISSIPPI VALLEY. "THE SUMMER OF THE EAST COAST TROUGH" CONTINUES TO HOLD ITS PATTERN WITH AMPLIFIED TROUGHING FOR LATE JULY COVERING THE EASTERN GREAT LAKES...MID ATLANTIC AND NEW ENGLAND STATES. THE TROUGH IS ANCHORED BY A CLOSED LOW OVER WESTERN NY/SE ONTARIO. FURTHER UPSTREAM WE FIND ANOTHER SHORTWAVE TROUGH MOVING INTO SOUTH-CENTRAL CANADA AND THE NORTHERN PLAINS. AS THE CURRENT EAST COAST TROUGH BEGINS TO LIFT OUT FRIDAY INTO SATURDAY...THIS NEXT PIECE OF ENERGY IN LINE WILL AMPLIFY AND TAKES IT PLACE INTO EARLY NEXT WEEK. OUR FORECAST AREA RESIDES IN A MID/UPPER LEVEL NW/N FLOW PATTERN WEDGED IN BETWEEN THE TROUGHING TO OUR NORTHEAST AND THE RIDGING TO OUR WEST. OVER THE PAST 24 HOURS THIS NW FLOW DELIVERED A SIGNIFICANTLY DRIER UPPER LEVEL AIRMASS INTO THE SOUTHEAST...HOWEVER THE BULK OF THIS DRIER AIR IS BEGINNING TO PUSH OFF TO THE EAST WITH INCREASING MID/UPPER LEVEL MOISTURE SEEN APPROACHING FROM NORTHERN GA/AL AT THE SURFACE...RUC ANALYSIS SHOWING SURFACE RIDGING TO OUR SOUTH OVER THE FL PENINSULA AND EASTERN GULF AND VERY WEAK TROUGHING FURTHER NORTH ACROSS GA/AL. CU FIELD HAS DEVELOPED THIS AFTERNOON WITH THE MOST ORGANIZED FIELD ACROSS OUR WESTERN ZONES CLOSER TO THE BETTER MOISTURE ALOFT AND ASSOCIATED WITH SEA-BREEZE CONVERGENCE. THIS IS ALSO WHERE SCT SHOWERS AND STORMS HAVE BEEN ABLE TO DEVELOP. && .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT. WITH THE MEAN 1000-700MB FLOW FROM THE NORTHWEST THIS EVENING...THE SEA BREEZE WILL HAVE DIFFICULTY PUSHING RAPIDLY INLAND AND THIS SHOULD KEEP THE BULK OF THE SHOWERS/STORMS ASSOCIATED WITH ITS CONVERGENCE SOUTH OF THE AL/GA BORDER. HOWEVER...WITH THE WEAK SURFACE TROUGH PROVIDING SOME FOCUS FOR CONVERGENCE FURTHER NORTH WILL EXPECT AT LEAST WDLY SCT STORMS FROM SOUTHEAST AL INTO PORTIONS OF SOUTHWEST GEORGIA. ACTIVITY IS LIKELY TO BE MORE ISOLATED IN NATURE EVEN FURTHER EAST CLOSEST TO THE MAIN AXIS OF DRY AIR ALOFT. ACTIVITY DIMINISHES OVER LAND DURING THE MIDDLE/LATE EVENING HOURS WITH SKIES GRADUALLY CLEARING. LOW TEMPERATURE EXPECTED IN THE UPPER 60S TO LOWER 70S INLAND AND MIDDLE 70S ALONG THE COAST. SUMMER TIME NOCTURNAL SHOWERS AND THUNDERSTORMS ARE LIKELY TO DEVELOP JUST OFFSHORE DURING THE LATE NIGHT HOURS AND A FEW OF THESE DEVELOPING CLOSE ENOUGH TO THE COAST TO EFFECT PORTIONS OF GULF...FRANKLIN... TAYLOR AND DIXIE COUNTIES TOWARD SUNRISE. PULLED A SLIGHT RISK OF STORMS UP INTO THESE COUNTIES INTO THE EARLY MORNING HOURS OF FRIDAY AS THESE AREAS OFTEN EXPERIENCE A BRIEF SHOWER OR STORMS UNDER THESE CONDITIONS. GENERAL UPPER LEVEL AND SURFACE PATTERN REMAINS QUITE STATIC THROUGH THE SHORT TERM PERIOD WITH A GENERAL UPPER LEVEL TROUGH TO OUR NORTHEAST AND UPPER RIDGING TO OUR WEST AND NORTHWEST. THIS RIDGING WILL AT TIMES MAKE PUSHES TO THE EAST. THIS FEATURE DOES APPEAR THAT IT WILL BUILD FAR ENOUGH EAST TO RESULT IN SOME CONVECTIVE SUPPRESSION DURING THE DAY ON FRIDAY...MAINLY ACROSS THE WESTERN ZONES. HOWEVER THE RIDGING IS LIKELY NOT GOING TO BE STRONG ENOUGH TO PUT A SIGNIFICANT DENT TO THE SEA BREEZE CONVECTION SOUTH OF THE AL/GA BORDER. FRIDAY SHOULD START OUT PARTLY SUNNY AND GENERALLY DRY FOR MOST AREA WITH THE EXCEPTION OF THE SLIGHT CHANCE OF STORMS ALONG THE IMMEDIATE COAST AROUND SUNRISE. NAM/GFS MODEL SOUNDINGS ACROSS THE AREA ARE SIMILAR IN PROFILE FRIDAY AFTERNOON SHOWING THE PRESENCE OF THE MID LEVEL RIDGING WITH POOR LAPSE RATES BETWEEN 700-500MB. THIS "CAP" SHOULD BE ENOUGH TO HOLD CONVECTION IN CHECK ALONG AND NORTH OF THE I-10 CORRIDOR UNTIL LATE IN THE DAY...ESPECIALLY FOR AREAS AWAY FROM THE SEA BREEZE ZONE. THESE LOCATIONS WILL NEED TO REACH NEAR MAX HEATING BEFORE THE SURFACE TROUGH CAN PROVIDE ENOUGH FOCUS. SOUTH OF I-10 THE CONVECTION SHOULD FIRE A BIT EARLIER AS THE SEA-BREEZE PROVIDES THE NECESSARY TRIGGER TO BREAK THE CAP BY EARLY AFTERNOON. POP GRIDS SHOW AROUND 40% SOUTH OF THE AL/GA BORDER RANGING DOWN TO 30% AND 20% RANGE HEADING NORTH. HIGH TEMPS GENERALLY IN THE LOWER TO MIDDLE 90S INLAND AND THE UPPER 80S TO LOWER 90S ALONG THE COAST. HOTTEST TEMPS SHOULD BE TOWARD ALBANY AND TIFTON WHERE CU DEVELOPMENT SHOULD BE HELD BACK LONGEST. UPPER RIDGE BACKS TO THE WEST ON SATURDAY LESSENING THE CONVECTIVE SUPPRESSION. EXPECTING A VERY TYPICAL SUMMER DAY WITH HIGHS IN THE LOWER 90S AND GENERALLY CHANCE AFTERNOON POPS REGION-WIDE. LATER SATURDAY AND SATURDAY NIGHT...GFS SHOWING THE APPROACH OF A DECENT MID-LEVEL SHORTWAVE IN THE NW FLOW THAT WOULD LIKELY KEEP POPS A BIT HIGHER INTO THE OVERNIGHT HOURS. AT THIS TIME THE GFS IS AN OUTLIER AND LEANED MORE TOWARD THE DRIER NAM AND ECMWF SOLUTIONS WHICH SHOW THIS SHORTWAVE STAYING FURTHER NORTH. && .LONG TERM...SUNDAY THROUGH WED. LARGE SCALE PATTERN TO REMAIN RELATIVELY UNCHANGED THROUGH THE NEXT SEVEN DAYS. UPPER FLOW WILL BE DOMINATED BY A PERSISTENT EASTERN CONUS TROUGH FLANKED BY RIDGES OVER THE WESTERN ATLANTIC AND SOUTHERN PLAINS. AT THE SFC...TROUGH WILL PERSIST NORTH OF THE CWA WITH RIDGE AXIS OVER THE GULF SOUTH OF THE COASTAL WATERS. THIS WILL KEEP A GENERAL WEST TO SOUTHWEST FLOW IN PLACE THROUGH THE FORECAST PERIOD. OVERALL...EXPECT NEAR CLIMO CONDITIONS THROUGH PERIOD WITH SCATTERED AFTERNOON AND EVENING CONVECTION AND NEAR NORMAL TEMPERATURES. && .MARINE... OUR COASTAL WATERS WILL REMAIN ON THE NORTHERN EDGE OF THE SUBTROPICAL RIDGE AND TO THE SOUTH OF A WEAK TROUGH OVER GEORGIA AND ALABAMA THROUGH THE DAY ON FRIDAY...KEEPING WINDS GENERALLY LIGHT. LEFTOVER SWELL FROM FORMER HURRICANE DOLLY CONTINUES TO PROPAGATE WESTWARD INTO THE NORTHEAST GULF OF MEXICO WITH SWELL HEIGHTS EXPECTED TO REMAIN IN THE 2 TO 4 FOOT RANGE THROUGH TONIGHT BEFORE BEGINNING TO SUBSIDE ON FRIDAY. GENERALLY LIGHT FLOW AND LOW SEAS EXPECTED FOR THE UPCOMING WEEKEND OUTSIDE OF AFTERNOON SEA BREEZES AND MAINLY OVERNIGHT AND MORNING SHOWERS AND THUNDERSTORMS. && .AVIATION... AFTER YESTERDAY`S WIDESPREAD RAINS...MID LEVEL DRY AIR SURGED SWD PROVIDING A CLASSIC SET UP FOR IFR CONDITIONS THIS MORNING. THE LOW STRATUS WAS LIFTING ABOVE MVFR THRESHOLDS AROUND TAF ISSUANCE TIME. VFR CEILINGS ARE FORECAST TO PREVAIL FOR THE REMAINDER OF THE DAY OUTSIDE OF THUNDERSTORMS. TS COVERAGE IS EXPECTED TO BE TOO ISOLATED TO MENTION IN THE FORECAST FOR ABY AND VLD. HOWEVER...SCATTERED CONVECTION IS EXPECTED FOR AREAS AROUND PFN...TLH AND DHN. WE DO NOT ANTICIPATE A REPEAT OF THE LOW STRATUS TONIGHT...EXCEPT AT PERHAPS ABY. THIS AND OTHER TERMINALS WILL SEE A BRIEF PERIOD OF MVFR VSBY AFTER 08Z. && .FIRE WEATHER...RED FLAG CONDITIONS ARE NOT ANTICIPATED. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 72 93 72 92 72 / 20 40 20 50 20 PANAMA CITY 76 90 77 90 77 / 20 30 20 50 20 DOTHAN 71 93 73 92 72 / 20 30 20 40 30 ALBANY 71 95 72 93 72 / 20 30 20 40 30 VALDOSTA 70 93 71 92 71 / 20 30 20 40 30 CROSS CITY 71 92 72 91 71 / 20 40 20 50 20 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$ AVIATION/FIRE WX...WOOL LONG TERM...CAMP REST OF DISCUSSION...MROCZKA fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIAMI FL 150 PM EDT THU JUL 24 2008 .AVIATION... FOR THE 18Z TAFS...EAST COAST SEA BREEZE IS FIRING TSTMS IN VCTY OF THE KOPF-KMIA-KTMB TERMINALS WITH MOST ACTIVITY INLAND FROM KFXE AND KFLL. WILL CARRY VCTS EXCEPT AT KOPF WHERE A TSTM WAS VERY CLOSE TO THE TERMINAL AT TAF ISSUANCE. EXPECT ACTIVITY TO CONTINUE DEVELOPING NEAR KPBI AND ALSO KAPF ON THE WEST COAST IN THE NEXT HOUR OR SO AS SEA BREEZE WILL HOLD CLOSER TO THOSE TERMINALS. ANY TSTM WILL MOVE VERY SLOWLY AND COULD PRODUCE VARIABLE WINDS GUSTING OVER 25KTS EVEN ON OUTFLOW BOUNDARIES...AND CAUSE SHORT MVFR REDUCTIONS TO CIGS/VSBY AND PERHAPS VERY BRIEF IFR CONDITIONS BEFORE STORMS MOVE ON. ACTIVITY SHOULD BEGIN WINDING DOWN TOWARDS SUNSET WITH MOSTLY DRY CONDITIONS OVERNIGHT THEREAFTER. /STRASSBERG && .PREV DISCUSSION... /ISSUED 956 AM EDT THU JUL 24 2008/ UPDATE...AFTER PERFORMING CAREFUL ANALYSIS, IT APPEARS THERE ARE SEVERAL BOUNDARIES AROUND THIS MORNING FOR CONVECTION TO INITIATE. IN OTHER WORDS, IT COULD EASILY FORM JUST ABOUT ANYWHERE ACROSS S FLA. IN THE UPPER LEVELS, THE LEFT OVER 50H TROUGH AND ABOVE REMAINS JUST OFF THE SE CST OF THE PENINSULA WHICH EXPLAINS THE CONVECTIVE PATTERN CURRENTLY OVR THE OPEN ATLANTIC WELL OFFSHORE. A WEAK COLD FRONT EXISTS ACROSS SOUTHERN GEORGIA WHICH IS ASSOCIATED WITH THE MAIN MID/UPPER TROUGH MOVING OFF THE MID ATLANTIC SEABOARD WITH A PRE-FRONTAL TROUGH MOVING INTO N FLA WHICH EXPLAINS THE CURRENT CONVECTION ALONG THE GULF COAST JUST NORTH OF TPA. COULD EVEN BE A WEAK VORT MAX ASSOCIATED WITH THIS FEATURE. WATER VAPOR IMAGERY CLEARLY SHOWS THE MAIN MID LEVEL TROUGH CONTINUING TO DIG SOUTHWARD BUT BOTH THE 06Z GFS AND NAM RUNS SHOW THE TROUGH BEGINNING TO LIFT NE THROUGH THE COURSE OF THE DAY. THE 12Z MFL SOUNDING SHOWS SOME DRYING THAT HAS OCCURRED DURING THE PAST 24 HOURS BUT IF THE TROUGH BOUNDARY NORTH OF OUR REGION MOVES FAR ENOUGH TO THE SOUTH, THEN WE COULD MOISTEN UP AGAIN BY AFTERNOON. IT APPEARS THE BEST COURSE OF ACTION WOULD BE JUST TO GO WITH PERSISTENCE CONSIDERING THE WEAK BOUNDARIES THAT REMAIN IN PLACE AND SO HAVE MENTIONED POSSIBILITY OF STRONG WIND GUSTS AND SMALL HAIL WITH THE STRONGEST CELLS THAT DEVELOPMENT MAINLY ACROSS ALL OF S FLA WITH THE EXCEPTION OF ALONG BOTH COASTS. 30/KOB PREV DISCUSSION... /ISSUED 745 AM EDT THU JUL 24 2008/ AVIATION... THE WINDS TODAY WILL BE FROM THE NORTHEAST THIS MORNING BEFORE SWINGING TO A SOUTHEAST DIRECTION THIS AFTERNOON ALONG THE EAST COAST TAF SITES. FOR APF TAF SITE...THE WINDS WILL BE NORTHEAST THIS MORNING BEFORE SWINGING TO A WESTERLY DIRECTION BY 17Z THIS AFTERNOON. THE SPEEDS WILL ALSO BE 10 KNOTS OR LESS TODAY AT ALL OF THE TAF SITES. FOR THE WX AT THE TAF SITES TODAY...PLAN ON KEEPING THE TAF SITES DRY UNTIL AROUND 17Z AND THEN PUT IN VCTS ALL OF THE TAF SITES FROM 17Z UNTIL 21Z FOR THE ACTIVITY ALONG BOTH SEA BREEZES. BETWEEN 21Z AND 01Z PLAN ON HAVING ONLY VCSH FOR THE EAST COAST TAF SITES...AS THE EAST COAST SEA BREEZE WILL BE PUSHING FURTHER INLAND...BUT WILL CONTINUE TO HOLD THE VCTS FOR APF TAF SITE DUE TO THE SLOWLY PUSH OF THE WEST COAST SEA BREEZE. THE CEILING AND VIS FOR THE TAF SITES TODAY WILL REMAIN IN THE VFR CONDITIONS DUE TO THE TIMING OF THE ACTIVITY. SO WHEN THE ACTIVITY GETS GOING WILL COVERAGE THE SITES WITH THE ADMINS. AVIATION...54/BNB PREV DISCUSSION... /ISSUED 518 AM EDT THU JUL 24 2008/ DISCUSSION... CONVECTION THAT DEVELOPED ALONG SOUTHEASTWARD MOVING OUTFLOW OVER THE MAINLAND LATE YESTERDAY EVENING CONTINUES TO DISSIPATE THIS MORNING...WITH SHOWERS/STORMS NOW BECOMING CONCENTRATED OVER THE ATLANTIC WATERS. LATEST WATER VAPOR ANIMATION ALONG WITH RUC ANALYSES INDICATE THAT THE FLORIDA PENINSULA REMAINS LOCATED BENEATH A WEAKNESS IN THE UPPER-LEVEL RIDGE...WITH AN AMPLIFYING MID-LEVEL TROUGH LOCATED OVER THE EASTERN GREAT LAKES REGION...AND A WEAKER INVERTED TROUGH CENTERED OVER THE FLORIDA STRAITS JUST OFF THE SOUTHEAST COAST OF THE PENINSULA. GUIDANCE FROM THE NGM/NAM/GFS IS IN GOOD AGREEMENT WITH SOLUTIONS FROM THE UKMET/ECMWF IN ADVERTISING THIS STAGNANT PATTERN TO PERSIST FOR MUCH OF THE SHORT TERM. SIMILAR TO YESTERDAY...LIGHT EASTERLY FLOW IN THE BOUNDARY LAYER WILL ALLOW THE ATLANTIC COAST SEA BREEZE TO SLOWLY MOVE INLAND LATER THIS MORNING...WITH THUNDERSTORMS EXPECTED TO DEVELOP ALONG THIS BOUNDARY BY LATE MORNING/EARLY AFTERNOON. GIVEN POTENTIAL FOR ADDITIONAL CONVECTIVE DEVELOPMENT ALONG NUMEROUS MESOSCALE BOUNDARIES...AND LIGHT NORTHERLY FLOW ALOFT...WILL SIDE WITH HIGHER FWC/MET POP NUMBERS BOTH TODAY AS WELL AS TONIGHT...TO ACCOUNT FOR LINGERING EVENING CONVECTION MAINLY ALONG THE EAST COAST. BY FRIDAY...THERE ARE SOME INDICATIONS THAT A STRONGER AND DEEPER EASTERLY FLOW REGIME MAY BECOME ESTABLISHED OVER THE AREA...AS CENTRAL PLAINS UPPER RIDGE STRENGTHENS AND SHIFTS SOUTHEASTWARD IN RESPONSE TO THE DEVELOPMENT OF A STRONGER UPPER LOW OVER ONTARIO/QUEBEC. DESPITE THIS...AN AXIS OF LOWER HEIGHTS ALOFT WILL REMAIN OVER THE FLORIDA PENINSULA...PROVIDING A FAVORABLE THERMAL ENVIRONMENT FOR AT LEAST SCATTERED AFTERNOON CONVECTION ALONG SEA BREEZE BOUNDARIES. WILL PLACE HIGHEST POPS ALONG THE GULF COAST TO REFLECT INCREASING -- ALTHOUGH STILL VERY WEAK -- EASTERLY FLOW. BOUNDARY LAYER EASTERLIES APPEAR TO STEADILY INCREASE FROM FRIDAY NIGHT INTO SATURDAY MORNING...WITH CORRESPONDINGLY HIGHER POPS WARRANTED FOR THE ATLANTIC WATERS AND SOUTHEAST COAST OF THE MAINLAND. EXPECT CONDITIONS SIMILAR TO FRIDAY ONCE AGAIN ON SATURDAY...WITH WEAK EASTERLY STEERING FLOW FOCUSING HIGHEST COVERAGE OF AFTERNOON SHOWERS/STORMS OVER WESTERN PORTION OF THE FORECAST AREA. MEDIUM RANGE GUIDANCE FROM THE GFS/ECMWF/CMC NOW SUGGESTS THAT THIS PERSISTENT WEAKNESS IN THE UPPER-LEVEL RIDGE MAY LINGER OVER THE PENINSULA THROUGH THE BEGINNING OF NEXT WEEK...AND WILL REFLECT THIS IN THE EXTENDED FORECAST WITH NEAR CLIMO VALUES FOR POPS...EXCEPT SLIGHTLY HIGHER THAN CLIMO ALONG THE GULF COAST. CONDITIONS MAY BEGIN TO CHANGE...HOWEVER...BY THE MIDDLE OF THE WEEK...AS UPPER LOW OVER SOUTHEASTERN CANADA IS EVENTUALLY FORCED EASTWARD...ALLOWING CENTRAL ATLANTIC BRANCH OF THE SUBTROPICAL UPPER RIDGE TO FINALLY BUILD OVER THE AREA. THIS...IN COMBINATION WITH SOUTHWEST FLOW...COULD LEAD TO WARMER THAN NORMAL TEMPERATURES LATE NEXT WEEK...ALONG WITH LOWER CHANCES FOR RAIN. MARINE... CONDITIONS WILL REMAIN FAVORABLE FOR THE FORMATION OF WATERSPOUTS THIS MORNING...ESPECIALLY OVER THE LOCAL ATLANTIC WATERS AND BISCAYNE BAY. OTHERWISE...THERE ARE NO SIGNIFICANT WEATHER-RELATED CONCERNS TO MARINERS THROUGHOUT THIS FORECAST PERIOD...WITH CONDITIONS OUTSIDE OF SHOWERS/THUNDERSTORMS EXPECTED TO INCLUDE PREVAILING EAST TO SOUTHEAST WINDS IN THE 5-10 KNOT RANGE. THIS WIND FLOW WILL MAINTAIN SEAS IN THE 1-3 FOOT RANGE ACROSS ALL OF THE LOCAL COASTAL WATERS. FIRE WEATHER... THERE ARE NO FIRE WEATHER CONCERNS THROUGHOUT THIS FORECAST PERIOD...WITH MINIMUM AFTERNOON RH VALUES EXPECTED TO RANGE FROM 45-55 PERCENT ACROSS THE NORTHWEST ZONES...TO 55-60 PERCENT ELSEWHERE. && .PRELIMINARY POINT TEMPS/POPS... WEST PALM BEACH 74 89 76 89 / 40 40 20 40 FORT LAUDERDALE 76 90 78 90 / 40 40 30 40 MIAMI 76 90 77 90 / 40 40 30 40 NAPLES 73 90 75 90 / 30 50 30 50 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. GM...NONE. && $$ LONG TERM...30/KOB SHORT TERM/AVIATION...54/BNB fl AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 140 PM EDT THU JUL 24 2008 UPDATED FOR 18Z TAF DISCUSSION .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW HI AMPLITUDE TROF CENTERED OVER SE ONTARIO...WITH SHARP UPR RDG FM MN INTO NW ONTARIO BTWN THE TROF AND FALLING HGTS OVER THE NRN PLAINS/SCNTRL CAN ASSOCIATED WITH A PAIR OF STRONG SHRTWS RIDING ENEWD OUT OF A MEAN TROF IN THE PAC NW/SW CAN. 00Z GRB RAOB DEPICTS A VERY DRY...STABLE AIRMASS (KINX 8...PWAT 0.74 INCH) DOMINATING THE UPR GRT LKS OVER SFC HI PRES CENTERED ACRS LK SUP AT 03Z. THERE ARE SOME MID CLDS MOVING INTO THE ERN CWA ASSOCIATED WITH SHRTWV ROTATING ARND DEEP TROF TO THE E. THE CNTRL CWA IS CLR...BUT THERE ARE SOME HI CLDS TO THE W PUSHING EWD THRU THE UPR RDG AXIS AND OVER VERY DRY...STABLE AIR ALSO SHOWN ON THE 00Z INL RAOB (KINX -13...PWAT 0.55 INCH THERE). LEADING EDGE OF THIS CI IS TENDING TO FADE AS IT PUSHES EWD INTO THE LARGER SCALE SUBSIDENCE OVER UPR MI TO THE W OF TROF TO THE E. A VERY SHAPR GRADIENT IN H85 DWPT IS APRNT FM MN INTO THE NRN PLAINS. WHILE 00Z H85 DWPT AT INL IS ONLY 5C...THE VALUE IS 17C AT BIS IN RETURN SW FLW BTWN RDG OVER THE GRT LKS AND TROFFING IN THE PAC NW. THE INTERACTION BTWN THE RESULTING INSTABILITY SHOWN ON THE 00Z BIS SDNG AND LEAD SHRTWV APRCHG LK WINNIPEG HAS RESULTED IN SOME CNVCTN AS FAR E AS THE MN/ND BORDER. HOWEVER...RATHER DRY NATURE OF THE MID LVLS (00Z H5 DWPT DEPRESSION 28C AT BIS) APPEARS TO BE LIMITING COVG OF SHRA/TSRA IN THAT AREA. MAIN FCST CONCERN TDAY THRU TMRW WL BE TIMING BREAKDOWN OF RDG/DRY AIR NOW IN PLACE AND THEN COVG/STRENGTH OF CNVCTN THAT CAN SPREAD INTO THE UPR GRT LKS ASSOCIATED WITH SHRTWVS TO THE W. FOR TDAY...THE DAY WL START ON THE QUIET SIDE WITH RDG STILL IN CONTROL. THE LLVL FLOW WL GRDLY SHIFT TO THE SW ONCE THE SFC-H85 RDG AXIS SHIFTS TO THE E. 00Z NAM/GFS SHOW ISENTROPIC LIFT ON THE 305K SFC (ARND H75) RESULTING IN INCRSG RH AT THAT LVL OVER THE W IN THE AFTN. 00Z NAM/RUC13 ALSO APPEAR TO GENERATE SOME ISOLD CNVCTN OVER THE INTERIOR W HALF OF THE FA IN THE AFTN. BUT SINCE THE HIER H85 DWPTS ARE TO THE W AND NOT THE SW (23Z TAMDAR SDNG FM MSP SHOWED H85 DWPT ONLY 6.5C THERE IN ABSENCE OF 00Z MPX RAOB)...PREFER THE DRIER 00Z GFS/00Z LOCAL WRF-ARW RUN AND SISTER MODEL RUN WITH KF CONVECTIVE SCHEME THAT GENERATES SCT CNVCTN ONLY OVER WRN LK SUP CLOSER TO THE DEEPER LARGE SCALE H85-3 QVECTOR CNVGC/DPVA ASSOCIATED WITH SHRTWV NOW NEAR LK WINNIPEG THAT IS RIDING INTO THE UPR RDG OVER ONTARIO. HAVE THUS REMOVED POPS OVER THE LAND FA EXCEPT FOR SOME SCHC VALUES OVER THE FAR W AFT 18Z. ELEVATED MSTR (MID CLD) RETURN/ WEAK DESTABILIZATION SHOWN ON FCST SDNGS WARRANTS EXCLUSION OF TS EXCEPT OVER FAR WRN LK SUP. GOING MAX TEMPS FCST NEEDED LTL ADJUSTMENT. SECOND SHRTWV UPSTREAM THAT WAS MOVING THRU THE NRN ROCKIES IS PROGGED TO REACH NEAR LK WINNIPEG BY 12Z FRI...FURTHER WEAKENING THE UPR RDG IN PLACE OVER THE GRT LKS AS ITS ACCOMPANYING SFC COLD FNT APRCHS THE WRN LK SUP SHORE BY 12Z. WITH THE LLVL FLOW FCST TO VEER MORE W OVERNGT...LOOKS LIKE A BETTER OPPORTUNITY FOR THE HIER DWPTS TO THE W TO SPREAD INTO THE FA. IN FACT...00Z GFS/NAM SHOW SOME SHARPER ISENTROPIC LIFT/MOISTENING ON THE 300K SFC SPRDG W-E DURING THE NGT AND SUPPORTING CHC POPS. WL GO WITH THE HIER POPS (40) ACRS THE NRN TIER CLOSER TO SHARPER H85-7 FGEN FCST BY NAM/GFS. ADJUSTED POPS CLOSE TO SHARPER ISENTROPIC LIFT...RESULTING IN REDUCED POPS OVER THE W WITH GUIDANCE SHOWING DRIER AIR INFLUX IN THE MID LVLS/ CAPPING. DID INCRS POPS AGAIN LATE OVER WRN LK SUP WITH APRCH OF COLD FNT AND WHERE 12Z ECMWF PERSISTS IN SHOWING SHARPER DPVA AHD OF INCOMING SHRTWV. MSTR INFLUX/CLDS GUARANTEE A MUCH WARMER OVERNGT THAN EARLY THIS MRNG. ON FRI...00Z GFS HAS TRENDED A BIT TOWARD THE 12Z ECMWF SHOWING SHARPER HGT FALLS WITH A SHRTWV THAT DIGS A BIT MORE AND EXHIBITS A BIT MORE DIFFLUENT UPR FLOW IN THE LEFT EXIT REGION OF A MORE POTENT LOOKING UPR JET. BUT WHILE THE 12Z ECMWF SHOWED LLVL DRY ADVCTN OVERSPREADING THE FA EVEN AHD OF THE COLD FROPA...THE 00Z GFS SLOWS DOWN THE BNDRY AND ALLOWS FOR ADDITIONAL MSTR ADVCTN/MUCH HIER QPF AS THE DYNAMICS INTERACT WITH THE GREATER MSTR FLUX. THE 00Z UKMET APPEARS TO TREND IN THE DIRECTION OF THE GFS...BUT IS NOT AS EXTREME EVEN THOUGH ITS FCST 90KT H3 JET MAX IN SRN MN BY 00Z SAT LOOKS LIKE THE STRONGER 12Z ECMWF. SINCE THE 00Z GFS IS SUCH A DRASTIC CHANGE FM PREVIOUS RUNS...WL TEND MORE TOWARD THE NAM/CNDN/UKMET/LOCAL WRF-ARW WITH KF CONVECTIVE SCHEME SCENARIO...WHICH SUPPORTS THE GOING FCST HIER AFTN POPS OVER THE SCNTRL AND E WHERE LATER ARRIVAL OF COLD FNT WL BE IN BETTER SYNC WITH DAYTIME HTG/PSBL LK BREEZE INTERACTION. DESPITE THE POTENTIAL DESTABILIZATION WITH DRYING ALF... WEAK LLVL CNVGC AND THE DRY ADVCTN WL LIMIT POPS. NEW SPC DAY2 CONVECTIVE OUTLOOK HAS CWA JUST N OF SLGT TSRA RISK AREA... BUT INCRSG UNIDIRECTIONAL MID LVL WINDS/0-6KM BULK SHEAR APRCHG 40 KT/ MODIFIED NAM FCST SDNG FOR MAX TEMPS IN THE LOW 80S AND DWPTS ARND 63 (VS EXPLICIT MODEL FCST TO 68) SBCAPE IN EXCESS OF 1100 J/KG/MID LVL DRYING...SUG A POTENTIAL FOR SVR STORMS. LINGERING EVNG CNVCTN ON FRI OVER THE SCNTRL AND E WL DIMINISH WITH COLD FROPA...INFLUX OF LLVL DRY AIR...LOSS OF DIURNAL HTG AND DEPARTURE OF LEFT EXIT DYNAMICS. BUT WITH TREND TOWARD MORE DIGGING OF SHRTWV/LOWER HGTS...BROUGHT BACKWASH MSTR POPS OVER NRN LK SUP A BIT FARTHER S TO TICKLE THE NRN CWA FRI NGT. BUT WITH BULK OF DEEP MSTR PROGGED TO REMAIN IN ONTARIO CLOSER TO DEEP UPR TROF FOR MID SUMMER...NOTHING MORE THAN SCHC POPS WARRANTED. GFS SEEMS TO BE THE OUTLIER IN MAINTAINING HIER BACKWASH MSTR/RH OVER LK SUP ON SAT... BUT WITH TREND TOWARD DEEPER TROF IN SE CAN...HESITANT TO DISCOUNT ITS FCST SCENARIO. WITH THAT TREND TOWARD LOWER HGTS IN MIND... TENDED TOWARD THE SOMEWHAT COOLER GFS MOS TEMPS FOR FRI NGT/SAT. COORDINATED WITH APX/GRB/DLH. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... HIGH CLOUDS HAVE SPREAD ACROSS THE WESTERN U.P. AHEAD OF THE CONVECTION THAT IS IN THE ARROWHEAD REGION OF MN. THE CONVECTION IS ASSOCIATED WITH AN INITIAL UPPER LEVEL DISTURBANCE AHEAD OF THE MAIN FRONTAL TROUGH. THE MAIN FRONTAL TROUGH IS NOT EXPECTED TO CROSS THE REGION UNTIL FRIDAY AFTERNOON. A FEW LIGHT SHOWERS OR SPRINKLES MAY REACH CMX BEFORE 06Z TONIGHT...BUT KEPT -SHRA OUT UNTIL AFTER 06Z WITH THE PASSAGE OF THE UPPER LEVEL DISTURBANCE SINCE THE INTIAL ATMOSPHERE IS VERY DRY. WENT WITH MVFR CONDITIONS AT CMX BEHIND THE FRONTAL TROUGH. MAIN FORCING FOR PCPN WILL BE TO THE NORTH...SO KEPT PROB30 FOR PCPN AND VFR AT SAW THROUGH THE TAF PERIOD. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WINDS SHOULD BE AT OR LESS THAN 20 KT THROUGH THE PERIOD. WINDS WILL REMAIN OUT OF THE SOUTH TODAY AS THE HIGH PRESSURE SLOWLY SHIFTS SOUTHEASTWARD. THE WINDS WILL VEER TO THE WEST AS THE COLD FRONT SLIDES ACROSS THE LAKE ON FRIDAY AND FRIDAY NIGHT. THEN WHEN THE HIGH PRESSURE SYSTEM RETURNS...WINDS WILL DIMINISH AND SHIFT SOUTH AGAIN ON MONDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...MRC MARINE...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 313 PM CDT THU JUL 24 2008 .DISCUSSION... CURRENT SFC ANALYSIS SHOWS A COLD FRONT PUSHING THROUGH NW. A STRONG LLJ THIS MORNING ALLOWED FOR DEW PTS IN THE 60S TO EVEN SOME LOW 70S TO MAKE THEIR WAY INTO THE FA AHEAD OF THE FRONT. BY 00Z...THE LEADING EDGE OF THE BAROCLINIC ZONE IS EXPECTED TO BE LOCATED ALONG THE KINL TO KBRD CORRIDOR...REACHING THE KHIB TO KDLH AND KHYR AFTER 06Z. THE LATEST RUC AND SPC MESO ANALYSIS SUGGEST THERE IS SUFFICIENT CAPE...SHEAR...AND INSTABILITY ALONG THE CF TO SUPPORT CONVECTION...WITH ISOLD STORMS POSSIBLY REACHING SVR LEVELS. CURRENT MOSAIC RADAR SHOWS THAT -TSRA HAVE BEGUN TO DEVELOP ALONG THE FRONT. THERE REMAINS UNCERTAINTY IN THE POSITION/SPEED OF THE FRONT DURING THE EVENING TIME FRAME...AS WELL AS HOW ORGANIZED ANY CONVECTION CAN BECOME. KEPT THE LOW CHC POPS WITH SCT WORDING THIS EVENING. BY 12Z...THE CF IS FCST TO BE EXITING THE FA AND MOVING INTO UPR MICHIGAN. HOWEVER...GFS/NAM IN GOOD AGREEMENT THAT A SHORT WAVE WILL SWEEP SE FROM CANADA OVER NRN MN FRIDAY MORNING...KEEPING THE CHC FOR SCT -TSRA FOR THE FA. THE LIMITING FACTOR FOR THESE SCT/ISOLD STORMS WILL BE THE AVAILABLE MOISTURE AS MUCH DRIER AIR ASSOCIATED WITH BUILDING HIGH PRESSURE PUSHES EAST IN TO THE WRN GREAT LAKES REGION BY LATE FRIDAY. && .AVIATION...MVFR CONDITIONS WILL BE WIDESPREAD FROM KINL TO KHIB AND KBRD THIS AFTERNOON...WITH MAINLY VFR CONDITIONS FOR KDLH AND KHYR. SCATTERED TSRA CAN BE EXPECTED THIS AFTERNOON...WITH MVFR AND POSSIBLY EVEN BRIEF IFR CONDITIONS POSSIBLE WITH ANY OF THE STORMS. TONIGHT WILL CONTINUE TO BE UNSETTLED WITH A WEAK FRONTAL BOUNDARY MOVING EASTWARD ACROSS THE REGION. HIGH DEWPOINTS WILL SLIDE EASTWARD THROUGH THE CWA...AND WILL HELP TO CAUSE THE SPOTTY THUNDERSTORMS. DUE TO FAIRLY WIDESPREAD RAIN IN SPOTS THIS MORNING AND SPOTTY THUNDERSTORMS THIS AFTERNOON AND TONIGHT...SOME FOG MAY DEVELOP. IFR CONDITIONS AND LOWER MAY BE FOUND IN SPOTS. CONDITIONS ARE EXPECTED TO IMPROVE ON FRIDAY MORNING AS DRIER WESTERLY WINDS PUSH ACROSS THE REGION BEHIND THE FRONT. && POINT TEMPS/POPS... DLH 60 80 57 81 / 30 30 10 10 INL 58 78 49 77 / 30 30 10 10 BRD 63 82 54 80 / 30 20 10 10 HYR 62 81 54 79 / 30 40 10 10 ASX 62 81 54 78 / 30 40 10 10 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ GRANING/DAP mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1213 PM CDT THU JUL 24 2008 .AVIATION.../18Z TAF ISSUANCE/ EXTENSIVE MVFR CEILINGS ACROSS THE WESTERN TWO THIRDS OF THE AREA AT THIS TIME IN ASSOCIATION WITH SOME 925-700MB WARM ADVECTION AND ASSOCIATED HIGHER RH VALUES. THIS WILL SLIDE SLOWLY EAST THROUGH THE DAY...AND FILTERED SUNSHINE AND RISING TEMPERATURES WILL TRY TO BUST SOME HOLES IN THE CLOUD DECK AS IT PUSHES EASTWARD. HOWEVER...WILL GENERALLY HAVE SOME 2-3K CEILINGS FOR ALL BUT KEAU FOR A GOOD PART OF THE AFTERNOON...WITH SLIGHTLY LOWER CEILINGS OVER THE WEST WHERE CURRENTLY OBSERVED. THE WESTERN SITES WILL SEE THIS MORE EXTENSIVE CLOUD DECK BREAK UP FIRST AS THE COLD FRONT TRUDGES INTO THE AREA. THIS FRONTAL BOUNDARY...ALONG WITH SOME FORCING FROM AN UPSTREAM SHORTWAVE OVER SOUTH DAKOTA...WILL TRY TO KICK OF SOME AFTERNOON SHRA/TSRA OVER THE WEST AND NORTHWEST PART OF THE FORECAST AREA...BUT AT THIS POINT IT LOOKS LIKE ONLY KAXN HAS THE POTENTIAL TO REALLY SEE ANYTHING DURING THE DIURNAL HEATING CYCLE...AND EVEN THERE PROBABILITIES SEEM SUFFICIENTLY LOW TO JUST MENTION A CB ALONG WITH SHRA AT THIS POINT. FARTHER SOUTH AND EAST...IT DOES NOT APPEAR THAT INSTABILITY WILL PHASE WITH THE FORCING FOR ANYTHING TO OCCUR DURING THE AFTERNOON OR EARLY EVENING...SO LEFT PCPN OUT OF THE TAFS. AS THE MORE EXTENSIVE CLOUD DECK SHIFTS EAST TONIGHT...SOME CLEAR TO PARTLY CLOUDY SKIES COULD COMBINE WITH THE LINGERING LOW LEVEL MOISTURE AHEAD OF THE FRONT TO PRODUCE SOME MVFR FOG ACROSS THE AREA...SO MENTIONED THIS ALONG WITH SOME CHANCE FOR LATE NIGHT SHRA AS THE FRONT WORKS TOWARD THE CENTRAL PORTION OF THE AREA. IT IS TOUGH TO SAY AT THIS POINT HOW MUCH SHRA THERE WILL BE SINCE THINGS WILL BE STABLE TO SURFACE BASED PARCELS AND THERE ISN/T MUCH OF A LOW LEVEL JET TO FORCE ANY ELEVATED CONVECTION. SO...AM GENERALLY UNDERWHELMED AT THE POTENTIAL FOR ANY SIGNIFICANT SHRA/TSRA THROUGH THE PERIOD. WINDS WILL SLOWLY VEER OVERALL AS THE FRONT PROGRESSES THROUGH THE AREA. && .PREV DISCUSSION... /ISSUED 1056 AM CDT THU JUL 24 2008/ LATEST VISIBLE IMAGERY SHOWS FAIRLY EXTENSIVE CLOUD COVER ACROSS THE CWFA AT THIS TIME...WITH ACTUALLY SOME FILLING IN OF LOW TO MID CLOUDS OVER THE PAST FEW HOURS OVER MINNESOTA. THINGS ARE CLEARER TO THE EAST WHERE 925-700MB WARM ADVECTION AND BETTER RH VALUES HAVE NOT YET ARRIVES...ALTHOUGH THERE SHOULD BE SOME INCREASE IN MID CLOUDS IN THAT AREA AS THE DAY PROGRESSES. RADAR IMAGERY SHOWS SOME SHRA EXITING INTO FAR NORTHEAST MINNESOTA AT THE CURRENT TIME. THESE WERE FORCED BY THE WARM ADVECTION AND A WEATHER SHORTWAVE THAT IS NOW PUSHING EAST OF THE AREA...AND WERE INITIALLY MORE ROBUST WHILE THEY TAPPED INTO THE ELEVATED INSTABILITY THAT WAS PRESENT OVER WESTERN MINNESOTA. THE MAIN FORECAST ISSUE FOR TODAY AND THIS EVENING IS THE CHANCES FOR CONVECTION ACROSS THE AREA. LATEST OBSERVED DATA AND 12Z NAM AND LATEST RUC SUGGEST LESSER CHANCES FOR PCPN OVER THE AREA...AND HAVE TRIMMED BACK POPS...WHICH WERE ALREADY FAIRLY LOW...TO ACCOUNT FOR THIS. INSTABILITY WILL INCREASE THROUGH THE DAY DUE TO DIURNAL HEATING...ALTHOUGH THAT IS BEING MITIGATED BY THE LOW-MID CLOUDS PRESENT AHEAD OF THE COLD FRONT WHICH STRETCHES FROM THE FAR NORTHWEST CORNER OF THE STATE THROUGH CENTRAL SOUTH DAKOTA. IT APPEARS CLEARING SHOULD BECOME A BIT MORE PREVALENT JUST AHEAD OF THE FRONT DURING THE AFTERNOON...WITH MLCAPES GETTING AOA 1500 J/KG...ALONG WITH 30-35KT OR SO OF DEEP LAYER SHEAR. BY LATE AFTERNOON...THE MLCIN IS EXPECTED TO DIMINISH SUFFICIENTLY FOR SOME STORMS TO INITIATE NEAR THE FRONTAL BOUNDARY...ALTHOUGH THE 12Z NAM AND LOCAL LAPSWRF MODEL RUNS ARE NOT VERY AMBITIOUS IN DEVELOPING MUCH. THE RUC IS A BIT MORE BULLISH...BUT IN ALL CASES IT APPEARS THE BEST CHANCES OF SEEING ANYTHING WILL BE OVER THE WESTERN AND NORTHWESTERN PORTION OF THE FORECAST AREA...WHERE THE BEST COMBINATION OF FORCING AND INSTABILITY WILL BE PRESENT. IN ADDITION...A WEAK SHORTWAVE CAN BE SEEN IN THE WATER VAPOR IMAGERY MOVING THROUGH WESTERN SOUTH DAKOTA...AND IT IS HELPING TO GET SOME WEAK CONVECTION GOING THERE AT THE CURRENT TIME. THIS FEATURE LOOKS LIKE IT WILL WORK INTO THE WESTERN PART OF THE CWFA BY LATE AFTERNOON...WHICH SHOULD FURTHER HELP TO GET A FEW STORMS GOING. ANY STORMS WHICH MANAGE TO DEVELOP COULD PRODUCE MARGINALLY SEVERE HAIL GIVEN THE DECENT MLCAPE VALUES AND SUFFICIENT DEEP LAYER SHEAR FOR SOME MULTI-CELL ORGANIZATION. WILL KEEP SOME LOW POPS INTO THE CENTRAL PART OF THE AREA BY LATE AFTERNOON AND EARLY EVENING...BUT CHANCES LOOK FAIRLY LIMITED EAST OF A LINE FROM REDWOOD FALLS TO SAINT CLOUD. THE SOUTHERN PART OF THE AREA WILL HAVE A TOUGH TIME AS WELL SINCE THE SOUTH PART OF THE FRONT WILL BE SLOWER TO MOVE EAST...AND IT LOOKS LIKE LOW LEVEL RIDGING WILL PREDOMINATE IN THAT AREA THROUGH THE AFTERNOON. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ TRH mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 340 PM CDT THU JUL 24 2008 .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT SVR WATCH 746 JUST ISSUED RECENTLY FOR PORTIONS OF SOUTHERN SOUTH DAKOTA...INCLUDING STANLEY...JONES AND LYMAN COUNTIES. LAPS DATA CURRENTLY SHOWS 2500-3000 J/KG CAPE WITH NO CAP IN PLACE. RUC ANALYSIS AND WATER VAPOR IMAGERY CONFIRM A WEAK DISTURBANCE OVER SOUTHWESTERN SOUTH DAKOTA AT THIS TIME WITH CONVECTION BEGINNING ACROSS EXTREME SOUTHERN SOUTH DAKOTA. ALSO SEEING CONVECTION BEGINNING ACROSS THE BLACK HILLS. NOT MUCH OF A LOW LEVEL FOCUS FOR DEVELOPMENT BUT PLENTY OF INSTABILITY IN PLACE AND PRESENCE OF UPPER LEVEL WAVE SHOULD MAINTAIN ISO TO WIDELY SCATTERED CONVECTION INTO THE EVENING HOURS. LATER TONIGHT MODELS INDICATING SOME OF THE ACTIVITY IN MONTANA AND NORTHWEST SOUTH DAKOTA TO SLIDE SOUTHEAST INTO CENTRAL SOUTH DAKOTA WHERE BEST INSTABILITY RESIDES. INCREASED POPS SLIGHTLY ACROSS CENTRAL SOUTH DAKOTA FOR THE OVERNIGHT HOURS. THE NORTHEASTERN CWA WILL HAVE A TOUGH TIME HAVING ANY PRECIP OVERNIGHT AND WILL LEAVE LOW CHANCE POPS IN THIS AREA. ON FRIDAY HIGH PRESSURE BEGINS TO BUILD INTO THE DAKOTAS WITH LOWERING DEWPOINTS AND INCREASING NORTHERLY WINDS. WILL MORE THAN LIKELY SEE WINDS IN THE BREEZY CATEGORY ACROSS THE EASTERN CWA DURING THE AFTERNOON HOURS. HIGH PRESSURE REMAINS IN THE AREA THROUGH SATURDAY WITH ANOTHER AREA OF LOW PRESSURE TAKING SHAPE ACROSS THE HIGH PLAINS/NORTHERN ROCKIES. THIS LOW SLOWLY SHIFTS EAST BY SATURDAY EVENING BRINGING ANOTHER CHANCE FOR SHOWERS AND THUNDERSTORMS TO MAINLY WESTERN AND CENTRAL SOUTH DAKOTA. .LONG TERM...SUNDAY THROUGH THURSDAY FAIRLY ACTIVE EXTENDED PORTION OF THE FORECAST WITH FOUR DIFFERENT SHORT WAVES MOVING ACROSS THE REGION. THE GFS STARTS THE PERIOD WITH THE NORTHERN PLAINS UNDER NORTHWEST FLOW ALOFT...WITH A SHORT WAVE DEVELOPING OVER WESTERN NORTH DAKOTA. THIS WAVE SLIDES ACROSS OUR EASTERN COUNTIES ON SUNDAY. THE NAM12 ALSO SHOWS THE NORTHERN PLAINS UNDER NORTHWEST FLOW ALOFT...HOWEVER THE SHORT WAVE PASSES OFF TO OUR SOUTHWEST...LEAVING THE CWA DRY. HAVE MADE MINOR CHANGES TO THE WX/POP GRIDS FOR SUNDAY. ANOTHER WAVE RIDES THE UPPER LEVEL RIDGE ON SUNDAY NIGHT...AND LOOKS TO CLIP OUR EASTERN COUNTIES. UPPER LEVEL RIDGE BECOMES SLIGHTLY ZONAL BEHIND THE LAST SHORT WAVE. A WEAK MID LEVEL TROF AXIS PUSHES THROUGH ON TUESDAY NIGHT WITH ANOTHER CHANCE FOR CONVECTION. TEMPERATURES IN THE EXTENDED ARE A BLEND OF PREVIOUS FORECAST/HPC GUIDANCE/12Z MEX GUIDANCE. && .AVIATION... KATY AND KPIR MAY SEE THUNDERSTORMS LATE THIS AFTERNOON/EARLY EVENING...ALTHOUGH CONFIDENCE IS LOW SO HAVE VCTS MENTIONED KPIR AND JUST CB IN KATY. AN UPPER LEVEL OVER EASTERN MONTANA WILL BRING VCTS THIS EVENING. RATHER DIFFICULT TO TIME THUNDERSTORM ACTIVITY SO HAVE MENTIONED VCTS...BEGINNING AT KMBG BY 04Z. THUNDERSTORM ACTIVITY WILL END BY FRIDAY MORNING WITH VFR CONDITIONS EXPECTED BY FRIDAY AFTERNOON. DEPENDING ON WITH THE THUNDERSTORMS END...SOME TAF SITES MAY SEE BR DURING THE MORNING HOURS. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ SHORT TERM...TMT LONG TERM...SD AVIATION...SD WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE ABERDEEN SD 1147 AM CDT THU JUL 24 2008 .UPDATE...REST OF TODAY RATHER DIFFICULT FORECAST TODAY CONCERNING HIGH TEMPS AND PRECIP POTENTIAL. STRATUS DECK HANGING IN TOUGH ACROSS THE EASTERN CWA BUT BREAKS/EROSION HAS BEEN NOTED ON VISIBLE SATELLITE OVER THE PAST HOUR OR TWO. NAM40 925 RH FIELDS INDICATE DRYING IN THIS LAYER FROM NORTH TO SOUTH INTO THE AFTERNOON HOURS. 15Z GFS LAMP GUIDANCE INDICATES BKN CONDITIONS HANGING ON INTO THE AFTERNOON FOR THE EASTERN CWA...WHICH IS A BIT LONGER THAN THE 13Z DATA SHOWED. HIGH TEMPS HAVE ALSO DROPPED A FEW DEGREES IN THE 15Z LAMP GUIDANCE. HAVE LOWERED HIGHS JUST A COUPLE DEGREES BUT STILL BELIEVE THERE WILL BE ENOUGH SUN THIS AFTERNOON TO ALLOW TEMPS TO REBOUND. FURTHER MODIFICATIONS MAY BE NEEDED TO TEMPS IN A COUPLE HOURS BASED ON SATELLITE TRENDS. 850 MB TEMPS ALSO INCREASE A BIT INTO THE AFTERNOON HOURS...ALTHOUGH MIXING IS MINIMAL. THUNDERSTORM POTENTIAL SEEMS LIMITED ALSO AS THE AREA WITH THE MOST MODEL PROGGED INSTABILITY THIS AFTERNOON IS ALSO THE SAME AREA WHERE CLOUD COVER IS EXPECTED TO HANG ON THE LONGEST...THEREFORE THIS INSTABILITY MAY NOT EVEN BE REALIZED. WILL KEEP LOW POPS IN THE FORECAST FOR THE AFTERNOON. && .PREV DISCUSSION... .SHORT TERM...TODAY THROUGH 00Z SUNDAY MAIN FCST CHALLENGE FACING THE SHORT TERM IS PCPN CHANCES AGAIN TODAY THROUGH FRIDAY MORNING. LATEST MSAS ANLYS SHOWS SFC BOUNDARY DRAPED NW-SE ACROSS WRN PART OF THE CWA...WITH ONLY TELLING DIFFERENCE IS THE L-M50 DWPTS LOCATED ACROSS THE NW PART OF SD. AREAS OF LOW STRATUS/FOG IS SETTING UP UNDER TROF AXIS WHERE MIXING WINDS ARE MINIMAL. HAVE INSERTED SOME PATCHY FOG WORDING FOR THIS MORNING ACROSS ALL THE CWA TO ACCOUNT FOR THIS. ATTENTION THEN TURNS TOWARD THIS AFTERNOON. MODELS ALL AGREE ON 85H/925H BOUNDARY REMAINING PROGRESSIVE ACROSS THE NORTH...WHILE HANGING UP ACROSS SRN SD BY 00Z. 5H WAVE THAT IS CURRENTLY TRACKING ACROSS MT WILL INTERSECT THE SFC/LOW LEVEL BOUNDARIES DURING PEAK HEATING ACROSS THE EAST...AND THERE SHOULDN`T BE THE CONVECTIVE DEBRIS CLOUDS IN PLACE SIMILAR TO YESTERDAY...AND WITH DWPTS ALREADY IN THE MID 60S...AND DWPTS IN THE LOWER 70S IN PLACE ACROSS PARTS OF NERN NEB...THE MECHANISM SHOULD BE RESET FOR CONVECTIVE DEVELOPMENT LATER THIS AFTERNOON. HOWEVER...WILL HAVE TO SEE HOW MUCH OF A ROLE THE LOW CLOUDS/STRATUS PLAY UNDER TROF AXIS...AND WHETHER OR NOT THEY CAN BE MIXED OUT. LATEST RUC SHOWS THAT 7H THETA-E DOWNGLIDE REMAINS IN PLACE THROUGH 18Z FOR MUCH OF THE CWA...WITH WAA RETURNING TO THE WEST LATER IN THE AFTN PER THE 06Z NAM12 SOLN. BY 00Z FRIDAY...NAM12 SHOWS AREA OF BEST LI`S LOCATED ALONG AND JUST AHEAD OF NE-SW DRAPED SFC BOUNDARY...WITH LI`S TO -8...ALONG WITH MOST UNSTABLE CAPES FROM 1500 TO 3000 J/KG. HAVE TRIED TO ORIENT POPS ALONG SFC BOUNDARY FOR LATER THIS AFTERNOON THROUGH THE NIGHT. WITH RESPECT FOR THE OVERNIGHT HOURS...MODELS AGREE ON PRESSURE RISES ON THE 305-315K LAYERS...ALONG WITH SPEC HUMIDIES DECREASING ACROSS MY NW CWA. THETA-E ANLYS POINTS TO DOWNGLIDE AND DRYING NOTED IN THE RH FIELDS. HAVE REMOVED MENTION OF POPS ACROSS THE NW FOR THE OVERNIGHT HOURS ON ACCOUNT OF THIS. OVERALL...VERY DIFFICULT AND COMPLEX CONVECTIVE FCST SETTING UP FOR TODAY...AND WILL BE HIGHLY DEPENDANT UPON LOCATION OF SFC BOUNDARY AND TIMING OF 5H/7H WAVES. THERE IS SOME CONCERN FOR FRIDAY AS THE NAM SHOWS SFC BOUNDARY REMAINING STALLED ACROSS SRN SD...ALLOWING MORE CONVECTIVE DEVELOPMENT TO TAKE PLACE LATER IN THE AFN. THE GFS REMAINS MORE PROGRESSIVE WITH THIS FEATURE...PUSHING IT OUT OF STATE DURING THE DAY FRIDAY...WHICH ALLOWS COOLER/DRY CANADIAN HIGH PRESSURE TO SETTLE IN FOR THE BEGINNING OF THE WEEKEND. GIVEN THE NEARLY ZONAL FLOW SETTING UP ALOFT AND THAT FLOW REMAINS NEARLY CROSSWISE TO SFC FRONTAL POSITION...HAVE OPTED WITH THE GFS SOLN AND KEPT PCPN OUT OF FCST FOR FRIDAY. TEMP WISE...THINK THAT TODAY WILL BE WARMEST DAY OF THE SHORT TERM...WITH DECENT SUNSHINE PROVIDED THAT LOW CLOUDS/STRATUS BURN OFF BY 15Z. DIDN`T GO REALLY WILD WITH HEATING AS AMPLE LOW LEVEL MOISTURE WILL ABSORB SOME OF THE HEATING ENERGY...BUT SHOULD PROVE TO BE A MUGGY DAY...ESPECIALLY ACROSS THE EAST. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY 00Z EC/GFS OPERATIONAL SOLUTIONS STILL SHOWING REASONABLY SIMILAR UPPER LEVEL AND SURFACE SOLUTIONS. OVER THIS CWA...MUCH OF THE EXTENDED FORECAST IS A PERIOD OF WEAK UPPER LEVEL RIDGING WITH STEERING FLOW PREDOMINANTLY FROM THE WNW. IN THE LOW LEVELS...HIGH PRESSURE IS PARKED OVER THE UPPER MISSISSIPPI RIVER VALLEY WITH THE WESTERN HALF OF THE CWA IN SERLY RETURN FLOW WHILE THE EASTERN HALF IS EITHER LIGHT AND VARIABLE WINDS OR WINDS OUT OF THE NORTHEAST. BEST CHANCES FOR MEASURABLE PRECIP OVER THE CWA CONTINUES TO EXIST SATURDAY NIGHT AND AGAIN MONDAY/MONDAY NIGHT...SATURDAY NIGHT IN THE FORM OF AN MCC MEATBALL ORIGINATING OVER EASTERN MONTANA/SWRN NODAK AND PROPAGATING SEWD THROUGH THIS CWA...AND MONDAY/MONDAY NIGHT IN THE FORM OF CONVECTION GOING UP ALONG AND AHEAD OF A SYNOPTIC SCALE COLD FRONTAL BOUNDARY PROGGED TO WORK THROUGH THE NORTHERN PLAINS STATES. NO CHANGES MADE TO MAX/MIN T GRIDS AS...THEY APPEAR SPOT ON WHEN COMPARED WITH 00Z LOW LEVEL THERMAL PROGS OF THE EC AND GFS MODELS. && .AVIATION... LOW CLOUDS...RANGING FROM 300 TO 1400 FEET WILL SLOWLY GIVE AWAY TO MID/HIGH CLOUDS AOA 12K FEET AGL. VISIBILITIES WILL ALSO SLOWLY INCREASE THIS AFTERNOON WITH KPIR THE LAST TAF SITE REPORTING IFR VISIBILITY. EXPECT ALL TAF SITES TO BE REPORTING MVFR CONDITIONS BY 18Z...WITH SOME SITES SEEING VFR. KATY AND KPIR MAY SEE THUNDERSTORMS LATER THIS AFTERNOON SO EXPECT THESE TWO TERMINALS TO BEGIN CARRYING SOME SORT OF CONVECTION MENTION /EITHER CB OR VCTS/ IN THE LATE AFTERNOON/EARLY EVENING TIME FRAME. WINDS WILL CONTINUE TO BE LIGHT AND VARIABLE THIS AFTERNOON. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...TMT SHORT TERM...HINTZ LONG TERM...DORN AVIATION...SD WEATHER.GOV/ABERDEEN sd