AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE PHOENIX AZ 1255 PM MST WED AUG 13 2008 SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA FORECAST DISCUSSION .UPDATE...UPDATED AVIATION SECTION. .SYNOPSIS... A LOW PRESSURE SYSTEM WITH INCREASING HUMIDITY AND CLOUDS FROM THE SOUTHEAST WILL RESULT IN SOMEWHAT LOWER TEMPERATURES TODAY...AND AT LEAST A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON THROUGH THURSDAY. RELATIVELY DRIER AIR FROM THE NORTHEAST IS EXPECTED TO RESULT IN SOMEWHAT WARMER WEATHER AGAIN FRIDAY AND CONFINE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO THE HIGHER TERRAIN. THERE IS ANOTHER CHANCE OF SHOWERS AND THUNDERSTORMS IN SOUTH-CENTRAL ARIZONA MAINLY EAST OF PHOENIX SATURDAY AFTERNOON AND EVENING. OTHERWISE...DRIER AIR FROM THE NORTHEAST IS EXPECTED TO CONFINE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS TO EAST OF THE GREATER PHOENIX AREA THIS WEEKEND AND EARLY NEXT WEEK. && .DISCUSSION... KPSR SOUNDING FROM THIS MORNING SHOWS A SIGNIFICANT INCREASE IN PWATER OVER THE PAST 24 HOURS...UP FROM 1.10" TUESDAY TO 1.52" TODAY. FCST SOUNDINGS INDICATE A DEEP LAYER OF MOISTURE WILL CONTINUE TO INCREASE OVER SOUTHEAST CA AND ARIZONA AS THE DAY WEARS ON. MEANWHILE...THE UPPER LEVEL LOW RESPONSIBLE FOR THE SOUTHERLY PUSH OF MOISTURE INTO THE REGION WILL CONTINUE TO MARCH NORTHWARD UP BAJA AND ROTATE THROUGH SOUTHEAST CA AND SOUTHWESTERN AZ TODAY/TONIGHT. SAT AND RADAR TRENDS THIS MORNING SHOW LIGHT SHOWERS OVER OUR WESTERN ZONES...AND HAVE INCREASED POPS TO LOW END CHANCE WORDING FOR THE REST OF TODAY. MEANWHILE...A QUICK LOOK AT NAM/GFS/RUC ALL SHOW UPPER LEVEL DIFFLUENCE OVER MUCH OF SOUTH-CENTRAL AZ FROM ABOUT 00-12 UTC (OVERNIGHT TONIGHT) WHILE A VORT LOBE ASSOCIATED WITH THE MAIN LOW MOVES SOUTH TO NORTH ACROSS THE CENTRAL CWA. HAVE INCREASED THE POPS FOR A CHANCE OF SHOWERS AND THUNDERSTORMS FROM MARICOPA COUNTY EASTWARD BETWEEN 00-06 UTC...AND ALSO INCREASED POPS OVERNIGHT FOR THE LOWER DESERTS...INCLUDING THE GREATER PHX AREA...FROM 06-12 UTC AS THESE WOULD BE DYMAMICALLY DRIVEN SHOWERS/TSTORMS RATHER THAN THE TYPICAL THERMALLY DRIVEN ONES WE SEE THIS TIME OF YEAR. && .AVIATION... LOW PRESSURE SYSTEM MOVING ALONG THE BAJA/SRN CA COAST RESPONSIBLE FOR SPREADING MID/HIGH LEVEL CLOUDS ACROSS THE AREA. SURFACE MOISTURE LEVELS ARE ALSO UP. THE LOW PRESSURE SYSTEM WILL INTERACT WITH ALL THE MOISTURE AND CAUSE SHOWERS AND THUNDERSTORMS TO DEVELOP ACROSS THE SOUTHWEST CONUS THIS AFTERNOON INTO THIS EVENING. ONSET WILL BE DELAYED DUE TO THE CLOUD COVER. AREA MOST LIKELY TO BE ACTIVE WILL BE SOUTHEAST CALIFORNIA. STILL UNCERTAINTY AS TO THE COVERAGE OF CONVECTION FOR THIS EVENING AND WILL THEREFORE HOLD WITH CB GROUP IN AREA TAFS EXCEPT FOR KIPL /VCTS/. COULD SEE SOME SHOWERS CONTINUE THROUGH THE OVERNIGHT HOURS ACROSS THE AREA. THURSDAY ALSO LOOKS TO BE CONVECTIVELY ACTIVE ALL AREAS WITH TSTM ENHANCEMENT SHIFTING TO ERN AZ. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... TODAY AND THURSDAY... INCREASING RH FROM A LARGE TROPICAL-LIKE SYSTEM IN MEXICO WILL LEAD TO A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS BOTH DAYS. TEMPERATURES WILL LIKELY REMAIN NEAR NORMAL. FOR THE UPCOMING WEEKEND... THE LOW PRESSURE SYSTEM WILL DRIFT TO THE NORTHWEST...AWAY FROM ARIZONA AND SOUTHEAST CALIF. AT THE SAME TIME...AN AREA OF HIGH PRESSURE AND DRIER AIR WILL SPREAD ACROSS ARIZONA AND NEVADA && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...WANEK AVIATION...INIGUEZ FIRE WEATHER...SIPPLE az AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 236 PM MDT WED AUG 13 2008 .SHORT TERM... (TONIGHT AND THURSDAY) SHORT TERM CONCERNS INCLUDE STRENGTH AND COVERAGE OF STORMS THIS EVENING AND AGAIN TOMORROW WITH COLD FRONT MOVING ACROSS THE PLAINS. CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS INDICATING WEAK TO MODERATE WESTERLY FLOW ALOFT ACROSS THE STATE AS UPPER LEVEL RIDGING PERSISTS ACROSS THE SOUTHERN HIGH PLAINS AND DESERT SW AND INTO THE SOUTHERN GREAT BASIN WITH A STRONG UPPER LOW DIVING ACROSS SOUTHERN SASKATCHEWAN EJECTING A FEW SHORT WAVES ACROSS THE NORTHERN TIER OF STATES ATTM. WATER VAPOR IMAGERY ALSO INDICATING MINOR WAVES EMBEDDED IN THE FLOW MOVING ACROSS SOUTHERN WYOMING AND CENTRAL COLORADO ATTM. AT THE SFC...LEE TROUGH IS CURRENTLY DEEPENING ACROSS THE EASTERN PLAINS AHEAD OF MINOR WAVE...WITH CURRENT DEW PTS IN THE 50S TO LOWER 60S ACROSS THE FAR EASTERN PLAINS AND WESTERN KANSAS. DEW PTS HAVE AGAIN TANKED ACROSS THE MTS AND IMMEDIATE ADJACENT PLAINS WITH READINGS IN THE 20S TO LOWER 40S ATTM. REGIONAL RADARS INDICATING MAINLY ISOLATED SHOWERS AND THUNDERSTORMS MOVING ACROSS THE HIGHER TERRAIN ATTM. TONIGHT...EMBEDDED WAVE TO CONTINUE TO MOVE ACROSS THE SOUTHERN EASTERN COLORADO THIS EVENING HELPING TO BREAK CAP AND AIDING IN THUNDERSTORM DEVELOPMENT ACROSS THE PLAINS. HAVE KEPT SCATTERED POPS ACROSS THE FAR EASTERN PLAINS THROUGH THE LATE EVENING WITH ISOLATED POPS THROUGH THE OVERNIGHT HOURS. WITH LOW LEVEL MOISTURE REMAINING IN PLACE ACROSS THE FAR EASTERN PLAINS YIELDING CAPES BETWEEN 1500-2500 AND BULK SHEARS BETWEEN 30-35KTS...COULD SEE A FEW STRONG TO SEVERE STORMS DEVELOPING ONCE AGAIN WITH UP TO GOLF BALL SIZED HAIL AND DAMAGING WINDS IN EXCESS OF 60 MPH THE MAIN THREATS. ACROSS THE MTS AND I-25 CORRIDOR...HAVE KEPT ISOLATED POPS THROUGH THE EARLY EVENING AND WITH THE DRY LOWER LEVELS WILL CONTINUE TO SEE MAINLY VIRGA AND GUSTY WINDS UP 50 MPH. HAVE ENDING PRECIP ACROSS THE HIGHER TERRAIN AFTER MIDNIGHT...THOUGH WILL SEE SOME INCREASING CLOUDS ACROSS THE CENTRAL MTS AHEAD OF NORTHERN TIER SHORT WAVE MOVING ACROSS THE NORTHERN ROCKIES. THURSDAY...ABOVE MENTIONED SHORT WAVE PROGGED TO CONTINUE TO MOVE ACROSS THE NORTHERN ROCKIES EARLY THURSDAY MORNING AND INTO SOUTHWESTERN NEBRASKA AND NORTHWESTERN KANSAS THROUGH THE AFTERNOON. PASSING WAVE SENDS BACK DOOR FRONT TO THE PALMER DVD AROUND 15Z AND CONTINUES ACROSS THE REST OF THE PLAINS AND IS BACK UP ACROSS THE EASTERN MTS BY EARLY AFTERNOON. GUSTY NORTH TO NORTHEAST WINDS BEHIND FRONT BECOMES MORE EASTERLY ACROSS THE PLAINS THROUGH THE AFTERNOON...AND HAVE GONE WITH SCATTERED POPS ACROSS THE PALMER DVD THROUGH THE EASTERN MTS AND RATON MESA REGION THROUGH THE AFTERNOON. BEST LIFT ASSOCIATED WITH WAVE AND MOISTURE PROGGED TO REMAIN ACROSS THE FAR EASTERN PLAINS...WHERE COULD SEE A FEW SEVERE STORMS DEVELOPING ONCE AGAIN. HAVE GONE AT OR BELOW COOLEST GUIDANCE FOR TEMPS WITH HIGHS BEING REACHED ACROSS THE PLAINS BY THE LATE MORNING WITH LOWERING TEMPS THROUGH THE AFTERNOON AS COOLER AIR CONTINUES TO MOVE ACROSS THE REGION. .LONG TERM... (FRIDAY THROUGH WEDNESDAY) ...BIG WEATHER CHANGES STILL ON TRACK FRI THROUGH THE WEEKEND... ...MINOR ACCUMULATING SNOW REMAINS POSSIBLE VERY HIGH TERRAIN FRI-SAT... FRIDAY...THIS CONTINUES TO BE THE BEGINNING OF THE BIG CHANGES... HOWEVER...THERE IS SOME SUBTLE 12Z/13 MODEL DIFFERENCES WITH THE APPROACHING LOW PRESSURE SYSTEM`S TIMING AS IT MOVES IN FROM THE NORTH. THE NAM-WRF IS A LITTLE SLOWER WITH THE UPPER LOW AND THE GFS IS A LITTLE FASTER WITH THE UPPER FEATURE. OVERALL...THE SURFACE COLD FRONT SHOULD BE THROUGH MUCH OF SOUTHERN CO WITH RELATIVELY COOL AND MOIST UPSLOPE EASTERLY FLOW ACROSS THE EASTERN 1/2 OF CO. JUST WAITING FOR THE UPPER LEVEL SYSTEM AND SYNOPTIC SCALE ASCENT. HAVE TWEAKED TEMPERATURES UP A DEGREE OR TWO IN THE CHANCE THE NAM-WRF SLOWER SOLUTION WOULD VERIFY. KEEP THE "SLIGHT CHANCE" AND "CHANCE" POPS FOR THUNDERSTORMS GIVEN PLENTY OF MOISTURE AND INSTABILITY IN PLACE. FRIDAY NIGHT THROUGH SATURDAY NIGHT...THESE FORECAST PERIODS SEEM TO HAVE THE RELATIVELY GREATEST POTENTIAL FOR WIDESPREAD QPF ACROSS MUCH OF CO. THE UPPER LEVEL LOW AND ASSOCIATED JET STREAK SLIDES SOUTH SOUTHEASTWARD INTO THE CENTRAL ROCKIES. AGAIN...THERE ARE SOME TIMING ISSUES OF THE LOW EXITING CO WITH THE GFS BEING THE FASTEST SAT AND THE NAM-WRF/ECMWF HANGING IT BACK FURTHER WEST. HAS PLENTY OF IMPLIED SYNOPTIC SCALE ASCENT NOTED IN THE Q-G AND ISENTROPIC(310K/305K) ANALYSES. IT JUST DEPENDS ON THE TRACK AND TIMING. A FAIRLY DEEP MOISTURE LAYER SHOULD EXIST BY LATE FRIDAY NIGHT THROUGH AT LEAST SATURDAY EVENING WITH A RELATIVELY BROAD AREA OF PRECIPITATION/QPF DEVELOPING ACROSS AT LEAST THE EASTERN 1/2 OF CO. STRATUS/FOG WILL CERTAINLY BE COMMON ACROSS OUR EASTERN CO MOUNTAINS AND SOUTHEAST CO PLAINS LATE FRIDAY NIGHT THROUGH SATURDAY. WHAT KIND OF PRECIPITATION WILL IT BE... FIRST...SURFACE PARCELS SHOULD BE RATHER STABLE ACROSS THE SOUTHEASTERN CO PLAINS SATURDAY AND SATURDAY NIGHT...AND EVEN THE 700-500MB STATIC STABILITIES ARE PRETTY STABLE(E.G. 5-6 C/KM)...HOWEVER...YOU COULDN`T RULE OUT ONE OR TWO LIGHTNING STRIKES DUE TO THE POTENTIAL OF THE MORE "UP- RIGHT" MOIST CONVECTION COULD COME OFF THE CONTINENTAL DIVIDE INTO SOUTHEAST CO. ALONG THE CONTINENTAL DIVIDE AND SAN LUIS VALLEY...THE 700-500MB STATIC STABILITIES ARE PROGGED TO BE 7-8.5 C/KM. FOR THE SOUTHEASTERN CO MOUNTAINS/PLAINS... I KEPT THE PRECIPITATION STABLE(E.G. R/S) WITH A "SLIGHT CHANCE" FOR T(THUNDER) AND FOR AROUND THE CONTINENTAL DIVIDE MORE MOIST CONVECTIVE(E.G. RW/TRW). CURRENTLY...NO LIGHTNING SHOWING UP WITH THE LOW SPINNING JUST NORTH OF MONTANA/NORTH DAKOTA. THERE IS STILL THE POTENTIAL FOR ACCUMULATING SNOW ACROSS THE MOUNTAIN PEAKS...ESPECIALLY THE SAWATCH/MOSQUITO RANGE(CENTRAL MOUNTAINS) AND PIKES PEAK WITH WET BULB ZERO/FREEZING LEVEL HEIGHTS 11K-13K FT MSL. SNOW LEVELS COULD VARY PER DAYTIME/NIGHTTIME AND MOIST CONVECTION INTENSITY. IF EVERYTHING SETS UP JUST RIGHT...THERE COULD BE 1-8 INCHES ACROSS THE CENTRAL MOUNTAINS AND PIKES PEAK SUMMIT BY SATURDAY EVENING. WITH THE WEATHER SYSTEM`S 70-90KT UPPER LEVEL JET STREAK OVER CO...WINDS MIGHT BE BRISK FOR THE MOUNTAIN PEAKS FRIDAY THROUGH THE WEEKEND. HIGH TEMPERATURES SATURDAY WILL BE 15-30 DEGREES BELOW AVERAGE AUGUST READINGS. IT SHOULD BE STRESSED TO THE PUBLIC THAT IF THEY HEADING INTO THE MOUNTAINS...ESPECIALLY MOUNTAIN PEAK HIKING...TO REMAIN AWARE OF THE WEATHER FORECASTS AND TAKE THE PROPER WINTER EQUIPMENT. THIS IS...GENERALLY...A FALL-LIKE WEATHER SYSTEM AND PEOPLE TEND TO GET FOULED BY CURRENT WARM WEATHER ONLY TO BE CAUGHT OFF GUARD WHEN SIGNIFICANTLY COLDER TEMPERATURES AND SNOW OCCURS THE NEXT DAY. SUNDAY THROUGH WEDNESDAY...THE GENERALLY TREND WILL BE FOR THE CLOSED LOW TO DRIFT EASTWARD SUNDAY OR MONDAY. THESE SYSTEM ARE ALWAYS TOUGH AS THEY BECOME ORPHANED FROM THE MAIN JET STREAM FLOW. A MODERATING AND RELATIVELY DRYING TREND IS STILL IN THE OFFING NEXT WEEK WITH WESTERN UNITED STATES LARGE RIDGE MOVING BACK INTO THE ROCKIES. THIS WOULD SUPPORT TEMPERATURES APPROACHING SEASONAL AVERAGES AND MAINLY DIURNAL SHOWERS/THUNDERSTORMS OVER THE MOUNTAINS...AND NEARBY VALLEYS AND I-25 CORRIDOR. METZE && .AVIATION... ISOLATED TO SCATTERED TSRA EXPECTED ACROSS THE HIGHER TERRAIN AND EASTERN PLAINS TONIGHT WITH BEST COVERAGE ACROSS THE FAR EASTERN PLAINS WHERE ISOLATED MVFR VIS AND CIGS WILL BE POSSIBLE NEAR STORMS. OTHERWISE VFR CONDITIONS EXPECTED WITH ANY STORMS THAT FIRE ACROSS THE HIGHER TERRAIN AND I-25 CORRIDOR WILL BE HIGH BASED AND PRODUCE GUSTY WINDS TO BETWEEN 40 AND 50 MPH THIS EVENING. COLD FRONT IS EXPECTED TO MOVE ACROSS THE EASTERN PLAINS TOMORROW MORNING WITH GUSTY NORTHERLY WINDS EXPECTED TO DEVELOP BETWEEN 15Z-18Z AT COS AND PUB WITH SCATTERED TSRA DEVELOPING ACROSS THE EASTERN MTS AND ADJACENT PLAINS AFTER 20Z. -MW && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 23/17 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 242 PM MDT TUE AUG 12 2008 .SHORT TERM... (TONIGHT AND WEDNESDAY) ...MAIN SHORT TERM CONCERNS REMAIN COVERAGE AND STRENGTH OF CONVECTION... CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS INDICATING DRY AND MODERATE WESTERLY FLOW ALOFT ACROSS THE REGION WITH A 70KT JET CORE TRANSLATING ACROSS THE GREAT BASIN AND INTO WEST CENTRAL COLORADO ATTM. AT THE SFC...A WEAK LOW IS INDICATED OVER EASTERN LAS ANIMAS COUNTY WITH LEE TROUGHING EVIDENT ALONG A LINE FROM NEAR LHX TO JUST EAST OF LIC. CURRENT DEW PTS MAINLY EAST OF THE TROUGH ARE IN THE 50S TO LOWER 60S...WITH GOOD MIXING WEST OF THE TROUGH OWNING TO DEW PTS IN THE MID 30S TO MID 40S ACROSS THE I-25 CORRIDOR WITH READINGS IN THE MID 20S TO MID 30S ACROSS THE HIGHER TERRAIN ATTM. REGIONAL SATELLITE AND RADARS INDICATING ISOLATED STORMS ACROSS NORTH CENTRAL NEW MEXICO WITH CU BUILDING ACROSS THE EASTERN PLAINS ALONG WITH ONE LONE STORM EAST OF LIC ATTM. TONIGHT...MODELS KEEPING MODERATE WESTERLY FLOW ALOFT WITH SOME UVV PROGGED ACROSS THE FAR EASTERN PLAINS AS UPPER JET CONTINUES TO TRANSLATE ACROSS CENTRAL COLORADO THIS EVENING AND INTO THE CENTRAL AND SOUTHERN HIGH PLAINS OVERNIGHT. MODEL SOUNDINGS INDICATING MODEST ELEVATED CAPES ACROSS THE I-25 CORRIDOR WITH CAPES BETWEEN 1000-2500 J/KG ACROSS THE FAR EASTERN PLAINS ATTM. WITH A FEW MORE HOURS OF HEATING...ALONG WITH THE PROGGED UVV AND LIFT ASSOCIATED WITH LEE TROUGH AND ANY OUTFLOWS...HAVE KEPT SCATTERED POPS ALONG WITH RATON MESA AND ACROSS THE FAR EASTERN PLAINS THROUGH THE EVENING WITH ISOLATED POPS CONTINUING THROUGH THE OVERNIGHT...AS MODELS INDICATING A POSSIBLE MCS MOVING INTO WESTERN KANSAS. WITH THE WESTERLY FLOW ALOFT PROVIDING AMPLE SHEAR...COULD SEE A FEW STRONG TO SEVERE STORMS DEVELOPING ACROSS THE EASTERN PLAINS...WITH HAIL UP TO 2 INCHES AND WIND GUSTS IN EXCESS OF 60 MPH POSSIBLE. HAVE KEPT ISOLATED POPS ACROSS THE HIGHER TERRAIN AND I-25 CORRIDOR THIS EVENING...THOUGH WITH THE DRIER AIR AT THE SFC...AM EXPECTING STORMS THAT CAN FIRE WILL PRODUCE MAINLY VIRGA WITH GUSTY WINDS UP TO 50 MPH. WEDNESDAY...DECREASING WEST TO NORTHWEST FLOW PROGGED ACROSS THE REGION AS JET CORE CONTINUES TO SLIDE SOUTH AND EAST OF THE STATE. MODELS INDICATING SOME INCREASE IN MID AND UPPER LEVEL MOISTURE AND UVV ACROSS WESTERN COLORADO ALONG WITH LEE TROUGHING PERSISTING ACROSS THE EASTERN PLAINS AS A SHORT WAVE EJECTING OFF DEEP NORTHERN TIER LOW ACROSS THE NORTHERN ROCKIES. MODELS SOUNDING INDICATE SIMILAR SET TO TODAY WITH DEEP MIXING AND AFTERNOON DEW PTS IN THE 30S TO LOW 40S THE HIGHER TERRAIN AND I-25...WITH BETTER LOW LEVEL MOISTURE EAST OF THE SFC TROUGH ACROSS THE FAR EASTERN PLAINS AND INTO WESTERN KANSAS...WITH LATEST SPC DAY2 OUTLOOK HAVING THIS AREA IN SLIGHT RISK ONCE AGAIN. WITH THAT SAID....HAVE KEPT ISOLATED POPS ACROSS THE AREA WITH BEST COVERAGE ACROSS THE FAR EASTERN PLAINS...THOUGH HAVE NOT ADDED SEVERE WORDING TO THE ZONES ATTM. TEMPERATURES ALOFT ONLY COOL SLIGHTLY AND HAVE KEPT HIGHS AROUND TODAYS READINGS. -MW .LONG TERM... (THURSDAY THROUGH TUESDAY) ...ONE MORE WARM DAY THURSDAY... ...POTENTIAL FOR SIGNIFICANT WEATHER CHANGE FRI-SUN... ...POSSIBLE MINOR SNOW ACCUMULATIONS ON MOUNTAIN PEAKS FRI-SUN... THURSDAY...NORTHWEST FLOW CONTINUES AHEAD OF THE NEXT WEATHER SYSTEM DROPPING INTO THE NORTHERN ROCKIES/NORTHERN PLAINS. PLENTY OF MOISTURE AND INSTABILITY AROUND TO SUPPORT THE CURRENT THUNDERSTORM FORECAST AND NEAR AVERAGE TEMPERATURES. FIRST WEAK COLD FRONTAL PASSAGE MOVES THROUGH EASTERN CO THURSDAY AFTERNOON. I DIDN`T MUCH CHANGES TO THIS FORECAST PERIOD. FRIDAY THROUGH SUNDAY...SHORT AND MEDIUM RANGE MODELS ARE FAIRLY CONSISTENT WITH SOME STOUT WEATHER CHANGES FRIDAY THROUGH AT LEAST THE WEEKEND. OBVIOUSLY...THE DEVIL IS IN THE DETAILS. GFS... NAM-WRF...DGEX...AND ECMWF ALL HAVE SIGNIFICANT 500MB HEIGHT CHANGES...588 DAM TO POSSIBLY 576-579 DAM...BY LATE THIS WEEK AND WEEKEND. LARGE LOW MOVES INTO CO AND CENTRAL PLAINS POSSIBLY FRIDAY. ASSOCIATED 1020-1025MB HIGH PRESSURE SYSTEM MOVES INTO THE NORTHERN ROCKIES/NORTHERN PLAINS WITH THE LEADING EDGE OF MUCH COLDER AIR MASS...E.G. COLD FRONT...MOVES INTO THE EASTERN 1/2 OF CO FRIDAY. WIDESPREAD STRATUS/FOG COULD BE POSSIBLE. ALSO...Q-G ANALYSES ARE SUGGESTING SYNOPTIC SCALE ASCENT WITH THE WEATHER SYSTEM FRIDAY AND FRIDAY NIGHT. CURRENTLY HAVE LOW "CHANCE" POPS AND THEY COULD INCREASED...BUT WILL GIVE IT A LITTLE MORE TIME SINCE THIS IS OUT IN DAY 3/DAY 3 NIGHT FORECAST PERIODS. MODEL MOS GUIDANCE HAS TAKEN HIGH TEMPERATURES INTO THE 70S ACROSS EASTERN CO AND I WOULDN`T BE SURPRISED TO SEE TEMPERATURES NOT EVEN MAKE IT INTO THE 70S ACROSS SOUTHEASTERN CO PLAINS IF THE STRATUS/FOG DEVELOPS AND LOW LEVEL COLD AIR ADVECTION CONTINUES. THE RAW NAM-WRF DIGITAL FORECAST HAS HIGHS IN THE 50S ACROSS THE PALMER DIVIDE AND 60S ACROSS SOUTHEASTERN CO FRIDAY. WET BULB ZERO/FREEZING LEVEL HEIGHTS ARE PROGGED TO BE 10K-12K FT MSL ACROSS THE CENTRAL MOUNTAINS INCLUDING PIKES PEAK...SO THE POTENTIAL FOR MINOR ACCUMULATING SNOW ACROSS THE MOUNTAIN PEAKS WILL BE POSSIBLE. CONFINED ANY THUNDERSTORMS TO BE ACROSS THE CONTINENTAL DIVIDE/SAN LUIS VALLEY AS THE MORE UNSTABLE AIR MASS SHOULD BE IN PLACE IN THAT AREA FRIDAY THROUGH THE WEEKEND. HIGH TEMPERATURES FRIDAY THROUGH THE WEEKEND WILL LIKELY BE SOME 15-25 DEGREES COLDER THAN AVERAGE AUGUST TEMPERATURES AND I WOULDN`T BE SURPRISED TO SEE SOME AREAS 30 DEGREES BELOW "NORMAL" TEMPERATURES. TEMPERATURES ACROSS THE HIGH TERRAIN MAY ONLY GET INTO THE 30S/40S THROUGH THE WEEKEND...AND PEOPLE HEADING INTO THE MOUNTAINS SHOULD MONITOR LATER WEATHER FORECASTS AND DRESS APPROPRIATELY IF HEADING INTO THE HIGH COUNTRY/MOUNTAIN PEAKS. I WENT AHEAD AND ADJUSTED TEMPERATURES DOWN QUITE A BIT BASED ON SURROUNDING OFFICES TO THE NORTH AND CONSISTENT MOS GUIDANCE. BESIDES THE RELATIVELY COLDER TEMPERATURES AT THE MOUNTAIN PEAKS...WINDS WILL BECOME BRISK TO WINDY FRIDAY AFTERNOON AND NIGHT AS 30-40KT MOUNTAIN TOP WINDS DEVELOP WITH THE UPPER LEVEL JET STREAK OVERHEAD. MONDAY AND TUESDAY...ENSEMBLE DATA SUGGEST THE LARGE RIDGE TO THE WEST WILL SLOWLY MOVE BACK INTO THE CENTRAL ROCKIES WITH MODERATING TEMPERATURES AND POSSIBLY DRYING OUT...BUT THE TYPICAL DIURNAL SHOWERS/THUNDERSTORMS WILL BE THE GENERAL RULE OR THAN THE EXCEPTION. HOWEVER...THE POTENTIAL CLOSED LOW BECOMES ORPHANED FROM THE MAIN JET STREAM FLOW AND MIGHT MEANDER AROUND THE CENTRAL ROCKIES AND CENTRAL PLAINS INTO EARLY NEXT WEEK. METZE && .AVIATION... ISOLATED TO SCATTERED TSRA EXPECTED ACROSS THE HIGHER TERRAIN AND EASTERN PLAINS TONIGHT AND AGAIN TOMORROW AFTERNOON...WITH BEST COVERAGE ACROSS THE FAR EASTERN PLAINS WHERE ISOLATED MVFR VIS AND CIGS WILL BE POSSIBLE NEAR STORMS. OTHERWISE VFR CONDITIONS EXPECTED WITH ANY STORMS THAT FIRE ACROSS THE HIGHER TERRAIN AND I-25 CORRIDOR WILL BE HIGH BASED AND PRODUCE GUSTY WINDS TO BETWEEN 40 AND 50 MPH THIS EVENING. -MW && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 23/17 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 300 PM EDT TUE AUG 12 2008 ...STRONG TO SEVERE STORMS AND LOCALLY HEAVY RAINFALL ARE POSSIBLE TONIGHT THROUGH WEDNESDAY... .SYNOPSIS... AT 2 PM EDT...IT WAS MOSTLY CLOUDY TO CLOUDY ACROSS THE LOCAL AREA. RADAR INDICATED SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TO MOVE EAST ACROSS THE REGION. AT UPPER LEVELS... LOOKING AT THE BIG PIX...SATELLITE SHOWS TROUGH OVER PAC NW...RIDGE OVER WRN CONUS...A DEVELOPING TROUGH OVER ERN PLAINS/WRN GREAT LAKES ...A TROUGH OVER ERN SEABOARD EXTENDING INTO WRN ATLC AND NEAR ZONAL FLOW OVER CWA. ERN TROUGH WITH H5 LOW OVER NJ/NY COAST WITH TROUGH EXTENDING SWWD INTO GA. THROUGH TOMORROW...CNTRL TROF WILL PHASE INTO ERN TROF AND DEEPEN IMPACTING LOCAL WEATHER. BROAD CYCLONIC FLOW EXISTS FROM MS VALLEY TO S ATLC COAST. SEVERAL IMPULSES IN FLOW AND MOVING EWD AND GUIDANCE SHOWERS THEY ARE LIKELY TO MERGE INTO STRONG SHORTWAVE OVER TN VALLEY OVERNIGHT BEFORE DROPPING SEWD INTO WRN CWA BY 06Z WED. 12Z REGIONAL SOUNDINGS SHOWS THAT AIRMASS HAS MOISTENED UP SIGNIFICANTLY IN LAST 24 HR. FOR EXAMPLE TLH,JAX AND BMX WITH 2.28, 2.11 AND 2.09 IN PWAT RESPECTIVELY. AT LOWER LEVELS... SURFACE ANALYSIS/MSAS SHOWED A 1007 MB LOW ACROSS WRN LA WITH A WAVY STATIONARY FRONT ESE CNTRL ALA...CNTRL GA...TO SC BORDER. FRONT WILL BECOME BETTER DEFINED THIS EVENING AS LOW IS FORECAST TO MOVE EAST ALONG IT TO ACROSS WEST CENTRAL AL BY 06Z TO CNTRL AL/GA BORDER BY 12Z WED TO NC COAST BY 18Z. A TRAILING COLD FRONT EXTENDED EWD THRU CENTRAL LA....CNTRL ALA/GA. FRONT EXPECTED TO BE DRAGGED SEWD AND PUSH THROUGH THE CWA LATE WED AFTERNOON INTO EVENING. GFS IS QUICKER IN ORGANIZING AND MOVING THE SYSTEM EAST THAN THE NAM AND SEEMS TO HAVE INITIALIZED BETTER. MODEL SOUNDINGS SHOWS THAT AIRMASSES TO REMAIN MOIST UNTIL LOW MOVES EAST OF CWA. I.E. GFS TAE SOUNDING AT 12Z TUES WITH 2.42 PWAT, 12Z WED WITH 2.23 PWAT DROPPING AT 12Z THURS TO 1.56 PWAT. && .SHORT TERM...(THIS EVENING THROUGH FRIDAY) TONIGHT INTO WED...APPROACH OF SFC LOW/COLD FRONT AND SHORTWAVE TROUGH WILL GENERATE NUMEROUS SHOWERS AND STORMS. THE APPROACHING LOW PRESSURE SYSTEM IS ITS ACCOMPANYING WIND FIELD MAKES THIS A TRICKY FORECAST. LARGELY UNIDIRECTIONAL WSW SFC-H5 FLOW WILL LIMIT SHEAR AND WEAK LAPSE RATES AND ABUNDANT CLOUD COVER WILL INHIBIT INSTABILITY. (NORMALLY IN THE SUMMER THE SITUATION IS REVERSED WITH POOR KINEMATICS AND AMPLE INSTABILITY). ALTHOUGH THE 0-1 KM VERTICAL WIND SHEAR WOULD NORMALLY BE FAVORABLE FOR TORNADOES (NEAR 30 KT)...THE 0-6 KM VERTICAL WIND SHEAR IS MARGINAL AT BEST FROM 30 TO 35 KT. HOWEVER...THE LOCAL AREA WILL BE IN THE WARM SECTOR WITH A 50KT+ 850MB JET FORECAST BY ALL THE NUMERICAL GUIDANCE TO BE IN OUR AL AND GA ZONES BY LATE TONIGHT AND WEDNESDAY MORNING. IF ANY OF THAT 850MB JET WINDS MIXES DOWN...DAMAGING WINDS WILL LIKELY OCCUR. THUS THE ENVIRONMENT MAY FAVOR SHALLOW MESOCYCLONES AND BOWING SEGMENTS. THE SPC HAS INCLUDED OUR GA AND AL ZONES IN A SLIGHT RISK FOR SEVERE STORMS FOR TONIGHT AND EARLY WEDNESDAY. BREEZY WINDS OF 15-20 MPH WITH HIGHER GUSTS EXPECTED AND A LAKE WIND ADVISORY MAY BE NEEDED ON WEDNESDAY DUE TO GUSTINESS. CONCERNS IS RAIN POTENTIAL. FLASH FLOOD WATCH WILL BE ISSUED FOR SOUTHEAST ALABAMA AND SOUTHWEST GEORGIA BEGINNING EFFECTIVE 00Z THIS EVENING. THIS IS A PARTICULARLY TRICKY WATCH TO FORECAST. HOWEVER THE 925-850MB THICKNESS AND MOISTURE ADVECTION SEEMS TO CHARACTERIZE THE EXISTING CONVECTIVE BOUNDARIES THAT CURRENTLY ALIGNED ALONG THE FLORIDA PANHANDLE AND BIG BEND COASTLINE. ESSENTIALLY THIS BOUNDARY IS A LEFT OVER WARM FRONT THAT IS MOVING EVER SO SLOWLY EASTWARD. THE INDIVIDUAL CONVECTIVE ELEMENTS ALONG THE BOUNDARY ARE FOLLOWING THE RUC13 NORTHWESTERLY 500 MB WIND PATTERN. THE AIR IS MUCH DRIER IN THE CENTRAL GULF OF MEXICO. RUC13 FORECASTS INCREASING WEST TO SOUTHWESTERLY MOISTURE ADVECTION AHEAD OF DEVELOPING LOW CENTER NOW OVER LOUISIANA. WHILE LOW LEVEL HIGH PRESSURE REMAINS LOCKED OVER THE EASTERN GOMEX. THIS WILL CREATE A CONDUIT FOR MOVEMENT OF MOIST UNSTABLE AIR FROM THE SOUTHWEST AND WEST TO FOCUS OVER THE FLORIDA PANHANDLE...SOUTHEAST ALABAMA AND SOUTHWEST GEORGIA. THE POTENTIAL EXISTS FOR ECHO TRAINING OVER THESE AREAS AND WILL NEED TO BE MONITORED FOR THE THREAT OF LOCAL FLASH FLOODING. AMOUNTS OF 2 TO 4 INCHES OVER NIGHT WITH LOCALLY HIGHER AMOUNTS ARE POSSIBLE. AN AREA OF PARTICULAR CONCERN WILL BE THE COASTAL URBAN AREAS OF THE FLORIDA PANHANDLE. THE RAIN WILL END FROM NORTHWEST TO SOUTHEAST DURING AFTERNOON AS STRONG DRYING DEVELOPS IN THE MID TO UPPER TROPOSPHERE. THURSDAY... WILL USE NW-SE 20-40 PCT POP GRADIENT AS SE THIRD CWA WILL REMAIN NEAR THE NORTHERN EDGE OF A BAND OF RICH DEEP LAYER MOISTURE. HIGH TEMPERATURES WILL CLIMB TO NEAR AVERAGE THURSDAY. FRIDAY... WITH MOST MOISTURE SOUTH OF CWA...WILL USE A 20-30 PCT N-S POP GRADIENT. .LONG TERM... (FRIDAY NIGHT THROUGH TUESDAY)...THE GFS AND EURO BOTH SHOW A CUTOFF UPPER LOW OVER THE NORTHERN PLAINS FRIDAY NIGHT. THERE ARE SOME DIFFERENCES BETWEEN THE TWO MODELS IN TERMS OF STRENGTH AND POSITION OF THE LOW THROUGH THE EXTENDED PERIOD. THE EURO TRACKS A DEEPER SYSTEM FURTHER TO THE SOUTH AND EAST OF THE GFS SOLUTION WITH THE LOW CENTERED OVER EASTERN IOWA BY LATE TUESDAY. THE GFS TRACKS IT FROM WYOMING TO CENTRAL NEBRASKA DURING THE ENTIRE EXTENDED PERIOD. EITHER WAY...THE NEARLY ZONAL UPPER FLOW AT THE BEGINNING OF THE PERIOD WILL GRADUALLY BE REPLACED BY UPPER RIDGING FROM THE EAST AS THE TROUGH SHARPENS TO OUR WEST. THE PRESSURE PATTERN AT THE SURFACE WILL BE WEAK AND TIME HEIGHT CROSS SECTIONS INDICATE MOST AVAILABLE MOISTURE BELOW 700 MB. WILL SHOW POPS ONLY IN THE LOWER END CHANCE CATEGORY EACH AFTERNOON WITH TEMPS AT OR JUST ABOVE CLIMO. ALSO THE 00Z EURO IS MORE BULLISH ON TRACKING A POSSIBLE TROPICAL SYSTEM ACROSS CUBA MONDAY AND INTO THE SOUTHEAST GULF TUESDAY. WITH THE AXIS OF THE SHARP UPPER TROUGH TO OUR WEST...THIS WILL HAVE TO WATCHED CLOSELY. && .AVIATION...PERIODS OF SHWRS/TSTMS WILL PROGRESS FROM WEST TO EAST ACROSS THE REGION THIS AFTERNOON AND EVENING IN ADVANCE OF A LOW PRESSURE SYSTEM TAKING SHAPE OVER THE ARKLATEX. PREVAILING MVFR CIGS WILL OCNLY LOWER TO IFR IN HEAVIER SHWRS/TSTMS, ALONG WITH IFR VSBYS. WINDS WILL BE FROM THE W-SW 5-10 KTS, BUT WILL BE VRBL/GUSTY INVOF TSTMS. AFTER A BRIEF LULL LATER TONIGHT, ADDITIONAL SHWRS/TSTMS WILL AFFECT THE REGION TOWARD MORNING AND LINGER INTO WEDNESDAY AS THE LOW PRESSURE SYSTEM AND COLD FRONT MOVE ACROSS THE GULF COAST STATES. THE STRONGER TSTMS WILL BE CAPABLE OF PRODUCING STRONG WINDS AND VERY HEAVY RAINFALL. && .MARINE... MID-AFTN BUOY DATA SHOWS WINDS AROUND 15 KNOTS WITH 3-4 FOOT SEAS WELL OFFSHORE...10 TO 15 KNOTS ELSEWHERE. EXPECT WINDS AND SEAS TO SLOWLY AND THEN STEADILY INCREASE THROUGH REST OF TODAY AND INTO TONIGHT. THIS IS VERY UNUSUAL FOR AUGUST. HAVE DIVIDED CWF INTO WRN AND ERN WATERS TO ACCOUNT FOR MORE RAPID INITIATION OF SCEC AND THE SCA CRITERIA. SCA ISSUED FOR WRN WATERS...SCEC ERN WATERS WITH SCA LIKELY TO BE EXTENDED E TONIGHT. WE MAY EVEN HAVE TO ISSUE A HIGH SURF ADVISORY FOR THE FL PANHANDLE TONIGHT AS THE SURF MAY REACH 6 FEET LATE WEDNESDAY AFTERNOON. && .FIRE WEATHER...NO CONCERNS TODAY DUE TO MOIST LOW LEVELS. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 73 86 71 91 / 50 70 40 30 PANAMA CITY 77 85 74 89 / 50 70 40 30 DOTHAN 71 86 69 92 / 70 60 20 20 ALBANY 72 85 68 92 / 70 60 20 20 VALDOSTA 72 86 69 91 / 60 60 20 30 CROSS CITY 75 85 72 87 / 50 60 40 50 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...FLASH FLOOD WATCH. GA...FLASH FLOOD WATCH. FL...FLASH FLOOD WATCH ALL BUT ERN BIG BEND. GM...SMALL CRAFT ADVISORY PANHANDLE WATERS. && $$ AVIATION/FIRE WX...JAMSKI PUBLIC/MARINE...BLOCK LONG TERM...BARRY fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 400 AM EDT TUE AUG 12 2008 ...SEVERE STORMS ARE POSSIBLE LATE TODAY THROUGH WEDNESDAY... ...PERIODS OF HEAVY RAINFALL TODAY AND WEDNESDAY... .SYNOPSIS...WATER VAPOR IMAGERY AND RUC MODEL SHOW 500 MB CLOSED LOW JUST OFF THE NJ AND NY COASTS WITH TROUGHING EXTENDING SW INTO FL. TO THE W...SHORTWAVE TROUGH AND OTHER UPPER DISTURBANCES ARE ACROSS TX...LA...MS AND AL PRODUCING SCT CONVECTION MAINLY IN TX. 00Z JAX SOUNDING SHOWS PWAT HAS INCREASED ABOUT 60% FROM 24 HRS AGO...NOW AT 1.99 INCHES AND MEAN 0-6KM FLOW IS 290 DEG AT 17 KT. RADAR SHOWS A FEW LIGHT SHOWERS OVER THE CWA AS HIGH MOISTURE AND WEAK LIFT STREAM EWD IN THE NEAR ZONAL FLOW AT 500 MB. AT SFC...MSAS SHOWS A NEARLY STATIONARY FRONTAL BOUNDARY WITH 1 OR 2 FRONTAL WAVES OVER SC TO ACROSS GA/AL/MS WITH WEAK HIGH PRESSURE RIDGE OVER TN AND VA AT 1015 MB. .SHORT TERM...TODAY-THURSDAY. MODELS SHOW DEEP LAYER MOISTURE CONTINUING OVER THE AREA AND IN FACT INCREASING WITH PWATS GOING ABOVE 2 INCHES. SHORTWAVE TROUGH OVER THE FL PANHANDLE AT 12Z WILL SHIFT EWD SUPPORTING LIFT IN THE AREA...WITH ANOTHER STRONGER SHORTWAVE TROUGH INITIALLY IN TX TO SHIFT EWD INTO AL 00Z TONIGHT THEN INTO THE CWA BY 12Z WED. AT SFC...MODELS CONTINUE TO SHOW THE CWA IN THE WARM SECTOR AND INDICATE THE FRONT WILL OSCILLATE OVER S CENTRAL GA TODAY (PERHAPS SAG TO NEAR THE ALTAMAHA RIVER) THEN LIFT NWD TONIGHT AS A SFC LOW CURRENTLY OVER TX MOVES INTO MS/AL TONIGHT CENTRAL GA WED MORNING. THE NAM IS NOTICEABLY SLOWER WITH THE MAIN SFC LOW AND WILL PREFER THE GFS AS ITS CLOSER TO THE ECMWF MODEL. FAIRLY TIGHT PRESSURE GRADIENT SETS UP LATER TONIGHT AND INTO WED WITH 850 MB WINDS MAXIMIZED AT 50-60 KT OVER SE GA WED MORNING THEN SHIFTS SWD INTO NE FL WED AFTERNOON. A 1004 MB SFC LOW EXPECTED TO TRACK FROM CENTRAL GA WED MORNING AND OFF THE SC/NC CAROLINA COASTS WED NIGHT. ATTENDANT COLD FRONT EXPECTED TO PUSH THROUGH THE CWA EARLY WED EVENING THEN SWD INTO THE SRN CWA INTO EARLY THU MORNING. BOTH NAM AND GFS IN AGREEMENT SHOWING FRONT BECOMING QUASI-STATIONARY THU WITH A SHARP N TO S MOISTURE GRADIENT. BEST RAIN CHANCES SHOULD BE ACROSS OUR SRN ZONES BY THEN. TODAY...DEEP LAYER MOISTURE AND LIFT ASSOCIATED SHORTWAVE SHOULD RESULT IN HIGH SHOWER AND STORM COVERAGE AND CAN`T ARGUE WITH CATEGORICAL POPS GIVEN BY BOTH NAM AND GFS. THUNDERSTORM CHANCES ARE SMALL TO START OFF AND THEN INCREASE BY THE AFTERNOON. TEMPS WILL BE HELD DOWN BY CLOUDY SKIES IN THE MID 80S. TONIGHT...LITTLE BIT OF A DRY SLOT MOVES IN AHEAD OF THE SFC LOW BUT ANTICIPATE LIKELY POPS OVER NRN 2/3RDS OF CWA FOR EVENING AND OVERNIGHT. SRN ZONES SHOULD SEE POPS DECREASE TO 10-20%. WED...APPROACH OF SFC LOW/COLD FRONT AND SHORTWAVE TROUGH WILL GENERATE NUMEROUS SHOWERS AND STORMS. POPS ARE PLACED AT 60-70% WITH SLIVER OF CATEGORICAL POSSIBLE CLOSER TO BEST LOW LEVEL LIFT. LLVL JET AND MARGINAL INSTABILITY (SBCAPE ~1000-1600J) WILL SUPPORT A RISK OF SEVERE STORMS AND SPC HAS CONTINUE WITH A SLIGHT RISK MAINLY OVER SE GA. BULK SHEAR VALUES OF 30-35 KT ARE LIKELY. MULTICELLULAR STORMS EXPECTED. TEMPS WILL BE ABLE TO MANAGE THE MID 80S TO NEAR 90 WITH WARMEST TEMPS S ZONES. BREEZY WINDS OF 15-20 MPH WITH HIGHER GUSTS EXPECTED AND A LAKE WIND ADVISORY MAY BE NEEDED DUE TO GUSTINESS. WED NIGHT AND THU...FRONT WILL PUSH THROUGH WITH POPS DECREASE FROM N TO S AS DYNAMICS AND MOISTURE BEGIN TO TAPER OFF. FRONT HUNG UP OVER N CENTRAL FL THU MAY CONTINUE A HIGH RAIN CHANCE FROM MARION TO FLAGLER COUNTIES. TEMPS ON THU WARMEST IN SE GA NEAR 90...BUT REMAINING IN MID 80S NEAR THE FRONTAL BOUNDARY. .LONG TERM...FRI-MON. FRONTAL BOUNDARY REMAINS DIFFUSE NEAR SRN ZONES ON FRI AND WILL SUPPORT CHANCE POPS FROM SUWANEE VALLEY TO MARION COUNTY WITH LOWER CHANCES IN SE GA. GFS SHOWS SFC LOW ALONG THE FRONT OFFSHORE OF CENTRAL FL MOVING NEWD BUT THIS LOOKS A BIT SUSPECT. BY SAT-MON...WEAK MID LEVEL RIDGING BUILDS IN AND WILL LIKELY RESULT IN LOWER RAIN CHANCES AND WARMER TEMPS...TO MORE SEASONABLE VALUES. ANOTHER STORM SYSTEM MAY MOVE INTO THE MID MS VALLEY AREA SUN AND MON BUT MOISTURE AND DYNAMICS SHOULD REMAIN WELL NW OF THE AREA. IN ADDITION...TROPICAL WAVE MOVING THROUGH THE BAHAMAS AND SRN PARTS OF FL NEXT WEEK WILL LIKELY NOT HAVE MUCH AFFECT ON THE SENSIBLE WX IN THE FORECAST AREA. && .AVIATION...CONDITIONS WILL DETERIORATE THROUGH THE DAY WITH PREVAILING VFR CONDITIONS LOWERING TO MVFR BY 15-16Z TODAY DUE TO CIGS AS CLOUD COVER INCREASES IN ADVANCE OF SURFACE LOW. TEMPO LIFR TO EVEN VLIFR IN HEAVY RAINFALL THIS AFTERNOON AS TSRA MOVE INLAND FROM THE GULF FIRST IMPACTING GNV BY LATE MORNING...THEN CONTINUING EAST TOWARD JAX...CRG AND SSI TERMINALS IN THE AFTN. STRONG LOW LEVEL WINDS TONIGHT AROUND 25-35 KTS AT 2 KFT WILL LIKELY SUPPORT WIND SHEAR MENTION IN FOLLOWING TAF PACKAGES. && .MARINE...HAVE ISSUED A SCA FOR OUR OFFSHORE WATERS BEGINNING LATE TONIGHT AS PRESSURE GRADIENT TIGHTENS ENOUGH TO SUPPORT 20-25 KT WINDS AS SURFACE LOW APPROACHES THE SE COAST. STILL BELIEVE THAT SCEC WILL SUFFICE FOR NEARSHORE LEGS. MENTIONED OCCASIONAL GUSTS TO GALE FORCE POSSIBLE OFFSHORE LATE WED AFTN/EVENING IN THE CWA...AND LATER SHIFTS MAY WISH TO CONSIDER A GALE WATCH BUT CONFIDENCE NOT HIGH ENOUGH AT THIS TIME TO SUPPORT ONE. SEAS SHOULD REMAIN BELOW 6 FT DUE TO PREVAILING OFFSHORE FLOW. LEANED TOWARD A GFS/NAM12 BLEND FOR WINDS IN THE SHORT TERM...WITH MORE FOCUS ON THE SLOWER NAM12 WED NIGHT INTO THU. FOR EXTENDED WINDS...USED THE DGEX IN THE GRIDS WHICH SUPPORT THE GFS ENSEMBLE INDICATING PREVAILING SSW FLOW THROUGH THE WEEKEND...GRADUALLY BECOMING SLY EARLY NEXT WEEK. && .HYDROLOGY...GIVEN THE HIGH PWATS OF AROUND 2-2.4 INCHES AND THE CWA S OF THE 250 MB JET OVER CENTRAL GA TO NC...PERIODS OF HEAVY RAIN ARE EXPECTED INTO WED. RAINFALL AMOUNTS TODAY THROUGH WED MORNING EXPECTED TO BE FAIRLY WIDESPREAD HALF AN INCH WITH POSSIBLE 1-2 INCH AMOUNTS FROM SE GA INTO EXTREME NE FL. LOCALLY HIGHER AMOUNTS POSSIBLE BY WED AND WED NIGHT AND ESPECIALLY WHERE THE FRONTAL BOUNDARY BECOMES QUASI STATIONARY AND BEST LIFT OCCURS. && .PRELIMINARY POINT TEMPS/POPS... AMG 85 71 85 66 / 80 60 70 20 SSI 84 73 85 71 / 80 60 70 30 JAX 86 73 88 68 / 80 60 70 30 SGJ 86 73 90 72 / 90 60 60 40 GNV 85 73 88 72 / 90 50 60 50 OCF 87 73 88 72 / 80 40 50 50 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...NONE. GA...NONE. AM...SMALL CRAFT ADVISORY FROM 6 AM WEDNESDAY TO 11 AM EDT THURSDAY FOR ALTAMAHA SOUND GA TO FERNANDINA BEACH FL 20 NM TO 60 NM OFFSHORE-FERNANDINA BEACH TO ST AUGUSTINE FL 20 NM TO 60 NM OFFSHORE-ST AUGUSTINE TO FLAGLER BEACH FL 20 NM TO 60 NM OFFSHORE. && $$ SHASHY/ENYEDI fl AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PEACHTREE CITY GA 1108 PM EDT WED AUG 13 2008 .UPDATE... SMALL CLUSTER OF ISOLATED SHOWERS OVER NORTH CENTRAL GA APPEARS TO BE THE RESULT OF WEAK SURFACE CONVERGENCE...TERRAIN EFFECTS...AND PERHAPS A SLIGHT ASSIST FROM THE NOSE OF AN H2 JET STREAK PASSING OVERHEAD. NAM AND RUC MODELS DO DEPICT SOME QPF IN THIS GENERAL AREA AND BOTH SUGGEST AN EASTWARD DRIFT THROUGH THE NIGHT. WILL UPDATE TO CONTINUE THE SLIGHT CHANCE THROUGH 12Z. REST OF THE FORECAST LOOKS ON TRACK. RRH && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... LONGWAVE TROUGH REMAINS IN PLACE ACROSS EASTERN UNITED STATES WITH FAIRLY SIGNIFICANT SHORT WAVE FOR AUGUST MOVING ACROSS THE SOUTHEAST. SURFACE LOW CENTERED NEAR SOUTH CAROLINA COAST THIS AFTERNOON...WITH ASSOCIATED FRONTAL BOUNDARY DRAPED ACROSS CENTRAL AND SOUTHERN GEORGIA. MAJORITY OF SHOWER AND THUNDERSTORM ACTIVITY HAS EXITED THE CWA. DRIER AIR ATTEMPTING TO PUSH INTO NORTHWEST GEORGIA...ALBEIT WITH SLOW PROGRESS. DEWPOINTS IN THE MID 50S NOTED ACROSS TENNESSEE...BEING ADVECTED SOUTH BY NORTHERLY WINDS. CHANCES FOR PRECIP MAY LINGER PAST 00Z THIS EVENING AS BOUNDARY STILL LINGERS ACROSS CENTRAL GEORGIA. ALSO ADDED LOW POPS FOR NORTHEAST GEORGIA AS SOME TOPOGRAPHICAL ENHANCEMENT APPEARS TO BE AIDING IN THE DEVELOPMENT OF A FEW SHOWERS IN THAT AREA...WHICH RUC/NAM/GFS SHOW CONTINUING THROUGH THE EVENING. AREAS OF FOG APPEAR LIKELY TONIGHT AS BOUNDARY LAYER NEARS SATURATION ACROSS MOST OF THE AREA...WESTERN PORTIONS OF THE STATE LOOK TO HAVE THE DRIEST AIR IN PLACE SO FOG MAY BE LESS OF A PROBLEM IN THOSE AREAS. NAM/GFS BOTH SHOW ANOTHER SHORTWAVE MOVING ACROSS GEORGIA ON FRIDAY. WHILE MOISTURE WILL BE LIMITED...ADDED SLIGHT CHANCE POPS ACROSS NORTHERN PORTION OF THE STATE WHERE TOPOGRAPHY AND BETTER MID- LEVEL MOISTURE MAY SLIGHTLY INCREASE POTENTIAL FOR PRECIPITATION. INCREASED MIN TEMPS OVER MOS FOR FRIDAY MORNING IN SEVERAL AREAS WHERE MAV IN PARTICULAR SEEMED TOO AGGRESSIVE WITH THE AMOUNT OF DRYING IN THE LOW-LEVELS. MAV HIGH TEMPS ON FRIDAY SEEMED TOO WARM ACROSS CENTRAL GEORGIA IN PARTICULAR. WENT CLOSER TO COOLER FWC TEMPS GIVEN RECENT RAINS ACROSS CENTRAL GEORGIA...OTHERWISE DID NOT STRAY TOO FAR FROM MOS. .LONG TERM /SATURDAY THROUGH WEDNESDAY/... LONGWAVE TROUGH WILL GRADUALLY LIFT OUT OF THE EASTERN UNITED STATES THROUGH THE WEEKEND...ALLOWING A WEAK UPPER-LEVEL RIDGE TO BUILD BACK ACROSS GEORGIA. SHORTWAVE DIVING FROM NORTHERN ROCKIES INTO THE PLAINS BECOMES CUTOFF UNDER THE BUILDING UPPER RIDGE ACROSS THE CENTRAL PORTION OF THE COUNTY BY EARLY NEXT WEEK...FORMING A REX BLOCK PATTERN...WHICH GFS SHOWS PERSISTING THROUGH WEDNESDAY. THIS PATTERN WILL BRING A RETURN TO MORE TYPICAL SUMMER CONDITIONS FOR GEORGIA...WITH SOUTHERLY FLOW BRINGING GULF MOISTURE BACK TO THE REGION BY MONDAY...AND TEMPERATURES NEAR SEASONAL AVERAGE VALUES. MSR && .AVIATION... A COUPLE OF SCATTERED TO BROKEN LAYERS ABOVE 4 THOUSAND FEET WILL LIKELY LINGER INTO THE EVENING ACROSS PORTIONS OF THE AREA AS NEXT UPPER SHORT WAVE APPROACHES. THIS PRESENTS A CHALLENGE DECIDING HOW MUCH RADIATIONAL COOLING WILL TAKE PLACE. THE MORE COOLING WE GET...THE LOWER THE VISIBILITIES WILL GO...SINCE THE GROUND IS WET AND WE FAILED TO SUFFICIENTLY MIX OUT THE BOUNDARY LAYER. CONDITIONS WILL LIKELY VARY FROM PLACE TO PLACE WITH SOME GOING IFR BY 08Z OR 09Z...AND OTHER REMAINING MVFR. ALSO NOT SURE ABOUT FORMATION OF CEILINGS BELOW 1 THOUSAND FEET. THE CONCEPTUAL MODEL WOULD FAVOR STRATUS...BUT THIS IS MID AUGUST. HAVE CHOSEN TO MENTION LOW CLOUDS AT MOST AIRPORTS TOWARD DAYBREAK. IF LOW CONDITIONS MATERIALIZE AT DAYBREAK...THEY MAY BE A BIT SLOW TO BREAK AS WINDS ARE LIGHT AND UPPER SHORT WAVE WILL BE OVERHEAD. BUT...VISIBILITIES ABOVE 5 MILES ARE EXPECTED BEFORE NOON WITH CEILINGS BREAKING AND HEATING GETTING MIXING GOING. 15 && .PRELIMINARY POINT TEMPS/POPS... ATHENS 65 87 62 92 68 / 20 20 10 10 10 ATLANTA 66 85 66 89 69 / 10 10 10 10 10 BLAIRSVILLE 62 83 57 86 62 / 20 20 10 10 10 CARTERSVILLE 63 86 58 90 62 / 10 10 10 10 10 COLUMBUS 68 88 66 92 70 / 10 10 5 10 5 GAINESVILLE 65 85 63 89 68 / 20 20 10 10 10 MACON 67 88 63 93 66 / 10 10 5 10 10 ROME 64 87 60 91 64 / 10 10 10 10 10 PEACHTREE CITY 64 86 58 90 60 / 10 10 5 10 10 VIDALIA 67 89 65 93 67 / 20 10 5 10 10 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 555 PM MDT WED AUG 13 2008 .DISCUSSION... 220 PM MDT WED AUG 13 2008 17Z WATER VAPOR IMAGERY/RUC ANALYSIS INDICATED NORTHWEST FLOW ALOFT ACROSS THE CWA...WITH A SMALL SHORT WAVE TROUGH MOVING ACROSS SOUTHERN NEBRASKA. A LARGER AND STRONGER TROUGH WAS LOCATED JUST TO THE NORTH OF THE MONTANA/CANADA BORDER. AT THE SFC...RIDGE WAS SLIDING TO THE SOUTHEAST OF THE AREA AS TROUGH DEVELOPED ACROSS EASTERN COLORADO. TONIGHT...MAIN CONCERN FOR THE PERIOD WILL BE PRECIPITATION CHANCES AND COVERAGE OVERNIGHT. NAM AND GFS VERY DIFFERENT OVERNIGHT WITH NAM MUCH MORE AGGRESSIVE DEVELOPING THUNDERSTORMS ACROSS THE AREA. PATTERN LOOKS SIMILAR TO THE PAST FEW DAYS WITH AREA OF SFC CONVERGENCE ALONG WESTERN FRINGE OF AREA. TD`S MUCH LOWER THAN PREVIOUS DAYS...AND WITH TEMPS ALOFT SIMILAR TO THOSE YESTERDAY AM CONCERNED THAT CAPPING MAY INHIBIT WIDESPREAD THUNDERSTORMS AND AT THIS POINT THINK NAM MAY NE A BIT OVERDONE. NEXT SHORTWAVE TROUGH NOT EXPECTED TO IMPACT THE CWA UNTIL TOMORROW MORNING...AND ALTHOUGH LLJ DOES GET GOING TONIGHT POINT SOUNDINGS SUGGEST CAPPING ABOVE THIS LEVEL WILL BE STRONG. SREF POPS REMAIN ARE IN THE 70-90 PERCENT RANGE TONIGHT HOWEVER...SO CONFIDENCE ON IT REMAINING DRY ARE NOT HIGH EITHER. FOR NOW ARE GOING TO KEEP MID RANGE POPS AND WATCH HOW AFTERNOON DEVELOPS BEFORE MAKING A FINAL CALL. TOMORROW-TOMORROW NIGHT...FIRST SHORT WAVE TROUGH WILL MOVE EAST ACROSS THE AREA AFTER 12Z...WHILE STRONGER SHORT WAVE TROUGH DIVES TO THE SOUTH ACROSS WYOMING. LARGE SCALE FORCING FOR ASCENT WILL OVERSPREAD THE AREA AHEAD OF THE TROUGH AS COLD FRONT SLIDES SOUTH ACROSS THE AREA. BEST CORRELATION OF UPPER FORCING AND SFC BASED INSTABILITY WILL OCCUR BTWN 18Z AND 00Z AHEAD OF THE COLD FRONT...AND WILL FOCUS HIGHEST POPS IN THIS TIME FRAME. BOTH NAM AND GFS QUICKLY MOVE THE FRONT THROUGH THE AREA...WITH NEARLY THE ENTIRE AREA POST FRONTAL BY 00Z. DIV Q FIELDS ALSO INDICATE WIDESPREAD FORCING FOR SUBSIDENCE ACROSS THE AREA...AND ALTHOUGH MODELS HOLDING ONTO PRECIPITATION THROUGH THE NIGHT...AM LESS OPTIMISTIC ABOUT THIS PERIOD. WILL LINGER SOME HIGHER POPS ACROSS THE EASTERN AND SOUTHERN FRINGE OF THE AREA EARLY TO ACCOMMODATE TIMING DIFFERENCES. FRIDAY-SATURDAY...STRONG TROUGH WILL BEGIN TO MOVE INTO NORTHERN COLORADO AND WILL SLOWLY MOVE TO THE SOUTHEAST THROUGH THE PERIOD. DIFFERENCES BEGIN TO EMERGE WITH HOW FAST THE TROUGH MOVES THROUGH...WITH THE NAM CONSIDERABLY SLOWER THAN THE GFS. SREF MEAN GENERALLY FAVORS THE MORE PROGRESSIVE GFS SO FAVORED THIS SOLUTION THROUGH THE PERIOD. WITH LOW TAKING A MORE WESTWARD TRACK...STRONGEST AND DEEPEST FORCING FOR ASCENT WILL GENERALLY BE WEIGHTED ACROSS THE WESTERN CWA...WITH MOST OF THE FORCING REMAINING WEST OF THE AREA. ADJUSTED POPS TO BE WEIGHTED MORE IN THE WEST...CLOSER TO THE H5 LOW. BY SATURDAY...DIFFERENCES IN MODEL SOLUTIONS BEGIN TO LOWER CONFIDENCE IN FORECAST. NAM CONTINUES TO HOLD LOW ALONG THE ROCKIES...WHILE GFS HAS LOW CENTERED OVER SOUTHEAST COLORADO. WITH SUCH DIFFERENCES IN POSITION...NOT GOING TO TRY TO PINPOINT MOST LIKELY AREA OF PRECIP AND WILL JUST KEEP CHANCE POPS EVERYWHERE. IN THE EXTENDED...PRIMARY CONCERN FOR THE PERIOD WILL BE THE SPEED AND TRACK OF CLOSED H5 LOW THAT WILL MOVE ACROSS THE AREA DURING THE START OF THE PERIOD. 12Z GFS MUCH MORE PROGRESSIVE WITH THIS SYSTEM THAN OVERNIGHT ECMWF...WHICH IS A DEPARTURE FROM 00 AND 06Z GFS. 00Z ENSEMBLE MEMBERS GENERALLY SUPPORT THE 12Z SOLUTION HOWEVER...SO GENERALLY WENT WITH GFS IDEA OF A QUICKER END TO PRECIPITATION AND BRINGING BACK WARMER TEMPS SOONER. EVEN WITH QUICKER SOLUTION...WOULD EXPECT COOLER TEMPS TO LINGER IN THE EAST THROUGH THE PERIOD. JRM && .AVIATION... 551 PM MDT WED AUG 13 2008 FOR THE 00Z TAF...MAIN CONCERN FOR THE TAF CYCLE WILL BE WHETHER OR NOT CONVECTION CURRENTLY DEVELOPING FROM NORTHEAST COLORADO THROUGH NORTHERN NEBRASKA WILL IMPACT TAF SITES TONIGHT. CURRENT TRENDS WOULD INDICATE IT WILL AVOID THEM SO HAVE OPTED TO LEAVE PRECIP MENTION OUT OF TAFS FOR NOW. WILL HAVE TO MONITOR RADAR TRENDS AND ADJUST ACCORDINGLY IF NECESSARY. WILL HAVE ANOTHER SHOT AT PRECIP BY THURSDAY AFTERNOON SO HAVE INSERTED PREVAILING PRECIP GROUP FOR KGLD BUT LEFT MENTION OUT AT KMCK AS IT APPEARS GREATEST COVERAGE WILL BE FROM THE KS/CO BORDER WESTWARD. HAVE MAINTAINED VFR CONDITIONS OUTSIDE OF THE PRECIP GROUP FOR KGLD FOR THURSDAY AFTERNOON. FOLTZ && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 1130 AM MDT WED AUG 13 2008 .DISCUSSION... FOR THE MORNING UPDATE TWEAKED 1ST PERIOD PARAMETERS TO MATCH CURRENT OBS AND LATEST RUC/RUC13 WHICH HAD A BETTER HANDLE ON CURRENT CONDITIONS. CONVECTIVE ACTIVITY THIS AFTERNOON HARD TO PIN DOWN BUT CAP WEAKENS ENOUGH AND THERE IS SOME WIND CONVERGENCE AREAS AROUND THE AREA TO AT LEAST PROMOTE ISOLATED THUNDERSTORM GROWTH. TEMPERATURES PER LATEST MOS/RUC/NAM GUIDANCE AROUND 90 BUT WILL NEED TO KEEP AN EYE THEM AS ABUNDANT SOIL MOISTURE SEEMS TO BE IMPACTING FULL MIXING POTENTIAL A BIT AND READINGS COULD BE A FEW DEGREES LOWER. DDT && .AVIATION... PRIMARY AVIATION CONCERN IS FOR STRATUS AND PERHAPS SOME FOG AFTER MIDNIGHT AT BOTH KGLD AND KMCK AS BOUNDARY LAYER SATURATES. HAVE SOME MVFR CIG FORECASTS TO START THINGS OFF AND WILL AWAIT 18Z GUIDANCE BEFORE GETTING TO AGGRESSIVE IN THE 00Z TAFS. OTHERWISE ISOLATED -TSRA POSSIBLE ACROSS THE AREA FOR MID TO LATE AFTERNOON INTO THE OVERNIGHT HOURS WITH TOO LOW OF CONFIDENCE TO PUT THEM IN THE TAFS. WILL TRY AND REFINE THEM ONCE ACTIVITY GETS GOING A BIT LATER TODAY. DDT && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ WFO GOODLAND ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 106 PM CDT TUE AUG 12 2008 .UPDATE... UPDATE FOR SHORT TERM FORECAST AND 18Z TAFS. && .DISCUSSION... IN THE SHORT TERM FORECAST CHANGED HIGH TEMPERATURE FORECAST A BIT TO FIT HOURLY TRENDS AND REORGANIZED THE SLIGHT CHANCE POP AREA TO HIGHLIGHT AREAS NEAR THE COLD FRONT/WEAK CONVERGENCE ZONE NEAR INTERSTATE 35 AND THEN ALONG THE FAR EASTERN PERIPHERY OF THE CWA DUE TO THE PROXIMITY OF AN MCV DIVING SOUTH THROUGH WESTERN MO AT THIS TIME. THE MCV IS MOVING JUST EAST OF SOUTH...SO IT MAY NOT HAVE MUCH EFFECT ON THE CWA. MORNING KTOP SOUNDING INDICATED NO MID LVL CAP...SO THE POTENTIAL FOR POP UP THUNDERSTORMS ASSOCIATED WITH PEAK HEATING THIS AFTERNOON CANNOT BE COMPLETELY RULED OUT...HOWEVER THE ENTIRE CWA LIES ON THE NVA SIDE OF EXITING SHORTWAVE TROUGH...SO AT LEAST MODEST UPPER LVL SUBSIDENCE IS IN PLACE...SO DID NOT EXTEND SLIGHT CHANCE POPS ACRS THE ENTIRE CWA TO ACCOUNT FOR THIS POSSIBILITY. WILL MONITOR SATELLITE TRENDS FOR CU FIELD APPEARANCE AND UPDATE IF NECESSARY. CAVANAUGH && .AVIATION... FOR THE 18Z TAFS...WITH BROAD SUBSIDENCE IN PLACE EXPECT VFR CONDITIONS OVER ALL TAF SITES FOR THE NEXT 24 HRS. ONLY FLY IN THE OINTMENT IS POTENTIAL FOR SOME SHALLOW FOG DEVELOPING IN RIVER VALLEY SITES TOP AND MHK NEAR SUNRISE. DID NOT PLACE IN TAFS AT THIS TIME BUT SOMETHING TO MONITOR IN FUTURE FORECASTS. EXPECT AFTERNOON CU FIELD TO DEVELOP IN THE 4-5 KFT RANGE AND DISSIPATE AFTER PEAK HEATING. CAVANAUGH && .PREV DISCUSSION... /ISSUED 659 AM CDT TUE AUG 12 2008/ UPDATE... UPDATED FOR 12Z TAFS DISCUSSION... SEE PREVIOUS DISCUSSION AVIATION... FRONT HAS JUST PASSED KMHK THIS PAST HOUR...AND RADAR AND SFC OBS INDICATE FRONT WILL BE MOVING THROUGH KTOP/KFOE AROUND 12Z. SOME PATCHY MVFR FOG AT 11Z SHOULD MIX OUT WITH THE FROPA. WIND SPEEDS WILL GENERALLY BE IN THE 5 TO 10 KT RANGE THROUGH THE DAY AS WINDS AT ALL SITES VEER AROUND TO THE NORTH/NORTHEAST BY MIDDAY THEN GENERALLY LIGHT/VARIABLE BY EARLY EVENING. PRECIP HAS TEMPORARILY DISSIPATED ACROSS THE AREA...BUT ISOLATED THUNDERSTORMS MAY DEVELOP IN THE AFTERNOON...MAINLY SOUTH OF THE TAF SITES CLOSER TO WEAKENING BOUNDARY...AND WILL ONLY CARRY CB IN THE TAFS FOR NOW WITH VFR STRATOCU. WILL LEAVE FOG OUT OF TAFS TONIGHT...ALTHOUGH IF DRYING AND MIXING OF THE BOUNDARY LAYER DOES NOT TAKE PLACE OVERNIGHT...SOME SHALLOW GROUND FOG WOULD BE POSSIBLE AFTER 09Z. PREV DISCUSSION... /ISSUED 420 AM CDT TUE AUG 12 2008/ DISCUSSION... PRECIPITATION FROM DECAYING MCS MOVING THROUGH THE CWA THIS MORNING. SHOWERS HAVE BEEN DISSIPATING ACROSS NORTHEAST AND EAST CENTRAL KANSAS EARLY THIS MORNING...BUT AN MCV WAS MOVING ACROSS CENTRAL KANSAS NEAR KCNK AND KEEPING SHOWERS GOING THERE. ALSO 500 MB SHORTWAVE TROUGH WAS MOVING ACROSS EASTERN NEBRASKA AND FAR NORTHERN KANSAS. WILL GO WITH SCATTERED SHOWERS EARLY THIS MORNING WITH SOME ISOLATED THUNDERSTORMS AS THE SHORTWAVE AND MCV MOVE THROUGH. FOR THIS AFTERNOON WITH A MOIST AND UNSTABLE AIRMASS COULD SEE SOME ISOLATED SHOWERS AND THUNDERSTORMS POP UP ACROSS THE EASTERN CWA AND HAVE KEPT SOME SMALL POPS THERE. FOR THE WEDNESDAY THROUGH FRIDAY PERIOD LEANED MORE TOWARD THE 12Z AND 00Z ECMWF SOLUTIONS WHICH IS SUPPORTED IN THE WEDNESDAY PERIOD BY THE GFS. BEST CHANCES FOR PRECIPITATION LOOK TO HOLD OFF ON WEDNESDAY UNTIL THE EVENING HOURS FOR THE NORTH CENTRAL KANSAS COUNTIES AS LIFT OCCURS AHEAD OF THE APPROACHING UPPER TROUGH. GOOD FETCH OF MOISTURE ACROSS CENTRAL KANSAS WITH LOW LEVEL JET WEDNESDAY EVENING TURNING SOUTHWEST BY 12Z THURSDAY AND INTO THE EASTERN CWA. FOR THURSDAY INTO FRIDAY INCREASED CHANCES OF PRECIPITATION AS GOOD MOISTURE AND INSTABILITY WILL BE IN PLACE AHEAD OF THE COLD FRONT UP IN NEBRASKA. A SHORTWAVE TROUGH WILL MOVE ACROSS THE CENTRAL PLAINS. GOOD SHEAR AND INSTABILITY FORECAST ACROSS THE CENTRAL PLAINS AND SOME SEVERE STORMS ARE POSSIBLE. LOOKS LIKE STORMS MAY FORM INTO AN MCS AND MOVE ACROSS THE CWA THURSDAY NIGHT INTO FRIDAY. ALSO LOWERED TEMPERATURES FOR THURSDAYS HIGHS. MODELS ARE STILL SHOWING AN UPPER TROUGH/LOW ACROSS THE PLAINS INTO THE WEEKEND. THIS WILL BRING A CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY AND HAVE LEFT THE EXTENDED UNTOUCHED AS IT HAS THIS COVERED WELL. MAY NEED TO LOWER TEMPERATURES MORE THAN CURRENTLY FORECAST. AVIATION... COMPLEX OF THUNDERSTORMS OVER CENTRAL NE DEVELOPED FURTHER WEST THAN PREVIOUSLY ANTICIPATED...THROWING A WRENCH INTO GOING TAF FORECAST. CLOUD TOP TEMPS HAVE WARMED SIGNIFICANTLY OVER THE PAST HOUR THOUGH...AND LINE SHOWING SIGNS OF WEAKENING. REGARDLESS...GFS AND NAM HANDLING ONGOING CONVECTION VERY POORLY...AND CONFIDENCE IN PRECIP TRACK IS LOW. THE RUC SHOWING A BIT OF PROMISE...ENDING CURRENT CONVECTION WITHIN THE NEXT TWO HOURS. WITH SOME INSTABILITY STILL AVAILABLE DOWNSTREAM...COMPLEX SHOULD SUSTAIN SOME SEMBLANCE OF ITSELF THROUGH TOP/FOE/MHK...AND WILL ADD A TEMPO FOR RA BETWEEN APX. 07Z AND 10Z. MOIST BOUNDARY LAYER AND LIGHT WINDS WILL PROVOKE BR AT EACH SITE BEFORE AND AFTER THE RA. VFR AFTER 15Z. && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 659 AM CDT TUE AUG 12 2008 .UPDATE... UPDATED FOR 12Z TAFS && .DISCUSSION... SEE PREVIOUS DISCUSSION && .AVIATION... FRONT HAS JUST PASSED KMHK THIS PAST HOUR...AND RADAR AND SFC OBS INDICATE FRONT WILL BE MOVING THROUGH KTOP/KFOE AROUND 12Z. SOME PATCHY MVFR FOG AT 11Z SHOULD MIX OUT WITH THE FROPA. WIND SPEEDS WILL GENERALLY BE IN THE 5 TO 10 KT RANGE THROUGH THE DAY AS WINDS AT ALL SITES VEER AROUND TO THE NORTH/NORTHEAST BY MIDDAY THEN GENERALLY LIGHT/VARIABLE BY EARLY EVENING. PRECIP HAS TEMPORARILY DISSIPATED ACROSS THE AREA...BUT ISOLATED THUNDERSTORMS MAY DEVELOP IN THE AFTERNOON...MAINLY SOUTH OF THE TAF SITES CLOSER TO WEAKENING BOUNDARY...AND WILL ONLY CARRY CB IN THE TAFS FOR NOW WITH VFR STRATOCU. WILL LEAVE FOG OUT OF TAFS TONIGHT...ALTHOUGH IF DRYING AND MIXING OF THE BOUNDARY LAYER DOES NOT TAKE PLACE OVERNIGHT...SOME SHALLOW GROUND FOG WOULD BE POSSIBLE AFTER 09Z. && .PREV DISCUSSION... /ISSUED 420 AM CDT TUE AUG 12 2008/ DISCUSSION... PRECIPITATION FROM DECAYING MCS MOVING THROUGH THE CWA THIS MORNING. SHOWERS HAVE BEEN DISSIPATING ACROSS NORTHEAST AND EAST CENTRAL KANSAS EARLY THIS MORNING...BUT AN MCV WAS MOVING ACROSS CENTRAL KANSAS NEAR KCNK AND KEEPING SHOWERS GOING THERE. ALSO 500 MB SHORTWAVE TROUGH WAS MOVING ACROSS EASTERN NEBRASKA AND FAR NORTHERN KANSAS. WILL GO WITH SCATTERED SHOWERS EARLY THIS MORNING WITH SOME ISOLATED THUNDERSTORMS AS THE SHORTWAVE AND MCV MOVE THROUGH. FOR THIS AFTERNOON WITH A MOIST AND UNSTABLE AIRMASS COULD SEE SOME ISOLATED SHOWERS AND THUNDERSTORMS POP UP ACROSS THE EASTERN CWA AND HAVE KEPT SOME SMALL POPS THERE. FOR THE WEDNESDAY THROUGH FRIDAY PERIOD LEANED MORE TOWARD THE 12Z AND 00Z ECMWF SOLUTIONS WHICH IS SUPPORTED IN THE WEDNESDAY PERIOD BY THE GFS. BEST CHANCES FOR PRECIPITATION LOOK TO HOLD OFF ON WEDNESDAY UNTIL THE EVENING HOURS FOR THE NORTH CENTRAL KANSAS COUNTIES AS LIFT OCCURS AHEAD OF THE APPROACHING UPPER TROUGH. GOOD FETCH OF MOISTURE ACROSS CENTRAL KANSAS WITH LOW LEVEL JET WEDNESDAY EVENING TURNING SOUTHWEST BY 12Z THURSDAY AND INTO THE EASTERN CWA. FOR THURSDAY INTO FRIDAY INCREASED CHANCES OF PRECIPITATION AS GOOD MOISTURE AND INSTABILITY WILL BE IN PLACE AHEAD OF THE COLD FRONT UP IN NEBRASKA. A SHORTWAVE TROUGH WILL MOVE ACROSS THE CENTRAL PLAINS. GOOD SHEAR AND INSTABILITY FORECAST ACROSS THE CENTRAL PLAINS AND SOME SEVERE STORMS ARE POSSIBLE. LOOKS LIKE STORMS MAY FORM INTO AN MCS AND MOVE ACROSS THE CWA THURSDAY NIGHT INTO FRIDAY. ALSO LOWERED TEMPERATURES FOR THURSDAYS HIGHS. MODELS ARE STILL SHOWING AN UPPER TROUGH/LOW ACROSS THE PLAINS INTO THE WEEKEND. THIS WILL BRING A CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY AND HAVE LEFT THE EXTENDED UNTOUCHED AS IT HAS THIS COVERED WELL. MAY NEED TO LOWER TEMPERATURES MORE THAN CURRENTLY FORECAST. AVIATION... COMPLEX OF THUNDERSTORMS OVER CENTRAL NE DEVELOPED FURTHER WEST THAN PREVIOUSLY ANTICIPATED...THROWING A WRENCH INTO GOING TAF FORECAST. CLOUD TOP TEMPS HAVE WARMED SIGNIFICANTLY OVER THE PAST HOUR THOUGH...AND LINE SHOWING SIGNS OF WEAKENING. REGARDLESS...GFS AND NAM HANDLING ONGOING CONVECTION VERY POORLY...AND CONFIDENCE IN PRECIP TRACK IS LOW. THE RUC SHOWING A BIT OF PROMISE...ENDING CURRENT CONVECTION WITHIN THE NEXT TWO HOURS. WITH SOME INSTABILITY STILL AVAILABLE DOWNSTREAM...COMPLEX SHOULD SUSTAIN SOME SEMBLANCE OF ITSELF THROUGH TOP/FOE/MHK...AND WILL ADD A TEMPO FOR RA BETWEEN APX. 07Z AND 10Z. MOIST BOUNDARY LAYER AND LIGHT WINDS WILL PROVOKE BR AT EACH SITE BEFORE AND AFTER THE RA. VFR AFTER 15Z. && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ 63 ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 420 AM CDT TUE AUG 12 2008 .DISCUSSION... PRECIPITATION FROM DECAYING MCS MOVING THROUGH THE CWA THIS MORNING. SHOWERS HAVE BEEN DISSIPATING ACROSS NORTHEAST AND EAST CENTRAL KANSAS EARLY THIS MORNING...BUT AN MCV WAS MOVING ACROSS CENTRAL KANSAS NEAR KCNK AND KEEPING SHOWERS GOING THERE. ALSO 500 MB SHORTWAVE TROUGH WAS MOVING ACROSS EASTERN NEBRASKA AND FAR NORTHERN KANSAS. WILL GO WITH SCATTERED SHOWERS EARLY THIS MORNING WITH SOME ISOLATED THUNDERSTORMS AS THE SHORTWAVE AND MCV MOVE THROUGH. FOR THIS AFTERNOON WITH A MOIST AND UNSTABLE AIRMASS COULD SEE SOME ISOLATED SHOWERS AND THUNDERSTORMS POP UP ACROSS THE EASTERN CWA AND HAVE KEPT SOME SMALL POPS THERE. FOR THE WEDNESDAY THROUGH FRIDAY PERIOD LEANED MORE TOWARD THE 12Z AND 00Z ECMWF SOLUTIONS WHICH IS SUPPORTED IN THE WEDNESDAY PERIOD BY THE GFS. BEST CHANCES FOR PRECIPITATION LOOK TO HOLD OFF ON WEDNESDAY UNTIL THE EVENING HOURS FOR THE NORTH CENTRAL KANSAS COUNTIES AS LIFT OCCURS AHEAD OF THE APPROACHING UPPER TROUGH. GOOD FETCH OF MOISTURE ACROSS CENTRAL KANSAS WITH LOW LEVEL JET WEDNESDAY EVENING TURNING SOUTHWEST BY 12Z THURSDAY AND INTO THE EASTERN CWA. FOR THURSDAY INTO FRIDAY INCREASED CHANCES OF PRECIPITATION AS GOOD MOISTURE AND INSTABILITY WILL BE IN PLACE AHEAD OF THE COLD FRONT UP IN NEBRASKA. A SHORTWAVE TROUGH WILL MOVE ACROSS THE CENTRAL PLAINS. GOOD SHEAR AND INSTABILITY FORECAST ACROSS THE CENTRAL PLAINS AND SOME SEVERE STORMS ARE POSSIBLE. LOOKS LIKE STORMS MAY FORM INTO AN MCS AND MOVE ACROSS THE CWA THURSDAY NIGHT INTO FRIDAY. ALSO LOWERED TEMPERATURES FOR THURSDAYS HIGHS. MODELS ARE STILL SHOWING AN UPPER TROUGH/LOW ACROSS THE PLAINS INTO THE WEEKEND. THIS WILL BRING A CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY AND HAVE LEFT THE EXTENDED UNTOUCHED AS IT HAS THIS COVERED WELL. MAY NEED TO LOWER TEMPERATURES MORE THAN CURRENTLY FORECAST. && .AVIATION... COMPLEX OF THUNDERSTORMS OVER CENTRAL NE DEVELOPED FURTHER WEST THAN PREVIOUSLY ANTICIPATED...THROWING A WRENCH INTO GOING TAF FORECAST. CLOUD TOP TEMPS HAVE WARMED SIGNIFICANTLY OVER THE PAST HOUR THOUGH...AND LINE SHOWING SIGNS OF WEAKENING. REGARDLESS...GFS AND NAM HANDLING ONGOING CONVECTION VERY POORLY...AND CONFIDENCE IN PRECIP TRACK IS LOW. THE RUC SHOWING A BIT OF PROMISE...ENDING CURRENT CONVECTION WITHIN THE NEXT TWO HOURS. WITH SOME INSTABILITY STILL AVAILABLE DOWNSTREAM...COMPLEX SHOULD SUSTAIN SOME SEMBLANCE OF ITSELF THROUGH TOP/FOE/MHK...AND WILL ADD A TEMPO FOR RA BETWEEN APX. 07Z AND 10Z. MOIST BOUNDARY LAYER AND LIGHT WINDS WILL PROVOKE BR AT EACH SITE BEFORE AND AFTER THE RA. VFR AFTER 15Z. && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 1158 PM CDT MON AUG 11 2008 .UPDATE... UPDATED FOR THE 06Z TAFS. && .DISCUSSION... SEE PREVIOUS DISCUSSION. && .AVIATION... COMPLEX OF THUNDERSTORMS OVER CENTRAL NE DEVELOPED FURTHER WEST THAN PREVIOUSLY ANTICIPATED...THROWING A WRENCH INTO GOING TAF FORECAST. CLOUD TOP TEMPS HAVE WARMED SIGNIFICANTLY OVER THE PAST HOUR THOUGH...AND LINE SHOWING SIGNS OF WEAKENING. REGARDLESS...GFS AND NAM HANDLING ONGOING CONVECTION VERY POORLY...AND CONFIDENCE IN PRECIP TRACK IS LOW. THE RUC SHOWING A BIT OF PROMISE...ENDING CURRENT CONVECTION WITHIN THE NEXT TWO HOURS. WITH SOME INSTABILITY STILL AVAILABLE DOWNSTREAM...COMPLEX SHOULD SUSTAIN SOME SEMBLANCE OF ITSELF THROUGH TOP/FOE/MHK...AND WILL ADD A TEMPO FOR RA BETWEEN APX. 07Z AND 10Z. MOIST BOUNDARY LAYER AND LIGHT WINDS WILL PROVOKE BR AT EACH SITE BEFORE AND AFTER THE RA. VFR AFTER 15Z. && PREV DISCUSSION... /ISSUED 342 PM CDT MON AUG 11 2008/ DISCUSSION... TWO SHRTWV TROFS WILL AFFECT THE AREA THROUGH THE NEXT 24 HOURS. EARLY AFTN WATER VAPOR IMAGERY CLEARLY DEPICTED BOTH WAVES. THE FIRST WAS CURRENTLY MOVG THRU CNTRL NEB INTO NW KS WITH THE NEXT UPSTRM WAVE OVR ERN WY. ATMOSPHERE ACRS NE KS HAS ONLY BECOME WEAKLY UNSTABLE THIS AFTN /ARND 500 J/KG MLCAPE/ WITH TMPS INCREASING THRU THE LOWER 80S. MAY STILL SEE AN ISO SHRA OR TSRA DVLP THIS AFTN...ESPECIALLY OVR THE SRN CWA WHERE DEEPER MOISTURE RESIDES BEFORE BOUNDARY LAYER COOLING KICKS IN LATER THIS EVNG. NW CWA IN REGION OF DNVA BEHIND INITIAL WAVE HAS LEAST CHC TO SEE ANY ACTIVITY THIS EVNG...BUT AFTR MIDNIGHT AS NEXT SHRTWV STARTS TO WORK THRU NEB...A BETTER CHC OF PRECIP MAY DVLP ACRS THE NRN FA. THIS MAY COME LATE TONIGHT IN THE FORM OF A WEAKENING MCS EXPECTED TO DVLP OVR PARTS OF NEB/SD...AND DRIFT SEWD. ALL SAID...WILL CONT WITH SOME CHC POPS IN THE S THIS EVNG LINGERING TO AROUND MIDNIGHT THEN A SLIGHT CHC AFTER AND THE OPPOSITE IN THE NRN CWA. ALSO SOME FOG POTENTIAL TONIGHT ALNG THE SFC RIDGE AXIS BASICALLY ALNG I-70...BUT WITH THE UNCERTAINTY OF THE CLDS HAVE KEPT OUT OF THE FORECAST ATTM. LOWS TONIGHT WILL BE SIMILAR TO LAST NIGHT WITH COOLER READINGS IN THE NW WHERE THE LEAST AMOUNTS OF CLDS ARE EXPECTED. TAIL END OF THE SECOND SHRTWV TROF WILL CONT TO AFFECT THE ERN CWA THRU THE DAY ON TUE. LARGE-SCALE FORCING FOR ASCENT WILL BE WEAKENING AS BEST ENERGY SHIFTS EWD...BUT MID LVL COLD POOL /SEEN THIS MRNG FM UT INTO CNTRL WY/ WILL BE MOVG EWD AND ALLOWS FOR THE ERN CWA TO DESTABILIZE THRU THE AFTN. LITTLE CAPPING IS IN PLACE TOMORROW AND THUS AN ISO SHRA OR TSRA WILL BE POSSIBLE THRU THE AFTN. DID TWEAK DOWN HIGHS FOR TUE ACRS MOST OF THE CWA WITH LIMITED MIXING AND FAIRLY COOL H85 TMPS. BOUSTEAD TUESDAY NIGHT AND WEDNESDAY...THIS PERIOD LOOKS THE MOST LIKELY 24 HR PERIOD WITHOUT PRECIPITATION AT THIS TIME. UPPER LVL SUBSIDENCE ON THE BACK SIDE OF THE EXITING SHORTWAVE TROUGH AND SFC RIDGE BUILDING INTO THE CWA WOULD INDICATE A DRY PERIOD IN AN OTHERWISE ACTIVE PATTERN. WEDNESDAY COULD ALSO BE THE WARMEST DAY OF THE WEEK WITH MOSTLY SUNNY SKIES EXPECTED WITH SUBSIDENCE ALOFT. EXTENDED...DID NOT MAKE MUCH IN THE WAY OF ADJUSTMENTS AS THE ENTIRE EXTENDED FORECAST DEPENDS ON THE TIMING AND POSITION OF A RETROGRADING UPPER LEVEL LOW. IN GENERAL THE EXTENDED GUIDANCE INDICATES THE UPPER LOW OVER ALBERTA AT FORECAST TIME WILL PUSH EAST INTO MANITOBA WEDNESDAY NIGHT AND THEN BEGIN TO RETROGRADE SOUTH SOUTHWEST INTO THE NORTHERN PLAINS DURING THE DAY ON THURSDAY. PRECIPITATION CHANCES WILL BEGIN THURSDAY AS THE GFS AND ECMWF BOTH INDICATE A LEAD SHORTWAVE TROUGH MOVING THROUGH THE FLOW AHEAD OF THE RETROGRADING LOW PUSHING THROUGH THE CENTRAL PLAINS THURSDAY AFTERNOON. AFTER THAT THE MODELS DIFFER FROM ONE ANOTHER...AND FROM RUN TO RUN ON THE SPEED OF THE UPPER LOW MOVING OVER THE CENTRAL PLAINS. IN TERMS OF 12Z RUNS...THE GFS OFFERED UP A SLOWER SOLUTION...KEEPING THE UPPER LOW PARKED OVER THE CENTRAL PLAINS FROM FRIDAY NIGHT THROUGH AT LEAST WEDNESDAY OF NEXT WEEK...WHILE THE ECMWF WAS FASTER AND MORE PROGRESSIVE WITH THE SYSTEM...BRINGING IT INTO THE CENTRAL PLAINS DURING THE DAY ON FRIDAY...AND ALLOWING IT TO EXIT THE REGION BY MONDAY. SINCE BOTH MODELS HAVE THE UPPER LOW OVER THE CWA FROM SATURDAY THROUGH MONDAY...THE WEEKEND AT LEAST LOOKS TO REMAIN WELL BELOW NORMAL TEMPERATURE WISE...WITH A CHANCE FOR PRECIPITATION EVERYDAY. BEYOND THIS...THE EXTENDED IS A FAIRLY LOW CONFIDENCE FORECAST AND WILL LIKELY REMAIN SO UNTIL MODELS CAN AGREE UPON A SOLUTION. ONLY CHANGE OF SIGNIFICANCE MADE DURING THE PERIOD WAS TO REMOVE MENTION OF THUNDER FROM SATURDAY NIGHT THROUGH MONDAY AND INSTEAD WENT WITH RAIN SHOWER WORDING. THE UPPER LOW LOOKS NEARLY BAROTROPIC BY THIS TIME AND SAW LITTLE INSTABILITY PRESENT TO SUPPORT THUNDERSTORM MENTION. CAVANAUGH && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$ KONOP ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 152 PM EDT TUE AUG 12 2008 .SHORT TERM.../THE REST OF TODAY/ 15Z H5 RUC ANALYSIS INDICATES A BROAD RIDGE ACROSS THE WRN CONUS AS A CLOSED LOW EXITS THE NERN CONUS. ERN KY IS UNDER A NWRLY FLOW ALOFT. AT THE SURFACE...A BROAD AREA OF HIGH PRESSURE EXTENDS FROM THE GREAT LAKES INTO WRN NC. A BNDRY STRETCHES WEST TO EAST ACROSS THE SERN CONUS FROM A WEAK LOW OVER THE ARKLATEX WITH EXPANSIVE CLOUD COVERAGE. LOCALLY...SOME MID TO UPPER CLOUDS ASSOCIATED WITH THE BNDRY TO THE SOUTH ARE APPROACHING THE SRN FRINGES OF THE CWA. THIS AFTERNOON...HIGH PRESSURE WILL REMAIN THE DOMINANT FEATURE THIS AFTERNOON...AS CLOUD COVERAGE INCREASES OVER THE SRN CWA ALONG WITH AN INCREASE FROM DIURNALLY DRIVEN CU. WINDS WILL REMAIN LIGHT WITH THE BROAD PRESSURE GRADIENT. MINOR CHANGES MADE ON SKY GRIDS TO INCREASE CLOUD COVERAGE OVER SRN ZONES. TEMPS APPEAR TO BE IN LINE WARMING INTO THE MID 80S OVER THE SRN CWA TO THE LOWER 80S OVER NERN KY. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /TODAY THROUGH THURSDAY NIGHT/ 06Z SFC ANALYSIS SHOWS HIGH PRESSURE IN CONTROL OF THE WEATHER OVER THE OHIO VALLEY WITH LOW PRESSURE ON THE FRINGES. THE OBSERVATIONS REFLECT THE CANADIAN AIR MASS IN PLACE WITH READINGS ACROSS THE CWA IN THE MIDDLE 50S VALLEYS TO LOWER 60S ON THE RIDGES. DEWPOINTS LIKEWISE DOCUMENT THE DRY AIR IN PLACE WITH READINGS IN THE LOWER 50S. ON SATELLITE...SKIES ARE CLEAR...ALTHOUGH HIGH CLOUDS WILL ENCROACH THE AREA FROM THE NORTHWEST AND ALSO FROM THE SOUTHWEST TOWARDS DAWN. IN THE MEANTIME...THE MOSTLY CLEAR SKIES...ALLOWING FOR GOOD VIEWING CONDITIONS FOR THE PEAKING PERSEID METEOR SHOWER...WILL CONTRIBUTE TO TEMPERATURES IN THE DEEPER VALLEYS FALLING TO THE DEWPOINT AND THE DEVELOPMENT OF PATCHY FOG. WHILE THE MODELS FEATURE A SIMILAR PATTERN ALOFT THROUGH THE SHORT TERM PORTION OF THE FORECAST...THEY EACH HAVE SIGNIFICANT DIFFERENCES IN THE HANDLING OF THE MAIN FEATURES AFFECTING THE COUNTRY DURING THIS TIME FRAME. A SIGNIFICANT TROUGH IN THE EASTERN PORTION OF NORTH AMERICA WILL PIVOT WESTWARD BY MIDDAY THURSDAY REACHING BACK INTO THE GREAT LAKES AND NORTHERN OHIO VALLEY. MEANWHILE A MORE COMPACT CLOSED LOW WILL EXIT A HOLDING PATTERN OVER SOUTHERN CANADA AND ENTER THE NORTH PLAINS DIVING MORE SOUTH THAN EAST...THOUGH FRIDAY. IN ADDITION...A SHORTWAVE WILL CROSS THE SOUTHEAST UNITED STATES FROM LATE TUESDAY INTO EARLY THURSDAY BEFORE EXITING OFF SHORE. THE ECMWF SOLUTION FROM 12Z MONDAY APPEARS TO OFFER THE MOST CONSISTENT AND REASONABLE SOLUTION FOR THESE FEATURES AND AS A RESULT WAS FOLLOWED FOR THE LARGER SCALE PATTERN. SENSIBLE WEATHER WILL CONSIST OF A CONTINUATION OF THE RELATIVELY DRY AND SOMEWHAT COOL CONDITIONS...FOR THIS TIME OF THE YEAR...THAT WE HAVE BEEN EXPERIENCING. HIGH CLOUDS WILL KEEP THE SKIES FROM BEING COMPLETELY SUNNY TODAY AND TEMPS WILL WARM A COUPLE OF EXTRA DEGREES FROM MONDAY. SIMILARLY...TONIGHT WILL BE JUST A TAD MILDER WITH THE CLOUDS HOLDING UP TEMPERATURES SOMEWHAT...BUT A NOTABLE RIDGE TO VALLEY TEMP SPLIT WILL REMAIN A FEATURE ALONG WITH PATCHY VALLEY FOG TOWARDS DAWN WEDNESDAY. A DEVELOPING SFC LOW WILL PASS BY TO THE SOUTH ON WEDNESDAY PERHAPS BRUSHING UP INTO FAR SOUTHEAST KENTUCKY WITH A FEW AFTERNOON SHOWERS OR THUNDERSTORMS A POSSIBILITY FROM THIS. FOR WEDNESDAY NIGHT INTO THURSDAY...WEAK LOW PRESSURE THROUGH THE OHIO VALLEY...BENEATH THE DESCENDING UPPER TROUGH...WILL KEEP THE SKIES FAIRLY CLOUDY ALONG WITH A CONTINUING LOW LEVEL THREAT OF A SHOWER OR THUNDERSTORM...BUT THE COVERAGE FROM THIS IS EXPECTED TO BE AROUND 20 PERCENT...NORTH AND LESS SOUTH. ANOTHER RELATIVELY COOL NIGHT WILL FOLLOW INTO FRIDAY MORNING. THE MOS NUMBERS WERE SIMILAR THROUGH THE PERIOD WITH THE COOLER VALUES PREFERRED FOR THE NIGHTS AND WARMER ONES FAVORED FOR DAYS. THROUGH THE PERIOD...CHOSE TO UNDERCUT MOS POPS FROM ALL SOURCES GIVEN THE LACK OF ANY KEY SFC FEATURES CROSSING THE AREA. .LONG TERM.../FRIDAY THROUGH MONDAY/ A QUIET START TO THE EXTENDED FORECAST WILL GIVE WAY TO AN UPPER LEVEL SYSTEM LATE IN THE FORECAST PERIOD. THE MAIN FOCUS FOR THE EXTENDED FORECAST WILL DEAL WITH POPS FOR THIS WEEKEND. MODELS AGREE ON CLOSED H5 LOW DEVELOPING OVER THE NORTHERN PLAINS EARLY IN THE PERIOD. HOWEVER...THE DIFFERENCES REMAIN IN PROGRESSION AND AMPLIFICATION OF THE TROUGH. HAVE LEANED MORE TOWARD THE STRONGER/MORE PROGRESSIVE ECMWF SOLUTION...HOWEVER CANNOT DISREGARD HOW CONSISTENT GFS HAS BEEN...SO WILL BLEND BETWEEN THE TWO. THE ECMWF SOLUTION SEEMS MORE BELIEVABLE FOR THIS TIME OF YEAR WITH ITS MORE NORTHWESTWARD EXIT AGAINST H5 HIGH PRESSURE OFF THE ATLANTIC COAST. DO NOT FEEL THAT TROUGH COULD PROGRESS AS FAR SOUTH AND EAST AS PROGGED BY 06/12Z GFS. WITH MUCH UNCERTAINTY INTO THE WEEKEND...HAVE LOWERED POPS SLIGHTLY TO MAINLY 40 PERCENT FOR THE WEEKEND MATCHING UP WITH LATEST GUIDANCE AND SURROUNDING OFFICES. AS FOR TEMPERATURES...AMPLE AMOUNTS OF CLOUD COVER ASSOCIATED WITH DEVELOPMENT OF UPPER LOW SHOULD KEEP HIGH TEMPERATURES EVER SO SLIGHTLY BELOW NORMAL AND LOW TEMPERATURES AT OR ABOVE NORMAL FOR MUCH OF THE EXTENDED. EXPECT ABOVE NORMAL LOW TEMPS ON FRIDAY AND SATURDAY NIGHTS WITH MOISTURE INCREASE DUE TO THE APPROACHING SYSTEM. ONLY MADE MINOR TWEAKS TO TEMPERATURES BASED ON LATEST GUIDANCE VALUES AND MODEL TRENDS. && .AVIATION.../18Z TO 18Z/...UPDATED VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE PERIOD. INITIALLY CIRRUS ASSOCIATED WITH THE SFC WAVE PASSING BY TO THE SOUTH WILL TRAVERSE THE REGION. IN ADDITION...SOME MID CLOUDS ASSOCIATED WITH A SW/V OVER THE PLAINS ARE MOVING INTO THE OH VALLEY. MID LEVEL MOISTURE WILL INCREASE ON WED AS THE SFC WAVE PASSES BY TO THE SOUTH AND THE SW/V NEARS THE REGION...AND SCATTERED CLOUDS NEAR THE 7 TO 8KFT RANGE ARE EXPECTED. THE CLOUD COVER SHOULD KEEP ANY VALLEY FOG CONFINED TO LESS COVERAGE THAN WHAT WAS EXPERIENCED THIS MORNING. NEAR THE END OF THE PERIOD...A SHOWER OR THUNDERSTORM COULD THREATEN LOCATIONS NEAR THE VA BORDER...BUT SHOULD NOT AFFECT THE TAF SITES. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...GREIF LONG TERM....SCHOETTMER AVIATION...JP ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY ISSUED BY NATIONAL WEATHER SERVICE WILMINGTON OH 1158 AM EDT TUE AUG 12 2008 .SHORT TERM.../THE REST OF TODAY/...UPDATED 15Z H5 RUC ANALYSIS INDICATES A BROAD RIDGE ACROSS THE WRN CONUS AS A CLOSED LOW EXITS THE NERN CONUS. ERN KY IS UNDER A NWRLY FLOW ALOFT. AT THE SURFACE...A BROAD AREA OF HIGH PRESSURE EXTENDS FROM THE GREAT LAKES INTO WRN NC. A BNDRY STRETCHES WEST TO EAST ACROSS THE SERN CONUS FROM A WEAK LOW OVER THE ARKLATEX WITH EXPANSIVE CLOUD COVERAGE. LOCALLY...SOME MID TO UPPER CLOUDS ASSOCIATED WITH THE BNDRY TO THE SOUTH ARE APPROACHING THE SRN FRINGES OF THE CWA. THIS AFTERNOON...HIGH PRESSURE WILL REMAIN THE DOMINANT FEATURE THIS AFTERNOON...AS CLOUD COVERAGE INCREASES OVER THE SRN CWA ALONG WITH AN INCREASE FROM DIURNALLY DRIVEN CU. WINDS WILL REMAIN LIGHT WITH THE BROAD PRESSURE GRADIENT. MINOR CHANGES MADE ON SKY GRIDS TO INCREASE CLOUD COVERAGE OVER SRN ZONES. TEMPS APPEAR TO BE IN LINE WARMING INTO THE MID 80S OVER THE SRN CWA TO THE LOWER 80S OVER NERN KY. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /TODAY THROUGH THURSDAY NIGHT/ 06Z SFC ANALYSIS SHOWS HIGH PRESSURE IN CONTROL OF THE WEATHER OVER THE OHIO VALLEY WITH LOW PRESSURE ON THE FRINGES. THE OBSERVATIONS REFLECT THE CANADIAN AIR MASS IN PLACE WITH READINGS ACROSS THE CWA IN THE MIDDLE 50S VALLEYS TO LOWER 60S ON THE RIDGES. DEWPOINTS LIKEWISE DOCUMENT THE DRY AIR IN PLACE WITH READINGS IN THE LOWER 50S. ON SATELLITE...SKIES ARE CLEAR...ALTHOUGH HIGH CLOUDS WILL ENCROACH THE AREA FROM THE NORTHWEST AND ALSO FROM THE SOUTHWEST TOWARDS DAWN. IN THE MEANTIME...THE MOSTLY CLEAR SKIES...ALLOWING FOR GOOD VIEWING CONDITIONS FOR THE PEAKING PERSEID METEOR SHOWER...WILL CONTRIBUTE TO TEMPERATURES IN THE DEEPER VALLEYS FALLING TO THE DEWPOINT AND THE DEVELOPMENT OF PATCHY FOG. WHILE THE MODELS FEATURE A SIMILAR PATTERN ALOFT THROUGH THE SHORT TERM PORTION OF THE FORECAST...THEY EACH HAVE SIGNIFICANT DIFFERENCES IN THE HANDLING OF THE MAIN FEATURES AFFECTING THE COUNTRY DURING THIS TIME FRAME. A SIGNIFICANT TROUGH IN THE EASTERN PORTION OF NORTH AMERICA WILL PIVOT WESTWARD BY MIDDAY THURSDAY REACHING BACK INTO THE GREAT LAKES AND NORTHERN OHIO VALLEY. MEANWHILE A MORE COMPACT CLOSED LOW WILL EXIT A HOLDING PATTERN OVER SOUTHERN CANADA AND ENTER THE NORTH PLAINS DIVING MORE SOUTH THAN EAST...THOUGH FRIDAY. IN ADDITION...A SHORTWAVE WILL CROSS THE SOUTHEAST UNITED STATES FROM LATE TUESDAY INTO EARLY THURSDAY BEFORE EXITING OFF SHORE. THE ECMWF SOLUTION FROM 12Z MONDAY APPEARS TO OFFER THE MOST CONSISTENT AND REASONABLE SOLUTION FOR THESE FEATURES AND AS A RESULT WAS FOLLOWED FOR THE LARGER SCALE PATTERN. SENSIBLE WEATHER WILL CONSIST OF A CONTINUATION OF THE RELATIVELY DRY AND SOMEWHAT COOL CONDITIONS...FOR THIS TIME OF THE YEAR...THAT WE HAVE BEEN EXPERIENCING. HIGH CLOUDS WILL KEEP THE SKIES FROM BEING COMPLETELY SUNNY TODAY AND TEMPS WILL WARM A COUPLE OF EXTRA DEGREES FROM MONDAY. SIMILARLY...TONIGHT WILL BE JUST A TAD MILDER WITH THE CLOUDS HOLDING UP TEMPERATURES SOMEWHAT...BUT A NOTABLE RIDGE TO VALLEY TEMP SPLIT WILL REMAIN A FEATURE ALONG WITH PATCHY VALLEY FOG TOWARDS DAWN WEDNESDAY. A DEVELOPING SFC LOW WILL PASS BY TO THE SOUTH ON WEDNESDAY PERHAPS BRUSHING UP INTO FAR SOUTHEAST KENTUCKY WITH A FEW AFTERNOON SHOWERS OR THUNDERSTORMS A POSSIBILITY FROM THIS. FOR WEDNESDAY NIGHT INTO THURSDAY...WEAK LOW PRESSURE THROUGH THE OHIO VALLEY...BENEATH THE DESCENDING UPPER TROUGH...WILL KEEP THE SKIES FAIRLY CLOUDY ALONG WITH A CONTINUING LOW LEVEL THREAT OF A SHOWER OR THUNDERSTORM...BUT THE COVERAGE FROM THIS IS EXPECTED TO BE AROUND 20 PERCENT...NORTH AND LESS SOUTH. ANOTHER RELATIVELY COOL NIGHT WILL FOLLOW INTO FRIDAY MORNING. THE MOS NUMBERS WERE SIMILAR THROUGH THE PERIOD WITH THE COOLER VALUES PREFERRED FOR THE NIGHTS AND WARMER ONES FAVORED FOR DAYS. THROUGH THE PERIOD...CHOSE TO UNDERCUT MOS POPS FROM ALL SOURCES GIVEN THE LACK OF ANY KEY SFC FEATURES CROSSING THE AREA. .LONG TERM.../FRIDAY THROUGH MONDAY/ A QUIET START TO THE EXTENDED FORECAST WILL GIVE WAY TO AN UPPER LEVEL SYSTEM LATE IN THE FORECAST PERIOD. THE MAIN FOCUS FOR THE EXTENDED FORECAST WILL DEAL WITH POPS FOR THIS WEEKEND. MODELS AGREE ON CLOSED H5 LOW DEVELOPING OVER THE NORTHERN PLAINS EARLY IN THE PERIOD. HOWEVER...THE DIFFERENCES REMAIN IN PROGRESSION AND AMPLIFICATION OF THE TROUGH. HAVE LEANED MORE TOWARD THE STRONGER/MORE PROGRESSIVE ECMWF SOLUTION...HOWEVER CANNOT DISREGARD HOW CONSISTENT GFS HAS BEEN...SO WILL BLEND BETWEEN THE TWO. THE ECMWF SOLUTION SEEMS MORE BELIEVABLE FOR THIS TIME OF YEAR WITH ITS MORE NORTHWESTWARD EXIT AGAINST H5 HIGH PRESSURE OFF THE ATLANTIC COAST. DO NOT FEEL THAT TROUGH COULD PROGRESS AS FAR SOUTH AND EAST AS PROGGED BY 06/12Z GFS. WITH MUCH UNCERTAINTY INTO THE WEEKEND...HAVE LOWERED POPS SLIGHTLY TO MAINLY 40 PERCENT FOR THE WEEKEND MATCHING UP WITH LATEST GUIDANCE AND SURROUNDING OFFICES. AS FOR TEMPERATURES...AMPLE AMOUNTS OF CLOUD COVER ASSOCIATED WITH DEVELOPMENT OF UPPER LOW SHOULD KEEP HIGH TEMPERATURES EVER SO SLIGHTLY BELOW NORMAL AND LOW TEMPERATURES AT OR ABOVE NORMAL FOR MUCH OF THE EXTENDED. EXPECT ABOVE NORMAL LOW TEMPS ON FRIDAY AND SATURDAY NIGHTS WITH MOISTURE INCREASE DUE TO THE APPROACHING SYSTEM. ONLY MADE MINOR TWEAKS TO TEMPERATURES BASED ON LATEST GUIDANCE VALUES AND MODEL TRENDS. && .AVIATION.../12Z TO 12Z/ ALTHOUGH THERE WAS PLENTY OF FOG IN THE DEEPER VALLEYS EARLY THIS MORNING...NONE OF THE TAF LOCATIONS REPORTED ANY. EXPECT SIMILAR CONDITIONS TOMORROW. AS A RESULT...VFR CONDITIONS WILL PREVAIL BENEATH A SCT TO BKN DECK OF HIGH CLOUDS AND GENERALLY LIGHT WINDS FROM THE EAST. FOR WEDNESDAY EXPECT MORE IN THE WAY OF LOW CLOUDS AND PERHAPS A LATE DAY THUNDERSTORM...AGAIN OUTSIDE OF THE TAF SITES...TO THE EAST...BUT THAT IS BEYOND THIS FORECAST. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM.../GUEST LONG TERM.... AVIATION... ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 917 PM EDT TUE AUG 12 2008 .SYNOPSIS... HIGH PRESSURE REMAINS OVER THE REGION TONIGHT. LOW PRESSURE MOVES EAST ACROSS THE CAROLINAS WEDNESDAY. THE LOW CONTINUES TO MOVE TO THE NORTHEAST AND EVENTUALLY OFFSHORE OF NORTH CAROLINA BY LATE WEDNESDAY NIGHT INTO THURSDAY MORNING. WEAK HIGH PRESSURE BUILDS IN BY LATE THIS WEEK THROUGH THE WEEKEND. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... UNUSUAL (NON TROPICAL) SYNOPTIC SYSTM FOR MID AUGUST IS EXPECTED TO EFFECT MID ATLNTC RGN NXT 24-36 HRS. HIGH/MID LVL CLDS FROM SRN STREAM SYSTM ALRDY BEGINNING TO OVRSPRD SRN CNTYS THIS EVE. THESE CLDS WILL CONT TO INCRS FROM THE S...BUT AT THE SAME TIME..RUNNING INTO WEAK RIDGE CRNTLY OVR W VA. ALL MODEL GUID THIS EVE KEEPS ANY PCPN S OF FA THRU 12Z (LWR LVLS JUST TO DRY). SO JIST OF EVE UPDATE WAS TO INCRSE CLD COVER OVR SRN HALF OF FA INTO "CLDY" RANGE BY MORN. TMPS SOMEWHAT TRICKY DUE TO THE INCRS IN CLOUD COVER...BUT XPCT THE LOWEST READINGS ACROSS NRN CNTYS UNDER PT CLDY SKIES. LOWS U50S NRTH TO M60S SOUTH. GIVEN SYNOPTIC SETUP...CHANGED CLOUD COVER TO "CLOUDY" VICE M CLDY WEDNESDAY AS PCPN OVRSPRDS SERN CNTYS. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... GOING CLSR TO COMBINATION OF 12Z ECMWF/NAM MDLS FOR THE TIMING/MOVEMENT OF SFC LO PRES THAT TRACKS ACRS THE SE STATES THEN OFF THE NC CST WED THRU THU MORNG. HIEST POPS (LIKELY) WILL BE ACRS EXTRM SE VA AND NE NC WED AFTN AND EVENG...WITH SLGT TO SML CHC POPS ACRS NRN 1/3 OF CWA. HIEST POPS REMAIN ALNG THE CST LATER WED NGT INTO THU MORNG...AS LO TRACKS OFF NC CST AND CONTINES NE. QPF AMTS OF ARND .50 INCH OR MORE WILL BE POSSIBLE OVR EXTRM SE VA AND (ESPLY) NE NC FM THIS EVENT...WITH LIGHTER AMTS POSSIBLE AS YOU GO NW ACRS REGION. CLDS AND PCPN WILL HOLD TEMPS DWN ON WED...WITH MAX TEMPS GENERALLY IN THE UPR 70S TO LWR 80S. INCLUDED ONLY SLGT CHC OF TSRAS DUE TO TRACK OF LO AND LIMITED INSTABILITY. ALTHO SFC LO PRES MOVES AWAY THU...FA WILL REMAIN IN A TROFINESS THRU FRI WITH LINGERING LO LVL MOIST. AS A RESULT...KEPT A SLGT CHC FOR PCPN ALL AREAS THU AFTN THRU FRI. MAX TEMPS IN THE UPR 70S TO MID 80S THU...AND RANGING THRU THE 80S FRI. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... A WEAK TROF WILL MOVE THROUGH THE MID ATLANTIC REGION LATE FRI THRU EARLY SAT...AROUND AN UPPER LEVEL LOW CENTERED OVER SRN QUEBEC. COULD HAVE A FEW LINGERING SHRAS/TSTMS IN THE LATE EVENING IN SE VA/NC AS THE TROF MOVES OFFSHORE...ALTHOUGH WILL CARRY SILENT POPS FOR FRI NIGHT AFTER MIDNIGHT AS THE TROF DEPARTS AND WITH THE LOSS OF DAYTIME HEATING. LOW TEMPS WILL RANGE FROM THE LWR 60S IN FAR WRN SECTIONS UP TO THE LWR 70S IN SE VA/NE NC ON FRI NIGHT. MODELS SHOW ANOTHER WEAK TROF ROTATING THRU ON SAT AFTN/EVNG AND WILL INCLUDE A SLIGHT CHANCE OF SHRAS/TSTMS ACROSS THE FA. THE UPPER LEVEL LOW FINALLY DEPARTS SRN QUEBEC MOVING TOWARDS THE CANADIAN MARITIMES ON SUN...WITH HIGH PRESSURE BUILDING IN BY SUN AFTERNOON THRU EARLY NEXT WEEK. WILL KEEP EARLY NEXT WEEK DRY FOR NOW WITH GOOD SUBSIDENCE IN PLACE AS THE HIGH MOVES OVERHEAD. HIGH TEMPS WILL BE IN THE LWR TO MID 80S FRI AND SAT...RISING INTO THE MID/UPR 80S BY SUN...AND EVENTUALLY UPR 80S/LWR 90S ON MON AND TUE AS S/SW FLOW STRENGTHENS AROUND THE AREA OF HIGH PRESSURE. LOW TEMPS WILL BE IN THE UPR 60S/LWR 70S SAT NIGHT THRU MON NIGHT. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... HIGH PRESSURE/DRY AIRMASS ACROSS THE REGION...VFR CONDITIONS WILL PERSIST TONIGHT THROUGH AT LEAST WED MORNING. THE REMAINS OF A STALLED FRONT IN SC WILL HAVE A SERIES OF LOWS MOVE ALONG IT WEDS AM BRINGING INCRSD CLD COVER AND A SLGT CHANCE OF RAIN INTO THE SOUTHERN PORTION OF OUR AREA LATE WEDS MORN. CHANCE FOR -RA AND LWRG CIGS (MVFR/IFR) LATE MAINLY ACROSS SERN VA AND NERN NC. VFR CONDITIONS WILL THEN ENSUE ON THU AS THE LOW PULLS OFF THE COAST. && .MARINE... A WEAK SEABREEZE HAS DEVELOPED LATE THIS AFTERNOON ALONG THE COAST AND WINDS HAVE BECOME ONSHORE/SE. NAM AND RUC INDICATE A SOUTHERLY SURGE OVER THE CHES BAY THIS EVENING (DUE TO THE THERMAL GRADIENT BETWEEN THE WARM BAY WATERS AND COOLER LAND AREAS AFTER SUNSET). EXPECT 10 TO 15 KT S WINDS FOR THE CHES BAY LATE THIS EVENING THRU EARLY SAT MORNING...WITH A FEW HIGHER GUSTS POSSIBLE (ALTHOUGH WINDS SHOULD REMAIN BELOW SCA CRITERIA). A BRIEF LULL WILL OCCUR WED MORNING. WINDS THEN BEGIN TO INCREASE ACROSS THE WATERS BY LATE WEDNESDAY...AS THE PRESSURE GRADIENT INCREASES BETWEEN DEPARTING HIGH PRESSURE AND AN APPROACHING AREA OF LOW PRESSURE (CURRENTLY OVER INLAND MISSISSIPPI). MODELS ARE NOT IN GOOD AGREEMENT AS FAR AS THE LOCATION/TRACK AND INTENSITY OF THE LOW. HAVE LEANED AWAY FROM THE STRONGER GFS SOLUTION AS THE OTHER MODELS HAVE BEEN MORE CONSISTENT IN THE PAST FEW RUNS. AFTER COORDINATING WITH MHX...RAISED SCA FLAGS FOR THE COASTAL WATERS FROM CAPE CHARLES LIGHT VA SOUTH TO CURRITUCK BEACH LIGHT NC...AND FOR THE CURRITUCK SOUND...FROM LATE WED NIGHT THRU EARLY THUR. WINDS WILL RAPIDLY DECREASE ON THUR AS THE LOW PULLS AWAY FROM THE NORTH CAROLINA COAST. HIGH PRESSURE WILL THEN BUILD IN BY LATE THIS WEEK THROUGH EARLY NEXT WEEK...WITH PLEASANT BOATING CONDITIONS RETURNING. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 AM TO 7 AM EDT THURSDAY FOR ANZ633- 656-658. && $$ SYNOPSIS...MPR NEAR TERM...MPR SHORT TERM...TMG LONG TERM...JRL AVIATION...CY MARINE...JRL md AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 445 PM EDT TUE AUG 12 2008 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH TONIGHT. A DEVELOPING AREA OF LOW PRESSURE CURRENTLY OVER MISSISSIPPI WILL MOVE TOWARDS THE COASTAL CAROLINAS THROUGH WEDNESDAY. THE LOW WILL CONTINUE TO MOVE TO THE NORTHEAST AND EVENTUALLY OFFSHORE OF NORTH CAROLINA BY LATE WEDNESDAY NIGHT INTO THURSDAY MORNING. WEAK HIGH PRESSURE WILL THEN BUILD IN BY LATE THIS WEEK THROUGH THE WEEKEND. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... HIGH PRES WILL PROVIDE A DRY AND RATHER COMFORTABLE NGT ACRS THE REGION. CLR OR MSTLY CLR THIS EVENG...THEN BECMG PRTLY CLDY OVR SRN CNTIES TWD WED MORNG. MIN TEMPS WILL RANGE FM THE UPR 50S TO UPR 60S. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... GOING CLSR TO COMBINATION OF 12Z ECMWF/NAM MDLS FOR THE TIMING/MOVEMENT OF SFC LO PRES THAT TRACKS ACRS THE SE STATES THEN OFF THE NC CST WED THRU THU MORNG. HIEST POPS (LIKELY) WILL BE ACRS EXTRM SE VA AND NE NC WED AFTN AND EVENG...WITH SLGT TO SML CHC POPS ACRS NRN 1/3 OF CWA. HIEST POPS REMAIN ALNG THE CST LATER WED NGT INTO THU MORNG...AS LO TRACKS OFF NC CST AND CONTINES NE. QPF AMTS OF ARND .50 INCH OR MORE WILL BE POSSIBLE OVR EXTRM SE VA AND (ESPLY) NE NC FM THIS EVENT...WITH LIGHTER AMTS POSSIBLE AS YOU GO NW ACRS REGION. CLDS AND PCPN WILL HOLD TEMPS DWN ON WED...WITH MAX TEMPS GENERALLY IN THE UPR 70S TO LWR 80S. INCLUDED ONLY SLGT CHC OF TSRAS DUE TO TRACK OF LO AND LIMITED INSTABILITY. ALTHO SFC LO PRES MOVES AWAY THU...FA WILL REMAIN IN A TROFINESS THRU FRI WITH LINGERING LO LVL MOIST. AS A RESULT...KEPT A SLGT CHC FOR PCPN ALL AREAS THU AFTN THRU FRI. MAX TEMPS IN THE UPR 70S TO MID 80S THU...AND RANGING THRU THE 80S FRI. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... A WEAK TROF WILL MOVE THROUGH THE MID ATLANTIC REGION LATE FRI THRU EARLY SAT...AROUND AN UPPER LEVEL LOW CENTERED OVER SRN QUEBEC. COULD HAVE A FEW LINGERING SHRAS/TSTMS IN THE LATE EVENING IN SE VA/NC AS THE TROF MOVES OFFSHORE...ALTHOUGH WILL CARRY SILENT POPS FOR FRI NIGHT AFTER MIDNIGHT AS THE TROF DEPARTS AND WITH THE LOSS OF DAYTIME HEATING. LOW TEMPS WILL RANGE FROM THE LWR 60S IN FAR WRN SECTIONS UP TO THE LWR 70S IN SE VA/NE NC ON FRI NIGHT. MODELS SHOW ANOTHER WEAK TROF ROTATING THRU ON SAT AFTN/EVNG AND WILL INCLUDE A SLIGHT CHANCE OF SHRAS/TSTMS ACROSS THE FA. THE UPPER LEVEL LOW FINALLY DEPARTS SRN QUEBEC MOVING TOWARDS THE CANADIAN MARITIMES ON SUN...WITH HIGH PRESSURE BUILDING IN BY SUN AFTERNOON THRU EARLY NEXT WEEK. WILL KEEP EARLY NEXT WEEK DRY FOR NOW WITH GOOD SUBSIDENCE IN PLACE AS THE HIGH MOVES OVERHEAD. HIGH TEMPS WILL BE IN THE LWR TO MID 80S FRI AND SAT...RISING INTO THE MID/UPR 80S BY SUN...AND EVENTUALLY UPR 80S/LWR 90S ON MON AND TUE AS S/SW FLOW STRENGTHENS AROUND THE AREA OF HIGH PRESSURE. LOW TEMPS WILL BE IN THE UPR 60S/LWR 70S SAT NIGHT THRU MON NIGHT. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... HIGH PRESSURE/DRY AIRMASS ACROSS THE REGION...VFR CONDITIONS WILL PERSIST TONIGHT THROUGH AT LEAST WED MORNING. THE REMAINS OF A STALLED FRONT IN SC WILL HAVE A SERIES OF LOWS MOVE ALONG IT WEDS AM BRINGING INCRSD CLD COVER AND A SLGT CHANCE OF RAIN INTO THE SOUTHERN PORTION OF OUR AREA LATE WEDS MORN. CHANCE FOR -RA AND LWRG CIGS (MVFR/IFR) LATE MAINLY ACROSS SERN VA AND NERN NC. VFR CONDITIONS WILL THEN ENSUE ON THU AS THE LOW PULLS OFF THE COAST. && .MARINE... A WEAK SEABREEZE HAS DEVELOPED LATE THIS AFTERNOON ALONG THE COAST AND WINDS HAVE BECOME ONSHORE/SE. NAM AND RUC INDICATE A SOUTHERLY SURGE OVER THE CHES BAY THIS EVENING (DUE TO THE THERMAL GRADIENT BETWEEN THE WARM BAY WATERS AND COOLER LAND AREAS AFTER SUNSET). EXPECT 10 TO 15 KT S WINDS FOR THE CHES BAY LATE THIS EVENING THRU EARLY SAT MORNING...WITH A FEW HIGHER GUSTS POSSIBLE (ALTHOUGH WINDS SHOULD REMAIN BELOW SCA CRITERIA). A BRIEF LULL WILL OCCUR WED MORNING. WINDS THEN BEGIN TO INCREASE ACROSS THE WATERS BY LATE WEDNESDAY...AS THE PRESSURE GRADIENT INCREASES BETWEEN DEPARTING HIGH PRESSURE AND AN APPROACHING AREA OF LOW PRESSURE (CURRENTLY OVER INLAND MISSISSIPPI). MODELS ARE NOT IN GOOD AGREEMENT AS FAR AS THE LOCATION/TRACK AND INTENSITY OF THE LOW. HAVE LEANED AWAY FROM THE STRONGER GFS SOLUTION AS THE OTHER MODELS HAVE BEEN MORE CONSISTENT IN THE PAST FEW RUNS. AFTER COORDINATING WITH MHX...RAISED SCA FLAGS FOR THE COASTAL WATERS FROM CAPE CHARLES LIGHT VA SOUTH TO CURRITUCK BEACH LIGHT NC...AND FOR THE CURRITUCK SOUND...FROM LATE WED NIGHT THRU EARLY THUR. WINDS WILL RAPIDLY DECREASE ON THUR AS THE LOW PULLS AWAY FROM THE NORTH CAROLINA COAST. HIGH PRESSURE WILL THEN BUILD IN BY LATE THIS WEEK THROUGH EARLY NEXT WEEK...WITH PLEASANT BOATING CONDITIONS RETURNING. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 1 AM TO 7 AM EDT THURSDAY FOR ANZ633- 656-658. && $$ SYNOPSIS...TMG NEAR TERM...TMG SHORT TERM...TMG LONG TERM...JRL AVIATION...CY MARINE...JRL md AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1148 PM EDT WED AUG 13 2008 LATEST UPDATE...AVIATION... .SYNOPSIS...(400 PM EDT WED AUG 13 2008) ISOLATED SHOWERS AND STORMS ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE AND WEAK COLD FRONT WILL END LATER THIS EVENING LEAVING PARTLY CLOUDY SKIES AND PATCHY FOG. YET ANOTHER UPPER LEVEL DISTURBANCE AND COLD FRONT WILL SLIP SOUTH FROM CANADA AND PASS THROUGH LOWER MICHIGAN ON THURSDAY. ISOLATED SHOWERS AND THUNDERSTORMS WILL FORM AGAIN IN THE AFTERNOON AND LINGER INTO THE EVENING... MAINLY SOUTH OF INTERSTATE 96. HIGH PRESSURE AND DRIER AIR WILL SETTLE INTO THE REGION ON FRIDAY RESULTING IN MOSTLY SUNNY AND PLEASANT CONDITIONS. A WARM UP IS IN STORE FOR THE COMING WEEKEND. && .SHORT TERM...(400 PM EDT WED AUG 13 2008) (TONIGHT THROUGH FRIDAY NIGHT) DIURNALLY DRIVEN ISOLATED SHOWERS/TSTMS WILL PROBABLY LINGER THROUGH ABOUT 02-03Z OR SO. RUC/NAM SHOW BEST SFC CONVERGENCE EARLY THIS EVENING EAST/NORTH OF A LINE FROM ROUGHLY CADILLAC TO BIG RAPIDS TO LANSING... SO BELIEVE THE NE HALF OF THE CWFA WILL SEE SOME CONVECTION DEVELOPING SOON. SOME PATCHY FOG WILL BE POSSIBLE LATE TONIGHT DUE TO LIGHT WINDS... PARTICULARLY IN SPOTS WHERE IT RAINED TODAY AND THIS EVENING. ON THURSDAY AFTERNOON AND EVENING THE NEXT CANADIAN H5 TROUGH AND COLD FRONT PIVOT SOUTH THROUGH THE STATE. LACK OF MOISTURE AND POSITIVE TILT OF THE H5 TROUGH WILL BE LIMITING FACTORS FOR WIDESPREAD CONVECTION SO WILL KEEP RAIN COVERAGE AT ONLY ISOLATED/20 PERCENT. THE BEST MOISTURE IS INDICATED TO BE IN THE SRN CWFA WHICH MAY BE WHERE COVERAGE (ALTHOUGH STILL QUITE LIMITED) IS BEST THURSDAY AFTERNOON AND EVENING. ON FRIDAY THE H5 TROUGH AXIS WILL BE OVER THE ERN GRTLKS REGION AND WE WILL BE ON THE BACK SIDE OF THE TROUGH. THIS SHOULD YIELD DRY/MOSUNNY WEATHER AS MAIN DIURNAL CUMULUS/SHOWER DEVELOP OCCURS OVER ERN LWR MI. && .LONG TERM...(400 PM EDT WED AUG 13 2008) (SATURDAY THROUGH WEDNESDAY) THE WEEKEND CONTINUES TO APPEAR DRY AND WARM AS SURFACE AND UPPER RIDGING PREVAILS. BY MONDAY...RETURN FLOW AND MOISTURE FROM THE GULF SHOULD COLLIDE WITH A COLD FRONT DROPPING DOWN FROM CANADA. THE FRONT APPEARS TO MOVE SLOWLY ACROSS THE CWA...FINALLY CLEARING THE AREA LATE TUESDAY. DEPENDING ON THE POSITION AND THE AMOUNT OF GULF MOISTURE THAT MOVES NORTH THIS COULD BE A FAIRLY WET PERIOD FOR THE SOUTHERN CWA. CANADIAN HIGH PRESSURE TRIES TO BUILD SOUTH OVER THE GREAT LAKES BY WEDNESDAY...HOWEVER THE MOISTURE PROFILES STILL SHOWS LEFTOVER RH WHICH COULD RESULT IN DIURNAL SHOWERS/STORMS ON WEDNESDAY. && .MARINE...(400 PM EDT WED AUG 13 2008) MODELS KEEP TRENDING TOWARD A STRONGER NORTH FLOW EVENT ON THURSDAY AFTERNOON AND EVENING. THIS WILL HAVE TO BE MONITORED FOR POSSIBLE SMALL CRAFT ADVISORIES AS WE TEND TO UNDER FCST NORTH FLOW COLD ADVECTION EVENTS THIS TIME OF YEAR. WE COULD SEE SOME RATHER CHOPPY/HAZARDOUS SEAS DEVELOPING NEAR BIG AND LITTLE SABLE POINTS THURSDAY AFTERNOON... SPREADING SOUTH THURSDAY NIGHT. THE BIG QUESTION THOUGH IS HOW MUCH OF A NORTHEAST COMPONENT TO THE WIND THERE WILL BE AS THAT WOULD KEEP THE HIGHEST WAVES OUT TOWARD OPEN WATERS. EVEN FRIDAY LOOKS POTENTIALLY RATHER WINDY FROM THE NORTH... UNTIL SFC RIDGING FIRMLY BUILDS IN FRIDAY NIGHT. && .AVIATION...(1148 PM EDT WED AUG 13 2008) THE SHORTWAVE IS ROTATING OUT OF THE AREA AS I WRITE THIS AT 1145 PM THIS EVENING. SKIES ARE CLEARING FROM NORTH TO SOUTH BEHIND THE SHORTWAVE AND THERE IS NOT MUCH COOL DRY AIR FOLLOWING THE FRONT. THUS GIVEN THE CLEARING SKIES...LIGHT WINDS AND RAIN OVER PARTS OF THE AREA TODAY...I NOW BELIEVE SOME FOG IS POSSIBLE OVERNIGHT. IT SHOULD MIX OUT BY MID MORNING THOUGH. THE NEXT SHORTWAVE ROTATING AROUND THE CLOSED UPPER LOW TO THE NORTHEAST OF GREAT LAKES WILL TOUCH OFF SOME SCATTERED SHOWERS DURING THURSDAY AFTERNOON. I STILL BELIEVE THE MOST LIKELY LOCATIONS ARE WEST OF US-131 AND NEAR AND SOUTH OF I-94. && .HYDROLOGY...(400 PM EDT WED AUG 13 2008) NO HYDRO CONCERNS. ANY SHOWERS OR STORMS THAT DEVELOP WILL ONLY RESULT IN A QUARTER INCH OR LESS OF PCPN. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. && $$ SYNOPSIS: MEADE SHORT TERM: MEADE LONG TERM: JK MARINE: MEADE AVIATION: WDM HYDROLOGY: MEADE mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1145 PM EDT WED AUG 13 2008 .AVIATION...DRY CONDITIONS EXPECTED OVERNIGHT...POSSIBLY SOME PATCHY FOG DEVELOPING AROUND TERMINALS. MORE DIURNAL SHOWERS EXPECTED THURSDAY AFTERNOON...BUT MOST OF IT SHOULD BE INLAND OF THE TERMINAL LOCATIONS. && .UPDATE... /ISSUED 1010 PM EDT WED AUG 13 2008/ LAST OF THE AFTERNOON SHOWER ACTIVITY CONTINUES TO FALL APART WITH LOSS OF DIURNAL HEATING. NOT ANTICIPATING ADDITIONAL DEVELOPMENT OVERNIGHT...EVEN WITH NEXT BIT OF SHORT WAVE ENERGY ROTATING SOUTHWEST TOWARD LAKE SUPERIOR. PRECIPITATION WITH THIS FEATURE WAS MAINLY DIURNAL ACROSS NORTHEAST ONTARIO THIS AFTERNOON...AND EXPECT THIS WILL BE THE CASE OVER LOWER MI THURSDAY AFTERNOON. EXPECT TO SEE SOME FOG/ST DEVELOP OVERNIGHT ESPECIALLY ACROSS PORTIONS OF NORTHERN LOWER THAT SAW A FAIR BIT OF RAIN TODAY...AND WHERE TEMPERATURE/DEW POINT SPREADS ARE ALREADY LESS THAN 5F. JPB PREV DISCUSSION... /ISSUED 341 PM EDT WED AUG 13 2008/ LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW A RATHER CONVOLUTED PRESSURE/WIND PATTERN ACROSS THE NORTHERN GREAT LAKES WITH A MORE DOMINANT SURFACE OVER NORTHERN ONTARIO. LAKE BREEZE CONVERGENCE ALONG WITH THE HIGHER TERRAIN HAVE AIDED IN THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS...NOW MOST NUMEROUS ACROSS SE PORTIONS OF THE FORECAST AREA. SOME AREAS HAVE RECEIVED UPWARDS OF 2-3 INCHES OF RAIN ACROSS IOSCO AND ALCONA COUNTIES WHERE STORMS HAVE STALLED ALONG LAKE BREEZES. A COUPLE STORMS HAVE BECOME MARGINALLY SEVERE DUE TO LARGE HAIL...BUT HAVE NOT BECOME CONVINCED ENOUGH TO ISSUE ANY WARNINGS AND DID NOT RECEIVE ANY REPORTS TO THE CONTRARY. MORE SCATTERED ACTIVITY RESIDES ACROSS NW LOWER AS WELL AS EASTERN UPPER AT THIS HOUR. OTHERWISE...MID-LEVEL CONVERGENCE ZONE BETWEEN UPPER LOWS OVER QUEBEC AND SASKATCHEWAN HAS SHIFTED TO THE SE...AND SOUTH OF NORTHERN MICHIGAN FOR THE MOST PART. ANOTHER POTENT WAVE NEAR JAMES BAY ALSO HAS EYES SET ON NORTHERN MICHIGAN...BUT THAT WILL POSE MORE OF A PROBLEM FOR TOMORROW. MAIN FORECAST CONCERNS OVER THE NEXT 24 HOURS INCLUDE ONGOING THUNDERSTORM ACTIVITY AND THUNDERSTORM CHANCES TOMORROW AFTERNOON. TONIGHT...SHORTWAVE ACROSS SE ONTARIO WILL CONTINUE TO DIVE SOUTHEAST AWAY FROM NORTHERN MICHIGAN. WITH LOSS OF HEATING... CONVECTION SHOULD BE ON THE DOWNWARD TREND AND PRIMARILY CONFINED TO NE LOWER WHERE OUTFLOW BOUNDARIES WILL BE PREVALENT. BUT WILL LEAVE A CHANCE OF THUNDERSTORMS FOR NE LOWER THROUGH ABOUT MIDNIGHT. THEREAFTER...SURFACE HIGH PRESSURE WILL NOSE IN FROM THE NORTH UNDER A DRY PREVAILING NNE WIND. THE LIGHT ONSHORE WIND COMBINED WITH CLEARING SKIES AND THE HEAVY RAINFALL NEAR OSC AND HARRISVILLE LOOKS LIKE A DECENT SETUP FOR FOG AND HAVE GIVEN THE FOG WORDING A BOOST. STRONG SHORTWAVE NEAR JAMES BAY WILL SWING TOWARDS EASTERN LAKE SUPERIOR LATE...BUT WILL KEEP EASTERN UPPER DRY DUE TO A LACK OF MOISTURE. TOMORROW...THE NEXT SPOKE OF ENERGY WILL ROTATE ACROSS NORTHERN MICHIGAN. EVEN THOUGH THIS SHORTWAVE LOOKS IMPRESSIVE ON THE NAM/GFS...MID-LEVEL MOISTURE IS IN SHORT SUPPLY AHEAD OF THE WAVE. IN ADDITION...LOW LEVEL COLD ADVECTION WILL OFFSET DPVA TO YIELD NEUTRAL OR SLIGHTLY DOWNWARD MOTION. NONETHELESS...500MB TEMPERATURES WILL FALL TO -19C TO -20C ACROSS NE LOWER AND SERVE TO STEEPEN MID-LEVEL LAPSE RATES TO BETWEEN 6.5-7.0 C/KM. NNE LOW LEVEL WINDS WILL KEEP DEW POINTS FROM MIXING OUT ACROSS NE LOWER. USING A 75/54F PARCEL...A 21Z PROGGED SOUNDING NEAR WEST BRANCH YIELDS ABOUT 700 J/KG OF ML CAPE WITH NO CIN. LOW LEVEL WINDS WILL BE STRONGER THAN TODAY...AND SHOULD PREVENT LAKE BREEZES FROM FORMING ACROSS NW LOWER...BUT LIGHT WINDS ON THE LAKE HURON SHORE MAY BE WEAK ENOUGH TO TURN WINDS MORE EAST OR SOUTHEAST...WHICH WOULD HELP FOCUS CONVECTION. THE HIGHER TERRAIN MAY ALSO PROVIDE A BOOST AS WELL. SO HAVE EXPANDED LOW PRECIP CHANCES TO INCLUDE ALL OF NE LOWER AND DRUMMOND ISLAND THROUGH THE AFTERNOON...BUT COVERAGE SHOULD NOT BE AS ROBUST AS TODAY. HIGHS IN THE LOW TO MID 70S. MPC THURSDAY NIGHT AND FRIDAY...ONE MORE SHORT WAVE WILL DROP THRU THE BASE OF THE 500 MB UPPER LOW AND THRU THE ERN HALF OF OUR CWA THURSDAY NIGHT...PROVIDING A CONTINUED CHANCE OF A FEW SHOWERS. STRONG SURFACE RIDGING AND DRY AIR WILL BUILD EASTWARD INTO MICHIGAN FOR FRIDAY AS THE UPPER LEVEL RIDGE BEGINS TO SHIFT NW AWAY FROM THE STATE. FRIDAY SHOULD BE A NICE LATE SUMMER DAY ACROSS MICHIGAN... WITH DRY WX AND MAINLY SUNNY CONDITIONS. HIGH TEMPS BOTH THURSDAY AND FRIDAY WILL BE IN THE 70S...WITH OVERNIGHT LOWS IN THE 50S. SATURDAY THRU WEDNESDAY...PERSISTENT UPPER LEVEL TROUGH OVER THE ERN US WILL LIFT NE FURTHER INTO QUEBEC....WHILE THE WRN RIDGE WILL HOLD ITS POSITION OVER THE US ROCKIES. CUT-OFF 500 MB LOW TO THE LEE OF THE ROCKIES OVER THE CENTRAL PLAINS WILL DEEPEN AND BECOME BETTER ESTABLISHED OVER THIS REGION DURING THE FIRST HALF OF NEXT WEEK. BOTH ECMWF AND GFS ARE POINTING TOWARD WEAK UPPER LEVEL RIDGING GRADUALLY BUILDING FROM THE SE US THRU THE OHIO VALLEY AND INTO THE GREAT LAKES REGION DURING THIS TIME. THE END RESULT IS A RATHER STAGNANT WX PATTERN SETTING UP ACROSS THE US OVER THE NEXT WEEK... WITH MICHIGAN STUCK IN WEAK RIDGING THRU THE COLUMN. CERTAINLY CANNOT COMPLETELY RULE OUT ANY CHANCE OF PRECIP THRU THE MIDDLE OF NEXT WEEK...BUT CHANCES ARE TOO SLIM TO KEEP IN THE FORECAST. THUS...HAVE OPTED TO REMOVE ALL POPS FOR THE FIRST HALF OF NEXT WORKWEEK. AFTERNOON HIGH TEMPS THRU THE PERIOD WILL BE IN THE UPPER 70S TO MID 80S...WITH OVERNIGHT LOWS IN THE UPPER 50S TO LOWER 60S. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1010 PM EDT WED AUG 13 2008 .UPDATE...LAST OF THE AFTERNOON SHOWER ACTIVITY CONTINUES TO FALL APART WITH LOSS OF DIURNAL HEATING. NOT ANTICIPATING ADDITIONAL DEVELOPMENT OVERNIGHT...EVEN WITH NEXT BIT OF SHORT WAVE ENERGY ROTATING SOUTHWEST TOWARD LAKE SUPERIOR. PRECIPITATION WITH THIS FEATURE WAS MAINLY DIURNAL ACROSS NORTHEAST ONTARIO THIS AFTERNOON...AND EXPECT THIS WILL BE THE CASE OVER LOWER MI THURSDAY AFTERNOON. EXPECT TO SEE SOME FOG/ST DEVELOP OVERNIGHT ESPECIALLY ACROSS PORTIONS OF NORTHERN LOWER THAT SAW A FAIR BIT OF RAIN TODAY...AND WHERE TEMPERATURE/DEW POINT SPREADS ARE ALREADY LESS THAN 5F. JPB && .PREV DISCUSSION... /ISSUED 341 PM EDT WED AUG 13 2008/ LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW A RATHER CONVOLUTED PRESSURE/WIND PATTERN ACROSS THE NORTHERN GREAT LAKES WITH A MORE DOMINANT SURFACE OVER NORTHERN ONTARIO. LAKE BREEZE CONVERGENCE ALONG WITH THE HIGHER TERRAIN HAVE AIDED IN THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS...NOW MOST NUMEROUS ACROSS SE PORTIONS OF THE FORECAST AREA. SOME AREAS HAVE RECEIVED UPWARDS OF 2-3 INCHES OF RAIN ACROSS IOSCO AND ALCONA COUNTIES WHERE STORMS HAVE STALLED ALONG LAKE BREEZES. A COUPLE STORMS HAVE BECOME MARGINALLY SEVERE DUE TO LARGE HAIL...BUT HAVE NOT BECOME CONVINCED ENOUGH TO ISSUE ANY WARNINGS AND DID NOT RECEIVE ANY REPORTS TO THE CONTRARY. MORE SCATTERED ACTIVITY RESIDES ACROSS NW LOWER AS WELL AS EASTERN UPPER AT THIS HOUR. OTHERWISE...MID-LEVEL CONVERGENCE ZONE BETWEEN UPPER LOWS OVER QUEBEC AND SASKATCHEWAN HAS SHIFTED TO THE SE...AND SOUTH OF NORTHERN MICHIGAN FOR THE MOST PART. ANOTHER POTENT WAVE NEAR JAMES BAY ALSO HAS EYES SET ON NORTHERN MICHIGAN...BUT THAT WILL POSE MORE OF A PROBLEM FOR TOMORROW. MAIN FORECAST CONCERNS OVER THE NEXT 24 HOURS INCLUDE ONGOING THUNDERSTORM ACTIVITY AND THUNDERSTORM CHANCES TOMORROW AFTERNOON. TONIGHT...SHORTWAVE ACROSS SE ONTARIO WILL CONTINUE TO DIVE SOUTHEAST AWAY FROM NORTHERN MICHIGAN. WITH LOSS OF HEATING... CONVECTION SHOULD BE ON THE DOWNWARD TREND AND PRIMARILY CONFINED TO NE LOWER WHERE OUTFLOW BOUNDARIES WILL BE PREVALENT. BUT WILL LEAVE A CHANCE OF THUNDERSTORMS FOR NE LOWER THROUGH ABOUT MIDNIGHT. THEREAFTER...SURFACE HIGH PRESSURE WILL NOSE IN FROM THE NORTH UNDER A DRY PREVAILING NNE WIND. THE LIGHT ONSHORE WIND COMBINED WITH CLEARING SKIES AND THE HEAVY RAINFALL NEAR OSC AND HARRISVILLE LOOKS LIKE A DECENT SETUP FOR FOG AND HAVE GIVEN THE FOG WORDING A BOOST. STRONG SHORTWAVE NEAR JAMES BAY WILL SWING TOWARDS EASTERN LAKE SUPERIOR LATE...BUT WILL KEEP EASTERN UPPER DRY DUE TO A LACK OF MOISTURE. TOMORROW...THE NEXT SPOKE OF ENERGY WILL ROTATE ACROSS NORTHERN MICHIGAN. EVEN THOUGH THIS SHORTWAVE LOOKS IMPRESSIVE ON THE NAM/GFS...MID-LEVEL MOISTURE IS IN SHORT SUPPLY AHEAD OF THE WAVE. IN ADDITION...LOW LEVEL COLD ADVECTION WILL OFFSET DPVA TO YIELD NEUTRAL OR SLIGHTLY DOWNWARD MOTION. NONETHELESS...500MB TEMPERATURES WILL FALL TO -19C TO -20C ACROSS NE LOWER AND SERVE TO STEEPEN MID-LEVEL LAPSE RATES TO BETWEEN 6.5-7.0 C/KM. NNE LOW LEVEL WINDS WILL KEEP DEW POINTS FROM MIXING OUT ACROSS NE LOWER. USING A 75/54F PARCEL...A 21Z PROGGED SOUNDING NEAR WEST BRANCH YIELDS ABOUT 700 J/KG OF ML CAPE WITH NO CIN. LOW LEVEL WINDS WILL BE STRONGER THAN TODAY...AND SHOULD PREVENT LAKE BREEZES FROM FORMING ACROSS NW LOWER...BUT LIGHT WINDS ON THE LAKE HURON SHORE MAY BE WEAK ENOUGH TO TURN WINDS MORE EAST OR SOUTHEAST...WHICH WOULD HELP FOCUS CONVECTION. THE HIGHER TERRAIN MAY ALSO PROVIDE A BOOST AS WELL. SO HAVE EXPANDED LOW PRECIP CHANCES TO INCLUDE ALL OF NE LOWER AND DRUMMOND ISLAND THROUGH THE AFTERNOON...BUT COVERAGE SHOULD NOT BE AS ROBUST AS TODAY. HIGHS IN THE LOW TO MID 70S. MPC THURSDAY NIGHT AND FRIDAY...ONE MORE SHORT WAVE WILL DROP THRU THE BASE OF THE 500 MB UPPER LOW AND THRU THE ERN HALF OF OUR CWA THURSDAY NIGHT...PROVIDING A CONTINUED CHANCE OF A FEW SHOWERS. STRONG SURFACE RIDGING AND DRY AIR WILL BUILD EASTWARD INTO MICHIGAN FOR FRIDAY AS THE UPPER LEVEL RIDGE BEGINS TO SHIFT NW AWAY FROM THE STATE. FRIDAY SHOULD BE A NICE LATE SUMMER DAY ACROSS MICHIGAN... WITH DRY WX AND MAINLY SUNNY CONDITIONS. HIGH TEMPS BOTH THURSDAY AND FRIDAY WILL BE IN THE 70S...WITH OVERNIGHT LOWS IN THE 50S. SATURDAY THRU WEDNESDAY...PERSISTENT UPPER LEVEL TROUGH OVER THE ERN US WILL LIFT NE FURTHER INTO QUEBEC....WHILE THE WRN RIDGE WILL HOLD ITS POSITION OVER THE US ROCKIES. CUT-OFF 500 MB LOW TO THE LEE OF THE ROCKIES OVER THE CENTRAL PLAINS WILL DEEPEN AND BECOME BETTER ESTABLISHED OVER THIS REGION DURING THE FIRST HALF OF NEXT WEEK. BOTH ECMWF AND GFS ARE POINTING TOWARD WEAK UPPER LEVEL RIDGING GRADUALLY BUILDING FROM THE SE US THRU THE OHIO VALLEY AND INTO THE GREAT LAKES REGION DURING THIS TIME. THE END RESULT IS A RATHER STAGNANT WX PATTERN SETTING UP ACROSS THE US OVER THE NEXT WEEK... WITH MICHIGAN STUCK IN WEAK RIDGING THRU THE COLUMN. CERTAINLY CANNOT COMPLETELY RULE OUT ANY CHANCE OF PRECIP THRU THE MIDDLE OF NEXT WEEK...BUT CHANCES ARE TOO SLIM TO KEEP IN THE FORECAST. THUS...HAVE OPTED TO REMOVE ALL POPS FOR THE FIRST HALF OF NEXT WORKWEEK. AFTERNOON HIGH TEMPS THRU THE PERIOD WILL BE IN THE UPPER 70S TO MID 80S...WITH OVERNIGHT LOWS IN THE UPPER 50S TO LOWER 60S. AVIATION... /ISSUED 738 PM EDT WED AUG 13 2008/ VALID ONLY FOR TAFS ISSUED AT 00Z...SPOTTY CONVECTION EXPECTED TO WIND DOWN THIS EVENING... WITH DRY CONDITIONS EXPECTED OVERNIGHT... AND POSSIBLY SOME FOG/ST ESPECIALLY AROUND TVC. MORE DIURNAL SHOWERS EXPECTED THURSDAY AFTERNOON...BUT MOST OF IT SHOULD BE INLAND OF THE TERMINAL LOCATIONS. JPB && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1005 PM EDT WED AUG 13 2008 .UPDATE... FOR THE MOST PART SHOWERS HAVE DIMINISHED ACROSS THE FORECAST AREA. PLAN TO ISSUE AN UPDATE TO REMOVE PRECIP WORDING FROM THE REST OF THIS EVENINGS FORECAST BASED ON RADAR TRENDS. THE LOW LEVEL MOISTURE PROFILE ON THE 00Z DTX SOUNDING AND THE CURRENT UPPER 50 SFC DEWPOINTS SUGGEST A MENTION OF PATCHY FOG OVERNIGHT IS STILL JUSTIFIED. AREAS OF MID AND HIGH CLOUDS UPSTREAM HOWEVER WILL LIMIT THE DEGREE OF RADIATIONAL COOLING OVERNIGHT. SO DO NOT ANTICIPATE COVERAGE OF FOG TO BE ANYTHING MORE THAN PATCHY. && .PREV DISCUSSION...ISSUED 716 PM EDT WED AUG 13 2008 AVIATION... THE RADAR IS SHOWING NUMEROUS SURFACE BOUNDARIES EXTENDING ACROSS THE REGION BETWEEN FNT AND DTW. THESE ARE A RESULT OF A COMBINATION OF CONVECTIVE OUTFLOW AND LAKE BREEZE BOUNDARIES. WANING DAYTIME INSTABILITY WILL RESULT IN A CONTINUED DIMINISHING TREND TO THE CONVECTION DURING THE COURSE OF THE EVENING. THUS...SEE NO REASON TO MENTION ANY EVENING THUNDER IN THE 00Z TAFS. ANTICIPATING THE OUTFLOW BOUNDARY NOW SLIDING SOUTH ACROSS OAKLAND COUNTY WILL WEAKEN OVER THE NEXT HOUR OR TWO. THUS...EXPECTING MORE OF A VARIABILITY IN THE WINDS AT DTW THIS EVENING AS OPPOSED TO AN ABRUPT WIND SHIFT TO THE NORTH. SURFACE DEWPOINTS IN THE UPPER 50S SUGGEST SOME FOG POTENTIAL. WITH SATELLITE SUPPORTING MODEL SOUNDINGS WHICH INDICATE A CONSIDERABLE AMOUNT OF MID LEVEL MOISTURE OVER THE REGION TONIGHT...PLAN TO JUST DROP VSBY INTO THE MVFR RANGE LATE TONIGHT/EARLY THU MORNING. PREV DISCUSSION...ISSUED 405 PM EDT WED AUG 13 2008 SHORT TERM...THIS AFTERNOON AND EVENING THUNDERSTORM BEHAVIOR THIS AFTERNOON SUPPORTS THE NOTION OF A MARGINAL INSTABILITY/WEAK SHEAR ENVIRONMENT. SURFACE BASED CAPES IN THE LATEST RUC ANALYSIS/BUFKIT SOUNDINGS ARE LESS THAN 1000 J/KG UNDER EXTREMELY MEAGER ENVIRONMENTAL LAPSE RATES (ABOVE 500MB). A COMPOSITE LAKE/CONVECTIVE THERMAL GRADIENT HAS ESTABLISHED FROM ROUGHLY PORT HURON TO BAY CITY. MODELS INDICATE A PUSH OF THE BOUNDARY SOUTHWESTWARD THROUGH THE CWA TONIGHT AS DIURNAL HEATING IS LOST AND WEAK MIDLEVEL ENERGY PUSHES IN BEHIND. WITH THE WEAKLY CAPPED ENVIRONMENT...ADDITIONAL DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG THIS FEATURE UNTIL A SURFACE INVERSION GROWS THIS EVENING. SEVERE WEATHER IS NOT ANTICIPATED THIS AFTERNOON OR EVENING...BUT A STORM OR TWO MAY BECOME STRONG ALONG ANY BOUNDARY INTERSECTIONS AND OR CELL MERGERS. GIVEN WEAK MEAN LAYER FLOW OF 5-10 KNOTS...THE MAIN THREAT WILL BE HEAVY RAINFALL UNDER SLOW MOVING/STALLED THUNDERSTORMS. HAIL TO HALF INCH AND FREQUENT LIGHTNING MAY ALSO BE EXPERIENCED. WITH AN INFILTRATING MARINE AIRMASS AND WEAK FLOW HAVE ADDED PATCHY FOG FOR AREAS OUTSIDE OF THE METRO...WITH ANY DENSE SPOTS REMAINING ISOLATED. LOWS TONIGHT WILL SETTLE INTO THE LOWER 50S NORTH TO LOWER 60S SOUTH. LONG TERM...THURSDAY THROUGH NEXT WEDNESDAY THE NEXT IN THE SERIES OF WAVES ROTATING AROUND THE LARGE EASTERN UPPER LOW IS ON SATELLITE MOVING INTO NORTHERN ONTARIO AND WILL AFFECT SE MICHIGAN ON THURSDAY. THIS WILL KEEP A CHANCE OF SHOWERS AND EVEN AN ISOLATED THUNDERSTORM POSSIBLE BY AFTERNOON. THE PROBLEM IS THAT THE SYSTEM FROM TODAY IS NOT EXPECTED TO SCOUR OUT ENOUGH MOISTURE BELOW 850 MB TO REDUCE THE EFFECTIVENESS OF SUPPORT FROM THE WAVE. DEEP CYCLONIC FLOW, AND THE ASSOCIATED DYNAMIC FORCING, WILL BE ACCOMPANIED BY TEMPERATURES DROPPING TO BETWEEN -14C AND -17C. THIS WILL COMBINE WITH A SURFACE PARCEL IN THE UPPER 70S/UPPER 50S TO PRODUCE POCKETS OF CAPE AROUND 1000 J/KG. THE 12Z MODELS ARE NOT GREATLY IMPRESSED WITH THE AMOUNT OF SURFACE PRESSURE REFLECTION BUT A PATTERN SIMILAR TO TODAY SEEMS LIKE A REASONABLE EXPECTATION, WHICH INCLUDES LAKE BOUNDARY CONTRIBUTIONS AS WELL AS WEAK SYNOPTIC CONTRIBUTIONS. THIS WAVE WILL DO A BETTER JOB OF SCOURING OUT THE MOISTURE IN THE LOW LEVELS BUT THERE WILL BE SOME LINGERING INFLUENCE OF THE SYSTEM DURING FRIDAY. CYCLONIC FLOW IN THE MID AND UPPER LEVELS, AND LINGERING COLD POOL ALOFT, WILL PROVIDE FOR AN ISOLATED SHOWER. THE LARGER STORY WILL BE YET ANOTHER SURGE OF COOL AIR ATTEMPTING TO TAKE 850 MB TEMPERATURES DOWN INTO THE SINGLE DIGITS AND LIMITING HIGH TEMPERATURES TO THE 70S. THE 12Z MODEL RUNS THEN LOOK REASONABLE IN MAINTAINING DRY CONDITIONS OVER SE MICHIGAN ON SATURDAY. THIS WILL BE ACCOMPLISHED BY DRY NW FLOW ALOFT COMBINED WITH SURFACE HIGH PRESSURE CENTERED TO OUR SOUTH. WESTERLY FLOW ON SUNDAY WILL REPRESENT A WARM ADVECTION PATTERN AHEAD OF A WAVE IN CENTRAL CANADA. THIS IS PART OF A TREND IN THE GLOBAL MODEL SOLUTIONS TOWARD A MORE ACTIVE NW UPPER LEVEL FLOW. THIS TREND LOOKS GOOD AFTER CONSIDERING THE FLOW WILL BE FORCED BY RELIABLE DEPICTIONS OF THE HIGHLY AMPLIFIED LONG WAVE PATTERN THROUGHOUT THE WESTERN HEMISPHERE. CONFIDENCE IS ON THE HIGH SIDE THAT THIS LARGE SCALE PATTERN WILL KEEP A LONG WAVE RIDGE ANCHORED OVER WESTERN NORTH AMERICA AND GUIDE THE WESTERLIES FROM CENTRAL CANADA INTO THE NORTHERN GREAT LAKES WHILE THE CUT OFF LOW LUMBERS AROUND OVER THE SOUTHERN PLAINS STATES. WE EXPECT THE WARM ADVECTION PATTERN OVER THE GREAT LAKES WILL BE TOO DRY FOR PRECIPITATION BUT SOME CLOUDS AND NORMAL TO SLIGHTLY ABOVE NORMAL TEMPERATURES LOOK LIKE A GOOD BET. GIVEN THAT A STRONGER NW FLOW ALOFT IS EXPECTED OVER THE GREAT LAKES, A REASONABLE SCENARIO FOR EARLY NEXT WEEK INCLUDES A COLD FRONT SETTLING INTO LOWER MICHIGAN DURING THE MONDAY AND TUESDAY PERIOD. AT THE SAME TIME, THE GLOBAL MODELS DRAW SOME MOISTURE INTO THE FRONTAL ZONE FROM THE CUT OFF LOW THAT IS STILL DRIFTING IN THE PLAINS. PREDICTABILITY IS RATHER LOW IN THIS ASPECT OF THE FORECAST CONSIDERING HOW MUCH VARIABILITY WILL BE INVOLVED IN THE POSITION OF THE LOW AND THE ASSOCIATED DEFORMATION AXIS. ONCE THE FRONT MOVES THROUGH, TUESDAY AND WEDNESDAY COULD END UP DRY AS THE UPPER LOW DRIFTS WESTWARD AND AWAITS THE NEXT PACIFIC COAST TROUGH BEFORE LIFTING BACK INTO THE WESTERLY FLOW. EITHER WAY, COOLER TEMPERATURES DO APPEAR TO BE A MORE SOLID PART OF THE FORECAST DURING THE MID WEEK PERIOD AS HIGH PRESSURE SETTLES INTO QUEBEC. MARINE... NORTHEAST WINDS WILL BECOME ESTABLISHED OVER THE REGION TONIGHT AS LOW PRESSURE MOVES TO OUR SOUTH AND HIGH PRESSURE MOVES INTO NORTHERN ONTARIO. WIND SPEED WILL BE MODEST BUT THE LONG NE FETCH OF WIND DIRECTION WILL KEEP WAVES ON THE HIGH SIDE ON THE BAY AND LAKE HURON WATERS BUT A SMALL CRAFT ADVISORY IS NOT PLANNED AT THIS TIME. THE NE WINDS WILL LAST THROUGH THURSDAY AND DRIVE THE CHANCE OF THUNDERSTORMS MORE OVER INLAND AREAS DURING THE AFTERNOON. THE WILL BE FOLLOWED BY A SLOW BACKING OF THE WIND TOWARD THE SW BY SATURDAY. FAVORABLE WIND AND WAVE CONDITIONS ARE THEN EXPECTED FOR THE WEEKEND. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ UPDATE.......SC AVIATION.....SC SHORT TERM...CB LONG TERM....BT MARINE.......BT YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE). mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 738 PM EDT WED AUG 13 2008 .AVIATION...SPOTTY CONVECTION EXPECTED TO WIND DOWN THIS EVENING... WITH DRY CONDITIONS EXPECTED OVERNIGHT...AND POSSIBLY SOME FOG/ST ESPECIALLY AROUND TVC. MORE DIURNAL SHOWERS EXPECTED THURSDAY AFTERNOON...BUT MOST OF IT SHOULD BE INLAND OF THE TERMINAL LOCATIONS. JPB && .DISCUSSION... /ISSUED 341 PM EDT WED AUG 13 2008/ LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW A RATHER CONVOLUTED PRESSURE/WIND PATTERN ACROSS THE NORTHERN GREAT LAKES WITH A MORE DOMINANT SURFACE OVER NORTHERN ONTARIO. LAKE BREEZE CONVERGENCE ALONG WITH THE HIGHER TERRAIN HAVE AIDED IN THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS...NOW MOST NUMEROUS ACROSS SE PORTIONS OF THE FORECAST AREA. SOME AREAS HAVE RECEIVED UPWARDS OF 2-3 INCHES OF RAIN ACROSS IOSCO AND ALCONA COUNTIES WHERE STORMS HAVE STALLED ALONG LAKE BREEZES. A COUPLE STORMS HAVE BECOME MARGINALLY SEVERE DUE TO LARGE HAIL...BUT HAVE NOT BECOME CONVINCED ENOUGH TO ISSUE ANY WARNINGS AND DID NOT RECEIVE ANY REPORTS TO THE CONTRARY. MORE SCATTERED ACTIVITY RESIDES ACROSS NW LOWER AS WELL AS EASTERN UPPER AT THIS HOUR. OTHERWISE...MID-LEVEL CONVERGENCE ZONE BETWEEN UPPER LOWS OVER QUEBEC AND SASKATCHEWAN HAS SHIFTED TO THE SE...AND SOUTH OF NORTHERN MICHIGAN FOR THE MOST PART. ANOTHER POTENT WAVE NEAR JAMES BAY ALSO HAS EYES SET ON NORTHERN MICHIGAN...BUT THAT WILL POSE MORE OF A PROBLEM FOR TOMORROW. MAIN FORECAST CONCERNS OVER THE NEXT 24 HOURS INCLUDE ONGOING THUNDERSTORM ACTIVITY AND THUNDERSTORM CHANCES TOMORROW AFTERNOON. TONIGHT...SHORTWAVE ACROSS SE ONTARIO WILL CONTINUE TO DIVE SOUTHEAST AWAY FROM NORTHERN MICHIGAN. WITH LOSS OF HEATING...CONVECTION SHOULD BE ON THE DOWNWARD TREND AND PRIMARILY CONFINED TO NE LOWER WHERE OUTFLOW BOUNDARIES WILL BE PREVALENT. BUT WILL LEAVE A CHANCE OF THUNDERSTORMS FOR NE LOWER THROUGH ABOUT MIDNIGHT. THEREAFTER...SURFACE HIGH PRESSURE WILL NOSE IN FROM THE NORTH UNDER A DRY PREVAILING NNE WIND. THE LIGHT ONSHORE WIND COMBINED WITH CLEARING SKIES AND THE HEAVY RAINFALL NEAR OSC AND HARRISVILLE LOOKS LIKE A DECENT SETUP FOR FOG AND HAVE GIVEN THE FOG WORDING A BOOST. STRONG SHORTWAVE NEAR JAMES BAY WILL SWING TOWARDS EASTERN LAKE SUPERIOR LATE...BUT WILL KEEP EASTERN UPPER DRY DUE TO A LACK OF MOISTURE. TOMORROW...THE NEXT SPOKE OF ENERGY WILL ROTATE ACROSS NORTHERN MICHIGAN. EVEN THOUGH THIS SHORTWAVE LOOKS IMPRESSIVE ON THE NAM/GFS...MID-LEVEL MOISTURE IS IN SHORT SUPPLY AHEAD OF THE WAVE. IN ADDITION...LOW LEVEL COLD ADVECTION WILL OFFSET DPVA TO YIELD NEUTRAL OR SLIGHTLY DOWNWARD MOTION. NONETHELESS...500MB TEMPERATURES WILL FALL TO -19C TO -20C ACROSS NE LOWER AND SERVE TO STEEPEN MID-LEVEL LAPSE RATES TO BETWEEN 6.5-7.0 C/KM. NNE LOW LEVEL WINDS WILL KEEP DEW POINTS FROM MIXING OUT ACROSS NE LOWER. USING A 75/54F PARCEL...A 21Z PROGGED SOUNDING NEAR WEST BRANCH YIELDS ABOUT 700 J/KG OF ML CAPE WITH NO CIN. LOW LEVEL WINDS WILL BE STRONGER THAN TODAY...AND SHOULD PREVENT LAKE BREEZES FROM FORMING ACROSS NW LOWER...BUT LIGHT WINDS ON THE LAKE HURON SHORE MAY BE WEAK ENOUGH TO TURN WINDS MORE EAST OR SOUTHEAST...WHICH WOULD HELP FOCUS CONVECTION. THE HIGHER TERRAIN MAY ALSO PROVIDE A BOOST AS WELL. SO HAVE EXPANDED LOW PRECIP CHANCES TO INCLUDE ALL OF NE LOWER AND DRUMMOND ISLAND THROUGH THE AFTERNOON...BUT COVERAGE SHOULD NOT BE AS ROBUST AS TODAY. HIGHS IN THE LOW TO MID 70S. MPC THURSDAY NIGHT AND FRIDAY...ONE MORE SHORT WAVE WILL DROP THRU THE BASE OF THE 500 MB UPPER LOW AND THRU THE ERN HALF OF OUR CWA THURSDAY NIGHT...PROVIDING A CONTINUED CHANCE OF A FEW SHOWERS. STRONG SURFACE RIDGING AND DRY AIR WILL BUILD EASTWARD INTO MICHIGAN FOR FRIDAY AS THE UPPER LEVEL RIDGE BEGINS TO SHIFT NW AWAY FROM THE STATE. FRIDAY SHOULD BE A NICE LATE SUMMER DAY ACROSS MICHIGAN... WITH DRY WX AND MAINLY SUNNY CONDITIONS. HIGH TEMPS BOTH THURSDAY AND FRIDAY WILL BE IN THE 70S...WITH OVERNIGHT LOWS IN THE 50S. SATURDAY THRU WEDNESDAY...PERSISTENT UPPER LEVEL TROUGH OVER THE ERN US WILL LIFT NE FURTHER INTO QUEBEC....WHILE THE WRN RIDGE WILL HOLD ITS POSITION OVER THE US ROCKIES. CUT-OFF 500 MB LOW TO THE LEE OF THE ROCKIES OVER THE CENTRAL PLAINS WILL DEEPEN AND BECOME BETTER ESTABLISHED OVER THIS REGION DURING THE FIRST HALF OF NEXT WEEK. BOTH ECMWF AND GFS ARE POINTING TOWARD WEAK UPPER LEVEL RIDGING GRADUALLY BUILDING FROM THE SE US THRU THE OHIO VALLEY AND INTO THE GREAT LAKES REGION DURING THIS TIME. THE END RESULT IS A RATHER STAGNANT WX PATTERN SETTING UP ACROSS THE US OVER THE NEXT WEEK... WITH MICHIGAN STUCK IN WEAK RIDGING THRU THE COLUMN. CERTAINLY CANNOT COMPLETELY RULE OUT ANY CHANCE OF PRECIP THRU THE MIDDLE OF NEXT WEEK...BUT CHANCES ARE TOO SLIM TO KEEP IN THE FORECAST. THUS...HAVE OPTED TO REMOVE ALL POPS FOR THE FIRST HALF OF NEXT WORKWEEK. AFTERNOON HIGH TEMPS THRU THE PERIOD WILL BE IN THE UPPER 70S TO MID 80S...WITH OVERNIGHT LOWS IN THE UPPER 50S TO LOWER 60S. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 716 PM EDT WED AUG 13 2008 .AVIATION... THE RADAR IS SHOWING NUMEROUS SURFACE BOUNDARIES EXTENDING ACROSS THE REGION BETWEEN FNT AND DTW. THESE ARE A RESULT OF A COMBINATION OF CONVECTIVE OUTFLOW AND LAKE BREEZE BOUNDARIES. WANING DAYTIME INSTABILITY WILL RESULT IN A CONTINUED DIMINISHING TREND TO THE CONVECTION DURING THE COURSE OF THE EVENING. THUS...SEE NO REASON TO MENTION ANY EVENING THUNDER IN THE 00Z TAFS. ANTICIPATING THE OUTFLOW BOUNDARY NOW SLIDING SOUTH ACROSS OAKLAND COUNTY WILL WEAKEN OVER THE NEXT HOUR OR TWO. THUS...EXPECTING MORE OF A VARIABILITY IN THE WINDS AT DTW THIS EVENING AS OPPOSED TO AN ABRUPT WIND SHIFT TO THE NORTH. SURFACE DEWPOINTS IN THE UPPER 50S SUGGEST SOME FOG POTENTIAL. WITH SATELLITE SUPPORTING MODEL SOUNDINGS WHICH INDICATE A CONSIDERABLE AMOUNT OF MID LEVEL MOISTURE OVER THE REGION TONIGHT...PLAN TO JUST DROP VSBY INTO THE MVFR RANGE LATE TONIGHT/EARLY THU MORNING. && .PREV DISCUSSION...ISSUED 405 PM EDT WED AUG 13 2008 SHORT TERM...THIS AFTERNOON AND EVENING THUNDERSTORM BEHAVIOR THIS AFTERNOON SUPPORTS THE NOTION OF A MARGINAL INSTABILITY/WEAK SHEAR ENVIRONMENT. SURFACE BASED CAPES IN THE LATEST RUC ANALYSIS/BUFKIT SOUNDINGS ARE LESS THAN 1000 J/KG UNDER EXTREMELY MEAGER ENVIRONMENTAL LAPSE RATES (ABOVE 500MB). A COMPOSITE LAKE/CONVECTIVE THERMAL GRADIENT HAS ESTABLISHED FROM ROUGHLY PORT HURON TO BAY CITY. MODELS INDICATE A PUSH OF THE BOUNDARY SOUTHWESTWARD THROUGH THE CWA TONIGHT AS DIURNAL HEATING IS LOST AND WEAK MIDLEVEL ENERGY PUSHES IN BEHIND. WITH THE WEAKLY CAPPED ENVIRONMENT...ADDITIONAL DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG THIS FEATURE UNTIL A SURFACE INVERSION GROWS THIS EVENING. SEVERE WEATHER IS NOT ANTICIPATED THIS AFTERNOON OR EVENING...BUT A STORM OR TWO MAY BECOME STRONG ALONG ANY BOUNDARY INTERSECTIONS AND OR CELL MERGERS. GIVEN WEAK MEAN LAYER FLOW OF 5-10 KNOTS...THE MAIN THREAT WILL BE HEAVY RAINFALL UNDER SLOW MOVING/STALLED THUNDERSTORMS. HAIL TO HALF INCH AND FREQUENT LIGHTNING MAY ALSO BE EXPERIENCED. WITH AN INFILTRATING MARINE AIRMASS AND WEAK FLOW HAVE ADDED PATCHY FOG FOR AREAS OUTSIDE OF THE METRO...WITH ANY DENSE SPOTS REMAINING ISOLATED. LOWS TONIGHT WILL SETTLE INTO THE LOWER 50S NORTH TO LOWER 60S SOUTH. LONG TERM...THURSDAY THROUGH NEXT WEDNESDAY THE NEXT IN THE SERIES OF WAVES ROTATING AROUND THE LARGE EASTERN UPPER LOW IS ON SATELLITE MOVING INTO NORTHERN ONTARIO AND WILL AFFECT SE MICHIGAN ON THURSDAY. THIS WILL KEEP A CHANCE OF SHOWERS AND EVEN AN ISOLATED THUNDERSTORM POSSIBLE BY AFTERNOON. THE PROBLEM IS THAT THE SYSTEM FROM TODAY IS NOT EXPECTED TO SCOUR OUT ENOUGH MOISTURE BELOW 850 MB TO REDUCE THE EFFECTIVENESS OF SUPPORT FROM THE WAVE. DEEP CYCLONIC FLOW, AND THE ASSOCIATED DYNAMIC FORCING, WILL BE ACCOMPANIED BY TEMPERATURES DROPPING TO BETWEEN -14C AND -17C. THIS WILL COMBINE WITH A SURFACE PARCEL IN THE UPPER 70S/UPPER 50S TO PRODUCE POCKETS OF CAPE AROUND 1000 J/KG. THE 12Z MODELS ARE NOT GREATLY IMPRESSED WITH THE AMOUNT OF SURFACE PRESSURE REFLECTION BUT A PATTERN SIMILAR TO TODAY SEEMS LIKE A REASONABLE EXPECTATION, WHICH INCLUDES LAKE BOUNDARY CONTRIBUTIONS AS WELL AS WEAK SYNOPTIC CONTRIBUTIONS. THIS WAVE WILL DO A BETTER JOB OF SCOURING OUT THE MOISTURE IN THE LOW LEVELS BUT THERE WILL BE SOME LINGERING INFLUENCE OF THE SYSTEM DURING FRIDAY. CYCLONIC FLOW IN THE MID AND UPPER LEVELS, AND LINGERING COLD POOL ALOFT, WILL PROVIDE FOR AN ISOLATED SHOWER. THE LARGER STORY WILL BE YET ANOTHER SURGE OF COOL AIR ATTEMPTING TO TAKE 850 MB TEMPERATURES DOWN INTO THE SINGLE DIGITS AND LIMITING HIGH TEMPERATURES TO THE 70S. THE 12Z MODEL RUNS THEN LOOK REASONABLE IN MAINTAINING DRY CONDITIONS OVER SE MICHIGAN ON SATURDAY. THIS WILL BE ACCOMPLISHED BY DRY NW FLOW ALOFT COMBINED WITH SURFACE HIGH PRESSURE CENTERED TO OUR SOUTH. WESTERLY FLOW ON SUNDAY WILL REPRESENT A WARM ADVECTION PATTERN AHEAD OF A WAVE IN CENTRAL CANADA. THIS IS PART OF A TREND IN THE GLOBAL MODEL SOLUTIONS TOWARD A MORE ACTIVE NW UPPER LEVEL FLOW. THIS TREND LOOKS GOOD AFTER CONSIDERING THE FLOW WILL BE FORCED BY RELIABLE DEPICTIONS OF THE HIGHLY AMPLIFIED LONG WAVE PATTERN THROUGHOUT THE WESTERN HEMISPHERE. CONFIDENCE IS ON THE HIGH SIDE THAT THIS LARGE SCALE PATTERN WILL KEEP A LONG WAVE RIDGE ANCHORED OVER WESTERN NORTH AMERICA AND GUIDE THE WESTERLIES FROM CENTRAL CANADA INTO THE NORTHERN GREAT LAKES WHILE THE CUT OFF LOW LUMBERS AROUND OVER THE SOUTHERN PLAINS STATES. WE EXPECT THE WARM ADVECTION PATTERN OVER THE GREAT LAKES WILL BE TOO DRY FOR PRECIPITATION BUT SOME CLOUDS AND NORMAL TO SLIGHTLY ABOVE NORMAL TEMPERATURES LOOK LIKE A GOOD BET. GIVEN THAT A STRONGER NW FLOW ALOFT IS EXPECTED OVER THE GREAT LAKES, A REASONABLE SCENARIO FOR EARLY NEXT WEEK INCLUDES A COLD FRONT SETTLING INTO LOWER MICHIGAN DURING THE MONDAY AND TUESDAY PERIOD. AT THE SAME TIME, THE GLOBAL MODELS DRAW SOME MOISTURE INTO THE FRONTAL ZONE FROM THE CUT OFF LOW THAT IS STILL DRIFTING IN THE PLAINS. PREDICTABILITY IS RATHER LOW IN THIS ASPECT OF THE FORECAST CONSIDERING HOW MUCH VARIABILITY WILL BE INVOLVED IN THE POSITION OF THE LOW AND THE ASSOCIATED DEFORMATION AXIS. ONCE THE FRONT MOVES THROUGH, TUESDAY AND WEDNESDAY COULD END UP DRY AS THE UPPER LOW DRIFTS WESTWARD AND AWAITS THE NEXT PACIFIC COAST TROUGH BEFORE LIFTING BACK INTO THE WESTERLY FLOW. EITHER WAY, COOLER TEMPERATURES DO APPEAR TO BE A MORE SOLID PART OF THE FORECAST DURING THE MID WEEK PERIOD AS HIGH PRESSURE SETTLES INTO QUEBEC. MARINE... NORTHEAST WINDS WILL BECOME ESTABLISHED OVER THE REGION TONIGHT AS LOW PRESSURE MOVES TO OUR SOUTH AND HIGH PRESSURE MOVES INTO NORTHERN ONTARIO. WIND SPEED WILL BE MODEST BUT THE LONG NE FETCH OF WIND DIRECTION WILL KEEP WAVES ON THE HIGH SIDE ON THE BAY AND LAKE HURON WATERS BUT A SMALL CRAFT ADVISORY IS NOT PLANNED AT THIS TIME. THE NE WINDS WILL LAST THROUGH THURSDAY AND DRIVE THE CHANCE OF THUNDERSTORMS MORE OVER INLAND AREAS DURING THE AFTERNOON. THE WILL BE FOLLOWED BY A SLOW BACKING OF THE WIND TOWARD THE SW BY SATURDAY. FAVORABLE WIND AND WAVE CONDITIONS ARE THEN EXPECTED FOR THE WEEKEND. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....SC SHORT TERM...CB LONG TERM....BT MARINE.......BT YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE). mi AREA FORECAST DISCUSSION...UPDATED FOR AVIATION DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 656 PM EDT WED AUG 13 2008 .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A MID LEVEL RIDGE OVER WESTERN ONTARIO SEPARATING A LOW OVER SOUTHWEST QUEBEC FROM A LOW OVER SOUTHEAST SASKATCHEWAN. A WEAK SHORTWAVE ROTATING AROUND THE BASE OF QUEBEC LOW IS OVER EASTERN ONTARIO. ANOTHER SHORTWAVE STRETCHES FROM MANITOBA SOUTHEAST THROUGH NORTHERN MINNESOTA AND WISCONSIN. SURFACE ANALYSIS DEPICTS A HIGH OVER SOUTHERN HUDSON BAY WITH A RIDGE EXTENDING SOUTH THROUGH THE UPPER MICHIGAN. A SURFACE LOW IS ALSO OVER SOUTHEAST SASKATCHEWAN WITH A WEAK FRONTAL SYSTEM EXTENDING SOUTHEAST THROUGH MINNESOTA INTO IOWA. FAIRLY DRY AIR REMAINS IN PLACE OVER WESTERN ONTARIO AND UPPER MICHIGAN. SCATTERED LIGHT RAIN SHOWERS ARE OVER LAKE SUPERIOR AND NORTHERN LAKE MICHIGAN AND EXTREME WESTERN UPPER MICHIGAN. .SHORT TERM...TONIGHT AND THURSDAY. THE LOW OVER SASKATCHEWAN WILL SETTLE A LITTLE SOUTHEAST TONIGHT...WHILE THE QUEBEC LOW BACKS UP INTO SOUTHEAST ONTARIO. A WEAK SHORTWAVE ROTATING AROUND THIS LOW WILL SWEEP INTO EASTERN LAKE SUPERIOR. THE WISCONSIN/MINNESOTA SHORTWAVE WILL BE DEFLECTED A LITTLE SOUTH INTO NORTHEAST IOWA AND SOUTHWEST WISCONSIN. MEANWHILE...THE SURFACE HUDSON BAY RIDGE WILL EXPAND ACROSS NORTH ONTARIO AND INTO THE UPPER GREAT LAKES. AN INVERTED TROUGH WILL DEVELOP OVERNIGHT OVER THE NORTHERN PLAINS AND SOUTH CENTRAL CANADA. A STATIONARY FRONT ASSOCIATED WITH THIS TROUGH WILL DEVELOP OVER NORTHERN PLAINS AND STRETCH SOUTHEAST INTO CENTRAL IOWA. DRY AIR WILL CONTINUE TO ADVANCE INTO THE AREA FROM NORTH OF LAKE SUPERIOR. THIS SHOULD HOLD OFF DEVELOPING ANY SHOWERS OVER THE FORECAST AREA. THE SHORTWAVE OVER EASTERN LAKE SUPERIOR WILL SWEEP SOUTHEAST THROUGH EASTERN UPPER MICHIGAN ON THURSDAY. UPPER LEVEL DIVERGENCE OVER EASTERN LAKE SUPERIOR WILL SUPPORT INCREASE INSTABILITY EARLY. HOWEVER...THE SURFACE RIDGE WILL SPREAD OVER THE AREA AND THE ACCOMPANYING DRY AIR WILL KEEP THE CHANCE OF SHOWERS AND THUNDERSTORMS FROM OCCURRING. .LONG TERM (THU NGT THRU WED)... EXPECT A DRY NITE THU NGT WITH HI PRES BLDG INTO THE MN ARROWHEAD BY 12Z FRI UNDER RISING UPR HGTS IN THE WAKE OF SHRTWV PASSING THE ERN CWA ON THU. THERE MAY BE A FEW CLDS OVER THE E TOWARD THE LOWER HTS/ LOWER MID LVL TEMPS...BUT THE W HALF WL BE MOCLR. EXPECT THE LOWEST MIN TEMPS BLO MOS GUIDANCE OVER THE INTERIOR W HALF CLOSER TO THE SFC HI/WEAKER PRES GRADIENT/LOWER PWAT AOB 0.5 INCH. THE MN HI CENTER IS PROGGED TO DRIFT SLOWLY INTO NW WI ON FRI AS SHRTWV RDG ALF JUTS INTO THE UPR LKS. EXCEPT FOR SOME SCT CU INLAND FM LK STABILIZATION...SKIES WL BE SUNNY WITH CORE OF DRY AIRMASS OVHD. MIXING TO H75 ON GFS FCST SDNGS (H85 TEMPS ARND 13C) YIELDS HI TEMPS ARND 80 AWAY OVER THE INTERIOR. PER THE FVRD DRIER GFS FCST SDNGS...DWPTS WL MIX OUT TO NEAR 40 IN THE AFTN...RESULTING IN MIN RH NEAR 25 PCT. FORTUNATELY WITH RDG AXIS NEARBY...WINDS WL BE LGT WHERE THE COMBINATION OF HIER TEMPS/LOWER DWPTS WL AGGRAVATE RECENT DRYNESS THE MOST. THE STRONGEST WINDS (NNW UP TO 15 MPH) ARE MOST LIKELY OVER THE E IN SOMEWHAT SHARPER PRES GRADIENT FARTHER FM ACYC CENTER...BUT THIS FLOW WL ALLOW FOR MORE EFFICIENT LK COOLING/ MOISTENING INTO THE E UNTIL THE WINDS DIMINISH IN THE AFTN WITH THE WEAKENING GRADIENT. FRI NGT WL BE ANOTHER MOCLR...QUIET ONE...BUT A STRENGTHENING LLVL WNW FLOW ON THE NRN FLANK OF SFC RDG SINKING TOWARD IA BY 12Z SAT WL LIMIT THE DIURNAL FALL OF TEMP. THE IMPACT OF THE STRONGER FLOW WL BE GREATEST NEAR THE QUICKLY WRMG WATERS OF LK SUP (SFC WATER TEMP IS UP TO 63 AT THE WRN BUOY AND 60 AT THE CNTRL/ERN BUOYS)...WITH THE LOWEST MINS NEAR THE WI BORDER CLOSER TO THE WEAKER GRADIENT AND CORE OF LOWER PWAT ARND 0.5 INCH. THERE ARE HINTS A SHRTWV EMBEDDED IN THE NW FLOW ALF WL PASS THRU ONTARIO ON SAT INTO SAT NGT...BUT THE ASSOCIATED HGT FALLS LOOK TO BE TOO FAR N CONSIDERING THE VERY DRY AIRMASS THAT WL BE IN PLACE. ALTHOUGH THERE MAY BE MORE CLD COVER ESPECIALLY OVER THE NRN TIER...WL RETAIN GOING DRY FCST. SAT WL BE WARMER THAN FRI WITH H85 TEMPS FCST 1-2C HIER IN LLVL WNW FLOW. GFS SHOWS SOME MOIST ADVCTN WITH RISING MIXING RATIO IN THE MIXED LYR...SO EXPECT DIURNAL CU DVLPMNT. EVEN WITH SOME INCRS IN LLVL MSTR...DWPTS WL MIX OUT INTO THE 40S IN THE AFTN OVER THE INTERIOR W HALF. THE RESULT WL BE ANOTHER DAY WITH MIN RH WITH AOB 30 PCT. SUN LOOKS TO BE A WARM DAY WITH DRY WLY FLOW IN ADVANCE OF BACK DOOR COLD FNT DROPPING SLOWLY THRU ONTARIO IN WNW FLOW ALF PRESENT THERE ON SW FLANK OF VORTEX OVER NE CAN. WITH H85 TEMPS PEAKING ARND 16C... EXPECT DAYTIME HI TEMPS PEAKING IN THE 80S AWAY FM LK MODERATION. BACK DOOR COLD FROPA FM THE N STILL LOOKS ON TRACK FOR MON...BUT RELATIVELY HI HGTS ON SRN FLANK OF MAIN BELT OF WESTERLIES TO THE N/DRY AIRMASS WL RESTRICT PCPN COVG. WL RETAIN GOING 20 POP. THEN DRY AND SOMEWHAT COOLER ON TUE WITH HUDSON BAY HI PRES BLDG IN BEHIND THE BACK DOOR COLD FROPA AS UPR TROFFING AMPLIFIES IN ERN CAN. AS THIS HI SINKS SE TOWARD THE NE CONUS ON WED...INCRSG SLY FLOW ON ITS WRN FLANK AND E OF DEEPENING TROF OVER THE W WL ADVECT MORE MSTR BACK TOWARD THE UPR LKS. WL GO WITH INCRSG CLDS ON WED AND INTRODUCE LO CHC POPS OVER THE SRN TIER IN THE AFTN. COORDINATED WITH APX/LOT/GRB/DLH. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... EAST/NORTHEAST WINDS SET UP THIS AFTERNOON AND PERSISTS INTO TONIGHT AND ADD MOISTURE OFF OF TORCH LAKE TO THE EAST OF KCMX COULD RESULT IN PATCHY FOG LATE TONIGHT SIMILAR TO LAST TWO NIGHTS. THIS WILL PRODUCE FOG AT KCMX...WOULD PROBABLY BE A BRIEF PERIOD OF ANYWHERE FROM LIFR TO MVFR VISIBILITY. VFR CONDITIONS WILL PREVAIL AT KSAW AND WILL PREVAIL FOR MOST OF THE PERIOD FOR KCMX AS WELL. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... SFC HIGH PRESSURE BUILDING OUT OF ONTARIO WILL SETTLE ACROSS GREAT LAKES TONIGHT THROUGH FRIDAY. NORTHEAST WINDS SHOULD APPROACH 20 KNOTS OVER WESTERN LAKE SUPERIOR THROUGH THURSDAY DUE TO CHANNELING BETWEEN MINNESOTA SHORELINE AND APOSTLE ISLANDS. AS THE HIGH MOVES SOUTH OF THE AREA SATURDAY AND SUNDAY...WINDS WILL REMAIN 20 KNOTS OR LESS THROUGH THE EST OF THE FORECAST PERIOD. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...DLG LONG TERM...KC AVIATION...GM MARINE...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 405 PM EDT WED AUG 13 2008 .SHORT TERM...THIS AFTERNOON AND EVENING THUNDERSTORM BEHAVIOR THIS AFTERNOON SUPPORTS THE NOTION OF A MARGINAL INSTABILITY/WEAK SHEAR ENVIRONMENT. SURFACE BASED CAPES IN THE LATEST RUC ANALYSIS/BUFKIT SOUNDINGS ARE LESS THAN 1000 J/KG UNDER EXTREMELY MEAGER ENVIRONMENTAL LAPSE RATES (ABOVE 500MB). A COMPOSITE LAKE/CONVECTIVE THERMAL GRADIENT HAS ESTABLISHED FROM ROUGHLY PORT HURON TO BAY CITY. MODELS INDICATE A PUSH OF THE BOUNDARY SOUTHWESTWARD THROUGH THE CWA TONIGHT AS DIURNAL HEATING IS LOST AND WEAK MIDLEVEL ENERGY PUSHES IN BEHIND. WITH THE WEAKLY CAPPED ENVIRONMENT...ADDITIONAL DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG THIS FEATURE UNTIL A SURFACE INVERSION GROWS THIS EVENING. SEVERE WEATHER IS NOT ANTICIPATED THIS AFTERNOON OR EVENING...BUT A STORM OR TWO MAY BECOME STRONG ALONG ANY BOUNDARY INTERSECTIONS AND OR CELL MERGERS. GIVEN WEAK MEAN LAYER FLOW OF 5-10 KNOTS...THE MAIN THREAT WILL BE HEAVY RAINFALL UNDER SLOW MOVING/STALLED THUNDERSTORMS. HAIL TO HALF INCH AND FREQUENT LIGHTNING MAY ALSO BE EXPERIENCED. WITH AN INFILTRATING MARINE AIRMASS AND WEAK FLOW HAVE ADDED PATCHY FOG FOR AREAS OUTSIDE OF THE METRO...WITH ANY DENSE SPOTS REMAINING ISOLATED. LOWS TONIGHT WILL SETTLE INTO THE LOWER 50S NORTH TO LOWER 60S SOUTH. && .LONG TERM...THURSDAY THROUGH NEXT WEDNESDAY THE NEXT IN THE SERIES OF WAVES ROTATING AROUND THE LARGE EASTERN UPPER LOW IS ON SATELLITE MOVING INTO NORTHERN ONTARIO AND WILL AFFECT SE MICHIGAN ON THURSDAY. THIS WILL KEEP A CHANCE OF SHOWERS AND EVEN AN ISOLATED THUNDERSTORM POSSIBLE BY AFTERNOON. THE PROBLEM IS THAT THE SYSTEM FROM TODAY IS NOT EXPECTED TO SCOUR OUT ENOUGH MOISTURE BELOW 850 MB TO REDUCE THE EFFECTIVENESS OF SUPPORT FROM THE WAVE. DEEP CYCLONIC FLOW, AND THE ASSOCIATED DYNAMIC FORCING, WILL BE ACCOMPANIED BY TEMPERATURES DROPPING TO BETWEEN -14C AND -17C. THIS WILL COMBINE WITH A SURFACE PARCEL IN THE UPPER 70S/UPPER 50S TO PRODUCE POCKETS OF CAPE AROUND 1000 J/KG. THE 12Z MODELS ARE NOT GREATLY IMPRESSED WITH THE AMOUNT OF SURFACE PRESSURE REFLECTION BUT A PATTERN SIMILAR TO TODAY SEEMS LIKE A REASONABLE EXPECTATION, WHICH INCLUDES LAKE BOUNDARY CONTRIBUTIONS AS WELL AS WEAK SYNOPTIC CONTRIBUTIONS. THIS WAVE WILL DO A BETTER JOB OF SCOURING OUT THE MOISTURE IN THE LOW LEVELS BUT THERE WILL BE SOME LINGERING INFLUENCE OF THE SYSTEM DURING FRIDAY. CYCLONIC FLOW IN THE MID AND UPPER LEVELS, AND LINGERING COLD POOL ALOFT, WILL PROVIDE FOR AN ISOLATED SHOWER. THE LARGER STORY WILL BE YET ANOTHER SURGE OF COOL AIR ATTEMPTING TO TAKE 850 MB TEMPERATURES DOWN INTO THE SINGLE DIGITS AND LIMITING HIGH TEMPERATURES TO THE 70S. THE 12Z MODEL RUNS THEN LOOK REASONABLE IN MAINTAINING DRY CONDITIONS OVER SE MICHIGAN ON SATURDAY. THIS WILL BE ACCOMPLISHED BY DRY NW FLOW ALOFT COMBINED WITH SURFACE HIGH PRESSURE CENTERED TO OUR SOUTH. WESTERLY FLOW ON SUNDAY WILL REPRESENT A WARM ADVECTION PATTERN AHEAD OF A WAVE IN CENTRAL CANADA. THIS IS PART OF A TREND IN THE GLOBAL MODEL SOLUTIONS TOWARD A MORE ACTIVE NW UPPER LEVEL FLOW. THIS TREND LOOKS GOOD AFTER CONSIDERING THE FLOW WILL BE FORCED BY RELIABLE DEPICTIONS OF THE HIGHLY AMPLIFIED LONG WAVE PATTERN THROUGHOUT THE WESTERN HEMISPHERE. CONFIDENCE IS ON THE HIGH SIDE THAT THIS LARGE SCALE PATTERN WILL KEEP A LONG WAVE RIDGE ANCHORED OVER WESTERN NORTH AMERICA AND GUIDE THE WESTERLIES FROM CENTRAL CANADA INTO THE NORTHERN GREAT LAKES WHILE THE CUT OFF LOW LUMBERS AROUND OVER THE SOUTHERN PLAINS STATES. WE EXPECT THE WARM ADVECTION PATTERN OVER THE GREAT LAKES WILL BE TOO DRY FOR PRECIPITATION BUT SOME CLOUDS AND NORMAL TO SLIGHTLY ABOVE NORMAL TEMPERATURES LOOK LIKE A GOOD BET. GIVEN THAT A STRONGER NW FLOW ALOFT IS EXPECTED OVER THE GREAT LAKES, A REASONABLE SCENARIO FOR EARLY NEXT WEEK INCLUDES A COLD FRONT SETTLING INTO LOWER MICHIGAN DURING THE MONDAY AND TUESDAY PERIOD. AT THE SAME TIME, THE GLOBAL MODELS DRAW SOME MOISTURE INTO THE FRONTAL ZONE FROM THE CUT OFF LOW THAT IS STILL DRIFTING IN THE PLAINS. PREDICTABILITY IS RATHER LOW IN THIS ASPECT OF THE FORECAST CONSIDERING HOW MUCH VARIABILITY WILL BE INVOLVED IN THE POSITION OF THE LOW AND THE ASSOCIATED DEFORMATION AXIS. ONCE THE FRONT MOVES THROUGH, TUESDAY AND WEDNESDAY COULD END UP DRY AS THE UPPER LOW DRIFTS WESTWARD AND AWAITS THE NEXT PACIFIC COAST TROUGH BEFORE LIFTING BACK INTO THE WESTERLY FLOW. EITHER WAY, COOLER TEMPERATURES DO APPEAR TO BE A MORE SOLID PART OF THE FORECAST DURING THE MID WEEK PERIOD AS HIGH PRESSURE SETTLES INTO QUEBEC. && .MARINE... NORTHEAST WINDS WILL BECOME ESTABLISHED OVER THE REGION TONIGHT AS LOW PRESSURE MOVES TO OUR SOUTH AND HIGH PRESSURE MOVES INTO NORTHERN ONTARIO. WIND SPEED WILL BE MODEST BUT THE LONG NE FETCH OF WIND DIRECTION WILL KEEP WAVES ON THE HIGH SIDE ON THE BAY AND LAKE HURON WATERS BUT A SMALL CRAFT ADVISORY IS NOT PLANNED AT THIS TIME. THE NE WINDS WILL LAST THROUGH THURSDAY AND DRIVE THE CHANCE OF THUNDERSTORMS MORE OVER INLAND AREAS DURING THE AFTERNOON. THE WILL BE FOLLOWED BY A SLOW BACKING OF THE WIND TOWARD THE SW BY SATURDAY. FAVORABLE WIND AND WAVE CONDITIONS ARE THEN EXPECTED FOR THE WEEKEND. && .PREV DISCUSSION...ISSUED 239 PM EDT WED AUG 13 2008 AVIATION... SHOWERS AND THUNDERSTORMS WILL AFFECT SOUTHEASTERN MICHIGAN THROUGH THIS EVENING. VARIOUS SURFACE BOUNDARIES LYING AROUND THE CWA WILL SUPPORT ADDITIONAL DEVELOPMENT. THE CONVECTION CURRENTLY UNDERWAY IS EXPECTED TO SLOWLY MIGRATE EASTWARD AND THUS...MISSING THE AREA TERMINALS THE NEXT COUPLE OF HOURS. MIDLEVEL SHORTWAVE ENERGY AND AN ASSOCIATED SURFACE TROUGH WILL PUSH INTO THE FORECAST AREA FROM THE NORTHEAST LATER THIS AFTERNOON AND EVENING (ACTIVITY NEAR TAWAS CITY IS ANCHORED ALONG THE FEATURE). ADDED A BR MENTION WITH MVFR VISIBILITIES LATER TONIGHT. SURFACE FLOW WILL TREND NORTHEASTERLY. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ SHORT TERM...CB LONG TERM....BT MARINE.......BT AVIATION.....CB YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE). mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 400 PM EDT WED AUG 13 2008 LATEST UPDATE...ALL SECTIONS BUT AVIATION... .SYNOPSIS...(400 PM EDT WED AUG 13 2008) ISOLATED SHOWERS AND STORMS ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE AND WEAK COLD FRONT WILL END LATER THIS EVENING LEAVING PARTLY CLOUDY SKIES AND PATCHY FOG. YET ANOTHER UPPER LEVEL DISTURBANCE AND COLD FRONT WILL SLIP SOUTH FROM CANADA AND PASS THROUGH LOWER MICHIGAN ON THURSDAY. ISOLATED SHOWERS AND THUNDERSTORMS WILL FORM AGAIN IN THE AFTERNOON AND LINGER INTO THE EVENING... MAINLY SOUTH OF INTERSTATE 96. HIGH PRESSURE AND DRIER AIR WILL SETTLE INTO THE REGION ON FRIDAY RESULTING IN MOSTLY SUNNY AND PLEASANT CONDITIONS. A WARM UP IS IN STORE FOR THE COMING WEEKEND. && .SHORT TERM...(400 PM EDT WED AUG 13 2008) (TONIGHT THROUGH FRIDAY NIGHT) DIURNALLY DRIVEN ISOLATED SHOWERS/TSTMS WILL PROBABLY LINGER THROUGH ABOUT 02-03Z OR SO. RUC/NAM SHOW BEST SFC CONVERGENCE EARLY THIS EVENING EAST/NORTH OF A LINE FROM ROUGHLY CADILLAC TO BIG RAPIDS TO LANSING... SO BELIEVE THE NE HALF OF THE CWFA WILL SEE SOME CONVECTION DEVELOPING SOON. SOME PATCHY FOG WILL BE POSSIBLE LATE TONIGHT DUE TO LIGHT WINDS... PARTICULARLY IN SPOTS WHERE IT RAINED TODAY AND THIS EVENING. ON THURSDAY AFTERNOON AND EVENING THE NEXT CANADIAN H5 TROUGH AND COLD FRONT PIVOT SOUTH THROUGH THE STATE. LACK OF MOISTURE AND POSITIVE TILT OF THE H5 TROUGH WILL BE LIMITING FACTORS FOR WIDESPREAD CONVECTION SO WILL KEEP RAIN COVERAGE AT ONLY ISOLATED/20 PERCENT. THE BEST MOISTURE IS INDICATED TO BE IN THE SRN CWFA WHICH MAY BE WHERE COVERAGE (ALTHOUGH STILL QUITE LIMITED) IS BEST THURSDAY AFTERNOON AND EVENING. ON FRIDAY THE H5 TROUGH AXIS WILL BE OVER THE ERN GRTLKS REGION AND WE WILL BE ON THE BACK SIDE OF THE TROUGH. THIS SHOULD YIELD DRY/MOSUNNY WEATHER AS MAIN DIURNAL CUMULUS/SHOWER DEVELOP OCCURS OVER ERN LWR MI. && .LONG TERM...(400 PM EDT WED AUG 13 2008) (SATURDAY THROUGH WEDNESDAY) THE WEEKEND CONTINUES TO APPEAR DRY AND WARM AS SURFACE AND UPPER RIDGING PREVAILS. BY MONDAY...RETURN FLOW AND MOISTURE FROM THE GULF SHOULD COLLIDE WITH A COLD FRONT DROPPING DOWN FROM CANADA. THE FRONT APPEARS TO MOVE SLOWLY ACROSS THE CWA...FINALLY CLEARING THE AREA LATE TUESDAY. DEPENDING ON THE POSITION AND THE AMOUNT OF GULF MOISTURE THAT MOVES NORTH THIS COULD BE A FAIRLY WET PERIOD FOR THE SOUTHERN CWA. CANADIAN HIGH PRESSURE TRIES TO BUILD SOUTH OVER THE GREAT LAKES BY WEDNESDAY...HOWEVER THE MOISTURE PROFILES STILL SHOWS LEFTOVER RH WHICH COULD RESULT IN DIURNAL SHOWERS/STORMS ON WEDNESDAY. && .MARINE...(400 PM EDT WED AUG 13 2008) MODELS KEEP TRENDING TOWARD A STRONGER NORTH FLOW EVENT ON THURSDAY AFTERNOON AND EVENING. THIS WILL HAVE TO BE MONITORED FOR POSSIBLE SMALL CRAFT ADVISORIES AS WE TEND TO UNDER FCST NORTH FLOW COLD ADVECTION EVENTS THIS TIME OF YEAR. WE COULD SEE SOME RATHER CHOPPY/HAZARDOUS SEAS DEVELOPING NEAR BIG AND LITTLE SABLE POINTS THURSDAY AFTERNOON... SPREADING SOUTH THURSDAY NIGHT. THE BIG QUESTION THOUGH IS HOW MUCH OF A NORTHEAST COMPONENT TO THE WIND THERE WILL BE AS THAT WOULD KEEP THE HIGHEST WAVES OUT TOWARD OPEN WATERS. EVEN FRIDAY LOOKS POTENTIALLY RATHER WINDY FROM THE NORTH... UNTIL SFC RIDGING FIRMLY BUILDS IN FRIDAY NIGHT. && .AVIATION...(200 PM EDT WED AUG 13 2008) A WEAK COLD FRONT WILL DROP SOUTH OVER THE REGION THIS EVENING. WIDELY SCATTERED SHOWERS SHOULD ACCOMPANY THIS FRONT...HOWEVER THE INSTABILITY IS WEAK ENOUGH TO KEEP ANY THUNDERSTORMS TO BE VERY ISOLATED. FOR THE MOST PART VFR CEILINGS AND VSBYS WILL PREVAIL THIS AFTERNOON AND OVERNIGHT. HOWEVER THERE COULD BE MVFR CEILINGS AROUND TOWARD DAYBREAK THURSDAY AS LOW LEVEL MOISTURE POOLS NEAR THE FRONT. DRIER AIR MOVES OVER THE AREA THROUGH THE MID/LATE MORNING HOURS OF THURSDAY...SO ANY MVFR CEILINGS SHOULD BE BRIEF AS CLEARING OCCURS TOWARD MID DAY. && .HYDROLOGY...(400 PM EDT WED AUG 13 2008) NO HYDRO CONCERNS. ANY SHOWERS OR STORMS THAT DEVELOP WILL ONLY RESULT IN A QUARTER INCH OR LESS OF PCPN. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. && $$ SYNOPSIS: MEADE SHORT TERM: MEADE LONG TERM: JK MARINE: MEADE AVIATION: JK HYDROLOGY: MEADE mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 341 PM EDT WED AUG 13 2008 .DISCUSSION...LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW A RATHER CONVOLUTED PRESSURE/WIND PATTERN ACROSS THE NORTHERN GREAT LAKES WITH A MORE DOMINANT SURFACE OVER NORTHERN ONTARIO. LAKE BREEZE CONVERGENCE ALONG WITH THE HIGHER TERRAIN HAVE AIDED IN THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS...NOW MOST NUMEROUS ACROSS SE PORTIONS OF THE FORECAST AREA. SOME AREAS HAVE RECEIVED UPWARDS OF 2-3 INCHES OF RAIN ACROSS IOSCO AND ALCONA COUNTIES WHERE STORMS HAVE STALLED ALONG LAKE BREEZES. A COUPLE STORMS HAVE BECOME MARGINALLY SEVERE DUE TO LARGE HAIL...BUT HAVE NOT BECOME CONVINCED ENOUGH TO ISSUE ANY WARNINGS AND DID NOT RECEIVE ANY REPORTS TO THE CONTRARY. MORE SCATTERED ACTIVITY RESIDES ACROSS NW LOWER AS WELL AS EASTERN UPPER AT THIS HOUR. OTHERWISE...MID-LEVEL CONVERGENCE ZONE BETWEEN UPPER LOWS OVER QUEBEC AND SASKATCHEWAN HAS SHIFTED TO THE SE...AND SOUTH OF NORTHERN MICHIGAN FOR THE MOST PART. ANOTHER POTENT WAVE NEAR JAMES BAY ALSO HAS EYES SET ON NORTHERN MICHIGAN...BUT THAT WILL POSE MORE OF A PROBLEM FOR TOMORROW. MAIN FORECAST CONCERNS OVER THE NEXT 24 HOURS INCLUDE ONGOING THUNDERSTORM ACTIVITY AND THUNDERSTORM CHANCES TOMORROW AFTERNOON. TONIGHT...SHORTWAVE ACROSS SE ONTARIO WILL CONTINUE TO DIVE SOUTHEAST AWAY FROM NORTHERN MICHIGAN. WITH LOSS OF HEATING...CONVECTION SHOULD BE ON THE DOWNWARD TREND AND PRIMARILY CONFINED TO NE LOWER WHERE OUTFLOW BOUNDARIES WILL BE PREVALENT. BUT WILL LEAVE A CHANCE OF THUNDERSTORMS FOR NE LOWER THROUGH ABOUT MIDNIGHT. THEREAFTER...SURFACE HIGH PRESSURE WILL NOSE IN FROM THE NORTH UNDER A DRY PREVAILING NNE WIND. THE LIGHT ONSHORE WIND COMBINED WITH CLEARING SKIES AND THE HEAVY RAINFALL NEAR OSC AND HARRISVILLE LOOKS LIKE A DECENT SETUP FOR FOG AND HAVE GIVEN THE FOG WORDING A BOOST. STRONG SHORTWAVE NEAR JAMES BAY WILL SWING TOWARDS EASTERN LAKE SUPERIOR LATE...BUT WILL KEEP EASTERN UPPER DRY DUE TO A LACK OF MOISTURE. TOMORROW...THE NEXT SPOKE OF ENERGY WILL ROTATE ACROSS NORTHERN MICHIGAN. EVEN THOUGH THIS SHORTWAVE LOOKS IMPRESSIVE ON THE NAM/GFS...MID-LEVEL MOISTURE IS IN SHORT SUPPLY AHEAD OF THE WAVE. IN ADDITION...LOW LEVEL COLD ADVECTION WILL OFFSET DPVA TO YIELD NEUTRAL OR SLIGHTLY DOWNWARD MOTION. NONETHELESS...500MB TEMPERATURES WILL FALL TO -19C TO -20C ACROSS NE LOWER AND SERVE TO STEEPEN MID-LEVEL LAPSE RATES TO BETWEEN 6.5-7.0 C/KM. NNE LOW LEVEL WINDS WILL KEEP DEW POINTS FROM MIXING OUT ACROSS NE LOWER. USING A 75/54F PARCEL...A 21Z PROGGED SOUNDING NEAR WEST BRANCH YIELDS ABOUT 700 J/KG OF ML CAPE WITH NO CIN. LOW LEVEL WINDS WILL BE STRONGER THAN TODAY...AND SHOULD PREVENT LAKE BREEZES FROM FORMING ACROSS NW LOWER...BUT LIGHT WINDS ON THE LAKE HURON SHORE MAY BE WEAK ENOUGH TO TURN WINDS MORE EAST OR SOUTHEAST...WHICH WOULD HELP FOCUS CONVECTION. THE HIGHER TERRAIN MAY ALSO PROVIDE A BOOST AS WELL. SO HAVE EXPANDED LOW PRECIP CHANCES TO INCLUDE ALL OF NE LOWER AND DRUMMOND ISLAND THROUGH THE AFTERNOON...BUT COVERAGE SHOULD NOT BE AS ROBUST AS TODAY. HIGHS IN THE LOW TO MID 70S. MPC THURSDAY NIGHT AND FRIDAY...ONE MORE SHORT WAVE WILL DROP THRU THE BASE OF THE 500 MB UPPER LOW AND THRU THE ERN HALF OF OUR CWA THURSDAY NIGHT...PROVIDING A CONTINUED CHANCE OF A FEW SHOWERS. STRONG SURFACE RIDGING AND DRY AIR WILL BUILD EASTWARD INTO MICHIGAN FOR FRIDAY AS THE UPPER LEVEL RIDGE BEGINS TO SHIFT NW AWAY FROM THE STATE. FRIDAY SHOULD BE A NICE LATE SUMMER DAY ACROSS MICHIGAN... WITH DRY WX AND MAINLY SUNNY CONDITIONS. HIGH TEMPS BOTH THURSDAY AND FRIDAY WILL BE IN THE 70S...WITH OVERNIGHT LOWS IN THE 50S. SATURDAY THRU WEDNESDAY...PERSISTENT UPPER LEVEL TROUGH OVER THE ERN US WILL LIFT NE FURTHER INTO QUEBEC....WHILE THE WRN RIDGE WILL HOLD ITS POSITION OVER THE US ROCKIES. CUT-OFF 500 MB LOW TO THE LEE OF THE ROCKIES OVER THE CENTRAL PLAINS WILL DEEPEN AND BECOME BETTER ESTABLISHED OVER THIS REGION DURING THE FIRST HALF OF NEXT WEEK. BOTH ECMWF AND GFS ARE POINTING TOWARD WEAK UPPER LEVEL RIDGING GRADUALLY BUILDING FROM THE SE US THRU THE OHIO VALLEY AND INTO THE GREAT LAKES REGION DURING THIS TIME. THE END RESULT IS A RATHER STAGNANT WX PATTERN SETTING UP ACROSS THE US OVER THE NEXT WEEK... WITH MICHIGAN STUCK IN WEAK RIDGING THRU THE COLUMN. CERTAINLY CANNOT COMPLETELY RULE OUT ANY CHANCE OF PRECIP THRU THE MIDDLE OF NEXT WEEK...BUT CHANCES ARE TOO SLIM TO KEEP IN THE FORECAST. THUS...HAVE OPTED TO REMOVE ALL POPS FOR THE FIRST HALF OF NEXT WORKWEEK. AFTERNOON HIGH TEMPS THRU THE PERIOD WILL BE IN THE UPPER 70S TO MID 80S...WITH OVERNIGHT LOWS IN THE UPPER 50S TO LOWER 60S. && .PREV DISCUSSION... /ISSUED 135 PM EDT WED AUG 13 2008/ AVIATION...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP THIS AFTERNOON ACROSS NORTHEAST AND NORTH-CENTRAL LOWER. A FEW STORMS MAY IMPACT APN WITH IFR VSBYS/MVFR CIGS...BUT NOT CONFIDENT ENOUGH IN COVERAGE TO INCLUDE TSRA AS PREVAILING. ANY STORMS SHOULD DIMINISH BY 00Z...LEAVING THE REST OF THE NIGHT MOSTLY CLEAR. QUIET CONDITIONS WILL THEN LINGER THROUGH THE REST OF THE TAF PERIOD. MPC && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 200 PM EDT WED AUG 13 2008 LATEST UPDATE...AVIATION... .SYNOPSIS...(334 AM EDT WED AUG 13 2008) AN UPPER LOW OVER JAMES BAY WILL CONTROL OUR WEATHER THROUGH FRIDAY. A COUPLE OF UPPER LEVEL DISTURBANCES WILL MOVE SOUTH FROM THE LOW AND INCREASE THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS. SEASONABLE TEMPERATURES ARE EXPECTED THROUGH FRIDAY. && .SHORT TERM...(1130 AM EDT WED AUG 13 2008) (TODAY THROUGH FRIDAY) ELONGATED SHORTWAVE AND ASSOCIATED AREA OF SHOWERS/ISOLATED TSTMS WHICH ATTEMPTED TO MOVE INTO THE AREA THIS MORNING FROM THE WEST IS NOW BEING SHEARED OUT AND PUSHED SOUTH AS THE LARGE UPR TROUGH IN EASTERN CANADA CONTINUES RETROGRADING SWWD. THE MAIN FOCUS FOR THE AFTERNOON WILL BE THE CONVECTION DEVELOPING AHEAD OF THE BACK DOOR COLD FRONT SLIPPING S/SW FROM FAR NRN LWR MI AND LK HURON. HIGHEST PROBABILITY OF STORMS THIS AFTERNOON SHOULD BE IN THE NE PORTION OF THE CWFA WHERE SOME SFC HEATING IS TAKING PLACE THIS MORNING AND WHERE BEST SFC CONVERGENCE WILL EXIST AS COLD FRONT APPROACHES. RUC SOUNDINGS LATER THIS AFTERNOON (21Z) ARE NOT PARTICULARLY IMPRESSIVE... WITH ONLY ABOUT 500 J/KG OF CAPE. MOST OF THAT CAPE IS DOWN LOW... BETWEEN 850 AND 500 MB... WITH VERY LITTLE CAPE IN THE -10C TO -30C RANGE. THAT SUGGESTS THAT THE PROBABILITY OF ANY HAIL IS EXTREMELY LOW. DEEP LAYER SHEAR VALUES ARE VERY LOW OVER THE CWFA... BUT ABOUT 25 KTS IN THE NE CORNER OF THE CWFA. THUS STORMS SHOULD BE PRIMARILY OF THE SCATTERED/PULSE VARIETY WITH LITTLE OR NO ORGANIZATION. ANOTHER SHORT WAVE WILL ROTATE SOUTH INTO LOWER MI THURSDAY AFTERNOON. FORECAST SOUNDINGS ARE PRETTY DRY THURSDAY. AS SUCH...WE DECREASED POPS TO SLGT CHC. DRY WX EXPECTED FRIDAY WITH HIGH PRESSURE IN CONTROL OF THE UPPER MIDWEST. && .LONG TERM...(334 AM EDT WED AUG 13 2008) (FRIDAY NIGHT THROUGH TUESDAY NIGHT) ONE TREND OF THE FORECAST WILL BE TO FEATURE SOME WARMER TEMPERATURES IN THE SUNDAY TO MONDAY TIME FRAME. THE GFS AND ECMWF SUPPORT THIS CHANGE AS 850 MB TEMPS ARE SHOWN TO CLIMB INTO THE TEENS. ALSO WITH A SOUTHEAST WIND...EVEN AREAS NEAR THE LAKESHORE SHOULD SEE THE WARMER TEMPS. LOOKING AT THE TUE TIME FRAME...WE WILL NEED TO MONITOR THE FORMATION AND TRACK OF A COLD FRONT THAT WILL BE TRYING TO DROP DOWN FROM THE NORTH NORTHEAST. BOTH THE GFS AND ECMWF HAVE THE FLOW TURNING NORTHEAST ON THAT DAY...SO I WILL KEEP THE HIGHS RELATIVELY CLOSE TO NORMAL. ALMOST LOOKS LIKE A HUDSON BAY HIGH TRYING TO SET UP...SO NO RAIN ON TUE. && .MARINE...(1130 AM EDT WED AUG 13 2008) MODELS KEEP TRENDING TOWARD A STRONGER NORTH FLOW EVENT ON THURSDAY AFTERNOON AND EVENING. ATTM IT LOOKS LIKE WAVES WILL STAY JUST BELOW SCA CRITERIA AT 2 TO 4 FEET... BUT THIS WILL HAVE TO BE MONITORED. COULD SEE SOME RATHER CHOPPY/HAZARDOUS SEAS DEVELOPING NEAR BIG AND LITTLE SABLE POINTS THURSDAY AFTERNOON... AND SOUTH OF HOLLAND THURSDAY NIGHT. && .AVIATION...(200 PM EDT WED AUG 13 2008) A WEAK COLD FRONT WILL DROP SOUTH OVER THE REGION THIS EVENING. WIDELY SCATTERED SHOWERS SHOULD ACCOMPANY THIS FRONT...HOWEVER THE INSTABILITY IS WEAK ENOUGH TO KEEP ANY THUNDERSTORMS TO BE VERY ISOLATED. FOR THE MOST PART VFR CEILINGS AND VSBYS WILL PREVAIL THIS AFTERNOON AND OVERNIGHT. HOWEVER THERE COULD BE MVFR CEILINGS AROUND TOWARD DAYBREAK THURSDAY AS LOW LEVEL MOISTURE POOLS NEAR THE FRONT. DRIER AIR MOVES OVER THE AREA THROUGH THE MID/LATE MORNING HOURS OF THURSDAY...SO ANY MVFR CEILINGS SHOULD BE BRIEF AS CLEARING OCCURS TOWARD MID DAY. && .HYDROLOGY...(334 AM EDT WED AUG 13 2008) NO HYDRO CONCERNS TODAY. ANY SHOWERS OR STORMS THAT DEVELOP WILL ONLY RESULT IN A QUARTER INCH OR LESS OF PCPN. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. && $$ SYNOPSIS: 93 SHORT TERM: MEADE LONG TERM: MJS MARINE: MEADE AVIATION: JK HYDROLOGY: 93 mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 135 PM EDT WED AUG 13 2008 .AVIATION...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP THIS AFTERNOON ACROSS NORTHEAST AND NORTH-CENTRAL LOWER. A FEW STORMS MAY IMPACT APN WITH IFR VSBYS/MVFR CIGS...BUT NOT CONFIDENT ENOUGH IN COVERAGE TO INCLUDE TSRA AS PREVAILING. ANY STORMS SHOULD DIMINISH BY 00Z...LEAVING THE REST OF THE NIGHT MOSTLY CLEAR. QUIET CONDITIONS WILL THEN LINGER THROUGH THE REST OF THE TAF PERIOD. MPC && .PREV DISCUSSION... /ISSUED 1042 AM EDT WED AUG 13 2008/ UPDATE...11Z SURFACE/RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW TWIN UPPER LOWS ONE SPINNING OVER QUEBEC AND ANOTHER OVER SASKATCHEWAN. MID-LEVEL CONVERGENCE BETWEEN THESE TWO FEATURES IS GENERATING A BAND OF CLOUDS STRETCHING FROM NORTHERN MN TO CENTRAL MI...WHICH HAVE BEEN SLOWLY SHRINKING THIS MORNING ACROSS SOUTHERN PORTIONS OF THE FORECAST AREA. A BIT FARTHER NORTH...SHORTWAVE OVER EASTERN QUEBEC IS ROTATING AROUND THE PARENT LOW AND IS TRIGGERING A FEW SHOWERS ACROSS EASTERN UPPER. SURFACE PATTERN IS RATHER CONVOLUTED AT THIS HOUR...BUT APPEARS TO BE A WEAK SURFACE TROUGH/CYCLONIC FLOW STRETCHING FROM ABOUT GREEN BAY TO SAGINAW BAY...WHICH MAY BE HELPING TO TRIGGER A FEW SHOWERS OVER NORTHERN LAKE MICHIGAN AS WELL. AN ADDITIONAL BACK-DOOR COOL FRONT MAY ALSO BE PRESENT OVER NE LAKE SUPERIOR. AS LAKE BREEZES GET ROLLING THIS AFTERNOON...COMBINED WITH WEAK UPWARD SUPPORT FROM THE SHORTWAVE JUST TO THE NORTH...SHOWER AND THUNDERSTORM CHANCES ARE THE MAIN FORECAST CONCERN FOR THE REST OF THE DAY. SURFACE TROUGH ACROSS CENTRAL MICHIGAN WILL TEND TO BECOME EVEN MORE ILL-DEFINED AS LIGHT WINDS ALOFT JUDGING BY THE 12Z APX SOUNDING BECOME OVERWHELMED BY LAKE BREEZE INDUCED CIRCULATIONS. MAX CONVERGENCE SEEMS TO ARRIVE MID TO LATE AFTERNOON OVER THE HIGHER TERRAIN EAST OF I-75...AND ALSO ACROSS SOUTHERN PORTIONS OF EASTERN UPPER...WHERE BACKDOOR COOL FRONT WILL SHIFT SOUTH AND CREATE ADDITIONAL CONVERGENCE. WEAK MID-LEVEL -DIVQ AHEAD OF THE EASTERN ONTARIO SHORTWAVE WILL ALSO PROVIDE A BIT OF UPPER SUPPORT HEADING INTO THE AFTERNOON OVER NE LOWER. MODIFYING A 12Z APX SOUNDING WITH HIGHS IN THE MID 70S AND DEWPOINTS IN THE MID 50S YIELDS ABOUT 400-500 J/KG OF ML CAPE WITH NO INHIBITION. BELIEVE AFOREMENTIONED FORCING AND INSTABILITY WILL BE ENOUGH TO GENERATE SCT SHOWER AND THUNDERSTORMS BY MID-AFTERNOON. SEVERE CHANCES REMAIN VERY VERY SMALL WITH THE LIGHT WIND FIELDS ALOFT AND SKINNY CAPE. JUST MADE A FEW OTHER TWEAKS TO SKY AND TEMPS TO REFLECT LATEST TRENDS...BUT GIST OF THE FORECAST REMAINS IN GOOD SHAPE. MPC DISCUSSION...ISSUED 258 AM WED AUG 13... AN AMPLIFIED AND SOMEWHAT CONVOLUTED UPPER FLOW PATTERN WILL BECOME A BIT SIMPLER LATE THIS WEEK. RIDGING OVER THE WEST WILL AMPLIFY. AN UPPER LOW OVER QUEBEC WILL RETROGRADE TO THE ONTARIO BORDER...WEAKENING AND EVENTUALLY OPENING UP. ANOTHER UPPER LOW WILL MOVE SOUTH FROM SASK TO THE CENTRAL ROCKIES...WITH THE RIDGE TO IT/S WEST FOLDING OVER THE TOP. SO BY FRIDAY...IT/S A BASIC RIDGE WEST AND TROF EAST PATTERN...WITH AN EXTRANEOUS CUT-OFF LOW IN COLORADO. THE RESIDUAL UPPER TROFFING MAY COMBINE WITH DIURNAL HEATING TO PRODUCE SMALL PRECIP CHANCES...THAT/S THE MAIN CHALLENGE. MODELS...DECENT AGREEMENT. GFS ALLOWS THE DECAYING EASTERN LOW TO DRIFT A BIT FURTHER EASTWARD ON FRIDAY. GIVEN MODEL TENDENCY TO BE TOO PROGRESSIVE...AND GIVEN THE WAY THE SUMMER HAS GONE...PREFER THE SLOWER NAM. TODAY...ONGOING SHOWERS OVER FAR NORTHERN LOWER MI AND NEARBY WATERS ARE LEFTOVER LAKE-BREEZE CONVECTION FROM YESTERDAY. THESE ARE BEING MAINTAINED (BARELY) BY AN UPPER TROF AXIS AND A RELATIVELY WARM/MOIST AIRMASS OVER THE LAKES (69/63 ON THE NORTHERN LAKE MI BUOY). AN 1000-850MB CONVERGENCE MAXIMUM WILL DRIFT SLOWLY SOUTHWARD...AND WILL MAINTAIN AN ISOLATED SHOWER OR SPRINKLE FOR THE MORNING HOURS BETWEEN THE BRIDGE AND M-72. WITH DAYTIME HEATING...A 74/55 PARCEL RESULTS IN MLCAPES OF ABOUT 400J/KG. NOTHING SPECTACULAR...BUT WITH NO INHIBITION...GENERAL LOW-LEVEL CONVERGENCE...AND DEVELOPING (WEAK) LAKE BREEZES...SCT SHOWERS/ISOLATED TSTORMS SHOULD DEVELOP IN THE AFTERNOON. BEST SHOT WILL BE IN THE INTERIOR OF NORTHERN LOWER. IN EASTERN UPPER MI... BACKGROUND NORTHERLY FLOW SHOULD ALLOW THE SUPERIOR BREEZE TO OVERWHELM THE SOUTHERN LAKES...KEEPING THE CHANCE OF RAIN SMALLER AND SOUTH OF M-28. MAX TEMPS MAINLY MID 70S. TONIGHT...WILL HANG ONTO AN ISOLATED LIGHT SHOWER OR TWO IN THE INTERIOR OF NORTHERN LOWER MI THRU LATE EVENING. THAT WILL BE IT...AS NE 1000-850MB FLOW BRINGS IN COOLER AND DRIER LOW LEVEL AIR...COMBINING WITH LOSS OF HEATING TO WIPE OUT INSTABILITY. OTHERWISE...SKIES WILL BECOME MOSTLY CLEAR. PRESUMING THAT THE INTERIOR OF NORTHERN LOWER MI SEES AT LEAST SPOTTY SHOWERS TODAY... THE LEFTOVER BOUNDARY LAYER MOISTURE WILL CONTRIBUTE TO PATCHY FOG TONIGHT AROUND HTL/CAD/GRAYLING. MIN TEMPS MAINLY LOW TO MID 50S... SOME UPPER 40S IN THE USUAL INLAND COOL SPOTS. THURSDAY...WE ONLY LOSE ABOUT 1C OFF OF 850MB TEMPS BETWEEN TODAY AND THURSDAY. BUT WITH INSTABILITY ALREADY MARGINAL...IT DOESN/T TAKE MUCH. MLCAPES ARE REDUCED TO 100-200J/KG WITH A 73/53 PARCEL. IN ADDITION...WE/RE DRIER ABOVE 850MB...PRODUCING ENTRAINMENT ISSUES. SO WE SHOULD HAVE A MUCH LOWER RISK OF RAIN. WILL GO WITH AN ISOLATED SHOWER OR TWO IN THE AFTERNOON IN THE SOUTHERN INTERIOR... NO FURTHER NORTH THAN GRAYLING. OTHERWISE A MOSTLY SUNNY START AND A PARTLY CLOUDY AFTERNOON...WITH MAX TEMPS A HAIR COOLER IN THE LOW TO MID 70S. THURSDAY NIGHT AND FRIDAY...QUIET THURSDAY NIGHT AFTER LOSS OF HEATING. TEMPS SIMILAR TO TONIGHT. NAM BRINGS A SPOKE OF ENERGY AROUND THE UPPER LOW TO OUR EAST. THE ASSOCIATED SLUG OF MOISTURE MOVES SOUTHWARD ACROSS THE EAST HALF OF THE FORECAST AREA ON FRIDAY. IF THIS HOLDS...A JUST OF SHOWERS MAY BE NEEDED IN NE LOWER MI ON FRIDAY. THIS IS CERTAINLY PLAUSIBLE...BUT THIS WAVE HAS NOT EXISTED IN EARLIER MODEL RUNS...AND PREFER TO KEEP THINGS DRY FOR ONE MORE MODEL CYCLE. MAX TEMPS FRIDAY VERY CLOSE TO THURSDAYS LEVELS. REST OF THE FORECAST...THE UPPER LOW TO OUR EAST WILL SLOWLY MOVE AWAY FROM THE REGION. THIS SHOULD RESULT IN DRY WX AND A SLOW WARMING TREND OVER THE WEEKEND. OF COURSE...WE HAVE SEEN THESE EASTERN TROFS HANG ON LONGER THAN EXPECTED ON NUMEROUS OCCASIONS THIS SUMMER...SO TAKE THAT WITH A GRAIN OF SALT. BUT FOR NOW APPEARS MOST PLACES WILL BREAK 80 BY SUNDAY. ECMWF ARGUES FOR EVEN WARMER WX BY MIDWEEK...THAT DEFINITELY CALLS FOR A /WAIT AND SEE/ APPROACH. FEW CHANGES MADE TO THIS PART OF THE FORECAST. JZ && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1130 AM EDT WED AUG 13 2008 LATEST UPDATE...SHORT TERM AND MARINE... .SYNOPSIS...(334 AM EDT WED AUG 13 2008) AN UPPER LOW OVER JAMES BAY WILL CONTROL OUR WEATHER THROUGH FRIDAY. A COUPLE OF UPPER LEVEL DISTURBANCES WILL MOVE SOUTH FROM THE LOW AND INCREASE THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS. SEASONABLE TEMPERATURES ARE EXPECTED THROUGH FRIDAY. && .SHORT TERM...(1130 AM EDT WED AUG 13 2008) (TODAY THROUGH FRIDAY) ELONGATED SHORTWAVE AND ASSOCIATED AREA OF SHOWERS/ISOLATED TSTMS WHICH ATTEMPTED TO MOVE INTO THE AREA THIS MORNING FROM THE WEST IS NOW BEING SHEARED OUT AND PUSHED SOUTH AS THE LARGE UPR TROUGH IN EASTERN CANADA CONTINUES RETROGRADING SWWD. THE MAIN FOCUS FOR THE AFTERNOON WILL BE THE CONVECTION DEVELOPING AHEAD OF THE BACK DOOR COLD FRONT SLIPPING S/SW FROM FAR NRN LWR MI AND LK HURON. HIGHEST PROBABILITY OF STORMS THIS AFTERNOON SHOULD BE IN THE NE PORTION OF THE CWFA WHERE SOME SFC HEATING IS TAKING PLACE THIS MORNING AND WHERE BEST SFC CONVERGENCE WILL EXIST AS COLD FRONT APPROACHES. RUC SOUNDINGS LATER THIS AFTERNOON (21Z) ARE NOT PARTICULARLY IMPRESSIVE... WITH ONLY ABOUT 500 J/KG OF CAPE. MOST OF THAT CAPE IS DOWN LOW... BETWEEN 850 AND 500 MB... WITH VERY LITTLE CAPE IN THE -10C TO -30C RANGE. THAT SUGGESTS THAT THE PROBABILITY OF ANY HAIL IS EXTREMELY LOW. DEEP LAYER SHEAR VALUES ARE VERY LOW OVER THE CWFA... BUT ABOUT 25 KTS IN THE NE CORNER OF THE CWFA. THUS STORMS SHOULD BE PRIMARILY OF THE SCATTERED/PULSE VARIETY WITH LITTLE OR NO ORGANIZATION. ANOTHER SHORT WAVE WILL ROTATE SOUTH INTO LOWER MI THURSDAY AFTERNOON. FORECAST SOUNDINGS ARE PRETTY DRY THURSDAY. AS SUCH...WE DECREASED POPS TO SLGT CHC. DRY WX EXPECTED FRIDAY WITH HIGH PRESSURE IN CONTROL OF THE UPPER MIDWEST. && .LONG TERM...(334 AM EDT WED AUG 13 2008) (FRIDAY NIGHT THROUGH TUESDAY NIGHT) ONE TREND OF THE FORECAST WILL BE TO FEATURE SOME WARMER TEMPERATURES IN THE SUNDAY TO MONDAY TIME FRAME. THE GFS AND ECMWF SUPPORT THIS CHANGE AS 850 MB TEMPS ARE SHOWN TO CLIMB INTO THE TEENS. ALSO WITH A SOUTHEAST WIND...EVEN AREAS NEAR THE LAKESHORE SHOULD SEE THE WARMER TEMPS. LOOKING AT THE TUE TIME FRAME...WE WILL NEED TO MONITOR THE FORMATION AND TRACK OF A COLD FRONT THAT WILL BE TRYING TO DROP DOWN FROM THE NORTH NORTHEAST. BOTH THE GFS AND ECMWF HAVE THE FLOW TURNING NORTHEAST ON THAT DAY...SO I WILL KEEP THE HIGHS RELATIVELY CLOSE TO NORMAL. ALMOST LOOKS LIKE A HUDSON BAY HIGH TRYING TO SET UP...SO NO RAIN ON TUE. && .MARINE...(1130 AM EDT WED AUG 13 2008) MODELS KEEP TRENDING TOWARD A STRONGER NORTH FLOW EVENT ON THURSDAY AFTERNOON AND EVENING. ATTM IT LOOKS LIKE WAVES WILL STAY JUST BELOW SCA CRITERIA AT 2 TO 4 FEET... BUT THIS WILL HAVE TO BE MONITORED. COULD SEE SOME RATHER CHOPPY/HAZARDOUS SEAS DEVELOPING NEAR BIG AND LITTLE SABLE POINTS THURSDAY AFTERNOON... AND SOUTH OF HOLLAND THURSDAY NIGHT. && .AVIATION...(740 AM EDT WED AUG 13 2008) A WEAK UPPER LEVEL DISTURBANCE WILL BRING THE RISK FOR SOME SHOWERS AND THUNDERSTORMS ACROSS THE AREA TODAY. I WOULD MONITOR RADAR THROUGH THE DAY...AS THERE FORMATION HAS BEEN RANDOM. THEY WILL BE HIT OR MISS...BUT THE MOST LIKELY AREA TO SEE SOME ARE FOR KLAN TO KJXN WHERE THE ATMOSPHERE IS SHOWN TO HAVE SOME BETTER INSTABILITY THIS AFTERNOON. I DID MENTION VCTS FOR THESE SITES. AS FOR THIS MORNING SOME CONVECTIVE SHOWERS WERE OVER LAKE MI. IT APPEARS THAT THEY WILL WEAKEN AS THEY MOVE INLAND. HOWEVER I DID MENTION VCSH FOR KMKG KGRR KAZO AND KBTL. VFR CONDITIONS ARE EXPECTED TO PERSIST INTO TONIGHT. THERE ARE SOME INDICATIONS THAT HZ OR BR WILL BE ON THE INCREASE NEAR KAZO KBTL AND KJXN LATER TONIGHT PRODUCING SOME MVFR VSBYS. && .HYDROLOGY...(334 AM EDT WED AUG 13 2008) NO HYDRO CONCERNS TODAY. ANY SHOWERS OR STORMS THAT DEVELOP WILL ONLY RESULT IN A QUARTER INCH OR LESS OF PCPN. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. && $$ SYNOPSIS: 93 SHORT TERM: MEADE LONG TERM: MJS MARINE: MEADE AVIATION: MJS HYDROLOGY: 93 mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1042 AM EDT WED AUG 13 2008 .UPDATE...11Z SURFACE/RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW TWIN UPPER LOWS ONE SPINNING OVER QUEBEC AND ANOTHER OVER SASKATCHEWAN. MID-LEVEL CONVERGENCE BETWEEN THESE TWO FEATURES IS GENERATING A BAND OF CLOUDS STRETCHING FROM NORTHERN MN TO CENTRAL MI...WHICH HAVE BEEN SLOWLY SHRINKING THIS MORNING ACROSS SOUTHERN PORTIONS OF THE FORECAST AREA. A BIT FARTHER NORTH...SHORTWAVE OVER EASTERN QUEBEC IS ROTATING AROUND THE PARENT LOW AND IS TRIGGERING A FEW SHOWERS ACROSS EASTERN UPPER. SURFACE PATTERN IS RATHER CONVOLUTED AT THIS HOUR...BUT APPEARS TO BE A WEAK SURFACE TROUGH/CYCLONIC FLOW STRETCHING FROM ABOUT GREEN BAY TO SAGINAW BAY...WHICH MAY BE HELPING TO TRIGGER A FEW SHOWERS OVER NORTHERN LAKE MICHIGAN AS WELL. AN ADDITIONAL BACK-DOOR COOL FRONT MAY ALSO BE PRESENT OVER NE LAKE SUPERIOR. AS LAKE BREEZES GET ROLLING THIS AFTERNOON...COMBINED WITH WEAK UPWARD SUPPORT FROM THE SHORTWAVE JUST TO THE NORTH...SHOWER AND THUNDERSTORM CHANCES ARE THE MAIN FORECAST CONCERN FOR THE REST OF THE DAY. SURFACE TROUGH ACROSS CENTRAL MICHIGAN WILL TEND TO BECOME EVEN MORE ILL-DEFINED AS LIGHT WINDS ALOFT JUDGING BY THE 12Z APX SOUNDING BECOME OVERWHELMED BY LAKE BREEZE INDUCED CIRCULATIONS. MAX CONVERGENCE SEEMS TO ARRIVE MID TO LATE AFTERNOON OVER THE HIGHER TERRAIN EAST OF I-75...AND ALSO ACROSS SOUTHERN PORTIONS OF EASTERN UPPER...WHERE BACKDOOR COOL FRONT WILL SHIFT SOUTH AND CREATE ADDITIONAL CONVERGENCE. WEAK MID-LEVEL -DIVQ AHEAD OF THE EASTERN ONTARIO SHORTWAVE WILL ALSO PROVIDE A BIT OF UPPER SUPPORT HEADING INTO THE AFTERNOON OVER NE LOWER. MODIFYING A 12Z APX SOUNDING WITH HIGHS IN THE MID 70S AND DEWPOINTS IN THE MID 50S YIELDS ABOUT 400-500 J/KG OF ML CAPE WITH NO INHIBITION. BELIEVE AFOREMENTIONED FORCING AND INSTABILITY WILL BE ENOUGH TO GENERATE SCT SHOWER AND THUNDERSTORMS BY MID-AFTERNOON. SEVERE CHANCES REMAIN VERY VERY SMALL WITH THE LIGHT WIND FIELDS ALOFT AND SKINNY CAPE. JUST MADE A FEW OTHER TWEAKS TO SKY AND TEMPS TO REFLECT LATEST TRENDS...BUT GIST OF THE FORECAST REMAINS IN GOOD SHAPE. MPC && .PREV DISCUSSION... /ISSUED 720 AM EDT WED AUG 13 2008/ AVIATION...BIT OF IFR CEILING AT PLN EARLY THIS MORNING SHOULD QUICKLY BURN OFF. RELATIVELY MOIST LOW LEVELS WILL KEEP A SMALL THREAT OF A SHOWER OR TSRA THIS AFTERNOON AND EARLY EVENING. BEST CHANCE WILL BE NEAR APN. VFR TONIGHT UNDER MOSTLY CLEAR SKIES. JZ DISCUSSION...ISSUED 258 AM WED AUG 13... AN AMPLIFIED AND SOMEWHAT CONVOLUTED UPPER FLOW PATTERN WILL BECOME A BIT SIMPLER LATE THIS WEEK. RIDGING OVER THE WEST WILL AMPLIFY. AN UPPER LOW OVER QUEBEC WILL RETROGRADE TO THE ONTARIO BORDER...WEAKENING AND EVENTUALLY OPENING UP. ANOTHER UPPER LOW WILL MOVE SOUTH FROM SASK TO THE CENTRAL ROCKIES...WITH THE RIDGE TO IT/S WEST FOLDING OVER THE TOP. SO BY FRIDAY...IT/S A BASIC RIDGE WEST AND TROF EAST PATTERN...WITH AN EXTRANEOUS CUT-OFF LOW IN COLORADO. THE RESIDUAL UPPER TROFFING MAY COMBINE WITH DIURNAL HEATING TO PRODUCE SMALL PRECIP CHANCES...THAT/S THE MAIN CHALLENGE. MODELS...DECENT AGREEMENT. GFS ALLOWS THE DECAYING EASTERN LOW TO DRIFT A BIT FURTHER EASTWARD ON FRIDAY. GIVEN MODEL TENDENCY TO BE TOO PROGRESSIVE...AND GIVEN THE WAY THE SUMMER HAS GONE...PREFER THE SLOWER NAM. TODAY...ONGOING SHOWERS OVER FAR NORTHERN LOWER MI AND NEARBY WATERS ARE LEFTOVER LAKE-BREEZE CONVECTION FROM YESTERDAY. THESE ARE BEING MAINTAINED (BARELY) BY AN UPPER TROF AXIS AND A RELATIVELY WARM/MOIST AIRMASS OVER THE LAKES (69/63 ON THE NORTHERN LAKE MI BUOY). AN 1000-850MB CONVERGENCE MAXIMUM WILL DRIFT SLOWLY SOUTHWARD...AND WILL MAINTAIN AN ISOLATED SHOWER OR SPRINKLE FOR THE MORNING HOURS BETWEEN THE BRIDGE AND M-72. WITH DAYTIME HEATING...A 74/55 PARCEL RESULTS IN MLCAPES OF ABOUT 400J/KG. NOTHING SPECTACULAR...BUT WITH NO INHIBITION...GENERAL LOW-LEVEL CONVERGENCE...AND DEVELOPING (WEAK) LAKE BREEZES...SCT SHOWERS/ISOLATED TSTORMS SHOULD DEVELOP IN THE AFTERNOON. BEST SHOT WILL BE IN THE INTERIOR OF NORTHERN LOWER. IN EASTERN UPPER MI... BACKGROUND NORTHERLY FLOW SHOULD ALLOW THE SUPERIOR BREEZE TO OVERWHELM THE SOUTHERN LAKES...KEEPING THE CHANCE OF RAIN SMALLER AND SOUTH OF M-28. MAX TEMPS MAINLY MID 70S. TONIGHT...WILL HANG ONTO AN ISOLATED LIGHT SHOWER OR TWO IN THE INTERIOR OF NORTHERN LOWER MI THRU LATE EVENING. THAT WILL BE IT...AS NE 1000-850MB FLOW BRINGS IN COOLER AND DRIER LOW LEVEL AIR...COMBINING WITH LOSS OF HEATING TO WIPE OUT INSTABILITY. OTHERWISE...SKIES WILL BECOME MOSTLY CLEAR. PRESUMING THAT THE INTERIOR OF NORTHERN LOWER MI SEES AT LEAST SPOTTY SHOWERS TODAY... THE LEFTOVER BOUNDARY LAYER MOISTURE WILL CONTRIBUTE TO PATCHY FOG TONIGHT AROUND HTL/CAD/GRAYLING. MIN TEMPS MAINLY LOW TO MID 50S... SOME UPPER 40S IN THE USUAL INLAND COOL SPOTS. THURSDAY...WE ONLY LOSE ABOUT 1C OFF OF 850MB TEMPS BETWEEN TODAY AND THURSDAY. BUT WITH INSTABILITY ALREADY MARGINAL...IT DOESN/T TAKE MUCH. MLCAPES ARE REDUCED TO 100-200J/KG WITH A 73/53 PARCEL. IN ADDITION...WE/RE DRIER ABOVE 850MB...PRODUCING ENTRAINMENT ISSUES. SO WE SHOULD HAVE A MUCH LOWER RISK OF RAIN. WILL GO WITH AN ISOLATED SHOWER OR TWO IN THE AFTERNOON IN THE SOUTHERN INTERIOR... NO FURTHER NORTH THAN GRAYLING. OTHERWISE A MOSTLY SUNNY START AND A PARTLY CLOUDY AFTERNOON...WITH MAX TEMPS A HAIR COOLER IN THE LOW TO MID 70S. THURSDAY NIGHT AND FRIDAY...QUIET THURSDAY NIGHT AFTER LOSS OF HEATING. TEMPS SIMILAR TO TONIGHT. NAM BRINGS A SPOKE OF ENERGY AROUND THE UPPER LOW TO OUR EAST. THE ASSOCIATED SLUG OF MOISTURE MOVES SOUTHWARD ACROSS THE EAST HALF OF THE FORECAST AREA ON FRIDAY. IF THIS HOLDS...A JUST OF SHOWERS MAY BE NEEDED IN NE LOWER MI ON FRIDAY. THIS IS CERTAINLY PLAUSIBLE...BUT THIS WAVE HAS NOT EXISTED IN EARLIER MODEL RUNS...AND PREFER TO KEEP THINGS DRY FOR ONE MORE MODEL CYCLE. MAX TEMPS FRIDAY VERY CLOSE TO THURSDAYS LEVELS. REST OF THE FORECAST...THE UPPER LOW TO OUR EAST WILL SLOWLY MOVE AWAY FROM THE REGION. THIS SHOULD RESULT IN DRY WX AND A SLOW WARMING TREND OVER THE WEEKEND. OF COURSE...WE HAVE SEEN THESE EASTERN TROFS HANG ON LONGER THAN EXPECTED ON NUMEROUS OCCASIONS THIS SUMMER...SO TAKE THAT WITH A GRAIN OF SALT. BUT FOR NOW APPEARS MOST PLACES WILL BREAK 80 BY SUNDAY. ECMWF ARGUES FOR EVEN WARMER WX BY MIDWEEK...THAT DEFINITELY CALLS FOR A /WAIT AND SEE/ APPROACH. FEW CHANGES MADE TO THIS PART OF THE FORECAST. JZ && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 700 AM EDT WED AUG 13 2008 ADDED UPDATE SECTION AND INCLUDED NEW AVIATION DISCUSSION FOR 12Z TAFS .UPDATE... ISOLATED SHRA HAVE POPPED UP OVR DELTA/SCHOOLCRAFT COUNTIES. LOOKS LIKE INCOMING SHORTWAVE PRODUCING THE SHRA OVR EASTERN LK SUPERIOR AND A POCKET OF H85-H7 MOISTURE AND EVEN PERHAPS REMNANTS OF A WEAK SFC TROUGH WERE THE CULPRITS. 40KM RUC AND 06Z NAM HAVE THIS HIGHER RH AND THE RUC EVEN SHOWS A HUNDREDTH OF QPF IN THE RIGHT SPOT. BOTH OF THESE SIGNALS DRIFT SOUTH INTO NRN LK MICHIGAN BY MID MORNING. UPDATED GRIDS/ZFPMQT. && .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A MIDLEVEL LOW OVER SRN SASKATCHEWAN...A MIDLEVEL HIGH OVER WRN HUDSON BAY WITH A RIDGE EXTENDING S TOWARD THE UPPER LAKES...AND A TROF/BROAD MIDLEVEL LOW OVER SE CANADA. THESE LARGER SCALE FEATURES ARE FORCING A SHORTWAVE OVER MN/WRN WI TO THE SSE. -SHRA ASSOCIATED WITH THIS FEATURE EXTEND FROM EXTREME WRN UPPER MI S THRU WI...BUT NOT ALL OF THE PCPN IS REACHING THE GROUND. TO THE E...A SHORTWAVE ROTATING S THRU ONTARIO AROUND THE MIDLEVEL LOW OVER SE CANADA WAS PRODUCING -SHRA OVER FAR NCNTRL AND NE LAKE SUPERIOR. THERE WERE A FEW TSRA NE OF THE LAKE EARLIER IN THE NIGHT. && .DISCUSSION (420 AM EDT)... OVER THE NEXT COUPLE OF DAYS...A RIDGE WILL BUILD N ALONG THE W COAST OF THE CONUS AND THEN E TO CONNECT WITH THE MIDLEVEL HIGH OVER WRN HUDSON BAY. THIS WILL FORCE THE MIDLEVEL LOW OVER SASKATCHEWAN TO THE S. MEANWHILE...THE TROF OVER SE CANADA WILL BRIEFLY EXTEND SW THRU THE WRN GREAT LAKES REGION BEFORE THE RIDGE SETTLES S INTO THE NCNTRL STATES. THIS PATTERN WILL NOT FAVOR MUCH IN THE WAY OF PCPN FOR THE FCST AREA. SHORTWAVE THAT WAS PRODUCING SHRA OVER NE LAKE SUPERIOR WILL PASS BY TO THE E THIS MORNING. HOWEVER...PER RADAR TRENDS...WRN EDGE OF THE -SHRA MAY BRUSH THE FAR ERN FCST AREA...AND WILL INCLUDE SLIGHT CHC OF MORNING -SHRA THERE. MEANWHILE...TO THE W...SHORTWAVE ENERGY WILL CONTINUE TO BE FORCED SSE THRU MN/WRN WI THOUGH FAR WRN UPPER MI MAY STILL GET CLIPPED BY A FEW -SHRA. ATTENTION THEN TURNS TO THE POTENTIAL FOR DIURNAL CONVECTION. IT APPEARS GRADIENT WILL BE WEAK ENOUGH TODAY FOR A LAKE BREEZE TO DEVELOP NEAR LAKE MICHIGAN. CONVERGENCE ALONG LAKE BREEZE FRONT WILL ALLOW LOW-LEVEL MOISTURE TO POOL. MODIFIED NAM/GFS FCST SOUNDINGS FOR A SFC T/TD OF MID 70S/MID 50S YIELD CAPE OF SEVERAL HUNDRED J/KG. IF DWPTS RISE TO NEAR 60F LOCALLY...SBCAPE WILL INCREASE TOWARD A 1000J/KG. SO...WILL MAINTAIN SLIGHT CHC POPS CLOSE TO LAKE MICHIGAN FOR POTENTIAL LAKE BREEZE FRONT CONVECTION. SINCE FCST SOUNDINGS LOOK SIMILAR TO THE W ACROSS SRN UPPER MI...WILL KEEP SLIGHT CHC POPS ACROSS THE S THIS AFTN. MAX TEMPS SHOULD BE SIMILAR OR JUST A FEW DEGREES LWR THAN YESTERDAY. ANY PCPN SHOULD END EARLY THIS EVENING. OVERNIGHT...A SHORTWAVE ROTATING AROUND THE LOW OVER SE CANADA WILL SWING TOWARD LAKE SUPERIOR. NO HEIGHT FALLS/FORCING ARE INDICATED AND AIRMASS PRECEEDING SHORTWAVE IS QUITE DRY...SO NO POPS ARE NEEDED TONIGHT. EVEN AS SHORTWAVE SWINGS THRU UPPER MI THU MORNING...HEIGHTS ARE RISING. LACK OF FORCING COMBINED WITH SHORTWAVE PASSING IN THE MORNING BEFORE PEAK HEATING SUGGESTS LITTLE THREAT OF PCPN...AND WILL THUS MAINTAIN A DRY FCST. EWD EXTENSION OF MID/UPPER RIDGE ACROSS SRN CANADA WILL THEN SETTLE S INTO THE UPPER LAKES FRI... MAINTAINING A DRY WEATHER REGIME. LENGTHENING DRY SPELL IN MANY PORTIONS OF THE FCST AREA IS RAISING FIRE WEATHER CONCERNS. BOTH THU AND FRI (ESPECIALLY FRI) WILL BE DAYS WITH LOW AFTN RH`S IN THE INTERIOR. MIXING UPWARDS OF 750MB ON PREFERRED DRIER GFS FCST SOUNDINGS INDICATES POTENTIAL FOR DWPTS TO DROP INTO THE LWR/MID 40S THU AFTN AWAY FROM LAKE SUPERIOR MODIFICATION. WITH MAX TEMPS REACHING THE MID/UPPER 70S...AFTN RH WILL DROP TOWARD 30PCT. FORTUNATELY...WINDS WILL BE RELATIVELY LIGHT THU. WITH DEEP MIXING UNDER FULL/NEARLY FULL SUN...GFS FCST SOUNDINGS FOR FRI INDICATE POTENTIAL FOR TEMPS TO BE A FEW DEGREES HIGHER AND DWPTS A FEW DEGREES LWR. RH MAY END UP AROUND 25PCT AWAY FROM LAKE SUPERIOR MODIFICATION. FORTUNATELY AGAIN...WINDS SHOULD BE RELATIVELY LIGHT. GFS/ECMWF INDICATE A COLD FRONT DROPPING S TOWARD LAKE SUPERIOR SAT. IT`S NOT OUT OF THE QUESTION THAT THERE COULD BE ISOLD -SHRA/TSRA LATE FRI NIGHT/SAT...BUT WITH FRONT PROBABLY NOT SLIPPING S ACROSS LAKE SUPERIOR AND HEIGHT FALLS PASSING BY TO THE NE...DRY WEATHER SHOULD PREVAIL HERE. THERMAL RIDGE AHEAD OF THE FRONT WILL REACH THE AREA SAT. UNDER WRLY WINDS...TEMPS SHOULD CONSERVATIVELY TOP OUT AROUND 80/LWR 80S IN MOST AREAS. DRY/WARM WEATHER SHOULD PERSIST THRU SUN BEFORE A COLD FRONT DROPS INTO THE UPPER LAKES MON... PROVIDING THE POTENTIAL FOR SOME PCPN. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... SCT MID CLOUDS INTO EARLY AFTN AS UPPER DISTURBANCES PASSES OVR ERN UPR MI. E/NE WINDS SET UP THIS AFTN AND PERSISTS INTO TONIGHT. LIGHT E WINDS/ADDED MOISTURE OFF OF TORCH LAKE TO THE EAST OF KCMX COULD RESULT IN PATCHY FOG LATE TONIGHT. SIMILAR TO LAST TWO NIGHTS FOG AT KCMX...WOULD PROBABLY BE A BRIEF PERIOD OF ANYWHERE FM LIFR TO MVFR VSBY WITH AN VLIFR CIG. SINCE IT IS A VERY LOW PROBABILITY EVENT... OPTED TO NOT INCLUDE IN THE TAF. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SFC HIGH PRESSURE BUILDING OUT OF ONTARIO WILL SETTLE ACROSS GREAT LAKES THROUGH FRIDAY. NE WINDS SHOULD APPROACH 20 KNOTS OVER FAR WESTERN LAKE SUPERIOR THROUGH THURSDAY DUE TO CHANNELING BETWEEN MINNESOTA SHORELINE AND APOSTLE ISLANDS. AS THE HIGH MOVES SOUTH OF THE AREA SATURDAY AND SUNDAY...INCREASING WEST WINDS MAY REACH 25 KNOTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...JLA SYNOPSIS/DISCUSSION...ROLFSON AVIATION...JLA MARINE...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 420 AM EDT WED AUG 13 2008 .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A MIDLEVEL LOW OVER SRN SASKATCHEWAN...A MIDLEVEL HIGH OVER WRN HUDSON BAY WITH A RIDGE EXTENDING S TOWARD THE UPPER LAKES...AND A TROF/BROAD MIDLEVEL LOW OVER SE CANADA. THESE LARGER SCALE FEATURES ARE FORCING A SHORTWAVE OVER MN/WRN WI TO THE SSE. -SHRA ASSOCIATED WITH THIS FEATURE EXTEND FROM EXTREME WRN UPPER MI S THRU WI...BUT NOT ALL OF THE PCPN IS REACHING THE GROUND. TO THE E...A SHORTWAVE ROTATING S THRU ONTARIO AROUND THE MIDLEVEL LOW OVER SE CANADA WAS PRODUCING -SHRA OVER FAR NCNTRL AND NE LAKE SUPERIOR. THERE WERE A FEW TSRA NE OF THE LAKE EARLIER IN THE NIGHT. && .DISCUSSION... OVER THE NEXT COUPLE OF DAYS...A RIDGE WILL BUILD N ALONG THE W COAST OF THE CONUS AND THEN E TO CONNECT WITH THE MIDLEVEL HIGH OVER WRN HUDSON BAY. THIS WILL FORCE THE MIDLEVEL LOW OVER SASKATCHEWAN TO THE S. MEANWHILE...THE TROF OVER SE CANADA WILL BRIEFLY EXTEND SW THRU THE WRN GREAT LAKES REGION BEFORE THE RIDGE SETTLES S INTO THE NCNTRL STATES. THIS PATTERN WILL NOT FAVOR MUCH IN THE WAY OF PCPN FOR THE FCST AREA. SHORTWAVE THAT WAS PRODUCING SHRA OVER NE LAKE SUPERIOR WILL PASS BY TO THE E THIS MORNING. HOWEVER...PER RADAR TRENDS...WRN EDGE OF THE -SHRA MAY BRUSH THE FAR ERN FCST AREA...AND WILL INCLUDE SLIGHT CHC OF MORNING -SHRA THERE. MEANWHILE...TO THE W...SHORTWAVE ENERGY WILL CONTINUE TO BE FORCED SSE THRU MN/WRN WI THOUGH FAR WRN UPPER MI MAY STILL GET CLIPPED BY A FEW -SHRA. ATTENTION THEN TURNS TO THE POTENTIAL FOR DIURNAL CONVECTION. IT APPEARS GRADIENT WILL BE WEAK ENOUGH TODAY FOR A LAKE BREEZE TO DEVELOP NEAR LAKE MICHIGAN. CONVERGENCE ALONG LAKE BREEZE FRONT WILL ALLOW LOW-LEVEL MOISTURE TO POOL. MODIFIED NAM/GFS FCST SOUNDINGS FOR A SFC T/TD OF MID 70S/MID 50S YIELD CAPE OF SEVERAL HUNDRED J/KG. IF DWPTS RISE TO NEAR 60F LOCALLY...SBCAPE WILL INCREASE TOWARD A 1000J/KG. SO...WILL MAINTAIN SLIGHT CHC POPS CLOSE TO LAKE MICHIGAN FOR POTENTIAL LAKE BREEZE FRONT CONVECTION. SINCE FCST SOUNDINGS LOOK SIMILAR TO THE W ACROSS SRN UPPER MI...WILL KEEP SLIGHT CHC POPS ACROSS THE S THIS AFTN. MAX TEMPS SHOULD BE SIMILAR OR JUST A FEW DEGREES LWR THAN YESTERDAY. ANY PCPN SHOULD END EARLY THIS EVENING. OVERNIGHT...A SHORTWAVE ROTATING AROUND THE LOW OVER SE CANADA WILL SWING TOWARD LAKE SUPERIOR. NO HEIGHT FALLS/FORCING ARE INDICATED AND AIRMASS PRECEEDING SHORTWAVE IS QUITE DRY...SO NO POPS ARE NEEDED TONIGHT. EVEN AS SHORTWAVE SWINGS THRU UPPER MI THU MORNING...HEIGHTS ARE RISING. LACK OF FORCING COMBINED WITH SHORTWAVE PASSING IN THE MORNING BEFORE PEAK HEATING SUGGESTS LITTLE THREAT OF PCPN...AND WILL THUS MAINTAIN A DRY FCST. EWD EXTENSION OF MID/UPPER RIDGE ACROSS SRN CANADA WILL THEN SETTLE S INTO THE UPPER LAKES FRI... MAINTAINING A DRY WEATHER REGIME. LENGTHENING DRY SPELL IN MANY PORTIONS OF THE FCST AREA IS RAISING FIRE WEATHER CONCERNS. BOTH THU AND FRI (ESPECIALLY FRI) WILL BE DAYS WITH LOW AFTN RH`S IN THE INTERIOR. MIXING UPWARDS OF 750MB ON PREFERRED DRIER GFS FCST SOUNDINGS INDICATES POTENTIAL FOR DWPTS TO DROP INTO THE LWR/MID 40S THU AFTN AWAY FROM LAKE SUPERIOR MODIFICATION. WITH MAX TEMPS REACHING THE MID/UPPER 70S...AFTN RH WILL DROP TOWARD 30PCT. FORTUNATELY...WINDS WILL BE RELATIVELY LIGHT THU. WITH DEEP MIXING UNDER FULL/NEARLY FULL SUN...GFS FCST SOUNDINGS FOR FRI INDICATE POTENTIAL FOR TEMPS TO BE A FEW DEGREES HIGHER AND DWPTS A FEW DEGREES LWR. RH MAY END UP AROUND 25PCT AWAY FROM LAKE SUPERIOR MODIFICATION. FORTUNATELY AGAIN...WINDS SHOULD BE RELATIVELY LIGHT. GFS/ECMWF INDICATE A COLD FRONT DROPPING S TOWARD LAKE SUPERIOR SAT. IT`S NOT OUT OF THE QUESTION THAT THERE COULD BE ISOLD -SHRA/TSRA LATE FRI NIGHT/SAT...BUT WITH FRONT PROBABLY NOT SLIPPING S ACROSS LAKE SUPERIOR AND HEIGHT FALLS PASSING BY TO THE NE...DRY WEATHER SHOULD PREVAIL HERE. THERMAL RIDGE AHEAD OF THE FRONT WILL REACH THE AREA SAT. UNDER WRLY WINDS...TEMPS SHOULD CONSERVATIVELY TOP OUT AROUND 80/LWR 80S IN MOST AREAS. DRY/WARM WEATHER SHOULD PERSIST THRU SUN BEFORE A COLD FRONT DROPS INTO THE UPPER LAKES MON... PROVIDING THE POTENTIAL FOR SOME PCPN. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... TWO UPPER LEVEL LOWS...ONE OVER QUEBEC AND A SECOND OVER MANITOBA... KEEPING THE REGION UNDER A NARROW RIDGE OF HIGH PRESSURE. THIS WILL KEEP WINDS LIGHT WITH VFR CIGS/VIS EXPECTED THROUGH THE CURRENT FORECAST. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SFC HIGH PRESSURE BUILDING OUT OF ONTARIO WILL SETTLE ACROSS GREAT LAKES THROUGH FRIDAY. NE WINDS SHOULD APPROACH 20 KNOTS OVER FAR WESTERN LAKE SUPERIOR THROUGH THURSDAY DUE TO CHANNELING BETWEEN MINNESOTA SHORELINE AND APOSTLE ISLANDS. AS THE HIGH MOVES SOUTH OF THE AREA SATURDAY AND SUNDAY...INCREASING WEST WINDS MAY REACH 25 KNOTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/DISCUSSION...ROLFSON AVIATION...RJT MARINE...JLA mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 135 AM EDT WED AUG 13 2008 UPDATED AVIATION DISCUSSION FOR 06Z TAFS .SYNOPSIS... 19Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER LEVEL TROUGHING IN SE CANADA INTO THE NORTHEAST U.S. WITH A SHRTWV ROTATING AROUND THE WEST SIDE IN NE ONTARIO...A RIDGE EXTENDING FROM NE MANITOBA SOUTHWARD INTO WI...AND AN UPPER LOW OVER CENTRAL SASKATCHEWAN. SE OF THE UPPER LOW IS A SHRTWV OVER NW MN...NOTED BY A COMMA IN WATER VAPOR AND VISIBLE IMAGERY. UPPER LEVEL MOISTURE IS SEEN EAST OF THIS SHRTWV ACROSS ERN MN...WI...WRN UPPER MI AND THEN NW INTO NRN SASKATCHEWAN. THIS UPPER LEVEL MOISTURE ALSO EXTENDS DOWN INTO THE LOW LEVELS...AT LEAST ACROSS MN AND WRN WI WHERE SCT -SHRA ARE OCCURRING ON RADAR AND SURFACE OBS. THE AIRMASS SO FAR HAS BEEN TOO DRY IN UPPER MI TO ALLOW FOR ANY -SHRA IN WRN WI TO MOVE IN...DESPITE THE RETURNS OFF OUR RADAR. DAYTIME CUMULUS CLOUDS HAVE DEVELOPED OVER THE REST OF UPPER MI IN BETWEEN LAKE BREEZES COMING OFF LAKES SUPERIOR AND MICHIGAN. HOWEVER...AGAIN BELIEVE THE AIRMASS IS TOO DRY TO SUPPORT PCPN...WITH DEWPOINTS INLAND FROM THE LAKE BREEZE BOUNDARIES THAT HAVE MIXED OUT TO AROUND 50F. 1740Z TAMDAR SOUNDING FROM SAW REFLECTS THE DRY AIR TOO...AND USING 77 TEMP OVER 50 DEWPOINTS RESULTS IN NO CAPE. SOME CUMULUS ARE A BIT TALLER RIGHT ALONG THE BOUNDARIES WHERE MOISTURE IS POOLING...ONE SHOWER HAS MANAGED TO DEVELOP NEAR GULLIVER. TO OUR NE...SOME CLOUDS AND A FEW DIURNAL SHOWERS ARE PRESENT ACROSS NE ONTARIO AHEAD OF THE SHRTWV THERE. && .SHORT TERM (TONIGHT AND WEDNESDAY)... SUBTLE FEATURES DOMINATE THE SHORT TERM PERIOD OF THE FORECAST... WITH UPPER RIDGING BASICALLY HOLDING ON FROM NE ONTARIO INTO WRN UPPER MI THROUGH 00Z THU. THIS UPPER RIDGE DOES GET UNDERCUT BY THE SHRTWV IN MN DROPPING SE...IN ADDITION TO SQUEEZED AS THE SHRTWV IN NE ONTARIO DROPS SOUTH ACROSS EASTERN LAKE SUPERIOR LATER TONIGHT. THEREFORE...DRY AIR OVER THE CWA WILL LIKELY BE HARD TO GET RID OF. HOWEVER...THE CLOUDS TO THE WEST ASSOCIATED WITH BOTH DEFORMATION AND DPVA FROM THE NW MN SHRTWV SHOULD CREEP A BIT FARTHER INTO UPPER MI...MAINLY ALONG THE WI BORDER. HAVE MAINTAINED SOME ISOLATED SHOWERS OVER GOGEBIC COUNTY TONIGHT THROUGH WED MORNING WITH ANY SHOWERS THAT CAN MOVE IN FROM WRN WI...OTHERWISE THE BULK OF THE PCPN WILL REMAIN OVER WI. ALSO HAVE MAINTAINED A SLIGHT CHANCE OF PCPN THIS EVENING OVER SOUTH CENTRAL UPPER MI IN THE EVENT ADDITIONAL SHOWERS DEVELOP WHEN THE TWO LAKE BREEZES OFF SUPERIOR AND MICHIGAN COME TOGETHER...AND WITH STORM MOTION BEING NORTH TO SOUTH. WED AFTERNOON IS A BIT TRICKY...ESPECIALLY NOW THAT IT LOOKS LIKE A LAKE BREEZE OFF LAKE MICHIGAN WILL FORM. THE LAKE BREEZE MAY NOT BE TOO STRONG...BUT THE WINDS BEHIND IT SHOULD BE ONSHORE COMPARED TO THE EAST WIND THAT WAS FORECAST FROM LAST NIGHT. STILL...EVEN IF THE LAKE BREEZE CONVERGES ON THE GENERAL NORTHEAST FLOW...THE AIRMASS IS STILL DRY WITH DEWPOINTS LIKELY MIXING INTO THE LOW 50S ON THE NORTH SIDE OF THE LAKE BREEZE. BASICALLY PUT IN A 20 POP IN THE FAR SE U.P. IN THE EVENT THE LAKE BREEZE CAN POP A STORM...SIMILAR TO THE 06Z GFS AND OUR 12Z LOCAL WRF ARW RUN WITH THE KF CONVECTIVE SCHEME. ALSO HAVE 20 POPS ALONG THE WI BORDER IN THE AFTERNOON WITH INDICATIONS OF COOLER MID-LEVEL AIR NEARBY FROM THE MN SHRTWV AIDING DIURNAL DESTABILIZATION. PRECIPITABLE WATER VALUES ARE ABOUT 0.20 OF AN INCH HIGHER TONIGHT COMPARED TO LAST NIGHT...AND WITH CLOUD COVER MOVING IN FOR SOME OF THE CWA...LOW TEMPERATURES SHOULD BE HIGHER. PREVIOUS FORECAST LOWS LOOKED GOOD WITH ONLY A FEW MINOR TWEAKS MADE. MORE OF A NE WIND IS EXPECTED ON WEDNESDAY AS HIGH PRESSURE REBUILDS OVER NORTHERN ONTARIO...EXCLUDING THE LAKE BREEZE AREA ALONG LAKE MICHIGAN. THEREFORE...COOLEST READINGS TOMORROW WILL BE NEAR LAKE SUPERIOR WITH READINGS NEAR 70. INLAND TEMPS SHOULD STILL REACH THE MID TO UPPER 70S SINCE 850MB TEMPS AR AROUND 11C. .LONG TERM (WED NGT THRU TUE)... ON WED NGT/THU...THE CWA WL REMAIN IN NW FLOW ALF BTWN CUTOFF LO OVER SE CAN AND SHRTWV DIGGING THRU THE NRN PLAINS. THE 12Z GFS/NAM ARE IN GOOD AGREEMENT WITH THE 00Z ECMWF SHOWING A SHRTWV ROTATING ARND VORTEX IN SE CAN APRCHG THE ERN ZNS AND PULLING THE VORTEX TO THE W 12Z-18 THU. EVEN SO...GFS/NAM FCST SDNGS DEPICT AN AIRMASS TOO DRY EVEN AT ERY TO SUPPORT PCPN (KINX/PWAT AOB 20/0.75 INCH). ARRIVAL OF ANY DPVA/HGT FALLS DOES NOT EVEN COINCIDE WITH PRIME HTG TIME OF DAY BEFORE DNVA/HGT RISES COMMENCE THU AFTN AND HUDSON BAY HI PRES POKES SWD IN THE WAKE OF THE SHRTWV. WL CARRY MORE CLDS OVER THE ERN ZNS TO ACCOUNT FOR THIS SHRTWV BUT MAINTAIN DRY FCST. MIXING TO H725 ON GFS FCST SDNGS FOR THU AFTN YIELDS HI TEMPS ARND 75 AWAY FM LK MODERATION...WHICH WL BE MAXIMIZED DOWNWIND OF LK SUP WITH DVLPG NE FLOW S OF HUDSON BAY HI. WITH DWPTS MIXING OUT INTO THE 40 TO 45 RANGE AWAY FM LK MOISTENING PER FVRD DRIER GFS FCST SDNGS WITH HUDSON BAY HI PRES/DRY GROUND...EXPECT MIN RH TO BOTTOM OUT BTWN 25-30 PCT AND AGGRAVATE RECENT DRYNESS. FORTUNATELY...THE WINDS SHOULD BE RELATIVELY LGT AT MOST SPOTS WHERE THE RH WL BE LOWEST. TRANQUIL...DRY WX WL CONTINUE THU NGT/FRI WITH HUDSON BAY HI PRES CENTER BLDG OVHD LATE FRI. EXPECT THE LOWEST MIN TEMPS BLO GUIDANCE OVER THE INTERIOR W ON THU NGT AS THESE PLACES WL BE SHELTERED IN LGT NE FLOW AND CLOSER TO THE FCST MIN PWAT ARND 0.5 INCH. GFS/NAM HINT AT SOME MID CLD OVER THE ERN ZNS ASSOCIATED WITH ANY WEAK SHRTWV ROTATING ARND PARENT VORTEX IN SE CAN...AND THESE CLDS WL LIMIT DIURNAL TEMP FALL THERE. HI TEMPS ON FRI WL APRCH 80 OVER THE INTERIOR...WITH DRY AIRMASS ALLOWING FOR WIDE DIURNAL TEMP RANGE. PLAN ON MIN RH AGAIN IN THE 25-30 PCT RANGE. AS WL BE THE CASE ON THU...RELATIVELY LGT WINDS WL MITIGATE INCRSG FIRE WX CONCERNS. HARD TO FIND MUCH IN THE WAY OF RA CHCS IN THE EXTENDED PD. UPR PATTERN WL FEATURE TROF OVER NE CAN...WITH NW FLOW ALF BTWN THIS TROF AND RDG OVER THE ROCKIES DOMINATING SRN CAN/NRN TIER CONUS AND HOLDING OFF ANY SHRTWV/MSTR RETURN FM THE S. SEEMS BEST CHC FOR ANY PCPN WOULD BE ON MON WITH HINT OF A BACKDOOR COLD FROPA IN ADVANCE OF NEXT HUDSON BAY HI PRES BLDG TOWARD THE UPR LKS...ESPECIALLY IF THE CNDN MODEL FCST WITH MORE HIER AMPLITUDE TROF DVPS. WL THROW IN A 20 POP FOR MON TO REFLECT THIS POTENTIAL. OTRW...THE WEEKEND THRU TUE PD WL BE DRY. WITH MORE OF A WLY FLOW TO THE N OF HI PRES RDG IN THE LOWER LKS...EXPECT AOA NORMAL TEMPS ON SAT INTO MON...THEN COOLER AIR WL ARRIVE ON TUE BEHIND THE BACK DOOR COLD FROPA. COORDINATED WITH APX/LOT/GRB/DLH. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... TWO UPPER LEVEL LOWS...ONE OVER QUEBEC AND A SECOND OVER MANITOBA...KEEPING THE REGION UNDER A NARROW RIDGE OF HIGH PRESSURE. THIS WILL KEEP WINDS LIGHT WITH VFR CIGS/VIS EXPECTED THROUGH THE CURRENT FORECAST. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... WITH SFC HIGH PRES OVER OR NEAR THE UPPER GREAT LAKES THRU SUN... WINDS ARE EXPECTED TO REMAIN MOSTLY BELOW 15 KT. HOWEVER...WESTERLY WINDS DEVELOPING OVER THE WEEKEND AS THE HIGH DRIFTS SOUTH OF UPPER MI COULD APPROACH 20 KT. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...KC AVIATION...RJT MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 715 PM EDT TUE AUG 12 2008 UPDATED AVIATION DISCUSSION FOR 00Z TAFS .SYNOPSIS... 19Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER LEVEL TROUGHING IN SE CANADA INTO THE NORTHEAST U.S. WITH A SHRTWV ROTATING AROUND THE WEST SIDE IN NE ONTARIO...A RIDGE EXTENDING FROM NE MANITOBA SOUTHWARD INTO WI...AND AN UPPER LOW OVER CENTRAL SASKATCHEWAN. SE OF THE UPPER LOW IS A SHRTWV OVER NW MN...NOTED BY A COMMA IN WATER VAPOR AND VISIBLE IMAGERY. UPPER LEVEL MOISTURE IS SEEN EAST OF THIS SHRTWV ACROSS ERN MN...WI...WRN UPPER MI AND THEN NW INTO NRN SASKATCHEWAN. THIS UPPER LEVEL MOISTURE ALSO EXTENDS DOWN INTO THE LOW LEVELS...AT LEAST ACROSS MN AND WRN WI WHERE SCT -SHRA ARE OCCURRING ON RADAR AND SURFACE OBS. THE AIRMASS SO FAR HAS BEEN TOO DRY IN UPPER MI TO ALLOW FOR ANY -SHRA IN WRN WI TO MOVE IN...DESPITE THE RETURNS OFF OUR RADAR. DAYTIME CUMULUS CLOUDS HAVE DEVELOPED OVER THE REST OF UPPER MI IN BETWEEN LAKE BREEZES COMING OFF LAKES SUPERIOR AND MICHIGAN. HOWEVER...AGAIN BELIEVE THE AIRMASS IS TOO DRY TO SUPPORT PCPN...WITH DEWPOINTS INLAND FROM THE LAKE BREEZE BOUNDARIES THAT HAVE MIXED OUT TO AROUND 50F. 1740Z TAMDAR SOUNDING FROM SAW REFLECTS THE DRY AIR TOO...AND USING 77 TEMP OVER 50 DEWPOINTS RESULTS IN NO CAPE. SOME CUMULUS ARE A BIT TALLER RIGHT ALONG THE BOUNDARIES WHERE MOISTURE IS POOLING...ONE SHOWER HAS MANAGED TO DEVELOP NEAR GULLIVER. TO OUR NE...SOME CLOUDS AND A FEW DIURNAL SHOWERS ARE PRESENT ACROSS NE ONTARIO AHEAD OF THE SHRTWV THERE. && .SHORT TERM (TONIGHT AND WEDNESDAY)... SUBTLE FEATURES DOMINATE THE SHORT TERM PERIOD OF THE FORECAST... WITH UPPER RIDGING BASICALLY HOLDING ON FROM NE ONTARIO INTO WRN UPPER MI THROUGH 00Z THU. THIS UPPER RIDGE DOES GET UNDERCUT BY THE SHRTWV IN MN DROPPING SE...IN ADDITION TO SQUEEZED AS THE SHRTWV IN NE ONTARIO DROPS SOUTH ACROSS EASTERN LAKE SUPERIOR LATER TONIGHT. THEREFORE...DRY AIR OVER THE CWA WILL LIKELY BE HARD TO GET RID OF. HOWEVER...THE CLOUDS TO THE WEST ASSOCIATED WITH BOTH DEFORMATION AND DPVA FROM THE NW MN SHRTWV SHOULD CREEP A BIT FARTHER INTO UPPER MI...MAINLY ALONG THE WI BORDER. HAVE MAINTAINED SOME ISOLATED SHOWERS OVER GOGEBIC COUNTY TONIGHT THROUGH WED MORNING WITH ANY SHOWERS THAT CAN MOVE IN FROM WRN WI...OTHERWISE THE BULK OF THE PCPN WILL REMAIN OVER WI. ALSO HAVE MAINTAINED A SLIGHT CHANCE OF PCPN THIS EVENING OVER SOUTH CENTRAL UPPER MI IN THE EVENT ADDITIONAL SHOWERS DEVELOP WHEN THE TWO LAKE BREEZES OFF SUPERIOR AND MICHIGAN COME TOGETHER...AND WITH STORM MOTION BEING NORTH TO SOUTH. WED AFTERNOON IS A BIT TRICKY...ESPECIALLY NOW THAT IT LOOKS LIKE A LAKE BREEZE OFF LAKE MICHIGAN WILL FORM. THE LAKE BREEZE MAY NOT BE TOO STRONG...BUT THE WINDS BEHIND IT SHOULD BE ONSHORE COMPARED TO THE EAST WIND THAT WAS FORECAST FROM LAST NIGHT. STILL...EVEN IF THE LAKE BREEZE CONVERGES ON THE GENERAL NORTHEAST FLOW...THE AIRMASS IS STILL DRY WITH DEWPOINTS LIKELY MIXING INTO THE LOW 50S ON THE NORTH SIDE OF THE LAKE BREEZE. BASICALLY PUT IN A 20 POP IN THE FAR SE U.P. IN THE EVENT THE LAKE BREEZE CAN POP A STORM...SIMILAR TO THE 06Z GFS AND OUR 12Z LOCAL WRF ARW RUN WITH THE KF CONVECTIVE SCHEME. ALSO HAVE 20 POPS ALONG THE WI BORDER IN THE AFTERNOON WITH INDICATIONS OF COOLER MID-LEVEL AIR NEARBY FROM THE MN SHRTWV AIDING DIURNAL DESTABILIZATION. PRECIPITABLE WATER VALUES ARE ABOUT 0.20 OF AN INCH HIGHER TONIGHT COMPARED TO LAST NIGHT...AND WITH CLOUD COVER MOVING IN FOR SOME OF THE CWA...LOW TEMPERATURES SHOULD BE HIGHER. PREVIOUS FORECAST LOWS LOOKED GOOD WITH ONLY A FEW MINOR TWEAKS MADE. MORE OF A NE WIND IS EXPECTED ON WEDNESDAY AS HIGH PRESSURE REBUILDS OVER NORTHERN ONTARIO...EXCLUDING THE LAKE BREEZE AREA ALONG LAKE MICHIGAN. THEREFORE...COOLEST READINGS TOMORROW WILL BE NEAR LAKE SUPERIOR WITH READINGS NEAR 70. INLAND TEMPS SHOULD STILL REACH THE MID TO UPPER 70S SINCE 850MB TEMPS AR AROUND 11C. .LONG TERM (WED NGT THRU TUE)... ON WED NGT/THU...THE CWA WL REMAIN IN NW FLOW ALF BTWN CUTOFF LO OVER SE CAN AND SHRTWV DIGGING THRU THE NRN PLAINS. THE 12Z GFS/NAM ARE IN GOOD AGREEMENT WITH THE 00Z ECMWF SHOWING A SHRTWV ROTATING ARND VORTEX IN SE CAN APRCHG THE ERN ZNS AND PULLING THE VORTEX TO THE W 12Z-18 THU. EVEN SO...GFS/NAM FCST SDNGS DEPICT AN AIRMASS TOO DRY EVEN AT ERY TO SUPPORT PCPN (KINX/PWAT AOB 20/0.75 INCH). ARRIVAL OF ANY DPVA/HGT FALLS DOES NOT EVEN COINCIDE WITH PRIME HTG TIME OF DAY BEFORE DNVA/HGT RISES COMMENCE THU AFTN AND HUDSON BAY HI PRES POKES SWD IN THE WAKE OF THE SHRTWV. WL CARRY MORE CLDS OVER THE ERN ZNS TO ACCOUNT FOR THIS SHRTWV BUT MAINTAIN DRY FCST. MIXING TO H725 ON GFS FCST SDNGS FOR THU AFTN YIELDS HI TEMPS ARND 75 AWAY FM LK MODERATION...WHICH WL BE MAXIMIZED DOWNWIND OF LK SUP WITH DVLPG NE FLOW S OF HUDSON BAY HI. WITH DWPTS MIXING OUT INTO THE 40 TO 45 RANGE AWAY FM LK MOISTENING PER FVRD DRIER GFS FCST SDNGS WITH HUDSON BAY HI PRES/DRY GROUND...EXPECT MIN RH TO BOTTOM OUT BTWN 25-30 PCT AND AGGRAVATE RECENT DRYNESS. FORTUNATELY...THE WINDS SHOULD BE RELATIVELY LGT AT MOST SPOTS WHERE THE RH WL BE LOWEST. TRANQUIL...DRY WX WL CONTINUE THU NGT/FRI WITH HUDSON BAY HI PRES CENTER BLDG OVHD LATE FRI. EXPECT THE LOWEST MIN TEMPS BLO GUIDANCE OVER THE INTERIOR W ON THU NGT AS THESE PLACES WL BE SHELTERED IN LGT NE FLOW AND CLOSER TO THE FCST MIN PWAT ARND 0.5 INCH. GFS/NAM HINT AT SOME MID CLD OVER THE ERN ZNS ASSOCIATED WITH ANY WEAK SHRTWV ROTATING ARND PARENT VORTEX IN SE CAN...AND THESE CLDS WL LIMIT DIURNAL TEMP FALL THERE. HI TEMPS ON FRI WL APRCH 80 OVER THE INTERIOR...WITH DRY AIRMASS ALLOWING FOR WIDE DIURNAL TEMP RANGE. PLAN ON MIN RH AGAIN IN THE 25-30 PCT RANGE. AS WL BE THE CASE ON THU...RELATIVELY LGT WINDS WL MITIGATE INCRSG FIRE WX CONCERNS. HARD TO FIND MUCH IN THE WAY OF RA CHCS IN THE EXTENDED PD. UPR PATTERN WL FEATURE TROF OVER NE CAN...WITH NW FLOW ALF BTWN THIS TROF AND RDG OVER THE ROCKIES DOMINATING SRN CAN/NRN TIER CONUS AND HOLDING OFF ANY SHRTWV/MSTR RETURN FM THE S. SEEMS BEST CHC FOR ANY PCPN WOULD BE ON MON WITH HINT OF A BACKDOOR COLD FROPA IN ADVANCE OF NEXT HUDSON BAY HI PRES BLDG TOWARD THE UPR LKS...ESPECIALLY IF THE CNDN MODEL FCST WITH MORE HIER AMPLITUDE TROF DVPS. WL THROW IN A 20 POP FOR MON TO REFLECT THIS POTENTIAL. OTRW...THE WEEKEND THRU TUE PD WL BE DRY. WITH MORE OF A WLY FLOW TO THE N OF HI PRES RDG IN THE LOWER LKS...EXPECT AOA NORMAL TEMPS ON SAT INTO MON...THEN COOLER AIR WL ARRIVE ON TUE BEHIND THE BACK DOOR COLD FROPA. COORDINATED WITH APX/LOT/GRB/DLH. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... EARLIER POTENTIAL FOR SHRA/TSRA NEAR KSAW ALONG THE LAKE BREEZE HAS DIMINISHED AS DIURNALLY DRIVEN INSTABILITY ON THE WANE...RESULTING IN CONVECTIVE ACTIVITY E OF KSAW WEAKENING AS SHOWN ON LATEST WSR-88D DATA. THUS WILL LEAVE OUT MENTION OF SHRA/TSRA FROM THIS FORECAST. WITH AREA STUCK UNDER RIDGE OF HIGH PRESSURE...VFR CIGS/VIS AND LIGHT WINDS TO PREVAIL THROUGH THE FORECAST. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... WITH SFC HIGH PRES OVER OR NEAR THE UPPER GREAT LAKES THRU SUN... WINDS ARE EXPECTED TO REMAIN MOSTLY BELOW 15 KT. HOWEVER...WESTERLY WINDS DEVELOPING OVER THE WEEKEND AS THE HIGH DRIFTS SOUTH OF UPPER MI COULD APPROACH 20 KT. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...KC AVIATION...RJT MARINE...AJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 345 PM EDT TUE AUG 12 2008 .SYNOPSIS... 19Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER LEVEL TROUGHING IN SE CANADA INTO THE NORTHEAST U.S. WITH A SHRTWV ROTATING AROUND THE WEST SIDE IN NE ONTARIO...A RIDGE EXTENDING FROM NE MANITOBA SOUTHWARD INTO WI...AND AN UPPER LOW OVER CENTRAL SASKATCHEWAN. SE OF THE UPPER LOW IS A SHRTWV OVER NW MN...NOTED BY A COMMA IN WATER VAPOR AND VISIBLE IMAGERY. UPPER LEVEL MOISTURE IS SEEN EAST OF THIS SHRTWV ACROSS ERN MN...WI...WRN UPPER MI AND THEN NW INTO NRN SASKATCHEWAN. THIS UPPER LEVEL MOISTURE ALSO EXTENDS DOWN INTO THE LOW LEVELS...AT LEAST ACROS MN AND WRN WI WHERE SCT -SHRA ARE OCCURRING ON RADAR AND SURFACE OBS. THE AIRMASS SO FAR HAS BEEN TOO DRY IN UPPER MI TO ALLOW FOR ANY -SHRA IN WRN WI TO MOVE IN...DESPITE THE RETURNS OFF OUR RADAR. DAYTIME CUMULUS CLOUDS HAVE DEVELOPED OVER THE REST OF UPPER MI IN BETWEEN LAKE BREEZES COMING OFF LAKES SUPERIOR AND MICHIGAN. HOWEVER...AGAIN BELIEVE THE AIRMASS IS TOO DRY TO SUPPORT PCPN...WITH DEWPOINTS INLAND FROM THE LAKE BREEZE BOUNDARIES THAT HAVE MIXED OUT TO AROUND 50F. 1740Z TAMDAR SOUNDING FROM SAW REFLECTS THE DRY AIR TOO...AND USING 77 TEMP OVER 50 DEWPOINTS RESULTS IN NO CAPE. SOME CUMULUS ARE A BIT TALLER RIGHT ALONG THE BOUNDARIES WHERE MOISTURE IS POOLING...ONE SHOWER HAS MANAGED TO DEVELOP NEAR GULLIVER. TO OUR NE...SOME CLOUDS AND A FEW DIURNAL SHOWERS ARE PRESENT ACROSS NE ONTARIO AHEAD OF THE SHRTWV THERE. && .SHORT TERM (TONIGHT AND WEDNESDAY)... SUBTLE FEATURES DOMINATE THE SHORT TERM PERIOD OF THE FORECAST... WITH UPPER RIDGING BASICALLY HOLDING ON FROM NE ONTARIO INTO WRN UPPER MI THROUGH 00Z THU. THIS UPPER RIDGE DOES GET UNDERCUT BY THE SHRTWV IN MN DROPPING SE...IN ADDITION TO SQUEEZED AS THE SHRTWV IN NE ONTARIO DROPS SOUTH ACROSS EASTERN LAKE SUPERIOR LATER TONIGHT. THEREFORE...DRY AIR OVER THE CWA WILL LIKELY BE HARD TO GET RID OF. HOWEVER...THE CLOUDS TO THE WEST ASSOCIATED WITH BOTH DEFORMATION AND DPVA FROM THE NW MN SHRTWV SHOULD CREEP A BIT FARTHER INTO UPPER MI...MAINLY ALONG THE WI BORDER. HAVE MAINTAINED SOME ISOLATED SHOWERS OVER GOGEBIC COUNTY TONIGHT THROUGH WED MORNING WITH ANY SHOWERS THAT CAN MOVE IN FROM WRN WI...OTHERWISE THE BULK OF THE PCPN WILL REMAIN OVER WI. ALSO HAVE MAINTAINED A SLIGHT CHANCE OF PCPN THIS EVENING OVER SOUTH CENTRAL UPPER MI IN THE EVENT ADDITIONAL SHOWERS DEVELOP WHEN THE TWO LAKE BREEZES OFF SUPERIOR AND MICHIGAN COME TOGETHER...AND WITH STORM MOTION BEING NORTH TO SOUTH. WED AFTERNOON IS A BIT TRICKY...ESPECIALLY NOW THAT IT LOOKS LIKE A LAKE BREEZE OFF LAKE MICHIGAN WILL FORM. THE LAKE BREEZE MAY NOT BE TOO STRONG...BUT THE WINDS BEHIND IT SHOULD BE ONSHORE COMPARED TO THE EAST WIND THAT WAS FORECAST FROM LAST NIGHT. STILL...EVEN IF THE LAKE BREEZE CONVERGES ON THE GENERAL NORTHEAST FLOW...THE AIRMASS IS STILL DRY WITH DEWPOINTS LIKELY MIXING INTO THE LOW 50S ON THE NORTH SIDE OF THE LAKE BREEZE. BASICALLY PUT IN A 20 POP IN THE FAR SE U.P. IN THE EVENT THE LAKE BREEZE CAN POP A STORM...SIMILAR TO THE 06Z GFS AND OUR 12Z LOCAL WRF ARW RUN WITH THE KF CONVECTIVE SCHEME. ALSO HAVE 20 POPS ALONG THE WI BORDER IN THE AFTERNOON WITH INDICATIONS OF COOLER MID-LEVEL AIR NEARBY FROM THE MN SHRTWV AIDING DIURNAL DESTABILIZATION. PRECIPITABLE WATER VALUES ARE ABOUT 0.20 OF AN INCH HIGHER TONIGHT COMPARED TO LAST NIGHT...AND WITH CLOUD COVER MOVING IN FOR SOME OF THE CWA...LOW TEMPERATURES SHOULD BE HIGHER. PREVIOUS FORECAST LOWS LOOKED GOOD WITH ONLY A FEW MINOR TWEAKS MADE. MORE OF A NE WIND IS EXPECTED ON WEDNESDAY AS HIGH PRESSURE REBUILDS OVER NORTHERN ONTARIO...EXCLUDING THE LAKE BREEZE AREA ALONG LAKE MICHIGAN. THEREFORE...COOLEST READINGS TOMORROW WILL BE NEAR LAKE SUPERIOR WITH READINGS NEAR 70. INLAND TEMPS SHOULD STILL REACH THE MID TO UPPER 70S SINCE 850MB TEMPS AR AROUND 11C. .LONG TERM (WED NGT THRU TUE)... ON WED NGT/THU...THE CWA WL REMAIN IN NW FLOW ALF BTWN CUTOFF LO OVER SE CAN AND SHRTWV DIGGING THRU THE NRN PLAINS. THE 12Z GFS/NAM ARE IN GOOD AGREEMENT WITH THE 00Z ECMWF SHOWING A SHRTWV ROTATING ARND VORTEX IN SE CAN APRCHG THE ERN ZNS AND PULLING THE VORTEX TO THE W 12Z-18 THU. EVEN SO...GFS/NAM FCST SDNGS DEPICT AN AIRMASS TOO DRY EVEN AT ERY TO SUPPORT PCPN (KINX/PWAT AOB 20/0.75 INCH). ARRIVAL OF ANY DPVA/HGT FALLS DOES NOT EVEN COINCIDE WITH PRIME HTG TIME OF DAY BEFORE DNVA/HGT RISES COMMENCE THU AFTN AND HUDSON BAY HI PRES POKES SWD IN THE WAKE OF THE SHRTWV. WL CARRY MORE CLDS OVER THE ERN ZNS TO ACCOUNT FOR THIS SHRTWV BUT MAINTAIN DRY FCST. MIXING TO H725 ON GFS FCST SDNGS FOR THU AFTN YIELDS HI TEMPS ARND 75 AWAY FM LK MODERATION...WHICH WL BE MAXIMIZED DOWNWIND OF LK SUP WITH DVLPG NE FLOW S OF HUDSON BAY HI. WITH DWPTS MIXING OUT INTO THE 40 TO 45 RANGE AWAY FM LK MOISTENING PER FVRD DRIER GFS FCST SDNGS WITH HUDSON BAY HI PRES/DRY GROUND...EXPECT MIN RH TO BOTTOM OUT BTWN 25-30 PCT AND AGGRAVATE RECENT DRYNESS. FORTUNATELY...THE WINDS SHOULD BE RELATIVELY LGT AT MOST SPOTS WHERE THE RH WL BE LOWEST. TRANQUIL...DRY WX WL CONTINUE THU NGT/FRI WITH HUDSON BAY HI PRES CENTER BLDG OVHD LATE FRI. EXPECT THE LOWEST MIN TEMPS BLO GUIDANCE OVER THE INTERIOR W ON THU NGT AS THESE PLACES WL BE SHELTERED IN LGT NE FLOW AND CLOSER TO THE FCST MIN PWAT ARND 0.5 INCH. GFS/NAM HINT AT SOME MID CLD OVER THE ERN ZNS ASSOCIATED WITH ANY WEAK SHRTWV ROTATING ARND PARENT VORTEX IN SE CAN...AND THESE CLDS WL LIMIT DIURNAL TEMP FALL THERE. HI TEMPS ON FRI WL APRCH 80 OVER THE INTERIOR...WITH DRY AIRMASS ALLOWING FOR WIDE DIURNAL TEMP RANGE. PLAN ON MIN RH AGAIN IN THE 25-30 PCT RANGE. AS WL BE THE CASE ON THU...RELATIVELY LGT WINDS WL MITIGATE INCRSG FIRE WX CONCERNS. HARD TO FIND MUCH IN THE WAY OF RA CHCS IN THE EXTENDED PD. UPR PATTERN WL FEATURE TROF OVER NE CAN...WITH NW FLOW ALF BTWN THIS TROF AND RDG OVER THE ROCKIES DOMINATING SRN CAN/NRN TIER CONUS AND HOLDING OFF ANY SHRTWV/MSTR RETURN FM THE S. SEEMS BEST CHC FOR ANY PCPN WOULD BE ON MON WITH HINT OF A BACKDOOR COLD FROPA IN ADVANCE OF NEXT HUDSON BAY HI PRES BLDG TOWARD THE UPR LKS...ESPECIALLY IF THE CNDN MODEL FCST WITH MORE HIER AMPLITUDE TROF DVPS. WL THROW IN A 20 POP FOR MON TO REFLECT THIS POTENTIAL. OTRW...THE WEEKEND THRU TUE PD WL BE DRY. WITH MORE OF A WLY FLOW TO THE N OF HI PRES RDG IN THE LOWER LKS...EXPECT AOA NORMAL TEMPS ON SAT INTO MON...THEN COOLER AIR WL ARRIVE ON TUE BEHIND THE BACK DOOR COLD FROPA. COORDINATED WITH APX/LOT/GRB/DLH. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... VFR CIGS/VIS AND LIGHT WINDS ARE EXPECTED AT KCMX/KSAW THRU THIS FCST PERIOD AS HIGH PRES REMAINS DOMINANT. HOWEVER...LAKE BREEZES CONVERGING OVER CENTRAL UPPER MI COULD TRIGGER A SHRA OR TSRA OVER SAW LATER THIS AFTN. HAVE CHANGED THE PROB30 GROUP TO A TEMPO AS CONFIDENCE IS HIGH ENOUGH FOR A SHOWER TO DEVELOP. HOWEVER... CONFIDENCE IS NOT AS HIGH TO INCLUDE TS OR REDUCED VSBY IN THE TAF GIVEN THAT THE COVERAGE OF SHRA/TSRA WILL BE ISOLATED AT BEST. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... WITH SFC HIGH PRES OVER OR NEAR THE UPPER GREAT LAKES THRU SUN... WINDS ARE EXPECTED TO REMAIN MOSTLY BELOW 15 KT. HOWEVER...WESTERLY WINDS DEVELOPING OVER THE WEEKEND AS THE HIGH DRIFTS SOUTH OF UPPER MI COULD APPROACH 20 KT. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...KC AVIATION...AJ MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 137 AM EDT TUE AUG 12 2008 UPDATED FOR 06Z AVIATION DISCUSSION .SYNOPSIS... 19Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED TROUGHING OVER SE CANADA INTO THE NORTHEAST U.S. WITH A SHRTWV OF INTEREST IN NW QUEBEC...RIDGING FROM IOWA NORTHWARD INTO NE MANITOBA...A SHRTWV OVER WESTERN NORTH DAKOTA AND AN UPPER LOW IN CENTRAL ALBERTA. WEATHER OVERALL IS QUIET OVER WI AND MI...WITH ONLY SOME DIURNAL CUMULUS CLOUDS. THIS IS DUE TO DRY AIR ASSOCIATED WITH 1019MB HIGH PRESSURE OVER THE AREA AT THE SURFACE...ON THE EAST SIDE OF THE UPPER RIDGE AXIS. PRECIPITABLE WATER WAS 0.75 INCHES AT GRB...WHICH IS ABOUT 75 PCT OF NORMAL. DESPITE THE PRESENCE OF THE HIGH PRESSURE AREA AND DECENT MIXING...DEWPOINTS INLAND HAVE ONLY DROPPED INTO THE MID 40S AT LNL AND IMT. LAKE BREEZES ON ALL SHORELINES HAVE KEPT DEWPOINTS AND WIND SPEEDS HIGHER. TO THE WEST...SHOWERS HAVE BEEN PROGRESSING SLOWLY INTO THE DRY AIR ACROSS WESTERN MN. THESE ARE IN AN AREA OF ISENTROPIC LIFT AND DPVA AHEAD OF THE SHRTWV IN WESTERN NORTH DAKOTA. HIGH CLOUDS FROM THESE SHOWERS ARE GRADUALLY MOVING INTO WESTERN LAKE SUPERIOR. && .SHORT TERM (TONIGHT AND TUESDAY)... GFS/NAM/UKMET BASICALLY KEEP THE UPPER RIDGE BLOCKED UP THROUGH TUESDAY AS THE UPPER TROUGH IN SE CANADA RELOADS (DUE TO THE SHRTWV OVER NW QUEBEC DROPPING INTO NE ONTARIO) AND THE UPPER LOW IN ALBERTA SLOWLY PROGRESSING EAST. THEREFORE...PROGRESS OF ANY PRECIPITATION EITHER FROM THE WEST OR EAST WILL BE SLOW TO OCCUR. HOWEVER...THE PRECIPITATION IN WESTERN MN HAS BEEN PROGRESSING A BIT FASTER THAN MODELS...SUGGESTING FOLLOWING A MODEL THAT BRINGS IT EASTWARD QUICKER. THIS HAPPENS TO BE WHAT OUR LOCAL WRF-ARW RUN SUGGESTS. STILL...FOR TONIGHT...THIS ONLY REQUIRED INCREASING POPS OVER FAR WESTERN LAKE SUPERIOR AS THE PCPN SHOULD REMAIN TO THE WEST OF IRONWOOD. OTHERWISE...CUMULUS CLOUDS SHOULD MOSTLY DISSIPATE THIS EVENING...WITH INCREASING HIGH CLOUDS OVERNIGHT. GIVEN THE LACK OF MUCH CLOUD COVER OVERALL AND THE DRY AIR PRESENT...THINK TEMPS COULD DROP QUITE A BIT. HOWEVER...GIVEN THAT DEWPOINTS HAVE NOT DROPPED AS LOW AS TEMPS DID LAST NIGHT...READINGS TONIGHT SHOULD BE WARMER. FOLLOWED 00Z MEX COOP GUIDANCE FOR COLDEST LOCATIONS WHICH WOULD BE IN THE UPPER 40S. ON TUESDAY...MAINTAINED CHANCE POPS OVER THE WESTERN U.P. THROUGH THE DAY AS THE SHRTWV IN WESTERN NORTH DAKOTA...WHICH SHOULD BE IN CENTRAL MN BY 12Z...PROGRESSES SE INTO WRN WI. THERE IS ANOTHER CONCERN FOR PCPN...HOWEVER. MODELS SHOW A SURFACE TROUGH DEVELOPING WEST TO EAST DURING THE DAY...EXTENDING FROM THE SHRTWV IN CENTRAL MN EASTWARD TO THE LOW PRESSURE SYSTEM IN SE CANADA. LAKE BREEZES INTERSECTING THIS TROUGH WILL PROVIDE CONVERGENCE OR TRIGGERING MECHANISM. IN FACT...THE GFS...CANADIAN...NAM AND THE UKMET TO SOME EXTENT ALL DEVELOP AFTERNOON CONVECTION ON THE SURFACE TROUGH. SURFACE DEWPOINTS ON THE NAM ARE A BIT HIGH (LOW 60S)...BUT EVEN THE REGIONAL CANADIAN GENERATES CONVECTION WITH MORE REASONABLE DEWPOINTS IN THE MID TO PERHAPS UPPER 50S. THE HIGHER DEWPOINTS APPEAR TO BE COMING FROM THE WARM LAKE MICHIGAN. THEREFORE...HAVE WENT AHEAD AND MENTIONED CHANCE POPS IN THE AFTERNOON. CAPE VALUES ARE FAIRLY LOW...AROUND 500 J/KG...AND WITH 0-6 KM SHEAR FAIRLY WEAK...NOT EXPECTING ANY SVR WEATHER. FOLLOWED MET GUIDANCE MOSTLY FOR HIGH TEMPERATURES TOMORROW SINCE THERE SHOULD BE PLENTY OF SUN THROUGH THE MORNING...AND SEEMED REASONABLE WITH 850MB TEMPS AROUND 12C. .LONG TERM (TUE NIGHT THROUGH NEXT MON)... SOME LINGERING 305K ISENTROPIC LIFT ASSOC WITH SHEARED OUT SHORTWAVE LOBE ALONG THE WI BDR WILL STILL WARRANT KEEPING SLIGHT CHC POPS FOR LINGERING CONVECTION OVER SW COUNTIES TUE NIGHT. KEPT IN SOME SLIGHT CHC POPS TUE EVENING OVER INLAND PORTIONS OF THE REST THE CWA FOR LINGERING DIURNAL CONVECTION ALONG SFC TROUGH. ANOTHER SHORTWAVE ROTATING DOWN FROM HUDSON BAY WILL BRING A COLD FRONT THROUGH THE AREA ON WED. WITH A NE FLOW BEHIND THE FRONT EXPECT GENERALLY COOLER TEMPS (INLAND HIGHS LOW TO MID 70S) FOR WED WITH DRY CONDITIONS PREVAILING. FOLLOWED BLEND OF 12Z GFS AND 00Z ECMWF FOR THU THROUGH MON FCST WHICH INDICATES MID-LVL RIDGE BUILDING ACROSS THE WRN GREAT LAKES SPELLING DRY AND GENERALLY SEASONABLE TEMPS THU INTO MON. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... VFR CIGS/VSBY AND LIGHT WINDS ARE EXPECTED AT BOTH SITES THROUGH EARLY TUE AFTERNOON WITH HIGH PRESSURE IN CONTROL. HOWEVER...LOW LEVEL CONVERGENCE INLAND ASSOCIATED WITH A WEAK TROUGH MAY SUPPORT DEVELOPMENT OF ISOLD SHRA/TSRA OVER CNTRL UPPER MI. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... OTHER THAN A WEAK TROUGH DROPPING SOUTH ACROSS LAKE SUPERIOR TUESDAY MORNING...EXPECT SFC HIGH PRESSURE TO REMAIN IN CONTROL. THEREFORE EXPECT WINDS AT OR BELOW 20 KNOTS THROUGH SATURDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...JV AVIATION...JLB MARINE...AJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 224 PM CDT TUE AUG 12 2008 .DISCUSSION... IMMEDIATE CONCERN IS BAND OF RAIN EXITING WC WI THIS EVENING...AND SCATTERED SHOWERS/ISOLD THUNDER MOVING THROUGH CENTRAL PARTS OF MN...MAINLY THIS EVENING. ENOUGH SUNSHINE ACROSS WESTERN AREAS TO GENERATE SOME MLCAPE TO 500 J/KG ALONG WEAK SFC BNDRY MOVING INTO CENTRAL MN THIS AFTERNOON. THIS WILL REMAIN FOCUS FOR SOME SHRA/ISOLD TSRA INTO THE EVENING...AS SFC TROUGH MOVES EAST/SOUTHEAST DURING THE NIGHT. EXPECT CLOUDS TO CLEAR IN THE FAR WEST DURING THE NIGHT...AND WITH LAST NIGHTS RAIN...LIGHT WINDS AND RELATIVELY HIGH DEWPOINTS...WE SHOULD SEE AT LEAST SOME PATCHY FOG OVER WESTERN AREAS LATER TONIGHT. MODELS SUGGEST WHATEVER IS LEFT OF THIS CIRCULATION TO MOVE INTO WC WI WED MORNING. WITH SOME SUNSHINE...INSTABILITY INCREASES SOME AGAIN WED AFTERNOON...AND WITH WEAK SFC CONVERGENCE ALONG BNDRY... HAVE TO MAINTAIN SMALL CHANCE OF SHRA/ISOLD THUNDER....MAINLY OVER FAR SOUTHERN MN AND WC WI. DURING THE DAY THURSDAY...UPPER LOW OVER SASKATCHEWAN CANADA NOW...DROPS SOUTH/EAST OVER THE DAKOTAS...AFFECTING MN PROBABLY THURSDAY AFTERNOON. HAVE CONTINUED CHANCE POPS OVER THE MAINLY MN PORTION OF FCST FOR THURSDAY AS FORCING MOVES INTO THE REGION. TEMPERATURES FOR THE NEAR TERM WILL BE DETERMINED BY EXTENT OF CLOUDS COVER DURING THE DAY/NIGHT. WILL SEE SOME LOWER 80S IF SUNSHINE IS PREVALENT...OTHERWSIE...70S WILL BE ALL THAT CAN BE EXPECTED FOR HIGHS THROUGH THURSDAY. LONGER RANGE HINGES ON MOVEMENT OF UPPER LOW OVER THE DAKOTAS... THEREFORE LOW CONFIDENCE IN THIS PORTION OF THE FCST. WENT MORE WITH THE 00Z ECMWF FOR THIS PERIOD. THIS WOULD LEAVE MOST OF THE AREA DRY THROUGH THE WEEKEND...BUT BOTH THE GFS AND THE ECMWF TRY TO LIFT THE CLOSED LOW EAST/NORTHEAST MON/TUE PERIOD...SO WILL MAINTAIN THE HPC CHANCE POPS FOR THE FAR SOUTHERN FRINGE AREA FOR POPS/WX DURING THIS PERIOD. FIRST LOOK AT 12Z ECMWF DROPS THE CLOSED CIRCULATION EVEN FARTHER SOUTH AND WEST. && .AVIATION.../18Z TAF ISSUANCE/ TAF CONCERNS THIS ISSUANCE CONTINUE TO REVOLVE AROUND THE TROUGH OF LOW PRESSURE MOVING ACROSS MN AND WI. EXPECT MVFR CEILINGS AND ISOLD RAIN SHOWERS TO CONTINUE TO BE POSSIBLE ACROSS CENTRAL MN INTO WEST CENTRAL WI THIS AFTERNOON AHEAD OF THE TROUGH OVER WEST CENTRAL AND NORTHWEST MN. THE RUC MODEL LOW LEVEL RELATIVE HUMIDITY PROGS REMAIN SATURATED INTO THIS EVENING FROM KSTC-KMSP- KRNH-KEAU. ALTHOUGH THERE MAY BE OCCASIONAL CEILING IMPROVEMENTS INTO THE VFR CATEGORY THIS AFTERNOON...EXPECT LOWER CLOUDS TO SWING ACROSS NORTH/EAST CENTRAL MN INTO WEST CENTRAL WISCONSIN THROUGH THIS EVENING ON THE SOUTHERN PERIPHERY OF THE NORTHERN MN/WI TROUGH. THE BULK OF THE SHOWERS WILL OCCUR AT KRNH AND KEAU THIS AFTERNOON...BUT ISOLD SHRA WILL BE POSSIBLE TO THE WEST NEAR KSTC AND KMSP. CLOUDS SHOULD GRADUALLY SCATTER OUT OVERNIGHT FROM WEST TO EAST. LIGHT WINDS OVERNIGHT MAY LEAD TO STRATUS/FOG DEVELOPMENT...ESPECIALLY AT KRNH AND KEAU. OTHERWISE...VFR CONDITIONS ARE EXPECTED BY MID MORNING WEDNESDAY...WITH PREDOMINATE LIGHT WEST/NORTHWEST WINDS. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ DWE/LS mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1241 PM CDT TUE AUG 12 2008 .UPDATE...FOR 18Z AVIATION DISCUSSION BELOW && .DISCUSSION.../ISSUED AT 314 AM CDT TUE AUG 12 2008/ RAIN AND ISOLATED THUNDERSTORMS EXPECTED TO CONTINUE AHEAD OF A SURFACE TROUGH TODAY. PRECIP EXPECTED TO MOVE OUT OF WEST CENTRAL WISCONSIN BY WEDNESDAY MRNG. THE LATEST WATER VAPOR SATELLITE IMAGERY SHOWED SOME MID LEVEL DRYING OVER THE DAKOTAS. CLOUDS AND PRECIP EXPECTED TO SLOWLY CLEAR FROM WEST TO EAST OVER THE CWA. TSRA CHANCES WILL BEGIN TO DIMINISH DURING THE DAY AS LOW LEVEL JET WEAKENS TO AROUND 10 KNOTS. UPPER LOW OVER CANADA WILL MEANDER OVER SOUTHERN CANADA TDA...THEN BEGIN TO SLIDE SOUTHEAST OVER THE UPPER MIDWEST OVER THE WEEKEND. THIS SYSTEM WILL SLIDE WEST AND SOUTH OF OUR FORECAST AREA. THUS...ALLOWING AN UPPER RIDGE TO BUILD OVER THE UPPER MIDWEST. BOTH THE LATEST GFS AND ECMWF (EUROPEAN MODEL) ARE IN CLOSE AGREEMENT. SO HAVE BACKED OFF ON THE PRECIP CHANCES FOR NOW OVER THE UPPER MIDWEST FOR FRIDAY AND SATURDAY. JUST KEPT A SMALL POP GOING IN THE FAR WEST AND SOUTHWEST ON FRIDAY. SMALL DIURNAL TEMP CHANGES TODAY WITH PRECIP ALONG WITH DEEP LAYER MOISTURE IN PLACE. MAX TEMPS OVER THE NEXT FEW DAYS...WILL BE SOMEWHAT ON THE COOL SIDE WITH READINGS MAINLY IN THE 70S. MEDIUM AND LONG RANGE FORECAST...MODELS SHOW THE UPPER RIDGE THAT WAS FORECAST TO PREVAIL OVER THE UPPER MIDWEST BY FRIDAY...WILL BEGIN TO RETREAT OFF TO THE WEST. UPPER LEVEL TROUGH FORECAST TO AMPLIFY BACK OVER THE MIDWEST BY THE START OF NEXT WEEK. && .AVIATION.../18Z TAF ISSUANCE/ TAF CONCERNS THIS ISSUANCE CONTINUE TO REVOLVE AROUND THE TROUGH OF LOW PRESSURE MOVING ACROSS MN AND WI. EXPECT MVFR CEILINGS AND ISOLD RAIN SHOWERS TO CONTINUE TO BE POSSIBLE ACROSS CENTRAL MN INTO WEST CENTRAL WI THIS AFTERNOON AHEAD OF THE TROUGH OVER WEST CENTRAL AND NORTHWEST MN. THE RUC MODEL LOW LEVEL RELATIVE HUMIDITY PROGS REMAIN SATURATED INTO THIS EVENING FROM KSTC-KMSP- KRNH-KEAU. ALTHOUGH THERE MAY BE OCCASIONAL CEILING IMPROVEMENTS INTO THE VFR CATEGORY THIS AFTERNOON...EXPECT LOWER CLOUDS TO SWING ACROSS NORTH/EAST CENTRAL MN INTO WEST CENTRAL WISCONSIN THROUGH THIS EVENING ON THE SOUTHERN PERIPHERY OF THE NORTHERN MN/WI TROUGH. THE BULK OF THE SHOWERS WILL OCCUR AT KRNH AND KEAU THIS AFTERNOON...BUT ISOLD SHRA WILL BE POSSIBLE TO THE WEST NEAR KSTC AND KMSP. CLOUDS SHOULD GRADUALLY SCATTER OUT OVERNIGHT FROM WEST TO EAST. LIGHT WINDS OVERNIGHT MAY LEAD TO STRATUS/FOG DEVELOPMENT...ESPECIALLY AT KRNH AND KEAU. OTHERWISE...VFR CONDITIONS ARE EXPECTED BY MID MORNING WEDNESDAY...WITH PREDOMINATE LIGHT WEST/NORTHWEST WINDS. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DULUTH MN 1204 PM CDT TUE AUG 12 2008 .UPDATE... DE-EMPHASIZED EASTWARD PROGRESSION OF PRECIPITATION AND CLOUDS ACROSS EASTERN ARROWHEAD. EMPHASIZED ONSHORE FLOW AND ITS IMPACT ON AFTERNOON TEMPERATURES. && .DISCUSSION... A WEAK TROUGH OVER WESTERN MN IS BUCKING INTO A SURFACE HIGH OVER LAKE SUPERIOR...ASSOCIATED RELATIVELY DRY AIR...AND A WEAK SURFACE RIDGE ALOFT. THE RAIN IS DECREASING IN BOTH STRENGTH AND COVERAGE AS IT MOVES EAST OVER OUR AREA. RAIN HAS GOTTEN AS FAR EAST AS SILVER BAY AND ELY...BUT DRYING MAY PREVENT MEASURABLE RAIN FROM GETTING ALL THE WAY TO THE EASTERN END OF THE ARROWHEAD...EITHER THIS AFTERNOON OR TONIGHT. IF THE PRECIPITATION SPREADS UP THERE...IT WILL BE RATHER LIGHT. THE PRECIPITATION PULLS AWAY TO THE SOUTHEAST LATE TONIGHT AND EARLY WEDNESDAY...THERE MAY BE LINGERING MOISTURE OVER SOME OF NORTHWEST WI...WE WILL BE WATCHING FOR THAT POSSIBILITY. ANY CLEARING WOULD BE ACPYD BY PATCHY FOG ACROSS INLAND VALLEYS LATE TONIGHT. WITH BUILDING HIGH PRESSURE FROM HUDSON BAY BUILDING IN...BEGINNING TONIGHT...WE ANCPT AN ONSHORE FLOW AND CHILLY TEMPERATURES ALONG THE LAKE SUPERIOR SHORE FOR SEVERAL DAYS. && .PREV DISCUSSION... /ISSUED 353 AM CDT TUE AUG 12 2008/ DISCUSSION... FORECAST CHALLENGE IS PRECIPITATION COVERAGE AND EXTENT DURING THE DAY TODAY. HIGH PRESSURE SLOW TO EXIT CWA TO THE EAST...AND IS CURRENTLY CENTERED OVER MICHIGAN. LOW PRES TROUGH IN THE DAKOTAS SLOWLY AND STEADILY ADVANCING EWRD INTO MN EARLY THIS MORNING...WITH SHOWERS OUT AHEAD OF IT IN NW AND CENTRAL MN. RIDGING OCCURRING DOWN LAKE SUPERIOR INTO THE ARROWHEAD HINDERING ADVANCEMENT OF PRECIP AND EVEN CLOUDS. TD`S CURRENTLY ONLY IN THE 30S AT KELO AND KCKC. WITH THAT SAID...THINK THAT MODELS ARE OVERDOING PRECIP IN THIS AREA TODAY...AND HAVE SCALED BACK POPS SIGNIFICANTLY HERE. LATEST RUC MOISTURE AND OMEGA FIELDS SEEM TO HAVE THE BEST IDEA OF KEEPING MUCH OF THE ARROWHEAD DRY TODAY. IN ADDITION...MODEL X-SECTIONS SHOWING SIGNIFICANT LOW LEVEL DRY AIR INTRUSION FROM KDLH AND POINTS NE THROUGH 18Z TODAY. TROUGH BEGINS TO WEAKEN AND SLIDE SOUTHEASTWARD BY TONIGHT... WITH SHOWERS GRADUALLY ENDING NORTHWEST TO SOUTHEAST. WEDNESDAY FORECAST QUESTIONABLE...AS ECMWF SHOWING LINGERING TROUGHINESS AND MOISTURE IN PLACE ACROSS CWA. OPTED TO LEAVE OUT PRECIP CHANCES FOR NOW AS HUDSON BAY HIGH BEGINS TO RIDGE DOWN INTO THE NORTHLAND ONCE AGAIN. LATER SHIFTS WILL HAVE TO MONITOR FOR UPDATES ON WEDNESDAY FORECAST. LATE WEEK FORECAST FEATURES AN UPPER LEVEL LOW PROGGED TO DRIFT SOUTHWARD OUT OF CANADA INTO THE HIGH PLAINS...WITH PRECIP CHANCES ON THURSDAY...MAINLY IN WRN ZONES. MODEL TRENDS HAVE BEEN WESTWARD AND SOUTHWARD WITH THIS FEATURE...SO THINKING IS THAT HEAVY RAIN CHANCES WILL STAY AWAY FROM THE NORTHLAND. AVIATION... SLOW MOVING SFC BDRY WILL SPREAD LOWERING CEILINGS EASTWARD TODAY. LOW CONFIDENCE IN CEILING HEIGHTS AS STRONG RIDGE AHEAD OF SYSTEM WILL TRY TO ERODE PROGRESSION OF CLOUDS INTO ERN CWA. SHOULD SEE MVFR SPREAD TO INL/HIB/BRD TERMINALS EARLY MORNING...DLH BY 18Z...HYR BY 21Z. AREA OF IFR PRIMARILY ASSOCIATED WITH IMMEDIATE CONVERGENT AREA NEAR SFC BDRY. THIS PRIMARILY AFFECTS BRD BY LATE MORNING. SHOULD SEE ONLY SCTD PRECIP TODAY AS SYSTEM WEAKENS. CONDITIONS DETERIORATE TUESDAY NIGHT/EARLY WEDNESDAY AS WIDESPREAD BR/FG SHOULD DEVELOP. && POINT TEMPS/POPS... DLH 68 52 69 54 / 70 30 10 10 INL 74 49 80 50 / 70 40 10 10 BRD 76 54 81 56 / 60 20 10 10 HYR 77 50 81 48 / 50 40 10 10 ASX 74 52 74 50 / 30 20 10 10 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ EOM/LILES mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 627 AM CDT TUE AUG 12 2008 .UPDATE... UPDATED FOR 12Z AVIATION DISCUSSION BELOW. && .DISCUSSION... /ISSUED AT 314 AM CDT TUE AUG 12 2008/ RAIN AND ISOLATED THUNDERSTORMS EXPECTED TO CONTINUE AHEAD OF A SURFACE TROUGH TODAY. PRECIP EXPECTED TO MOVE OUT OF WEST CENTRAL WISCONSIN BY WEDNESDAY MRNG. THE LATEST WATER VAPOR SATELLITE IMAGERY SHOWED SOME MID LEVEL DRYING OVER THE DAKOTAS. CLOUDS AND PRECIP EXPECTED TO SLOWLY CLEAR FROM WEST TO EAST OVER THE CWA. TSRA CHANCES WILL BEGIN TO DIMINISH DURING THE DAY AS LOW LEVEL JET WEAKENS TO AROUND 10 KNOTS. UPPER LOW OVER CANADA WILL MEANDER OVER SOUTHERN CANADA TDA...THEN BEGIN TO SLIDE SOUTHEAST OVER THE UPPER MIDWEST OVER THE WEEKEND. THIS SYSTEM WILL SLIDE WEST AND SOUTH OF OUR FORECAST AREA. THUS...ALLOWING AN UPPER RIDGE TO BUILD OVER THE UPPER MIDWEST. BOTH THE LATEST GFS AND ECMWF (EUROPEAN MODEL) ARE IN CLOSE AGREEMENT. SO HAVE BACKED OFF ON THE PRECIP CHANCES FOR NOW OVER THE UPPER MIDWEST FOR FRIDAY AND SATURDAY. JUST KEPT A SMALL POP GOING IN THE FAR WEST AND SOUTHWEST ON FRIDAY. SMALL DIURNAL TEMP CHANGES TODAY WITH PRECIP ALONG WITH DEEP LAYER MOISTURE IN PLACE. MAX TEMPS OVER THE NEXT FEW DAYS...WILL BE SOMEWHAT ON THE COOL SIDE WITH READINGS MAINLY IN THE 70S. MEDIUM AND LONG RANGE FORECAST...MODELS SHOW THE UPPER RIDGE THAT WAS FORECAST TO PREVAIL OVER THE UPPER MIDWEST BY FRIDAY...WILL BEGIN TO RETREAT OFF TO THE WEST. UPPER LEVEL TROUGH FORECAST TO AMPLIFY BACK OVER THE MIDWEST BY THE START OF NEXT WEEK. && .AVIATION.../12Z TAF ISSUANCE/ TOUGH FIRST 6 TO 12 HRS OF THE TAF...WITH SCT SHRA AND PATCHES OF MVFR CIGS ACROSS THE AREA AT PRESENT. RUC 925MB RH SFCS HAVE A GOOD HANDLE ON WHERE THE MVFR CIGS ARE LOCATED...SO FOLLOWED THIS FOR THE MRNG LO CIGS. IN GNRL...AXN AND STC SHUD BE MOST AFFECTED BY THE MVFR CIGS...WHICH SHUD LIFT BY MID TO LATE MRNG. RNH AND MSP COULD SEE MVFR CIGS IF A DECENT ENUF SHWR MOVES OVHD. SHWR ACTIVITY IS SCT ENUF THAT COVERED IT WITH VCSH AND/OR TEMPO GROUPS. DRIER AIR WILL GRADUALLY MOVE IN FROM THE SW...LIFTING CIGS. THE POSSIBILITY EXISTS THAT...IF WE CAN GET ENUF SOLAR INSOLATION...THERE COULD BE SOME ADDITIONAL SHWR REGENERATION THIS AFTN...ESPECIALLY AT RNH AND EAU. MSP IS IFFY ENUF TO COVER IT WITH A VCSH. LO LVL MSTR HANGS AROUND RNH AND EAU THRU THE BULK OF THE NGT...SO FOG AND PSBL IFR CIGS LOOK VERY PSBL. MSP AGAIN LOOKS ON THE EDGE OF THE FOG/STRATUS RGN...BUT HINTED AT THE POSSIBILITY WITH A SCT CLD DECK AT IFR HGTS. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ JVM/KAT mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 353 AM CDT TUE AUG 12 2008 .DISCUSSION... FORECAST CHALLENGE IS PRECIPITATION COVERAGE AND EXTENT DURING THE DAY TODAY. HIGH PRESSURE SLOW TO EXIT CWA TO THE EAST...AND IS CURRENTLY CENTERED OVER MICHIGAN. LOW PRES TROUGH IN THE DAKOTAS SLOWLY AND STEADILY ADVANCING EWRD INTO MN EARLY THIS MORNING...WITH SHOWERS OUT AHEAD OF IT IN NW AND CENTRAL MN. RIDGING OCCURRING DOWN LAKE SUPERIOR INTO THE ARROWHEAD HINDERING ADVANCEMENT OF PRECIP AND EVEN CLOUDS. TD`S CURRENTLY ONLY IN THE 30S AT KELO AND KCKC. WITH THAT SAID...THINK THAT MODELS ARE OVERDOING PRECIP IN THIS AREA TODAY...AND HAVE SCALED BACK POPS SIGNIFICANTLY HERE. LATEST RUC MOISTURE AND OMEGA FIELDS SEEM TO HAVE THE BEST IDEA OF KEEPING MUCH OF THE ARROWHEAD DRY TODAY. IN ADDITION...MODEL X-SECTIONS SHOWING SIGNIFICANT LOW LEVEL DRY AIR INTRUSION FROM KDLH AND POINTS NE THROUGH 18Z TODAY. TROUGH BEGINS TO WEAKEN AND SLIDE SOUTHEASTWARD BY TONIGHT... WITH SHOWERS GRADUALLY ENDING NORTHWEST TO SOUTHEAST. WEDNESDAY FORECAST QUESTIONABLE...AS ECMWF SHOWING LINGERING TROUGHINESS AND MOISTURE IN PLACE ACROSS CWA. OPTED TO LEAVE OUT PRECIP CHANCES FOR NOW AS HUDSON BAY HIGH BEGINS TO RIDGE DOWN INTO THE NORTHLAND ONCE AGAIN. LATER SHIFTS WILL HAVE TO MONITOR FOR UPDATES ON WEDNESDAY FORECAST. LATE WEEK FORECAST FEATURES AN UPPER LEVEL LOW PROGGED TO DRIFT SOUTHWARD OUT OF CANADA INTO THE HIGH PLAINS...WITH PRECIP CHANCES ON THURSDAY...MAINLY IN WRN ZONES. MODEL TRENDS HAVE BEEN WESTWARD AND SOUTHWARD WITH THIS FEATURE...SO THINKING IS THAT HEAVY RAIN CHANCES WILL STAY AWAY FROM THE NORTHLAND. && .AVIATION... SLOW MOVING SFC BDRY WILL SPREAD LOWERING CEILINGS EASTWARD TODAY. LOW CONFIDENCE IN CEILING HEIGHTS AS STRONG RIDGE AHEAD OF SYSTEM WILL TRY TO ERODE PROGRESSION OF CLOUDS INTO ERN CWA. SHOULD SEE MVFR SPREAD TO INL/HIB/BRD TERMINALS EARLY MORNING...DLH BY 18Z...HYR BY 21Z. AREA OF IFR PRIMARILY ASSOCIATED WITH IMMEDIATE CONVERGENT AREA NEAR SFC BDRY. THIS PRIMARILY AFFECTS BRD BY LATE MORNING. SHOULD SEE ONLY SCTD PRECIP TODAY AS SYSTEM WEAKENS. CONDITIONS DETERIORATE TUESDAY NIGHT/EARLY WEDNESDAY AS WIDESPREAD BR/FG SHOULD DEVELOP. && POINT TEMPS/POPS... DLH 68 52 69 56 / 50 30 10 10 INL 71 49 79 52 / 40 20 10 10 BRD 72 56 81 57 / 40 20 10 10 HYR 73 50 80 51 / 50 40 10 10 ASX 73 52 74 52 / 20 20 10 10 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ LONKA/CANNON mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DULUTH MN 1231 AM CDT TUE AUG 12 2008 .UPDATE... UPDATED TO SLOW DOWN EASTWARD PROGRESSION OF PRECIP LATE TONIGHT. LATEST RUC/NAM12 AND RADAR TRENDS SHOWING PRECIP HAVING A HARD TIME PROGRESSING EAST WITH HIGH PRES CONTINUING TO RIDGE INTO THE EASTER CWA. && .PREV DISCUSSION... /ISSUED 931 PM CDT MON AUG 11 2008/ UPDATE... ZFP UPDATED FOR TIME REFERENCES. NO CHG TO FCST. PREV DISCUSSION... /ISSUED 258 PM CDT MON AUG 11 2008/ DISCUSSION... A NORTH-SOUTH TROUGH OVER THE DAKOTAS IS TRYING TO BUCK AND UPPER RIDGE CENTERED OVER DLH...A COLD MARITIME HIGH OVER LAKE SUPERIOR AND EXCESSIVE DRYING ALONG THE NORTH SHORE AND ARROWHEAD THAT HAS DRIVEN DEW POINTS BELOW 5C ACROSS SOME AREAS. PRECIPITATION FROM THE TROUGH HAS AGGRESSIVELY PUSHED TO OUR WESTERN BORDER BUT SEEMS LIKELY TO HAVE TROUBLE CONTINUING ITS PUSH OR ITS TENDENCY. THE NAM SEEMS TO HAVE A FEEDBACK SITUATION WHERE A SMALL AND DEEP SURFACE LOW FORMS OVER SD AND MOVES UP JUST WEST OF DLH TONIGHT. THE GFS IS MORE REASONABLE BY WEAKENING A SURFACE LOW OVER THE MANITOBA LAKES...WRAPPING A STATIONARY/WARM FRONT AROUND THE MARINE AIR MASS...AND SENDING MOISTURE SOUTH...THEN SOUTHEAST ALONG THE COLD SIDE OF THIS FRONT TONIGHT AND TUESDAY. IT IS UNCLEAR TO US WHETHER THIS FRONT WILL ACTUALLY PUSH INTO OUR AREA OR MERELY ALLOW ENERGY TO PASS AROUND US...REINFORCING THE CONTINUING ONSHORE FLOW BEGINNING ON TUESDAY. AFTER THE TROUGH PASSES...A STRONG HUDSON BAY HIGH WILL AGAIN ESTABLISH STRONG RIDGING OVER LAKE SUPERIOR...SPCLY WESTERN LAKE SUPERIOR...FURTHER REINFORCING THE ONSHORE FLOW. PRIND THE ONSHORE FLOW WILL PRST THROUGH THE REST OF THE WEEK AND POSSIBLY INTO THE COMING WEEKEND. WITH THE ONSHORE FLOW AND OUR ANCPTN OF DRIER CONDITIONS THAN ANY OF THE GUIDANCE ANCPTS...WE ANCPT WIDE DAY-NIGHT TEMPERATURE VARIATIONS WELL INLAND...WITH DAYS NEAR 25C...AND A BRISK AND CHILLY ONSHORE FLOW ANYWHERE NEAR THAT LAKE...SPCLY ALONG THE NORTH SHORE AND DLH AND THE TWIN PORTS. THE DRY AND COOL AIRMASS WILL PROVIDE A TOUCH OF AUTUMN TO INLAND VALLEYS IN THE MORNINGS. AVIATION... VFR CONDITIONS WILL DETERIORATE TO MVFR OVERNIGHT...ESPECIALLY FROM KHIB TO KMZH AND POINTS WEST...AS A LOW PRESSURE AREA OVER THE DAKOTAS MOVES INTO WESTERN MINNESOTA. MID LEVEL CLOUDS IN ADVANCE OF THIS FEATURE WILL SPREAD FROM WEST TO EAST DURING THE EARLY EVENING HOURS. THE CHANCE FOR RAIN SHOWERS AND ASSOCIATED MVFR CEILINGS/VSBYS WILL INCREASE BY 00Z IN THE SOUTHWEST...AND THEN SLOWLY PUSH EAST OVERNIGHT...NOT REACHING KHYR UNTIL AFTER 12Z TUESDAY. THE BEST CHANCE FOR THUNDER APPEARS TO BE LIMITED TO THE SOUTHERN AND WESTERN PORTION OF THE AREA. RAIN CHANCES WILL PERSIST THROUGH 18Z TUESDAY ACROSS MUCH OF THE AREA...BUT CONDITIONS SHOULD SLOWLY IMPROVE TUESDAY AFTERNOON AS SOMEWHAT DRIER LOW LEVEL AIR ARRIVES FROM THE WEST AND THE BEST SOURCE OF LIFT DEPARTS. && POINT TEMPS/POPS... DLH 68 52 71 56 / 40 30 10 10 INL 75 49 79 52 / 40 30 10 10 BRD 78 56 81 57 / 40 20 10 10 HYR 80 51 81 51 / 50 30 10 10 ASX 75 52 73 52 / 40 30 10 10 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ TL/CANNON mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1201 AM CDT TUE AUG 12 2008 .UPDATE... .DISCUSSION... SATELLITE AND RADAR TRENDS SHOWING SHOWERS BEGINNING TO EVOLVE EASTWARD INTO THE CWA AS UPPER LEVEL JET COMES IN FROM THE WEST AND LOW LEVEL JET BEGINS TO INCREASE FROM THE SOUTH. SFC TROUGH...THOUGH DEEPENING...HAS LITTLE TO MOVE IT EASTWARD UP TO THIS POINT. THIS ALONG WITH LIMITED CAPE FROM MEAGER SFC HEATING TODAY HAS INHIBITED EASTWARD DEVELOPMENT OF SHOWERS TO THIS POINT. RUC MODEL FORECASTS OF 925-700MB HEIGHT FALLS ARE PROJECTED TO INCREASE IN WRN MN THROUGH THE NEXT SEVERAL HOURS. RESPONSIVE LLJ SHOULD INCREASE AS WELL /ALREADY 30 KTS ON FSD VAD/ WITH ISENTROPIC UPGLIDE ON THE 305K AND 310K SFCS BECOMING SATURATED. MOST UNSTABLE LIS SHOW A DECREASE IN STABILITY BUT GRADUAL. LIGHTNING HAS BEEN WIDELY SCATTERED AT BEST. SO MINIMIZED THUNDER WORDING IN THE GRIDS. POPS BASICALLY LEFT THE SAME...WITH LIKELY TO CATEGORICAL IN FOR OVERNIGHT ACROSS MUCH OF THE MN CWA. CHANCE FOR SVR SEEMS MINIMAL. BROOKINGS SD MEASURED 48 KT GUST RECENTLY BUT THAT WAS WITH A BETTER STORM STRUCTURE THAN WHAT IS ENTERING WEST CTRL MN. ALSO A GREATER INSTABILITY POOL EXISTS FURTHER SW...INCLUDING DOWNDRAFT POTENTIAL. IN ADDITION...COLD POOL PROPAGATION SHOULD ADVECT THE BRUNT OF THESE STORMS INTO FAR SW MN. SO THE RECENT MEASUREMENT OF A 33 KT GUST AT CANBY IS ON THE ORDER OF WHAT WE EXPECT THE NEXT COUPLE HOURS IN THE SW CWA. RAINFALL AMOUNTS PROJECTED TONIGHT POSSIBLY EXCEEDING ONE INCH IN PLACES OF THE MN CWA DUE TO HIGH PWAT AND STORM PROPAGATION POTENTIALLY OFFERING SOME TRAINING. FLASH FLOOD POTENTIAL APPEARS EXTREMELY LOW THOUGH GIVEN THE HIGH FFG AND OVERALL ONLY MARGINAL CONDITIONS FOR SUSTAINED HEAVY RAIN. && .PREV DISCUSSION... /ISSUED 700 PM CDT MON AUG 11 2008/ FORECAST CONCERN NEAR TERM...THUNDER/RAIN MOVING ACROSS MAINLY MN PORTION OF CWA THROUGH 12Z TUE. INITIAL SURGE OF DEEPER MOISTURE/INSTABILITY GENERATED BAND OF TSRA THIS AFTERNOON...AND WILL LIKELY SEE THIS LIFT NORTHEAST INTO CENTRAL PORTIONS THE REMAINDER OF THE AFTERNOON. BRIEF HEAVY RAIN IS ALL THAT IS ANTICIPATED AS DEEP SHEAR/STRONG INSTABILITY IS LACKING. SURFACE TROUGH OVER CENTRAL SOUTH DAKOTA NOW...PROGGED TO MOVE INTO WESTERN CWA LATER TONIGHT. UPPER TROUGH OVER ALBERTA...BECOMES MORE NEGATIVELY TILTED OVER EASTERN MT/WY REGION. THIS PROGGED TO MOVE INTO WESTERN MN LATER TONIGHT AS WELL. EXPECTED AREA OF TSRA MOVING ACROSS THE AREA OVERNIGHT/TUESDAY MORNING. WENT HIGHER POPS FROM WEST TO NORTH OVERNIGHT. COULD HAVE SOME DECENT RAINFALL IS LARGER AREA OF RAIN MATERIALIZES OVER THE AREA LATER TONIGHT...AS HIGH PRECIPITABLE WATER VALUES/1.75 INCHES/ MOVES ACROSS. TROUGH FORECAST TO WEAKEN TUESDAY AFTERNOON...WITH WEAK NORTH TO SOUTH SFC TROUGH OVER CENTRAL CWA. INSTABILITY INCREASES AND THERE MAY BE ENOUGH CONVERGENCE ALONG THE BOUNDARY TO INITIATE CONVECTION AT LEAST ALONG THE BOUNDARY. DEEPER SHEAR MOVES INTO THE WESTERN CWA AS WELL...SO DEPENDING ON HEATING/DEGREE OF DESTABILIZATION...COULD HAVE A CHANCE OF AT LEAST STRONG STORMS WITH HAIL/WIND. WILL MAINTAIN CHANCE POPS INTO THE EVENING/ALONG EAST OF THE TROUGH. FORECAST TEMPERATURES WILL DEPEND ON SUNSHINE...SO WONT STRAY TOO FAR FROM MAV GUIDANCE VALUES THROUGH WEDNESDAY. 12Z GFS SHOWS UPPER LEVEL RIDGING DEVELOPING OVER WESTERN MN...AND COLLABORATION HAS YIELDED A DRY WEDNESDAY FORECAST. SHOULD SEE MORE SUNSHINE AND FORECAST H85 TEMPERATURES PROGGED INTO THE MID/UPPER TEENS. SHOULD SEE AT LEAST LOW-MID 80S FOR HIGHS OVER MOST OF THE REGION. LONGER RANGE PROBLEM IS DEVELOPMENT OF CLOSED LOW SOMEWHERE OVER THE NORTHERN PLAINS FRIDAY THROUGH AT LEAST SUNDAY PERIOD. 00Z ECMWF AND 06Z GFS HAVE THIS DEVELOPING WITH THE ECMWF SLOWER...WITH CIRCULATION WAITING FOR ANOTHER TROUGH OVER THE NORTHWEST TO KICK IT EAST. 500 HPA HGHTS STANDARDIZED ANOMALIES FROM BOTH THE 00Z GFS AND ECMWF HAVE BULLSEYE 4-6 STANDARD DEVIATIONS MOVING ACROSS DAKS/NEB/IA REGION DURING THE PERIOD. BEST FIT ANALOG OF UPPER AIR PATTERN IS MID JULY 1990. SHOULD SEE MAX TEMPERATURES RANGING ABOUT 10 DEGREES BELOW NORMAL/MAINLY 70S/ ACROSS SOUTHERN MN AS SYSTEM MOVES THROUGH FRI-SUN PERIOD. WENT ALONG WITH HIGH CHANCE POP SCENARIO FOR FRIDAY ACROSS WESTERN AREAS AS LOW DROPS SOUTH...THEN RETAIN CHANCE POPS THROUGH SATURDAY NIGHT. HOPEFULLY SYSTEM WILL HAVE OCCLUDED ENOUGH TO LIMIT MOISTURE AND WILL BE FAR ENOUGH EAST TO SALVAGE SUNDAY FOR THE WEEKEND FCST. WILL MAINTAIN SLGT CHANCE POPS THEN. WENT DRY FOR MON TO AT LEAST START MENTIONING A DRYING TREND LATE IN PERIOD. && .AVIATION.../06Z TAF ISSUANCE/ RAIN CONTINUES TO BE SLOW TO PROPOGATE EASTWARD FROM WRN MN. AS SFC TROUGH AND LOW LEVEL JET DO EVOLVE SLOWLY EASTWARD...SCT SHOWERS ARE EXPECTED TO MOVE EASTWARD TOWARDS STC AND MSP. THESE WILL LIKELY BE LIGHT HOWEVER DUE TO VERY LIMITED INSTABILITY AND ORGANIZED SHEAR. TAMDAR SOUNDINGS NEAR MSP SHOW THE SATURATION LAYER FOR CLOUD BASE LIKELY TO BE ABOVE MVFR. HOWEVER...SOON AFTER DAYBREAK...ESPECIALLY IF THERE IS GREATER SHOWER COVERAGE...THERE IS THE POSSIBILITY OF MVFR CIGS AT MSP. THIS WILL BE AIDED WITH LIGHT LOW LEVEL FLOW. SOME FORM OF CIGS ARE EXPECTED MUCH OF THE DAY AT AND AROUND ERN MN AND WRN WI TAF SITES DUE TO THE LIGHT FLOW AND INCREASING MOISTURE. REDEVELOPMENT OF SHRA POSSIBLE DURING THE AFTN AS NARROW AXIS OF INSTABILITY EXPECTED TO BUILD ALONG SFC TROUGH. SHOWERS LIKELY TO BE PULSY AND SCT IN COVERAGE WITH THUNDER POSSIBLE. TROUGH WILL GRADUALLY FADE AS IT WORKS SOUTHEASTWARD THIS EVE PULLING RAIN CHANCES WITH IT FOR TONIGHT. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ DWE/MTF mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON MS 950 PM CDT TUE AUG 12 2008 .UPDATE...SURFACE ANALYSIS PLACES SURFACE LOW JUST EAST OF JACKSON THIS HOUR. LAST HOUR JAN AND HKS SHOWED 1004MB AND THE PRESSURE IS NOW RISING. LINE OF SHOWERS AND THUNDERSTORMS ALONG THE ASSOCIATED COLD FRONT WERE NOW SOUTH OF HIGHWAY 84 WEST OF INTERSTATE 59. SATELLITE IMAGERY/RUC ANALYSIS HAS THE SHORTWAVE OVER THE DELTA REGION WITH VERY DRY AIR ALOFT. APPEARS FRONT AND CONVECTIVE ACTIVITY WILL HAVE ENOUGH MOMENTUM TO CLEAR THE CWFA AFTER MIDNIGHT. HAVE CUT POPS OVER THE DELTA AND TRIMMED BACK POPS FOR CURRENT RADAR TRENDS. LOW LEVEL DRIER AIR IS EXPECTED TO FILTER INTO OUR AREA AFTER MIDNIGHT AS THE LOW SHIFTS EAST. THIS SHOULD ALLOW FOR SITES IN THE WEST TO DROP INTO THE 60S FOR MORNING LOWS. AM CONCERNED THAT IN THE NORTHEAST TEMPS MAY REMAIN UP HIGHER THAN FORECAST LOWS THOUGH AS AFFECTS OF THE SFC LOW LINGERS INTO THE MORNING HOURS. THE FLASH FLOOD WATCH THAT WAS IN EFFECT FOR THE SOUTH HAS BEEN CANCELLED. UPDATES HAVE BEEN POSTED. /22/ && .PREVIOUS DISCUSSION...SHORT TERM...FOR WEDNESDAY...NLY LOW LEVEL FLOW DEVELOPS TOMORROW IN THE WAKE OF THE LOW SYSTEM AND THE AIR MASS DRIES RAPIDLY FROM THE N. PRECIPITABLE WATER VALUES ARE FORECAST TO DROP QUICKLY WITH VALUES NEAR 1.5 INCHES OVER EXTREME SERN ZONES BY NOON. WILL FOLLOW PREVIOUS FORECAST THINKING TO DROP POPS TO SLIGHT CHANCE SERN AREAS...SLIGHTLY UNDERCUTTING MOS. ALSO UNDERCUT MOS HIGH TEMPS SLIGHTLY FOR TOMORROW AND THURSDAY. WE WILL SEE NOTICEABLE WARMING OVER THE NEXT COUPLE OF DAYS BUT SATURATED SOILS SHOULD HAMPER AFTERNOON HEATING SLIGHTLY. LONG TERM...FRIDAY AND BEYOND...THE PERIOD OF DRIER WEATHER MAY LAST UNTIL THE WEEKEND AS SURFACE HIGH PRESSURE BUILDS OVER THE AREA. WITH THE DRIER WEATHER WILL COME HOTTER AFTERNOONS AND HIGH TEMPERATURES WILL GET BACK INTO THE LOW TO MID 90S. NORTHWEST FLOW ALOFT WILL SEND THE NEXT SIGNIFICANT SHORTWAVE TROUGH OUR WAY THIS WEEKEND. MODELS DIFFER ON JUST HOW MUCH THIS TROUGH WILL DIG WITH SOME SOLUTIONS INDICATING THE TROUGH WILL CUT OFF BEFORE REACHING THE AREA THUS DELAYING EFFECTS ON OUR WEATHER. RAIN CHANCES WILL INCREASE THIS WEEKEND IN ANY CASE...BUT THERE IS POTENTIAL THAT MORE HEAVY RAIN COULD FALL OVER THE LOWER MS VALLEY REGION IF THE TROUGH MANAGES TO DIG FAR ENOUGH SOUTH BEFORE SLOWING DOWN. /EC/ && .AVIATION...DRIER AIR IS MOVING INTO THE NORTHWEST BUT MVFR/IFR CONDITIONS WILL PREVAIL AT MOST SITES THROUGH THE NIGHT. VFR CIGS MAY DEVELOP FROM THE NW BRIEFLY BUT AREAS OF FOG WILL BE POSSIBLE FOR PATCHES OF IFR/LIFR CIGS/VSBYS TOWARD MORNING. VFR CONDITIONS WILL RETURN TO MOST AREAS BY WEDNESDAY AFTERNOON AS THE DRIER AIR FILTERS IN. /22/ && .PRELIMINARY POINT TEMPS/POPS... JACKSON 69 88 62 92 / 30 6 6 7 MERIDIAN 70 86 61 90 / 60 8 8 8 VICKSBURG 69 89 64 93 / 20 5 5 7 HATTIESBURG 73 88 65 91 / 67 21 11 5 NATCHEZ 71 86 64 92 / 63 10 6 3 GREENVILLE 66 89 62 93 / 8 3 4 6 GREENWOOD 65 89 64 92 / 11 3 5 6 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...NONE. LA...NONE. AR...NONE. && $$ 03/19/EC ms AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 1154 PM CDT MON AUG 11 2008 ...UPDATED AVIATION DISCUSSION... .DISCUSSION... /923 PM CDT MON AUG 11 2008/ WATCHING BOWING LINE OF STORMS IN NEBRASKA DROPPING SOUTHEAST. RUC SHOWING SOME INSTABILITY EXTENDING INTO NORTHEAST KANSAS AND NORTHWEST CORNER OF MISSOURI OVERNIGHT. WILL INCREASE AREA COVERED BY CHANCE POPS OVERNIGHT TO INCLUDE THE ST JOSEPH AND ATCHISON KANSAS AREAS IN CASE THIS LINE CAN MAINTAIN ITSELF AS IT DROPS SOUTH SOUTHEAST ON THIS INSTABILITY AXIS. LLJ SHOULD BE VEERING AFTER MIDNIGHT...AND CORFIDI VECTORS SUGGEST A SLOWER PROPAGATION SOUTHWARD AFTER MIDNIGHT...BUT COLD POOL EFFECTS FROM THIS COMPLEX SHOULD HELP TO KEEP THEM MOVING AT A DECENT CLIP. JUST A QUESTION IF THERE IS ENOUGH INSTABILITY FURTHER SOUTH TO SUSTAIN THEM...SO WILL ONLY KEEP SLIGHT CHANCES GOING FOR THE KANSAS CITY METRO AREA. PC && .PREV DISCUSSION... /337 PM CDT MON AUG 11 2008/ MADE VERY FEW CHANGES TO THE FIRST 3 DAYS OR SO OF THE FORECAST. MOISTURE AXIS JUST CLIPS THE WESTERN BORDER OF THE FORECAST AREA THIS EVENING. WOULD NOT BE SURPRISED TO SEE SCATTERED TSRA DEVELOP WITHIN THAT AXIS. ANY ACTIVITY THAT DEVELOPS WILL STRUGGLE TO MAKE IT VERY FAR EAST...WITH RELATIVELY DRY EASTERLY FLOW PERSISTING ACROSS THE FORECAST AREA. EXPECT THIS SAME DRY AIR TO AFFECT PRECIP CHANCES OVERNIGHT. ACTIVITY POSSIBLY DEVELOPING OVER NEBRASKA LATE THIS EVENING AND OVERNIGHT AS SHORTWAVE TRANSLATING THROUGH THE NORTHERN STREAM IMPACTS THE WEAK SURFACE TROUGH. EXPECT ACTIVITY TO GENERALLY MOVE EAST. WILL TRY TO MOVE SOUTH INTO THE FORECAST AREA. HOWEVER EXPECT AREAL COVERAGE TO BE SCATTERED WITH RELATIVE DRY AIR FEEDING INTO IT. THE SURFACE TROUGH IS PROGGED TO CONTINUE TO MOVE SOUTH ACROSS MUCH OF THE REGION DURING THE DAY TUESDAY. SHOULD SEE SOME SURFACE MOISTURE POOLING ALONG THE BOUNDARY. WILL BE OVER THE FORECAST AREA AT PEAK HEATING. INSTABILITY DUE TO POOLING DEW POINTS AND DAYTIME HEATING MAY LEAD TO A FEW STRONG TO POSSIBLY SEVERE STORMS. NRR MEDIUM RANGE (THURSDAY-MONDAY)... A RATHER VIGOROUS UPPER LEVEL LOW WILL START TO SLIDE SOUTHEAST FROM SOUTHERN CANADA...ACROSS THE NORTHERN PLAINS AND EVENTUALLY INTO THE CENTRAL PLAINS AS THE WEEK PROGRESSES. AS THIS UPPER LOW EDGES CLOSER TO THE FORECAST AREA TOWARD THE END OF THE WEEK...VARIOUS SMALLER SCALE SHORTWAVE IMPULSES ARE FORECAST TO ROTATE CYCLONICALLY AROUND THE UPPER CLOSED LOW. THE MEDIUM RANGE MODELS OF COURSE TIME AND PLACE THESE INDIVIDUAL SHORTWAVE IMPULSES DIFFERENTLY FROM ONE MODEL TO THE NEXT...AND FROM ONE MODEL RUN TO THE NEXT. STILL...THIS PATTERN GENERALLY LENDS ITSELF TO A PERIOD OF INCREASED RAIN CHANCES AND COOLER TEMPERATURES FROM LATE WEEK AND THROUGH THE WEEKEND. CONTINUED THE TREND OF LOWERING TEMPERATURES A BIT MORE...WELL BELOW THE SEASONAL NORMALS...AND KEPT PRECIPITATION CHANCES GENERALLY IN THE 30-40 PERCENT RANGE. STOFLET && .AVIATION... FOR THE 06Z TAFS...TIMING IN CONVECTION FROM NEBRASKA...ALTHOUGH IT SHOULD BE IN A MUCH WEAKENED STATE...APPEARS TO HAVE THE POTENTIAL TO MAKE IT THROUGH ALL THE TAF SITES LATE TONIGHT. THIS CONVECTION MAY AID IN PUSHING A WEAK SURFACE TROUGH THROUGH THE TAF SITES IN THE MORNING. BIG QUESTION ON WHETHER THIS WILL WASH OUT AND BETTER MOISTURE AXIS WILL REMAIN ACROSS THE TAF SITES IN THE AFTERNOON ALLOWING CONVECTION TO REDEVELOP. THINKING THAT WITH POOR LAPSE RATES IN THE AREA...AND LACK OF ANY SIGNIFICANT SURFACE CONVERGENCE...CHANCES OF STORMS DEVELOPING IN THE AFTERNOON ARE TOO LOW TO WARRANT PUTTING IN THE TAFS AT THIS POINT. PC && .EAX WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. $$ mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 1103 AM CDT TUE AUG 12 2008 .UPDATE... NEW GRIDS AND TEXT PRODUCTS HAVE BEEN SENT. .DISCUSSION... HAVE DROPPED CLOUD COVERAGE THIS MORNING AS THE MAJORITY OF THE CWA HAS CLEARED OUT...AS SEEN ON VISIBLE SATELLITE IMAGERY. HAVE KEPT CLOUD COVER OVER SOUTHWEST IOWA AS CLOUDS ASSOCIATED WITH LAST NIGHTS SYSTEM CONTINUE TO MOVE EASTWARD. ALSO LOWERED TEMPS ACROSS THE AREA SINCE WE HAVE NOT WARMED AS QUICKLY AS PREVIOUSLY THOUGHT...HAVE ALSO LOWERED DEW POINTS A SMIDGEN THRU THE AFTERNOON. && .PREV DISCUSSION... /ISSUED 344 AM CDT TUE AUG 12 2008/ DISCUSSION... SHORT TERM CONCERNS WILL BE THE PRECIPITATION SHIFTING EAST OF THE AREA TODAY...THEN CHANCE OF PRECIPITATION WED THRU THE EXTENDED. PER THE WSR-88D MOSAIC..THE MAIN AREA OF SHOWERS AND ISOLD -TSRA EXTEND FM WRN IA AND NE KS WITH OTHER ISOLD -SHRA LINGERING IN ERN NEB. THIS LINGERING PRECIP WAS IN AN AREA WHERE THERE WAS A WEAK SFC LOW CIRCULATION...AS THE SFC ANALYSIS REVEALED SOUTH WINDS IN WRN IA...E WNDS AT SUX AND WEST WNDS FET WESTWARD. THE LATEST NAM CONTINUES TO END THE SHOWERS THIS MORNING AS THE SHORTWAVE TROF MOVES INTO MN/IA AND THE WNDSHIFT MOVES THRU SHIFTING THE DEEPER MOISTURE TO THE EAST. THE RUC AND GFS TEND TO HOLD ON TO SOME CHC OF PRECIP INTO THE AFTERNOON WITH SOME LINGERING SHORTWAVE TROF ENERGY. DID LEAVE SOME LOW POPS IN SW IA AS LINGERING MOISTURE AND HEATING COULD POPS SOME SHOWERS AS FCST SOUNDINGS STILL SHOWING SOME INSTABILITY. MORE SUNSHINE SHOULD BOOST TEMPERATURES INTO THE MID AND UPR 80S FOR HIGHS. LEFT TONIGHT DRY. WED AND THUR HAS SHORTWAVE TROF ENERGY MOVING ACRS THE PLAINS AHEAD OF THE LARGE CLOSED LOW THAT WILL SETTLE INTO THE PLAINS. LOW CONFIDENCE ON THE TIMING OF PRECIP CHANCES...BUT COULD SEE PRECIP EACH DAYS WITH COOLING ALOFT AND UVV. LEANED TOWARD THE WETTER/SLOWER ECMWF SOLUTION COMPARED TO THE GFS THAT BRINGS PRECIP IN WED NIGHT THRU THU NIGHT THEN DROPS THE PRECIP SOUTH. THE MODELS HAVE HAD A LARGE RANGE OF SOLUTIONS OVER THE LAST SEVERAL DAYS AND STILL ARE HAVING TROUBLE WITH IT. PROGS SUGGEST BELOW NORMAL TEMPERATURES THURSDAY THROUGH THE EXTENDED. AVIATION... FOR TAF SITES KOMA/KLNK/KOFK THROUGH 13/06Z. SCT SHWRS SHOULD MOVE E OF THE AREA WITH PATCHY IFR CIGS DISSIPATING BY 11Z AT OMA. CONDITIONS IMPROVING FROM W TO E WITH MID CLOUDS BREAKING UP BEFORE 15Z. DIFFUSE SFC TROUGH WILL BRING VBL WINDS INTO THE NW BY 18Z...BUT WITH SPEEDS AOB 10KT. WNDS WILL BECOME LGT AND VBL AROUND SUNSET WITH FEW CLDS. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ KURTZ ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 344 AM CDT TUE AUG 12 2008 .DISCUSSION... SHORT TERM CONCERNS WILL BE THE PRECIPITATION SHIFTING EAST OF THE AREA TODAY...THEN CHANCE OF PRECIPITATION WED THRU THE EXTENDED. PER THE WSR-88D MOSAIC..THE MAIN AREA OF SHOWERS AND ISOLD -TSRA EXTEND FM WRN IA AND NE KS WITH OTHER ISOLD -SHRA LINGERING IN ERN NEB. THIS LINGERING PRECIP WAS IN AN AREA WHERE THERE WAS A WEAK SFC LOW CIRCULATION...AS THE SFC ANALYSIS REVEALED SOUTH WINDS IN WRN IA...E WNDS AT SUX AND WEST WNDS FET WESTWARD. THE LATEST NAM CONTINUES TO END THE SHOWERS THIS MORNING AS THE SHORTWAVE TROF MOVES INTO MN/IA AND THE WNDSHIFT MOVES THRU SHIFTING THE DEEPER MOISTURE TO THE EAST. THE RUC AND GFS TEND TO HOLD ON TO SOME CHC OF PRECIP INTO THE AFTERNOON WITH SOME LINGERING SHORTWAVE TROF ENERGY. DID LEAVE SOME LOW POPS IN SW IA AS LINGERING MOISTURE AND HEATING COULD POPS SOME SHOWERS AS FCST SOUNDINGS STILL SHOWING SOME INSTABILITY. MORE SUNSHINE SHOULD BOOST TEMPERATURES INTO THE MID AND UPR 80S FOR HIGHS. LEFT TONIGHT DRY. WED AND THUR HAS SHORTWAVE TROF ENERGY MOVING ACRS THE PLAINS AHEAD OF THE LARGE CLOSED LOW THAT WILL SETTLE INTO THE PLAINS. LOW CONFIDENCE ON THE TIMING OF PRECIP CHANCES...BUT COULD SEE PRECIP EACH DAYS WITH COOLING ALOFT AND UVV. LEANED TOWARD THE WETTER/SLOWER ECMWF SOLUTION COMPARED TO THE GFS THAT BRINGS PRECIP IN WED NIGHT THRU THU NIGHT THEN DROPS THE PRECIP SOUTH. THE MODELS HAVE HAD A LARGE RANGE OF SOLUTIONS OVER THE LAST SEVERAL DAYS AND STILL ARE HAVING TROUBLE WITH IT. PROGS SUGGEST BELOW NORMAL TEMPERATURES THURSDAY THROUGH THE EXTENDED. && .AVIATION... FOR TAF SITES KOMA/KLNK/KOFK THROUGH 13/06Z. SCT SHWRS SHOULD MOVE E OF THE AREA WITH PATCHY IFR CIGS DISSIPATING BY 11Z AT OMA. CONDITIONS IMPROVING FROM W TO E WITH MID CLOUDS BREAKING UP BEFORE 15Z. DIFFUSE SFC TROUGH WILL BRING VBL WINDS INTO THE NW BY 18Z...BUT WITH SPEEDS AOB 10KT. WNDS WILL BECOME LGT AND VBL AROUND SUNSET WITH FEW CLDS. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ ZAPOTOCNY/POLLACK ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBUQUERQUE NM 300 AM MDT TUE AUG 12 2008 .DISCUSSION...NORTHWEST FLOW PATTERN TO PERSIST FOR THE NEXT FEW DAYS. LOW LEVEL BOUNDARY APPARENTLY HAS PUSHED OUT TO PORTIONS OF CONTDVD BASED ON RADAR IMAGERY...AND HAVE SEEN AT LEAST SMALL INCREASES IN DEWPOINTS ON SOME OF THE AREA RAWS. ANOTHER BOUNDARY SEEMS TO BE DRAPED ACROSS THE EASTERN PLAINS ORIENTED FROM WEST TO EAST...LIKELY ASSOCIATED WITH EARLIER CONVECTION OR RELATED TO AREA OF MID LEVEL CLOUDINESS CURRENTLY PASSING OVER NORTHEAST NEW MEXICO. NEEDLESS TO SAY...MODELS DON/T REALLY PICK UP ON THIS...EXCEPT COULD MAKE A CASE FOR THE RUC WHICH SUGGESTS SOMETHING ACROSS THE NORTHEAST/EAST CENTRAL. DESPITE THE CONSIDERABLE DRYING NOTED IN THE KABQ SOUNDING YESTERDAY EVENING...SUSPECT THERE MAY BE A BIT MORE ACTIVITY AROUND THIS AFTERNOON/EVENING THAN THE GUIDANCE POPS WOULD SUGGEST. GENERAL CONSENSUS IS 850-500MB THETA-E AXIS WILL REMAIN ORIENTED FROM SOUTHWEST TO THE NORTHEAST/EAST CENTRAL REGION OF THE STATE...WITH SOME ADDITIONAL DRYING IN THE FAR NORTHWEST. THE AXIS MAY SHIFT WITHIN THE NEXT 48 HOURS TO A MORE WEST TO EAST ORIENTATION BUT WITH HIGHEST VALUES REMAINING MOSTLY SOUTH OF INTERSTATE 40. THURSDAY THROUGH FRIDAY...MODELS CONTINUE TO INDICATE THE RIDGE OF HIGH PRESSURE WILL SHARPEN AS IT TAKES ON A NORTH TO SOUTH PLACEMENT FROM ARIZONA THROUGH WASHINGTON AND IDAHO WHILE AN UPPER LOW DROPS SOUTHWARD ALONG THE EAST SLOPES OF THE ROCKIES. MEANWHILE...A SURFACE FRONT WILL AFFECT THE EASTERN PLAINS. LATEST ECMWF FORECASTS A WET PERIOD FOR THE EASTERN HALF OF NEW MEXICO THROUGH SATURDAY...BUT WHAT MODELS DO WITH THE UPPER LOW DURING THE COMING WEEKEND WILL LIKELY CHANGE WITH TIME. && .AVIATION...SHOWERS AND STORMS WILL BE SLIGHTLY MORE ACTIVE TODAY ALONG AND SOUTHEAST OF A LINE FROM KCAO TO KLVS...KSAF...KABQ...AND KSRR. DRIER AIR WILL CREATE GUSTY OUTFLOW ALONG THE WESTERN EDGE OF THIS AREA. MOST ACTIVITY WILL TAPER OFF BY MID/LATE EVENING. PERIODS OF MVFR CONDITIONS WILL BE ASSOCIATED WITH THE STRONGER CELLS ACROSS THE SOUTH AND EAST. NEXT AVIATION DISCUSSION SCHEDULED FOR 21Z. && .FIRE WEATHER...THE DRIER TREND HAS EASED IN OVER AT LEAST THE WESTERN HALF OF NEW MEXICO OVER THE PAST 2 DAYS. SHOWERS/STORMS WILL BE A LITTLE MORE ACTIVE TODAY AND WEDNESDAY OVER THE CENTRAL MTNS/GILA REGION ALTHOUGH THE WETTING RAIN WILL NOT BE AS SIGNIFICANT. THE DEEP MOISTURE OVER THE PLAINS WILL CONTINUE PRODUCING WETTING RAINS FROM ANY STORMS. MIN RH VALUES WILL RANGE FROM THE TEENS IN THE NW PLATEAU TO THE MID 30S ALONG THE TEXAS BORDER THROUGH FRIDAY...WITH GOOD TO EXCELLENT RECOVERIES RESPECTIVELY. EXTENDED MODELS INTO THE WEEKEND CONTINUE TO INDICATE AN UPPER LOW MOVING SOUTH ALONG THE FRONT RANGE..HOWEVER MODELS ARE STILL STRUGGLING TO AGREE. OVERALL IMPACTS AT THIS TIME WOULD BE AN INCREASE IN STORM ACTIVITY FROM THE CENTRAL MTNS EAST ACROSS THE PLAINS INTO EARLY NEXT WEEK. && .PRELIMINARY POINT TEMPS/POPS... FARMINGTON...................... 95 59 93 60 / 5 5 5 10 GALLUP.......................... 88 54 87 53 / 10 10 10 10 GRANTS.......................... 89 55 88 54 / 10 10 10 10 GLENWOOD........................ 89 60 89 64 / 20 30 20 40 CHAMA........................... 82 44 83 47 / 20 10 10 20 LOS ALAMOS...................... 84 57 86 54 / 30 20 10 10 RED RIVER....................... 75 43 76 41 / 20 20 10 20 TAOS............................ 85 51 84 50 / 10 20 10 10 SANTA FE........................ 86 57 88 57 / 20 30 10 10 SANTA FE AIRPORT................ 89 58 90 57 / 20 30 10 10 ESPANOLA........................ 90 56 91 55 / 10 20 10 10 ALBUQUERQUE HEIGHTS............. 91 66 92 67 / 20 30 10 10 ALBUQUERQUE VALLEY.............. 93 63 93 64 / 20 30 10 10 ALBUQUERQUE FOOTHILLS........... 89 62 89 63 / 20 30 10 10 ALBUQUERQUE WEST MESA........... 93 64 93 65 / 10 30 10 10 SOCORRO......................... 92 60 91 63 / 10 30 20 20 SANDIA PARK/CEDAR CREST......... 85 59 85 53 / 20 30 10 10 MORIARTY/ESTANCIA............... 85 57 87 57 / 30 30 20 10 CARRIZOZO....................... 90 62 90 62 / 30 40 30 20 RUIDOSO......................... 84 57 82 55 / 30 50 30 30 RATON........................... 86 52 86 52 / 30 40 20 20 LAS VEGAS....................... 81 52 83 55 / 30 40 20 10 ROY............................. 86 57 86 61 / 30 40 20 20 CLAYTON......................... 86 60 90 64 / 30 30 20 20 SANTA ROSA...................... 89 61 95 61 / 30 30 20 10 TUCUMCARI....................... 91 65 95 66 / 20 30 20 10 FORT SUMNER..................... 91 65 92 65 / 20 30 10 10 CLOVIS.......................... 93 65 94 64 / 20 30 10 10 PORTALES........................ 93 65 96 65 / 20 30 10 10 ROSWELL......................... 94 67 97 69 / 20 30 20 20 && .ABQ WATCHES/WARNINGS/ADVISORIES... NONE. && $$ nm AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 733 PM EDT WED AUG 13 2008 .SYNOPSIS... A PERSISTENT UPPER LEVEL LOW OVER ONTARIO WILL BRING A CHANCE OF SHOWERS NOW AND THEN THROUGH FRIDAY...THEN HIGH PRESSURE WILL BRING FAIR WEATHER THROUGH THE WEEKEND. && .NEAR TERM /THROUGH THURSDAY/... SCATTERED SHOWERS/THUNDERSTORMS CONTINUE ALONG THE AXIS OF THE UPPER TROUGH ACROSS THE NIAGARA FRONTIER AND FINGER LAKES. THIS ACTIVITY WILL CONTINUE TO DRIFT SOUTH INTO THE EVENING HOURS AND LESSEN WITH THE LOSS OF DIURNAL HEATING. CLEARING SKIES OVERNIGHT WILL AGAIN ALLOW FOR THE FORMATION OF FOG ACROSS THE SOUTHERN TIER VALLEYS. WHILE MUCH OF THE AREA WILL BE RAIN FREE FOR MOST OF THE DAY THURSDAY...THE COOL CYCLONIC FLOW WILL AGAIN ALLOW FOR SHOWERS/THUNDERSTORMS TO REDEVELOP WITH DAYTIME HEATING. THIS ACTIVITY WILL MAINLY BE CONFINED TO THE AFTERNOON HOURS AND INLAND FROM THE LAKES. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... THE NEXT AREA OF CONCERN IS CURRENTLY OVER THE SOUTHEAST END OF JAMES BAY...ROUGHLY DENOTED BY THE RUC ANALYSIS OF THE -20C TEMPERATURE CONTOUR AT 500MB. LOOPING THE WATER VAPOR IMAGERY ALSO SHOWS BROAD CYCLONIC ROTATION WITH THIS FEATURE. EXPECT THIS TO WORK ITS WAY SOUTHWARD ON THURSDAY AND BY OVER LAKE HURON AND MI THURSDAY AFTERNOON. EXPECT ANY SHOWER ACTIVITY THURSDAY AFTERNOON AND EVENING TO DIE OFF FOR A WHILE...BUT THEN SOME NOCTURNAL REDEVELOPMENT IS POSSIBLE AS THE ABOVE MENTIONED FEATURE APPROACHES WESTERN NY. THIS SHOWER POTENTIAL WILL PUSH EASTWARD INTO CENTRAL NY DURING FRIDAY MORNING WITH MINIMAL SHOWER POTENTIAL FOR PART OF THE DAY OVER WESTERN NY WHILE THE THREAT FOR PRECIPITATION INCREASES OVER THE EASTERN LAKE ONTARIO REGION AS THE UPPER LEVEL SHORT WAVE TOWARD THIS REGION BY THE AFTERNOON. FOR WESTERN NY...EARLIER MODELS HAD THE AIRMASS WARMING DURING THIS TIME PERIOD...BUT THE LATEST RUNS KEEP THE AIRMASS COOL WITH THE UPPER LEVEL LOW JUST NORTH OF LAKE ONTARIO BY THE END OF THE DAY. SO...WITH THE COLD AIRMASS STILL IN PLACE...SHOWER ACTIVITY MAY AGAIN REDEVELOP DURING THE AFTERNOON WITH LITTLE OR NO CAP. THE WARMING COMES LATER FRIDAY NIGHT AND INTO SATURDAY AS THE UPPER LEVEL LOW WEAKENS OPENS UP AS IT HEADS EAST. WITH HIGH PRESSURE BUILDING INTO THE AREA...WILL CONTINUE TO ADVERTISE A QUIET WEATHER DAY FOR THE FIRST PART OF THE WEEKEND. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... THE GEFS HAS COME IN LINE WITH THE OPERATIONAL RUNS FOR SUNDAY...WITH HIGH CONFIDENCE FOR A DRY DAY. THE UNCERTAINTY IS MORE TOWARD THE BEGINNING OF NEXT WEEK WITH THE HIGHEST THREAT FOR SHOWER ACTIVITY ON TUESDAY AS ANOTHER UPPER LEVEL SYSTEM TRIES TO WORK ITS WAY ACROSS ONTARIO TOWARD QUEBEC. THE FLOW UPSTREAM BY THIS TIME SHOULD BE FAIRLY BLOCKED WITH A SLOW EASTWARD PROGRESSION. THIS MAY FINALLY BE A SIGNAL FOR CHANGE IN THE WEATHER PATTERN ONCE WE GET RID OF THE LAST UPPER LEVEL LOW FOR THE FIRST PART OF NEXT WEEK. THIS WOULD MEAN THE POSSIBILITY TOWARD DRY WEATHER WITHOUT A PERSISTENT AN UPPER LEVEL LOW DEVELOPING OVERHEAD LATER NEXT WEEK. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... VFR CONDITIONS WILL PREVAIL THIS EVENING AND INTO THE OVERNIGHT HOURS. 23Z SURFACE ANALYSIS SHOWED SEVERAL LOW LEVEL BOUNDARIES IN PLACE ACROSS THE AREA WHICH RESULTED FROM LAKE BREEZE BOUNDARIES AND CONVECTIVE OUTFLOW EARLIER IN THE DAY. KBUF AND KTYX RADARS SHOWING CONVECTIVE ACTIVITY DIMINISHING. THIS DIMINISHING TREND WILL CONTINUE THIS EVENING AS DAYTIME INSTABILITY LESSENS WITH LACK OF HEATING. AT THIS POINT...SEE LITTLE REASON TO INCLUDE THE MENTION OF ANY THUNDER IN THE TAF SITES. SURFACE DEWPOINTS IN THE UPPER 50S TO LOWER 60S SUGGEST THE POTENTIAL FOR FOG DEVELOPMENT TOWARD MORNING...ESPECIALLY IN THE SOUTHERN TIER VALLEYS. THEREFORE...PATCHY IFR/LIFR CONDITIONS ACROSS THE INTERIOR VALLEYS OF THE SOUTHERN TIER WILL BE POSSIBLE LATE TONIGHT AND EARLY THURSDAY. OUTLOOK... THURSDAY THROUGH SUNDAY...GENERALLY VFR. && .MARINE... WEAK HIGH PRESSURE WILL KEEP FAIR WEATHER AND GENERALLY LIGHT WINDS THROUGH THE WEEKEND WITH NO MARINE FLAGS EXPECTED. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...ZAFF NEAR TERM...LEVAN SHORT TERM...ZAFF LONG TERM...ZAFF AVIATION...LEVAN/TMA MARINE...ZAFF ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BUFFALO NY 200 AM EDT WED AUG 13 2008 .SYNOPSIS... A WEAK SYSTEM WILL DROP SOUTH FROM CANADA AND SWEEP EASTWARD ACROSS WESTERN AND CENTRAL NEW YORK ON WEDNESDAY. THEN HIGH PRESSURE WILL BRING FAIR WEATHER THROUGH SATURDAY. && .NEAR TERM /THROUGH TODAY/... REGIONAL RADARS SHOWING ONLY ISOLATED SHOWERS REMAINING ACROSS THE SOUTHERN TIER. THESE SHOWERS WILL CONTINUE TO DIMINISH THROUGH MIDNIGHT. RADIATIONAL FOG WILL THEN AGAIN DEVELOP OVERNIGHT... ESPECIALLY IN THE SOUTHERN TIER VALLEYS. ON WEDNESDAY AN UPPER TROUGH SINKS SOUTH ACROSS THE REGION SO ANOTHER ROUND OF SCATTERED AFTERNOON CONVECTION IS ON TAP WITH THE HIGHEST PROBS ACROSS THE NORTHERN SECTIONS OF THE CWA EAST OF LAKE ONTARIO. && .SHORT TERM /TONIGHT THROUGH FRIDAY/... THE NEXT FEATURE OF INTEREST CAN CURRENTLY BE SEEN ON WATER VAPOR IMAGERY OVER JAMES BAY WITH THE LATEST RUC ANALYSIS SHOWING AN 80KT JET OVER THIS REGION. THIS FEATURE WILL BE OVER SOUTHERN ONTARIO OR LAKE ONTARIO BY WEDNESDAY EVENING AND WILL EVOLVE INTO THE NEXT UPPER LEVEL CLOSED LOW FOR THE REGION. HOWEVER...THE STRENGTH OF THIS SYSTEM WILL BE GENERALLY UNIMPRESSIVE WHEN COMPARED TO OTHER RECENT UPPER LEVEL LOWS. WILL KEEP A CHANCE OF PRECIPITATION IN FROM WAYNE COUNTY EAST FOR THIS...AND THEN TRANSITION TO PATCHY FOG LATER IN THE NIGHT. THURSDAY SHOULD BE DRY OVER MOST OF WESTERN AND CENTRAL NY WITH A RELATIVELY STRONG CAP NEAR 700MB AND A DRIER ATMOSPHERE IN PLACE. THE UPPER LEVEL LOW WILL BE HANGING OUT NORTH OF THE ST LAWRENCE VALLEY DURING THIS TIME. IN FACT...THE ATMOSPHERE OVER MUCH OF THE EASTERN US WILL BE UNDER A LONG WAVE TROUGH WITH THE ATMOSPHERE COOLER THAN NORMAL. IF THE CAP IS BROKEN...AIR PARCELS WILL BE ABLE TO RISE INTO A RELATIVELY COOL ATMOSPHERE ALOFT. WILL KEEP A CHANCE OF SHOWERS IN FOR PORTIONS OF THE SOUTHERN TIER AND CLOSER TO THE CORE OF THE UPPER LEVEL LOW EAST OF LAKE ONTARIO WHERE THE CAP MAY BE BROKEN. A CORE OF COLD AIR WILL SWEEP ACROSS WESTERN NY OVERNIGHT ON THURSDAY. HOWEVER...THE TIMING OF THIS TROUGH PASSAGE IS NOT IDEAL WITHOUT ANY DIURNAL HEATING...AND WILL LITTLE AVAILABLE MOISTURE TO GET SHOWER ACTIVITY GOING. WILL THEREFORE KEEP THE FORECAST DRY DURING THIS TIME AND ONLY NOTE THE POSSIBILITY OF PATCHY FOG OVERNIGHT. ANOTHER PRIMARILY DRY DAY IS EXPECTED ON FRIDAY. THE MAIN CORE OF THE UPPER LEVEL LOW WILL BE PASSING INTO THE ADIRONDACKS WITH WARMING ALOFT AND HENCE A MORE STABLE AIRMASS EXPECTED FOR WESTERN NY. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... HIGH PRESSURE SHOULD DOMINATE ON SATURDAY WITH ANOTHER DRY DAY EXPECTED. THEN...THERE IS SOME UNCERTAINTY FOR THE REMAINDER OF THE FORECAST PERIOD. THE GFS AND THE ECMWF KEEP HIGH PRESSURE IN PLACE...BUT THE GEFS SHOWS A BIMODAL DISTRIBUTION WHEN LOOKING AT THE INDIVIDUAL MEMBERS OF THE PRECIPITABLE WATER...WITH ONE GROUP SHOWING A DRY AND STABLE AIRMASS...WHILE ANOTHER GROUP SHOWS A MUCH MORE MOIST ATMOSPHERE. AM NOT CONFIDENT WITH THE DRY SOLUTION WITH SUCH VARIABILITY IN THE MODEL OUTPUT. SO WILL INTRODUCE A CHANCE OF PRECIPITATION FOR THE REMAINDER OF THE FORECAST PERIOD...BEGINNING ON SUNDAY. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... FOR THE REMAINDER OF THE NIGHTTIME HOURS...MAINLY CLEAR SKIES AND GENERAL VFR CONDITIONS ARE EXPECTED...THOUGH SOME MID-LEVEL CLOUDS ASSOCIATED WITH THE NEXT SHORTWAVE WILL BEGIN TO SPREAD ACROSS POINTS FROM KROC EASTWARD AFTER 09Z. SOME PATCHY MVFR/IFR FOG WILL ALSO BE POSSIBLE VCNTY KIAG...AND ACROSS THE INTERIOR VALLEYS OF THE SOUTHERN TIER. THEREAFTER...THE AFOREMENTIONED SHORTWAVE TROUGH IS THEN EXPECTED TO BRING AN GENERAL INCREASE IN CLOUDS TO THE AREA TODAY...ALONG WITH THE RISK OF SOME CONVECTION THAT COULD PRODUCE SOME LOCALIZED REDUCTIONS TO MVFR CONDITIONS. THE RISK OF ANY SHRA/TSRA WILL BE HIGHEST FROM LATE THIS MORNING THROUGH EARLY THIS EVENING...THEN WILL DIMINISH AFTER SUNSET WITH THE LOSS OF DIURNAL HEATING. OUTSIDE OF ANY CONVECTION...GENERAL VFR CONDITIONS ARE EXPECTED THROUGH THE REMAINDER OF THE FORECAST PERIOD. OUTLOOK... THURSDAY THROUGH SUNDAY...GENERALLY VFR. && .MARINE... WEAK HIGH PRESSURE WILL KEEP FAIR WEATHER AND GENERALLY LIGHT WINDS THROUGH THE WEEKEND WITH NO MARINE FLAGS EXPECTED. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...NONE. MARINE...NONE. && $$ SYNOPSIS...ZAFF NEAR TERM...LEVAN/TMA SHORT TERM...ZAFF LONG TERM...ZAFF AVIATION...JJR MARINE...ZAFF ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BINGHAMTON NY 218 PM EDT TUE AUG 12 2008 .SYNOPSIS... A NORTHWEST FLOW OF COOL AIR WILL KEEP A FEW SHOWERS IN CENTRAL NEW YORK TODAY. WIDESPREAD RAIN SHOWERS ARE NOT EXPECTED...ESPECIALLY IN PENNSYLVANIA. ON WEDNESDAY AND THURSDAY...ANOTHER UPPER LEVEL LOW PRESSURE SYSTEM WILL APPROACH THE REGION FROM SOUTHERN ONTARIO...BRINGING AN INCREASED CHANCE OF SHOWERS AND THUNDERSTORMS. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A FEW SHOWERS POPPING ALONG THE SE SHORE OF LAKE ONTARIO ATTM. UPDATED THE GRIDS FOR INCREASED POPS/QPF/CLOUDS IN THIS AREA. BUFKIT AND 12Z SOUNDINGS SHOWING AMPLE LL MOISTURE. SOME LAKE ENHANCEMENT BUT TEMP DIFFERENCES NOT ENOUGH FOR TRUE LAKE EFFECT. WITH MORE CLOUDS AND A FEW SHOWERS HAVE LOWERED MAX TEMPS A TAD. SLOW IMPROVEMENT THIS AFTN AS LL MOISTURE MIXES OUT AND DRIER AIR MOVES IN. TONIGHTS GRIDS LOOK GOOD WITH CLEARING SKIES AND LIGHT WINDS. PATCHY FOG OVERNIGHT. PREVIOUS DISCUSSION...THROUGH EARLY MORNING...EXPECT A FEW SHRA TO CONTINUE ON THE NORTHWEST PERIPHERY OF THE UPPER LOW AS TEMPS ALOFT SUGGEST POTENTIAL ENHANCEMENT OFF OF THE WARM WATERS OF LAKE ONTARIO. THIS ACTIVITY SHOULD CONTINUE TO WANE...HOWEVER...AS NVA DEVELOPS WITH UPPER LOW CONTINUING TO PULL EAST OF OUR AREA. FOR THE DAY TODAY...OUR WET WEATHER MAKER OF LATE...A CLOSED LOW CURRENTLY SITTING SOUTH OF NEW ENGLAND WILL MOVE NORTHEAST AS ANOTHER UPPER LOW CENTERED JUST EAST OF JAMES BAY ACTS AS A KICKER AS IT DROPS SOUTH. THIS WILL ALLOW FOR RISING HEIGHTS AND TEMPERATURES ALOFT WITH NORTHWESTERLY FLOW TAKING OVER ALOFT. THIS WILL CERTAINLY BRING A DRIER DAY THAN ON MONDAY. HOWEVER...THE NAM/GFS/RUC ALL BRING A WEAK SHORTWAVE SOUTHEAST IN THIS FLOW TODAY...CENTERING IT OVER OUR CWA AROUND 18Z. ALTHOUGH DRIER AIR WILL BE FILTERING IN FROM THE NORTH...THE GFS/NAM SUGGEST THE POSSIBILITY OF A FEW SHRA DEVELOPING AS THIS WAVE PASSES. THIS DOES NOT SEEM ALL THAT UNREALISTIC GIVEN THAT EVENING CANADIAN RADAR IMAGERY SHOWED SOME ISOLATED SHRA ACTIVITY SOUTH OF THE WAVE...EVEN WITH MUCH LOWER SFC DEWPOINTS THAN EXPECTED HERE TODAY. SO...HAVE PAINTED A SCHC OF SHRA OVER JUST ABOUT THE ENTIRE CWA...BUT THESE SHRA SHOULD NOT AMOUNT TO MUCH. IN ADDITION...GIVEN WARMING TEMPERATURES ALOFT...ESP AROUND THE H5 LEVEL...DO NOT SEE ANY THUNDER DEVELOPING. T850 WILL WARM TO ABOUT +11C TODAY...WHICH SHOULD BE GOOD FOR HIGHS IN THE MID 70S. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... SKIES CLEAR TONIGHT ALLOWING FOR A GOOD BIT OF COOLING. GIVEN A DRIER AIRMASS IN PLACE...SHOULD SEE LOWS DROP TO THE 50-55F RANGE...WITH VALLEY FOG LIKELY AFTER MIDNIGHT. INTERESTING WX DAY ON TAP FOR WEDNESDAY AS UPPER LOW OVER SOUTHERN ONTARIO/QUEBEC CONTINUES TO SLOWLY SETTLE SOUTH WHILE A SHORTWAVE OVER THE SOUTHEASTERN CONUS SPAWNS SFC LOW DEVELOPMENT ALONG THE CAROLINA COAST WITH THIS LOW CENTERED NEAR CAPE HATTERAS BY WEDNESDAY EVENING. WE WILL FIND OURSELVES IN BROADLY CYCLONIC FLOW WITH SOME WEAK PVA/QVEC CONVERGENCE SKIRTING MY NORTHERN ZONES ON THE SOUTHERN PERIPHERY OF THE UPPER LOW. THE FLOW ALOFT WILL BE BACKING THROUGH THE DAY WITH WARMER H5 AND H7 AIR MOVING OVERHEAD. BUFKIT PROFILES FROM BOTH THE GFS AND NAM SHOW A GOOD DEAL OF CAPPING AND SO WHILE SOME SHRA SEEM LIKE A GOOD BET GIVEN THE UPPER FORCING /ESP OVER NORTHERN AREAS/...TSRA ARE LOOKING LESS LIKELY...AND HAVE ONLY INCLUDED A SCHC OF TSRA IN THE GRIDS. T850 WARMS ANOTHER DEGREE...TO AROUND +12C...WHICH SHOULD BE GOOD FOR HIGHS IN THE MID TO UPPER 70S GIVEN A DECENT BIT OF SUNSHINE. SHRA ACTIVITY SHOULD WANE WEDNESDAY NIGHT AS WE LOSE DAYTIME HEATING AND THE COASTAL LOW STAYS WELL SOUTH AND EAST OF OUR AREA. HAVE KEPT VERY LOW CHC POPS AS THE NAM SUGGESTS AN INVERTED TROUGH FEATURE NORTHWEST OF THE NW ATLANTIC LOW...BUT FEEL THIS IS A LOWER PROBABILITY OUTCOME...AND WITH TEMPS ALOFT CONTINUING TO WARM WITH LITTLE UPPER FORCING FOR ASCENT...EXPECT MOST AREAS WILL REMAIN DRY. LOWS ARE EXPECTED TO FALL INTO THE MID AND UPPER 50S. FOR THURSDAY...THE UPPER LOW NORTH OF OUR REGION BEGINS TO GET STRETCHED ZONALLY WITH A SPOKE OF VORTICITY ROTATING INTO THE UPPER GREAT LAKES BY AFTERNOON. AS WITH THE DAY BEFORE...THERE WILL BE SOME WEAK FORCING FOR ASCENT DUE TO OUR PROXIMITY TO THE UPPER LOW. IN ADDITION...TEMPS ALOFT WILL BEGIN COOLING...SO EXPECT SHRA WITH A CHANCE FOR A TSRA GIVEN SOMEWHAT BETTER INSTABILITY. HOWEVER...CERTAINLY DO NOT EXPECT THE DAY TO BE A WASHOUT. T850 AROUND +13C SHOULD ALLOW MANY PLACES TO SEE HIGHS REACH 80F...LIKELY FOR THE FIRST TIME IN OVER A WEEK! THURSDAY NIGHT...THE STRUNG OUT STRIPE OF VORTICITY ASSOCIATED WITH THE DEPARTING UPPER LOW APPROACHES FROM THE WEST...AND MAY KEEP A FEW SHRA GOING THROUGH THE NIGHT...SO HAVE KEPT SCHC POPS. EXPECT LOWS TO FALL INTO THE MID 50S. && .LONG TERM /FRIDAY THROUGH TUESDAY/... THIS PERIOD SEES A TRANSITION FROM A MEAN NORTHEASTERN TROF TO A BUILDING RIDGE. GFS THIS MORNING SHOWED A WEAK MID ATLANTIC TROF SLIDING EAST ON FRIDAY, THAT MAY BRING CHC FOR SHRA/TSRA...MAINLY TO THE SOUTHEAST PORTIONS OF THE FA. SFC HIGH BUILDING EAST LOOKS LIKE IT WILL PROVIDE A DRY AND PLEASANT WEEKEND...WITH TEMPS BY SUNDAY NIGHT OHIO VALLEY RIDGE SLIDES EASTWARD, WITH NEAR AVERAGE TEMPERATURES. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... SCATTERED SHRA AND ISOLATED TSRA HAVE DEVELOPED WITH MOD SFC HEATING TODAY. THESE MAY BRIEFLY CAUSE MVFR CONDITIONS AT ANY TAF LOCATION NEXT FEW HOURS BEFORE DISSIPATING WITH LOSS OF DAYTIME HEATING. OTHERWISE...VFR THIS EVENING WITH PATCHING FOG DEVELOPING OVERNIGHT. MAY SEE IFR OR LOWER LATE TONIGHT AT KELM. SOME OTHER LOWER LEVEL MOISTURE WILL TRY TO WORK IN LATE TONIGHT TWD RME AND SYR AS ANOTHER TROF WRKS IT/S WAY EAST FROM THE WRN GREAT LAKES. NAM IS FASTER THAN GFS IN BRINING LOWER CLDS AND CHC FOR SHRA TO THE AREA WEDNESDAY MORNING. GENERALLY BROUGHT SOME MVFR CONDITIONS INTO RME, BUT HELD OFF ELSEWHERE. BEST CHC FOR ANY SHRA LOOKS TO BE AFTER 18Z WED. NORTHWEST WINDS THIS AFTN ARND 10 KTS, BECOME LGT THIS EVENING. OUTLOOK... WEDNESDAY AFTN THRU THURSDAY...SCATTERED SHRA DIMINISH WEDNESDAY NGT WITH VFR. RESTRICTIONS EXPECTED IN FOG...ESPECIALLY AT ELM. FRIDAY THRU SUNDAY...VFR WITH POSSIBLE IFR FOG IN THE MORNING. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...NONE. NY...NONE. && $$ SYNOPSIS...TAC NEAR TERM...JMA/TAC SHORT TERM...JMA LONG TERM...JML AVIATION...JML ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BINGHAMTON NY 614 AM EDT TUE AUG 12 2008 .SYNOPSIS... A WELCOME REPRIEVE TO THE RECENT WET WEATHER IS EXPECTED TODAY AS LOW PRESSURE LIFTS AWAY FROM THE REGION...WITH SOMEWHAT WARMER CONDITIONS ALONG WITH JUST ONLY A SLIGHT CHANCE OF A SHOWER. BY WEDNESDAY AND THURSDAY...AND UPPER LEVEL LOW PRESSURE SYSTEM WILL APPROACH THE REGION FROM SOUTHERN CANADA...BRINGING WITH IT AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS...ALONG WITH TEMPERATURES CLOSER TO SEASONAL NORMS. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THROUGH EARLY MORNING...EXPECT A FEW SHRA TO CONTINUE ON THE NORTHWEST PERIPHERY OF THE UPPER LOW AS TEMPS ALOFT SUGGEST POTENTIAL ENHANCEMENT OFF OF THE WARM WATERS OF LAKE ONTARIO. THIS ACTIVITY SHOULD CONTINUE TO WANE...HOWEVER...AS NVA DEVELOPS WITH UPPER LOW CONTINUING TO PULL EAST OF OUR AREA. FOR THE DAY TODAY...OUR WET WEATHER MAKER OF LATE...A CLOSED LOW CURRENTLY SITTING SOUTH OF NEW ENGLAND WILL MOVE NORTHEAST AS ANOTHER UPPER LOW CENTERED JUST EAST OF JAMES BAY ACTS AS A KICKER AS IT DROPS SOUTH. THIS WILL ALLOW FOR RISING HEIGHTS AND TEMPERATURES ALOFT WITH NORTHWESTERLY FLOW TAKING OVER ALOFT. THIS WILL CERTAINLY BRING A DRIER DAY THAN ON MONDAY. HOWEVER...THE NAM/GFS/RUC ALL BRING A WEAK SHORTWAVE SOUTHEAST IN THIS FLOW TODAY...CENTERING IT OVER OUR CWA AROUND 18Z. ALTHOUGH DRIER AIR WILL BE FILTERING IN FROM THE NORTH...THE GFS/NAM SUGGEST THE POSSIBILITY OF A FEW SHRA DEVELOPING AS THIS WAVE PASSES. THIS DOES NOT SEEM ALL THAT UNREALISTIC GIVEN THAT EVENING CANADIAN RADAR IMAGERY SHOWED SOME ISOLATED SHRA ACTIVITY SOUTH OF THE WAVE...EVEN WITH MUCH LOWER SFC DEWPOINTS THAN EXPECTED HERE TODAY. SO...HAVE PAINTED A SCHC OF SHRA OVER JUST ABOUT THE ENTIRE CWA...BUT THESE SHRA SHOULD NOT AMOUNT TO MUCH. IN ADDITION...GIVEN WARMING TEMPERATURES ALOFT...ESP AROUND THE H5 LEVEL...DO NOT SEE ANY THUNDER DEVELOPING. T850 WILL WARM TO ABOUT +11C TODAY...WHICH SHOULD BE GOOD FOR HIGHS IN THE MID 70S. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... SKIES CLEAR TONIGHT ALLOWING FOR A GOOD BIT OF COOLING. GIVEN A DRIER AIRMASS IN PLACE...SHOULD SEE LOWS DROP TO THE 50-55F RANGE...WITH VALLEY FOG LIKELY AFTER MIDNIGHT. INTERESTING WX DAY ON TAP FOR WEDNESDAY AS UPPER LOW OVER SOUTHERN ONTARIO/QUEBEC CONTINUES TO SLOWLY SETTLE SOUTH WHILE A SHORTWAVE OVER THE SOUTHEASTERN CONUS SPAWNS SFC LOW DEVELOPMENT ALONG THE CAROLINA COAST WITH THIS LOW CENTERED NEAR CAPE HATTERAS BY WEDNESDAY EVENING. WE WILL FIND OURSELVES IN BROADLY CYCLONIC FLOW WITH SOME WEAK PVA/QVEC CONVERGENCE SKIRTING MY NORTHERN ZONES ON THE SOUTHERN PERIPHERY OF THE UPPER LOW. THE FLOW ALOFT WILL BE BACKING THROUGH THE DAY WITH WARMER H5 AND H7 AIR MOVING OVERHEAD. BUFKIT PROFILES FROM BOTH THE GFS AND NAM SHOW A GOOD DEAL OF CAPPING AND SO WHILE SOME SHRA SEEM LIKE A GOOD BET GIVEN THE UPPER FORCING /ESP OVER NORTHERN AREAS/...TSRA ARE LOOKING LESS LIKELY...AND HAVE ONLY INCLUDED A SCHC OF TSRA IN THE GRIDS. T850 WARMS ANOTHER DEGREE...TO AROUND +12C...WHICH SHOULD BE GOOD FOR HIGHS IN THE MID TO UPPER 70S GIVEN A DECENT BIT OF SUNSHINE. SHRA ACTIVITY SHOULD WANE WEDNESDAY NIGHT AS WE LOSE DAYTIME HEATING AND THE COASTAL LOW STAYS WELL SOUTH AND EAST OF OUR AREA. HAVE KEPT VERY LOW CHC POPS AS THE NAM SUGGESTS AN INVERTED TROUGH FEATURE NORTHWEST OF THE NW ATLANTIC LOW...BUT FEEL THIS IS A LOWER PROBABILITY OUTCOME...AND WITH TEMPS ALOFT CONTINUING TO WARM WITH LITTLE UPPER FORCING FOR ASCENT...EXPECT MOST AREAS WILL REMAIN DRY. LOWS ARE EXPECTED TO FALL INTO THE MID AND UPPER 50S. FOR THURSDAY...THE UPPER LOW NORTH OF OUR REGION BEGINS TO GET STRETCHED ZONALLY WITH A SPOKE OF VORTICITY ROTATING INTO THE UPPER GREAT LAKES BY AFTERNOON. AS WITH THE DAY BEFORE...THERE WILL BE SOME WEAK FORCING FOR ASCENT DUE TO OUR PROXIMITY TO THE UPPER LOW. IN ADDITION...TEMPS ALOFT WILL BEGIN COOLING...SO EXPECT SHRA WITH A CHANCE FOR A TSRA GIVEN SOMEWHAT BETTER INSTABILITY. HOWEVER...CERTAINLY DO NOT EXPECT THE DAY TO BE A WASHOUT. T850 AROUND +13C SHOULD ALLOW MANY PLACES TO SEE HIGHS REACH 80F...LIKELY FOR THE FIRST TIME IN OVER A WEEK! THURSDAY NIGHT...THE STRUNG OUT STRIPE OF VORTICITY ASSOCIATED WITH THE DEPARTING UPPER LOW APPROACHES FROM THE WEST...AND MAY KEEP A FEW SHRA GOING THROUGH THE NIGHT...SO HAVE KEPT SCHC POPS. EXPECT LOWS TO FALL INTO THE MID 50S. && .LONG TERM /FRIDAY THROUGH MONDAY/... THIS PERIOD SEES A TRANSITION FROM A MEAN NORTHEASTERN TROF TO A BUILDING RIDGE. LATEST GFS SHOWS A WEAK MIDATLANTIC TROF SLIDING EAST AT THE BEGINNING OF THE WEEKEND, WITH A CHANCE FOR A FEW THUNDERSTORMS ACCOMPANYING IT INTO NY/PA. BY SUNDAY NIGHT OHIO VALLEY RIDGE SLIDES EASTWARD, WITH A WARMUP SOON TO FOLLOW. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... PATCHY MVFR FOG SHOULD LIFT BY 13Z, AND VFR CONDITIONS ARE ANTICIPATED FOR THIS AFTERNOON. IMPROVEMENT IS ALSO EXPECTED WITH RESPECT TO CLOUD COVER, AS WE WILL BE PARTLY SUNNY AFTER THE MORNING HOURS. WINDS WILL BE NORTHWESTERLY AROUND 10 KNOTS. SKIES WILL CLEAR OUT TONIGHT, LIKELY LEADING TO VALLEY FOG TOWARD SUNRISE. SOME OF THIS MAY RISE UP TO AFFECT BGM AND ITH. OUTLOOK... WEDNESDAY THRU THURSDAY...SCATTERED SHRA WITH MVFR CIGS AND VSBY. RESTRICTIONS EXPECTED IN FOG...ESPECIALLY AT ELM. FRIDAY THRU SATURDAY...VFR WITH POSSIBLE IFR FOG IN THE MORNING. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...NONE. NY...NONE. && $$ SYNOPSIS...JMA NEAR TERM...JMA SHORT TERM...JMA LONG TERM...DJP AVIATION...DJP ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC 1041 PM EDT WED AUG 13 2008 .SYNOPSIS... AN AREA OF LOW PRESSURE WILL MOVE NORTHEAST JUST OFFSHORE TONIGHT...THEN AWAY FROM THE AREA ON THURSDAY. A WEAK COLD FRONT WILL APPROACH FROM THE NORTHWEST ON FRIDAY AND MOVE ACROSS THE AREA FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL SETTLE OVER THE AREA SUNDAY THROUGH TUESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... ABUNDANT CLOUD COVER WITH RAIN PERSISTING MUCH OF THE DAY BROUGHT AN UNSEASONABLY COOL DAY ACROSS ERN NC WITH MAX TEMPS MORE THAN 10 DEGREES BELOW NORMAL. MOST AREAS SAW THEIR ACTUAL HIGH IN THE UPPER 70S BETWEEN 2 AND 8 AM...OUTSIDE OF THE 8AM-8PM HIGH TEMPS SHOWN IN THE RTP...WHILE LOWER 70S PERSISTED THROUGH MOST OF THE DAYLIGHT HOURS. THIS WASN`T THE COOLEST AUGUST 13TH HOWEVER AS 1967 SAW MAX TEMPS OF 68 AT GREENVILLE AND KINSTON AND 70 AT NEW BERN AND MOREHEAD CITY. THE SFC LOW IS PUSHING E OF DIAMOND SHOALS LATE THIS EVENING AND PRECIP IS BEGINNING TO DIMINISH ACROSS THE REGION. AT 10 PM THE HEAVIEST RAIN WAS ROUGHLY FROM OCRACOKE TO ROPER IN CENTRAL WASHINGTON COUNTY AND EXPECT PRECIP TO PUSH E OF THE NRN OBX BY MIDNIGHT WITH A CLEARING TREND CONTINUING OVERNIGHT. WITH ALL THE RAIN TODAY...THE GROUND IS VERY MOIST AND OBSERVATIONS AROUND THE REGION ARE NEARLY SATURATED. LITTLE SFC DRYING OVERNIGHT SHOULD ALLOW FOR FOG DEVELOPMENT AFTER MIDNIGHT...ESPECIALLY W OF HIGHWAY 17 WHERE CLEARING WILL BE THE GREATEST. UPDATED FORECAST TO FOLLOW DECREASING POP WITH PCPN PUSHING E OF THE REGION AND TO ADD AREAS OF FOG ACROSS WRN SECTIONS. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... CYCLONIC MID/UPPER FLOW FROM BROAD UPPER TROUGH WILL REMAIN OVER THE EASTERN US THROUGH THE SHORT TERM. S/W ENERGY WILL DIVE SE FROM THE GREAT LAKES ON FRI THEN OFF THE MID ATLANTIC EARLY SAT WITH A TRAILING COLD FRONT MOVING ACROSS THE AREA LATE FRI NIGHT/EARLY SAT. DRY CONDITIONS EXPECTED THU/THU NIGHT THEN WILL INTRODUCE SLIGHT CHANCE POPS FRI/FRI NIGHT WITH THE APPROACHING FRONT. NEAR SEASONAL TEMPS THROUGH THE PERIOD. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... FRONT WILL MOVE OFFSHORE EARLY SAT WITH BERMUDA RIDGE STRENGTHENING THROUGH THE BEGINNING OF NEXT WEEK. PATTERN WILL BE CONDUCIVE FOR MAINLY DIURNALLY DRIVEN CONVECTION THROUGH THE PERIOD WITH DAYTIME HIGHS MAINLY IN THE UPPER 80S TO LOWER 90S INLAND AND MID/UPPER 80S BEACHES AND OUTER BANKS. ONE KINK IN THE FORECAST WILL BE A TROPICAL SYSTEM THAT IS PROGGED TO MOVE ACROSS THE BAHAMAS INTO FLORIDA DURING THE MON/TUE TIME FRAME. WILL NEED TO WATCH THIS CLOSELY OVER THE NEXT FEW DAYS AS THIS SYSTEM MAY INFLUENCE OUR WEATHER IN SOME FASHION SOMETIME NEXT WEEK. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... CLEARING SKIES AND LIGHT WINDS AFTER ALL-DAY RAIN A GOOD SET-UP FOR IFR CONDITIONS OVER INLAND SITES OVERNIGHT. KEWN CLOSER TO COAST AND EXPECTED TO HAVE ENOUGH WIND TO KEEP VSBYS AT MVFR. CONDITIONS IMPROVING TO VFR QUICKLY THU MORNING WITH HEATING AND VFR EXPECTED REST OF DAY. MAINLY VFR CONDITIONS EXPECTED FOR FRIDAY THROUGH MONDAY. && .MARINE... SFC LOW BEGINNING TO CONSOLIDATE E OF HAT AND WILL BE MOVING NE OVERNIGHT. MODELS HAVE BEEN OVERDONE WITH WINDS AND ONLY SEEING SOME GUSTS TO NEAR 25 KTS...BUT SOME STRENGTHENING EXPECTED OVERNIGHT ALONG WITH CAA SURGE. RUC13 LOOKS TO HAVE BEST HANDLE AND ADJUSTED WINDS OVERNIGHT BASED ON 21Z AND 00Z RUNS. SEAS HAVE BUILD TO 5-7 FT OVER MOST OF COASTAL WATERS AND WV HGT FCST GENERALL ON TRACK EXCEPT INCREASED IT FOR CURRENT 5-6 FT OBSERVED AT 41035 AND 41036. BASED ON ABOVE...DROPPED SCA FOR ALB SOUND BUT KEPT REST OF AREA WITH SOME ADJUSTMENTS ON TIMING. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR AMZ135-156- 158. SMALL CRAFT ADVISORY UNTIL 2 PM EDT THURSDAY FOR AMZ152-154. SMALL CRAFT ADVISORY UNTIL 11 AM EDT THURSDAY FOR AMZ150. && $$ SYNOPSIS...JW NEAR TERM...SK SHORT TERM...JW LONG TERM...JW AVIATION...JBM MARINE...JBM nc AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAND FORKS ND 1056 AM CDT WED AUG 13 2008 .DISCUSSION...APPEARS CLOUD COVER IN THE BDE AREA IS NOT GOING TO MAKE MUCH MOVEMENT UNTIL LATE AFTERNOON WITH THE 700MB TROUGH REMAINING STATIONARY. ALREADY UPDATED FOR ISOLD PRECIP...NOW WILL LOWER MAX TEMP AND INCREASE SKY COVER FOR THE EXTREME NE FA. AFTER COORD WITH BIS AND ABR...FEEL ISOLD THUNDER THREAT WILL BE MORE TOWARD LATER AFTERNOON WHEN NEXT WAVE ARRIVES...AND WILL UPDATE TO ACCOUNT FOR THIS THINKING. THINK MOST AREAS WILL BE DRY TODAY...WITH BEST CHANCES ACROSS THE DVL BASIN CLOSEST TO SFC TROUGH AND UPPER WAVE. && .AVIATION...THERE WILL BE A THREAT FOR AFTERNOON THUNDERSTORMS...BUT COVERAGE SHOULD BE LIMITED...SO WE WON/T MENTION IN THE CURRENT TAF SET. OTHERWISE EXPECT VFR CONDITIONS. && .PREV DISCUSSION... /ISSUED 911 AM CDT WED AUG 13 2008/ DISCUSSION...RADAR IMAGERY SHOWING ISOLD SHOWERS ACROSS THE SE AND NE FA. ACROSS THE SE FA...WEAK WAVE (AS SEEN IN WATER VAPOR IMAGERY) COMBINED WITH WEAK INSTABILITY (AS SEEN WITH RUC 850MB CAPE) CREATING SHOWER ACTIVITY. THIS ACTIVITY WILL CONTINUE TO MOVE E/SE THROUGH THE MORNING (AS INDICATED BY MODEL GUIDANCE). ACROSS THE NE FA...700MB TROUGH EXTENDS INTO THIS AREA FROM MAIN UPPER LOW TO THE NW IN CANADA. ASSOCIATED DEFORMATION CAUSING CLOUD COVER AND WEAK SHOWERS. WILL UPDATE FORECAST TO ACCOUNT FOR THE ABOVE. PREV DISCUSSION... /ISSUED 335 AM CDT WED AUG 13 2008/ DISCUSSION... MODELS ARE IN OVERALL GOOD AGREEMENT...WITH THE NAM HAVING A BETTER HANDLE ON QPF FIELDS AND NATIONAL SUPPORT FOR THE TRACK OF THE UPPER LOW. NO MODEL IS RESOLVING SFC DEWPOINTS WELL THOUGH...AND ANTICIPATED INCREASE TODAY/THU FROM EVAPOTRANSPIRATION (ET)...SO WILL NEED TO MODIFY SOUNDINGS AND RESULTANT INSTABILITY FIELDS OVER THE NEXT FEW DAYS. FOR TODAY...OUR LOCAL CANADIAN ET MODEL INDICATES THAT DEWPOINTS WILL RECOVER INTO THE LOW 60S IN THE VALLEY. THIS COUPLED WITH INCREASING LIFT FROM APPROACHING TROUGH AND SFC CAPES TO AROUND 1000 J/KG SHOULD MEAN THE THREAT FOR ISOLATED AFTERNOON THUNDER IN ALL AREAS...SO WILL MENTION. SHEAR FIELDS ARE RATHER WEAK THOUGH...UNDER 30KT SO NOT EXPECTING ANY SEVERE STORMS. TONIGHT-THU...UPPER LOW WILL MOVE TO THE WEST OF THE REGION. THIS WILL PROVIDE UPPER LEVEL DIVERGENCE AND INCREASING MOISTURE WITH POOLING ALONG THE SFC TROUGH. THE BEST FOCUS FOR SUSTAINED CONVECTION THU AFTERNOON WILL BE ALONG AND WEST OF THE VALLEY...AND HAVE HIT POPS HARDEST HERE. WITH A SLOW STORM MOTION AND PWATS APPROACHING 1.3...SOME LOCALIZED HEAVY RAIN IS ALSO POSSIBLE. SHEAR AGAIN WILL BE VERY WEAK...WITH PERHAPS A FEW PULSE TYPE SEVERE EVENTS AT MOST. TEMPS WILL BE A BIT COOLER THU THAN TODAY WITH LOWER CONVECTIVE TEMPS AND COOLER TEMPS ALOFT. CONVECTION SHOULD DIMINISH LATER THU NIGHT AS LOW PULLS SW OF THE REGION. FOR FRI...THE COLUMN WILL DRY WITH UPPER RIDGING BUILDING IN. THEREFORE EXPECT A DRY DAY WITH TEMPS WARMING TO NEAR NORMAL. ON SAT-TUE...A WARMING TREND SHOULD DEVELOP WITH 925-850MB TEMPS WARMING WELL ABOVE NORMAL. A FAVORABLE WESTERLY SFC FLOW IS ALSO EXPECTED WITH PLENTY OF SUN...SO HAVE INCREASED TEMPS SOME WITH A DRY PERIOD EXPECTED AND TEMPS LIKELY WARMING ABOVE NORMAL. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ TG nd AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAND FORKS ND 911 AM CDT WED AUG 13 2008 .DISCUSSION...ALLOWED DENSE FOG ADVISORY TO EXPIRE AT 9AM. PATCHY DENSE FOG DOES REMAIN ACROSS THE NORTHERN VALLEY...BUT OBSERVATION SITES WITH DENSE FOG ARE BECOMING MORE ISOLATED. WITH THE THREAT FOR WIDESPREAD DENSE FOG NO LONGER AN ISSUE THE ADVISORY DID NOT NEED TO BE EXTENDED. ALSO...SOLAR SHOULD QUICKLY DISSIPATE THE REMAINING FOG. RADAR IMAGERY SHOWING ISOLD SHOWERS ACROSS THE SE AND NE FA. ACROSS THE SE FA...WEAK WAVE (AS SEEN IN WATER VAPOR IMAGERY) COMBINED WITH WEAK INSTABILITY (AS SEEN WITH RUC 850MB CAPE) CREATING SHOWER ACTIVITY. THIS ACTIVITY WILL CONTINUE TO MOVE E/SE THROUGH THE MORNING (AS INDICATED BY MODEL GUIDANCE). ACROSS THE NE FA...700MB TROUGH EXTENDS INTO THIS AREA FROM MAIN UPPER LOW TO THE NW IN CANADA. ASSOCIATED DEFORMATION CAUSING CLOUD COVER AND WEAK SHOWERS. WILL UPDATE FORECAST TO ACCOUNT FOR THE ABOVE. REMAINDER OF FORECAST IN GOOD SHAPE FOR TODAY...AND UNLESS ADDITIONAL CHANGES ARE NEEDED THIS WILL BE THE ONLY MORNING UPDATE. && .AVIATION...THERE WILL BE A THREAT FOR AFTERNOON THUNDERSTORMS...BUT COVERAGE SHOULD BE LIMITED...SO WE WON/T MENTION IN THE CURRENT TAF SET. && .PREV DISCUSSION... /ISSUED 335 AM CDT WED AUG 13 2008/ DISCUSSION... MODELS ARE IN OVERALL GOOD AGREEMENT...WITH THE NAM HAVING A BETTER HANDLE ON QPF FIELDS AND NATIONAL SUPPORT FOR THE TRACK OF THE UPPER LOW. NO MODEL IS RESOLVING SFC DEWPOINTS WELL THOUGH...AND ANTICIPATED INCREASE TODAY/THU FROM EVAPOTRANSPIRATION (ET)...SO WILL NEED TO MODIFY SOUNDINGS AND RESULTANT INSTABILITY FIELDS OVER THE NEXT FEW DAYS. FOR TODAY...OUR LOCAL CANADIAN ET MODEL INDICATES THAT DEWPOINTS WILL RECOVER INTO THE LOW 60S IN THE VALLEY. THIS COUPLED WITH INCREASING LIFT FROM APPROACHING TROUGH AND SFC CAPES TO AROUND 1000 J/KG SHOULD MEAN THE THREAT FOR ISOLATED AFTERNOON THUNDER IN ALL AREAS...SO WILL MENTION. SHEAR FIELDS ARE RATHER WEAK THOUGH...UNDER 30KT SO NOT EXPECTING ANY SEVERE STORMS. TONIGHT-THU...UPPER LOW WILL MOVE TO THE WEST OF THE REGION. THIS WILL PROVIDE UPPER LEVEL DIVERGENCE AND INCREASING MOISTURE WITH POOLING ALONG THE SFC TROUGH. THE BEST FOCUS FOR SUSTAINED CONVECTION THU AFTERNOON WILL BE ALONG AND WEST OF THE VALLEY...AND HAVE HIT POPS HARDEST HERE. WITH A SLOW STORM MOTION AND PWATS APPROACHING 1.3...SOME LOCALIZED HEAVY RAIN IS ALSO POSSIBLE. SHEAR AGAIN WILL BE VERY WEAK...WITH PERHAPS A FEW PULSE TYPE SEVERE EVENTS AT MOST. TEMPS WILL BE A BIT COOLER THU THAN TODAY WITH LOWER CONVECTIVE TEMPS AND COOLER TEMPS ALOFT. CONVECTION SHOULD DIMINISH LATER THU NIGHT AS LOW PULLS SW OF THE REGION. FOR FRI...THE COLUMN WILL DRY WITH UPPER RIDGING BUILDING IN. THEREFORE EXPECT A DRY DAY WITH TEMPS WARMING TO NEAR NORMAL. ON SAT-TUE...A WARMING TREND SHOULD DEVELOP WITH 925-850MB TEMPS WARMING WELL ABOVE NORMAL. A FAVORABLE WESTERLY SFC FLOW IS ALSO EXPECTED WITH PLENTY OF SUN...SO HAVE INCREASED TEMPS SOME WITH A DRY PERIOD EXPECTED AND TEMPS LIKELY WARMING ABOVE NORMAL. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ TG/DK nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 808 PM EDT WED AUG 13 2008 .SYNOPSIS... A SERIES OF UPPER AIR DISTURBANCES WILL MOVE ACROSS THE AREA THROUGH FRIDAY....BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS. SURFACE HIGH PRESSURE WILL BUILD ACROSS THE REGION FRIDAY NIGHT AND SATURDAY. THIS HIGH WILL REMAIN ACROSS THE REGION ON SUNDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... HAVE USED A BLEND OF THE LATEST RUC MODEL AND THE 12Z OPERATIONAL NAM-WRF FOR THE NEAR TERM FCST. AN UPPER LEVEL VORT MAX CENTERED NEAR NE INDIANA THIS AFTN WILL DRIFT ESE ACRS NORTHERN OHIO THROUGH 06Z...THEN IT WILL MOVE EAST OF THE FORECAST AREA BY 12Z. WEAK INSTABILITY AND WEAK LOW LVL CONVERGENCE AHEAD OF THIS FEATURE WILL KEEP A SMALL THREAT FOR SHOWERS AND THUNDERSTORMS ACRS THE NRN THIRD OF THE FORECAST AREA THROUGH MIDNIGHT. THEREAFTER...PCPN SHOULD PRETTY MUCH DISSIPATE AS THE AIRMASS STABILIZES. SKY CONDITION OVERNIGHT WILL BE TOUGH TO PINPOINT ONCE AGAIN AS MOST OF THE REGION WILL LIKELY GO MOSTLY CLEAR AFTER SUNSET. MID AND HIGH LVL CLOUDS SHOULD INCREASE FROM THE NW AFTER MIDNIGHT AS ANOTHER S/WV APCHES THE REGION. LOWS WILL RANGE FROM THE MID 50S TO THE LOWER 60S. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... OPERATIONAL MODEL RUNS WERE SIMILAR IN THE SOLUTIONS FOR THE SHORT TERM FORECAST. THESE FORECASTS WILL MOSTLY ACCEPTED AND A BLEND OF THE MODELS WERE USED FOR THE SHORT TERM FCST. UPPER LEVEL CLOSED LOW CENTERED OVER SW QUEBEC THIS AFTN WILL PIVOT SLOWLY SWD THROUGH 12Z FRIDAY...THEN IT WILL MOVE SE TOWARD THE NEW ENGLAND REGION BY 12Z SATURDAY. EMBEDDED S/WVS ROTATING AROUND THIS LOW WILL KEEP A THREAT FOR SHOWERS AND THUNDERSTORMS GOING...ESPECIALLY THURSDAY AFTERNOON AND EARLY EVENING. ONE SUCH S/WV...OVER SRN WISCONSIN THIS AFTERNOON...WILL DIVE SE AND MOVE ACRS THE FCST AREA THURSDAY AFTN. WEAK LOW LVL FORCING IN THE FORM OF A WEAK BOUNDARY/SFC TROF WILL ACCOMPANY THIS FEATURE. THE COMBINATION OF THE UPR LVL S/WV AND WEAK LOW LVL FORCING IN THE PRESENCE OF WEAK INSTABILITY WILL RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS. WILL CONTINUE WITH 30 AND 40 POPS ACROSS THE REGION THURSDAY AFTN...AND WILL USE AREAL COVERAGE WORDING. WILL NOT GO ANY HIGHER THAN THIS DUE TO THE FACT THAT THE LOW LVL FORCING IS VERY WEAK. THE UPR LVL S/WV WILL MOVE EAST OF THE REGION THURSDAY EVENING. A TANDEM OF EMBEDDED DISTURBANCES WILL PIVOT ACRS THE REGION AGAIN LATE THURSDAY NIGHT INTO FRIDAY. WITH THE LACK OF LOW LVL FORCING AND WEAKER INSTABILITY...WILL ONLY CARRY SMALL CHANCE POPS THURSDAY NIGHT INTO THE FIRST PART OF FRIDAY. FOR FRIDAY NIGHT...SURFACE HIGH PRESSURE WILL BEGIN TO BUILD INTO THE REGION FROM THE NW...ALLOWING SKIES TO BECOME MOSTLY CLEAR. HAVE BASICALLY USED A BLEND OF THE MAV/MET VALUES FOR FORECAST HIGHS AND LOWS THROUGH THE PERIOD. HIGHS WILL RANGE FROM THE UPPER 70S TO LOWER 80S WITH LOWS MAINLY IN THE 50S. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... MODELS HAVE ARE IN DECENT AGREEMENT WITH SPREADING SPRAWLING SFC HI PRES ACRS THE NRN PLAINS AND INTO THE OH VLY FOR MUCH OF THE WEEKEND AS REGION BECOMES SANDWICHED BTWN SLOWLY DEPARTING UPR TROF OVER ERN CANADA...AND EVEN SLOWER EVOLVING UPR LO CUTOFF FROM MEAN FLOW AND SETTLING IN THE LEE OF THE CNTRL ROCKIES. MODEL SOUNDINGS INDCG FAIR AMOUNT OF SUBSIDENCE ASSOCD WITH SFC HI WHICH SHOULD TRANSLATE INTO MSTLY CLR SKIES SAT/SAT NIGHT. WITH LIGHT NE FLO...HAVE UNDERCUT MOS GUID AGAIN WITH HIGHS GENERALLY IN THE L80S. SOME DIFFERENCES THEN DVLP WRT MOVEMENT AND EFFECTS OF UPR LO OVER THE CNTRL PLAINS THRU REMAINDER OF EXTENDED. IT IS BECMG INCREASINGLY APPARENT THAT THIS FEATURE MAY IN FACT NEVER GET TO THE OH VLY...AND REMAIN IN THE CNTRL PLAINS BEFORE BECMG PICKED UP BY THE DEEPENING UPR TROF OVER THE WRN CONUS BY LATE NEXT WEEK. ECMWF CONTINUES TO INDCG REX BLOCK LIKE PATTERN DVLPG WITH UPR TROF HOLDING ACRS CANADIAN MARITIMES AND UPR LO STALLING IN THE CNTRL PLAINS. WRN ATLC UPR RIDGE GETS SQUEEZED NORTH INTO REGION BY MIDWEEK WITH TROPICAL SYSTEM MOVING INTO FLORIDA. THIS IS AN OVERALL DRIER AND LESS STORMY SOLN FOR OH VLY. OP GFS/GFS ENSEMBLE MEAN ON OTHER HAND ARE LESS DRAMATIC WITH ALL OF THESE FEATURES...NAMELY THE TROPICAL SYSTEM AND THE RIDGING DVLPG INTO OH VLY BY MIDWEEK. THIS CONSENSUS SOLN IS ALSO SUGGESTIVE OF MAINTAINING ENHANCED SRLY FLO FROM THE GULF BTWN THE UPR LO AND THE RIDGE...ALLOWING AN INCREASINGLY MOIST HUMID AIRMASS TO INVADE THE REGION DURING FIRST HALF OF THE WEEK. PREFER MORE UNSETTLED OP GFS/GFS ENSEMBLE SOLN FOR NEXT WEEK AND WILL CONTINUE TO INDCG MODEST CONVECTIVE CHANCES MON-WED. HAVE MADE SOME MINOR ADJUSTMENTS TO FOCUS BEST PCPN CHANCES ON TUES AS WARM FRONT LIFTS NORTH THRU REGION. TEMPS WILL REMAIN GENERALLY AT OR SLIGHTLY BELOW NORMAL THRU THE EXTENDED. MEX GUID CONTINUES TO BE TOO WARM WITH AFTN HIGHS. UNDERCUT GUID TEMPS THRU MUCH OF THE PERIOD...KEEPING HIGHS IN THE L80S THRU TUES...POSSIBLY REMAINING IN THE U70S MON/TUES IF MORE WIDESPREAD CONVECTION IS REALIZED. WILL ALLOW FOR WARMEST TEMPS WED AS WARM FRONT PROGGED TO BE NORTH OF REGION OVER GRT LKS. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... MIX OF CLOUDS IN AREA...WITH SOUTHERN TAF SITES ONLY SCT HIGH CLOUDS TONIGHT...AND BKN MID DECK TO DEVELOP OVERNIGHT AS UPR LEVEL DISTURBANCE SKIRTS TO THE NORTH. VFR CIGS EXPECTED THROUGH THE FCST PERIOD...THOUGH KILN/KLCK MAY APPROACH MVFR VSBYS IN THE 10-12Z TIMEFRAME AS SFC DEWPOINTS INCREASE OVERNIGHT. CONTINUED THE MENTION OF CD FROM PREVIOUS FORECAST...THOUGH PUSHED IT BACK A BIT AS SHOULD NOT BE EXPECTED UNTIL INCREASE MOISTURE COINCIDES WITH BETTER INSTABILITY IN THE 16-22Z TIMEFRAME. KDAY/KCMH/KLCK HAVE VCSH AS SCATTERED SHOWERS MOST LIKELY THESE LOCATIONS CLOSER TO THE BOUNDARY. SHRA SHOULD BE HIGH BASED...SO AM NOT EXPECTING A DROP TO MVFR CIGS NOR VSBYS IN SHRA OR ISOLD TSTMS. OUTLOOK...TSTMS POSSIBLE THURSDAY AFTERNOON AND EVENING. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HICKMAN NEAR TERM...HICKMAN SHORT TERM...HICKMAN LONG TERM...RYAN AVIATION...JDR oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 148 PM EDT WED AUG 13 2008 .SYNOPSIS... HIGH PRESSURE WILL PROVIDE MAINLY DRY WEATHER THIS AFTERNOON WITH A SHORT WAVE PASSING NORTH OF THE AREA THIS EVENING. A SERIES OF UPPER AIR DISTURBANCES WILL MOVE THROUGH THE REGION ON THURSDAY AND FRIDAY...BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS. TEMPERATURES WILL AVERAGE SLIGHTLY BELOW NORMAL THROUGH THE PERIOD. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE LATEST H5 RUC ANALYSIS INDICATES A CLOSED LOW OVER ERN CANADA WITH A TROF EXTENDING FROM THE LOW SWWD INTO THE GREAT LAKES. A BROAD RIDGE IS CENTERED OVER THE WRN CONUS WITH ANOTHER DEEPER CLOSED LOW OVER CNTRL CANADA. LOCALLY...A WEAK SHORT WAVE IS OVER SWRN MICHIGAN WITH THE CWA UNDER MORE OF A WESTERLY FLOW THAN THE NORTHWESTERLY FLOW WHICH HAS BEEN THE PREDOMINATE PATTERN THIS MONTH. AT THE SURFACE...HIGH PRESSURE IS TRANSLATING EWD INTO THE MID-ATLANTIC...WITH A WEAK PRESSURE GRADIENT ACROSS THE OHIO VALLEY. THE NRN FRINGES OF AN INVERTED TROF FROM A LOW CURRENTLY OVER GA EXTEND INTO NE KY. TO THE NW...SCT SHOWERS ALONG THE SHORT WAVE ARE MOVING SE OVER SRN PORTIONS OF LAKE MICHIGAN. THIS AFTERNOON...THE SHORT WAVE TO THE NW WILL MOVE INTO NRN OHIO...WITH SHOWERS AND THUNDERSTORMS ENDUCED BY AFTN HEATING ALONG WITH IT. A NWRLY FLOW ALOFT WILL RETURN THIS AFTN. LITTLE CHANGE IN POPS GRIDS AS RUC AND GFS DEVELOP SOME SHOWERS AND TSTMS INTO NWRN PORTIONS OF THE CWA LATE THIS AFTERNOON. WITH WEAK INSTABILITY AND RELATIVELY DRY SFC CONDITIONS...ONLY THE DEVELOPMENT OF ISOLD AND SHORT LIVED CONVECTION SEEMS PLAUSIBLE. HIGH TEMPS INCREASED 2 DEGREES ACROSS CWA...AS LATEST TRENDS AND CLEARING WEST OF THE CWA WILL BE SUPPORTIVE OF TEMPS WARMING ABOVE MAV GUIDANCE AND THE PREVIOUS FORECAST. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... DRY WEATHER IS ANTICIPATED FOR TONIGHT SINCE INSTABILITY WILL DISAPPEAR WITH LOSS OF DAYTIME HEATING. INSTABILITY AND FORCING IS SHOWN TO INCREASE ON THURSDAY BY THE GFS NAM AND ECMWF. THIS WARRANTS AN INCREASE TO HIGH CHANCE POPS FOR THUNDERSTORMS. LIGHT WIND FIELDS AND LACK OF MID LEVEL DRY AIR WILL PREVENT WIDESPREAD SEVERE WEATHER. A FEW THUNDERSTORMS MAY LINGER INTO FRIDAY THOUGH SYNOPTIC SCALE FORCING WILL DIMINISH. DO NOT FORESEE A GREAT DEAL OF CHANGE IN TEMPERATURES IN WEAK ADVECTION PATTERN. HIGHS WILL STAY IN THE LOWER 80S...WITH LOWS AROUND 60...WHICH WILL BE A BIT BELOW CLIMATOLOGICAL NORMALS. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... EXTENDED MODELS HAVE COME INTO REASONABLE AGREEMENT IN POSITIONING FRNTL BNDRY FURTHER SOUTH ACRS TN VLY OVER THE WEEKEND WITH SFC HI PRES KEEPING MAINLY DRY WX NORTH OF THE OHIO RIVER. 12Z GFS ENSEMBLE MEMBERS CONTINUE TO OFFER A PLETHORA OF SOLNS WRT FRNTL BNDRY LOCATION SAT/SUN...BUT 12Z OP GFS HAS SWUNG AROUND TO THE DRIER SOLN BEING SUGGESTED BY THE LAST FEW RUNS OF THE ECMWF AND THE CANADIAN. MODELS HAVE ALSO BETTER ALIGNED WRT UPR LO DIVING SOUTH THRU THE HIGH PLAINS THIS WEEKEND ON BACK SIDE OF MEAN ERN CONUS TROF. TREND THE LAST FEW DAYS HAS BEEN FOR A SLOWER EJECTION OF THE UPR LO ACRS THE CNTRL PLAINS AND MID MISSISSIPPI VLY. THE SLOWER EASTWARD PROGRESSION OF THE UPR LO IS ALLOWING FOR A WESTWARD EXPANSION OF THE WRN ATLC UPR RIDGE BACK INTO THE SE CONUS BY ERLY NEXT WEEK. SRLY FLO DVLPG BTWN THESE TWO FEATURES WILL FUNNEL MUCH DEEPER GULF MOISTURE INTO THE OH VLY BEGINNING SUN NIGHT AND CONTINUING THRU THE FIRST HALF OF NEXT WEEK. COMBINATION OF DEEP MOISTURE AND UPR LO MOVING INTO MID MISSISSIPPI VLY WILL ALLOW FOR GOOD CHANCE FOR CONVECTION MON/TUES FOR THE ENTIRE REGION. TEMPS WILL REMAIN GENERALLY AT OR SLIGHTLY BELOW NORMAL THRU THE EXTENDED. FELT MEX GUID WAS TOO WARM WITH AFTN HIGHS...PARTICULARLY FOR SUN-TUES TIME FRAME. UNDERCUT GUID TEMPS BY ROUGHLY FIVE DEG THRU THIS PERIOD...KEEPING HIGHS IN THE L80S. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... HIGH PRESSURE WILL MOVE OFF TO THE EAST AS AN UPPER LEVEL DISTURBANCE APPROACHES FROM THE NW AND PASSES NORTH OF THE TAF SITES THIS EVENING. BKN MID-LEVEL CU WILL DEVELOP OVERNIGHT WITH VFR CONDITIONS PREVAILING THROUGHOUT THE FCST PERIOD. TEMPO GROUPS AT ILN AND LCK DURING 10-12Z FOR BRIEF MVFR FOG WITH INCREASED DEW POINTS OVERNIGHT AND NEAR CALM WINDS EXPECTED. CB GROUPS ADDED AFTER 12Z EVERYWHERE EXCEPT CVG AND LUK WITH AN UNCERTAINTY IN THE DEVELOPMENT OF ISOLD CONVECTION. OUTLOOK...TSTMS POSSIBLE THURSDAY AFTERNOON AND EVENING. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...CONIGLIO/WOODRUM NEAR TERM...WOODRUM SHORT TERM...CONIGLIO LONG TERM...RYAN AVIATION...WOODRUM oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TULSA OK 513 AM CDT TUE AUG 12 2008 .UPDATE... SCATTERED LIGHT SHOWERS HAVE DEVELOPED OVER SOUTHEAST KANSAS AND WILL LIKELY REACH NORTHEAST OKLAHOMA EARLY THIS MORNING. RUC HINTS AT THIS...SO WILL GO AHEAD AND INCLUDE SOME LOW POPS AND ISSUE NEW SET OF ZONES. EXPECT PRECIPITATION TO BE LIGHT AND SHOULD NOT LAST THE MORNING. ALSO WILL UPDATE THE FLASH FLOOD WATCH TO DROP SOME OF THE WESTERN COUNTIES. /02 && .PREV DISCUSSION... /ISSUED 408 AM CDT TUE AUG 12 2008/ DISCUSSION... TIMING OF CURRENT RAIN THROUGH THE FORECAST AREA IS PROBLEMATIC THIS MORNING...BUT HAVE MADE THE EFFORT. EXPECT PRECIP TO MOVE THROUGH THE FSM AREA AROUND 7 AM AND HIGH PROBABILITY IT WILL LEAVE THE ALL OF THE FORECAST AREA RAIN FREE BEFORE NOON. UPPER TROUGH PUSHES WELL THROUGH THE AREA LATER TODAY...AND SHOULD LEAD TO DRIER WEATHER THE NEXT COUPLE OF DAYS. ISSUE IS A POSSIBLE MCS DEVELOPING WEDNESDAY NIGHT...SLIDING DOWN THROUGH KANSAS INTO NORTHERN OKLAHOMA LATE AND INTO EARLY THURSDAY MORNING. GFW HAS THE SYSTEM FARTHER WEST...BUT NAM AND ECMWF AGREE IT WILL AFFECT NORTHEAST OK. HAVE INCLUDED SOME SMALL POPS FOR THAT CONTINGENCY. MORE IMPORTANT SYSTEM COMES OVER THE WESTERN RIDGE AND DROPS SOUTH INTO THE PLAINS ON THURSDAY NIGHT AND FRIDAY. BOTH GFW AND ECMWS DEVELOP THIS INTO A CLOSED LOW OVER THE CENTRAL PLAINS OVER THE WEEKEND. THIS SHOULD MAKE THE WEATHER UNSETTLED...BUT LIKELY COOLER THAN NORMAL. HAVE ADJUSTED TEMPS AND POPS FOR THIS. WENT COOLER THAN MAV MOS THE NEXT COUPLE OF DAYS DUE THE AMOUNT OF RAIN THAT HAS FALLEN. EXPECT THE MOS WILL USE CLIMATOLOGY FOR SOIL TEMPS FOR ANOTHER COUPLE OF DAYS AND WILL NOT ACCOUNT FOR EVAPORATION. ALSO...MOS HAS HAD A COLD BIAS AT NIGHT...PROBABLY BECAUSE IT THINKS THE GROUND SHOULD BE DRY. THAT NOT THE CASE...PLUS TRANSPIRATION FROM PLANT AT NIGHT SEEMS TO HAVE BEEN RAISING THE DEW POINTS. SO...HAVE ADJUSTED HIGHS DOWN AND LOWS UP A LITTLE. ALSO...CLEAR SKIES AND LIGHT WINDS TUESDAY NIGHT SHOULD LEAD TO POSSIBILITY OF RADIATION FOG. HAVE ONLY MENTIONED IT FOR NOW. && .PRELIMINARY POINT TEMPS/POPS... TUL 86 66 92 70 / 20 10 0 20 FSM 85 64 91 69 / 30 10 0 10 MLC 85 65 92 67 / 20 10 0 10 BVO 86 61 91 63 / 20 0 0 20 FYV 81 60 87 60 / 20 10 0 10 BYV 82 62 86 64 / 30 10 0 10 MKO 84 65 90 66 / 20 10 0 10 MIO 86 64 91 66 / 20 10 10 20 F10 85 65 90 67 / 20 10 0 10 HHW 87 65 92 70 / 30 10 0 10 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...FLASH FLOOD WATCH UNTIL 7 AM TUESDAY FOR OKZ049-OKZ070-OKZ072- OKZ074-OKZ075-OKZ076. AR...FLASH FLOOD WATCH UNTIL 7 AM TUESDAY FOR ARZ019-ARZ020-ARZ029. && $$ SHORT TERM...17 LONG TERM....02 ok AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 300 PM MDT WED AUG 13 2008 .DISCUSSION...CURRENT SURFACE ANALYSIS SHOWS LOW PRESSURE OVER SOUTHEASTERN SASKATCHEWAN...WHILE HIGH PRESSURE REMAINS OVER THE SOUTHERN PLAINS. UPPER LEVEL ANALYSIS PLACES LOW OVER SOUTHEAST SASKATCHEWAN...WITH FLOW REMAINING NORTHWESTERLY OVER OUR AREA. A VARIETY OF SHORT WAVES NOTED ON WATER VAPOR...WITH THE MOST VIGOROUS ONE NOW SLIDING THROUGH EASTERN WYOMING INTO CENTRAL SOUTH DAKOTA. SOME SHOWERS AND THUNDERSTORMS HAVE POPPED UP AS THIS WAVE PROGRESSES THROUGH FROM NORTHEAST WYOMING INTO SOUTH CENTRAL CENTRAL SOUTH DAKOTA. PRIMARY FOCUS ON TODAYS PACKAGE WAS ON PROGRESSION OF AFOREMENTIONED LOW OVER THE NEXT FEW DAYS. WITH SOME PROBLEMS OBTAINING MODEL DATA THIS AFTERNOON DUE TO NEW AWIPS BUILD...HAVE NOT MADE TOO MANY LARGE CHANGES TO THE FORECAST. FOR THE REST OF THIS AFTERNOON INTO THIS EVENING...EXPECT CONVECTION TO CONTINUE AS AFOREMENTIONED WAVE CONTINUES ITS PROGRESS. THE GREATEST HAIL THREAT WILL BE OVER SOUTH CENTRAL SOUTH DAKOTA WHERE RUC PLACES THE GREATEST INSTABILITY. INTO NORTHEAST WYOMING...DEWPOINTS HAVE DROPPED INTO THE 30S...SO GUSTY WIND NEAR THE STORMS WOULD BE THE MAIN THREAT. UPPER LOW WHICH HAS BEEN VERY SLOW MOVING WILL START ITS SOUTHERN DIVE LATER TONIGHT...WITH THE CHANCES FOR PRECIP CONTINUING OVERNIGHT. FOR THURSDAY...UPPER LOW WILL SLIDE SOUTH ALONG THE MONTANA/NORTH DAKOTA BEFORE HEADING TOWARDS NORTHEAST WYOMING IN THE EVENING. THIS WILL BRING SHOWERS AND THUNDERSTORMS TO THE AREA THROUGH THE DAY...BECOMING MORE RAIN SHOWERS AT NIGHT. 18Z NAM DATA CONTINUES TO BE CONSISTENT WITH PREVIOUS RUNS...WHICH WAS ALSO SEEMS TO AGREE DECENTLY WITH THE GFS. THEREFORE...HAVE CONTINUED THE INCREASE IN POPS. FOR FRIDAY...UPPER LOW CONTINUES ITS SOUTHWARD PROGRESSION TOWARDS COLORADO BEFORE SLOWING DOWN AND SLIDING INTO THE CENTRAL PLAINS. SHOWER AND ISOLATED THUNDERSTORMS ACTIVITY WILL TAPER OFF FROM NORTH TO SOUTH AS THE LOW PROGRESSES. EXTENDED...MODELS IN GOOD AGREEMENT AS UPPER LEVEL CUTOFF LOW SLOWLY MOVES ACROSS THE CENTRAL PLAINS THROUGH SATURDAY. GENERALLY...THE BULK OF THE PRECIPITATION TO REMAIN SOUTH OF FORECAST AREA...HOWEVER A FEW LINGERING SHOWERS ON THE NORTHERN EDGE OF THE LOW HAVE THE POTENTIAL TO IMPACT PORTIONS OF THE SOUTHERN FORECAST AREA. THUS WILL CONTINUE TO MENTION SLIGHT CHANCE POPS THERE. NORTHERN ZONES TO SEE AT OR ABOVE NORMAL TEMPS WITH MOSTLY CLEAR SKIES. FURTHER SOUTH CLOSER TO SEASONAL TEMPERATURES. && .AVIATION...MOSTLY VFR CONDITIONS EXPECTED THROUGH THURSDAY MORNING. THUNDERSTORMS POSSIBLE THIS AFTERNOON AND TONIGHT AS UPPER LOW IN CANADA SINKS SOUTH. LOCALIZED MVFR CIGS/VSBYS WILL OCCUR WITH THE STRONGEST STORMS. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. && $$ sd AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE AMARILLO TX 109 PM CDT WED AUG 13 2008 .UPDATE... UPDATED THE FORECAST TO LOWER THE POPS ACROSS THE WEST AND CENTRAL PARTS OF THE CWA. INCREASED THE POPS ACROSS THE EAST FOR THIS AFTERNOON AS PER RADAR TRENDS. AN OUTFLOW BOUNDARY IS MOVING WEST ACROSS THE CENTRAL PANHANDLES FROM THE ACTIVITY IN THE EAST. THIS OUTFLOW MAY BECOME A PLAYER IN THUNDERSTORM DEVELOPMENT LATER ON THIS AFTERNOON. OTHERWISE...WILL LOOK TOWARD THE MOUNTAINS FOR ADDITIONAL DEVELOPMENT. && .PREV DISCUSSION... /ISSUED 1245 PM CDT WED AUG 13 2008/ AVIATION... TSTMS SEEN ON KAMA 88D E OF AMA SHOULD CONTINUE TO MOVE FARTHER FROM TAF SITES DURING THE NEXT FEW HOURS...AS SHORTWAVE TROF MOVES SEWD THRU ERN TX PNHDL. OUTFLOW BNDRY SEEN ON RADAR MAY REACH AMA EARLY THIS AFTN...PRODUCING A WIND SHIFT TO MORE ELY. BELIEVE THAT TSTMS WILL DELAY IMPACTING TAF SITES TIL THIS EVE...WHEN NEXT SHORTWAVE TROF DROPS SEWD INTO FCST AREA. STILL ANOTHER SHORTWAVE PROGGED TO MOVE TOWARD DHT AND AMA...WITH CHANCES FOR TSTMS CONTINUING PAST 09Z THU. EXCEPT FOR BRIEF MVFR VSBYS IN TSTMS...VFR FCST CONTINUES NEXT 24 HOURS. COCKRELL PREV DISCUSSION... /ISSUED 650 AM CDT WED AUG 13 2008/ AVIATION... 12 UTC TAFS...MAIN AVIATION FORECAST CONCERN DEALS WITH ONGOING CONVECTION AND THEN CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH THE 24 HOUR TAF PERIOD. WEAK UPPER LEVEL DISTURBANCE AS NOTED PER CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS HAS PUSHED SOUTH OF THE PANHANDLES EARLY THIS MORNING. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THIS FEATURE CONTINUE TO PUSH SOUTHEAST. RADAR TRENDS SHOW MOST OF THE SHOWERS EAST OF THE TERMINALS ALTHOUGH WILL CARRY A TEMPO GROUP AT AMARILLO THROUGH 14Z FOR STORMS HEADING TOWARD THE TERMINAL. SATELLITE LOOPS SHOW CLEARING TAKING PLACE FURTHER UPSTREAM IN SOUTHEAST COLORADO. CAN SEE SOME THINNING OF THE MID CLOUD DECK...ESPECIALLY AT GUY. HOWEVER EXPECT SHOWERS AND THUNDERSTORMS TO REDEVELOP LATER TODAY AS ANOTHER UPPER DISTURBANCE HEADS TOWARD THE PANHANDLES ON NORTHWEST FLOW ALOFT. EXPECT STORMS TO GENERATE LATER THIS AFTERNOON AND COVERED THIS POSSIBILITY WITH A PROB GROUP OUT TO 03Z AT ALL THREE TERMINALS. STILL A POSSIBILITY FOR MORE SHOWERS AND THUNDERSTORMS BEYOND THIS PERIOD HOWEVER CONFIDENCE IS LOW SO JUST INSERTED CB REMARKS FOR NOW. CLK PREV DISCUSSION... /ISSUED 604 AM CDT WED AUG 13 2008/ UPDATE... UPON FURTHER REVIEW...WE BELIEVE THAT THERE IS A HEAVY RAIN THREAT THURSDAY THROUGH FRIDAY GIVEN THE POTENTIAL FOR STORMS TRAINING ALONG THE FRONTAL BOUNDARY. WEATHER GRIDS AND HAZARDOUS WEATHER OUTLOOK WERE UPDATED TO MATCH LATEST THINKING. NUNEZ PREV DISCUSSION... /ISSUED 501 AM CDT WED AUG 13 2008/ DISCUSSION... FORECAST STARTS OFF WITH SHOWERS AND THUNDERSTORMS OVER MUCH OF THE PANHANDLES EARLY THIS MORNING AS A WEATHER DISTURBANCE SLIDES DOWN THE NORTHWEST FLOW ALOFT. THERE MAY BE A BRIEF LULL IN THE ACTION LATER THIS MORNING BEFORE SURFACE HEATING DESTABILIZES THE ATMOSPHERE THIS AFTERNOON AND EVENING. ANOTHER WEATHER DISTURBANCE APPEARS TO BE LOCATED NEAR THE UT AND CO BORDER AT THIS TIME...TRACKING TOWARDS THE SOUTH CENTRAL U.S. AND SHOULD TAP INTO THE MOIST AND CONDITIONALLY UNSTABLE AIRMASS...PRIMARILY OVER THE WESTERN AND CENTRAL PARTS OF THE PANHANDLES. A COLD FRONT WILL ENHANCE THE RAINFALL OPPORTUNITIES WHEN IT ARRIVES THURSDAY NIGHT. POPS WERE RAISED INTO THE LIKELY CATEGORY AS A RESULT. THE WEATHER PATTERN BECOMES INTERESTING BY THE WEEKEND WHEN A LOW PRESSURE SYSTEM DRIFTS INTO THE SOUTHERN HIGH PLAINS. RAIN CHANCES WILL REMAIN GOOD WHILE THE PANHANDLES REMAIN POSITIONED ON THE SOUTHERN AND EASTERN SECTORS EARLY. BY MONDAY HOWEVER...THE CENTER OF THE UPPER LOW WILL TRACK SLOWLY EAST ACROSS SRN KS/NRN OK. THIS COURSE WILL CREATE A DOWNSLOPE COMPONENT OVER THE WESTERN PARTS OF THE PANHANDLES...EVENTUALLY SPREADING EAST ACROSS THE AREA WHILE THE UPPER LOW EDGES EAST. THEREFORE...RAIN CHANCES WILL DECREASE FROM WEST TO EAST THOUGH THE EAST MAY BE FAVORED AT THE END OF THE EXTENDED FORECAST. NUNEZ FIRE WEATHER... FIRE WEATHER CONDITIONS WILL REMAIN LOW WHILE PERIODS OF SHOWERS AND THUNDERSTORMS DEVELOP THROUGH THE WEEKEND. NUNEZ && .AMA WATCHES/WARNINGS/ADVISORIES... TX...NONE. OK...NONE. && $$ 03/15 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE AMARILLO TX 1245 PM CDT WED AUG 13 2008 .AVIATION... TSTMS SEEN ON KAMA 88D E OF AMA SHOULD CONTINUE TO MOVE FARTHER FROM TAF SITES DURING THE NEXT FEW HOURS...AS SHORTWAVE TROF MOVES SEWD THRU ERN TX PNHDL. OUTFLOW BNDRY SEEN ON RADAR MAY REACH AMA EARLY THIS AFTN...PRODUCING A WIND SHIFT TO MORE ELY. BELIEVE THAT TSTMS WILL DELAY IMPACTING TAF SITES TIL THIS EVE...WHEN NEXT SHORTWAVE TROF DROPS SEWD INTO FCST AREA. STILL ANOTHER SHORTWAVE PROGGED TO MOVE TOWARD DHT AND AMA...WITH CHANCES FOR TSTMS CONTINUING PAST 09Z THU. EXCEPT FOR BRIEF MVFR VSBYS IN TSTMS...VFR FCST CONTINUES NEXT 24 HOURS. COCKRELL && .PREV DISCUSSION... /ISSUED 650 AM CDT WED AUG 13 2008/ AVIATION... 12 UTC TAFS...MAIN AVIATION FORECAST CONCERN DEALS WITH ONGOING CONVECTION AND THEN CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH THE 24 HOUR TAF PERIOD. WEAK UPPER LEVEL DISTURBANCE AS NOTED PER CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS HAS PUSHED SOUTH OF THE PANHANDLES EARLY THIS MORNING. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THIS FEATURE CONTINUE TO PUSH SOUTHEAST. RADAR TRENDS SHOW MOST OF THE SHOWERS EAST OF THE TERMINALS ALTHOUGH WILL CARRY A TEMPO GROUP AT AMARILLO THROUGH 14Z FOR STORMS HEADING TOWARD THE TERMINAL. SATELLITE LOOPS SHOW CLEARING TAKING PLACE FURTHER UPSTREAM IN SOUTHEAST COLORADO. CAN SEE SOME THINNING OF THE MID CLOUD DECK...ESPECIALLY AT GUY. HOWEVER EXPECT SHOWERS AND THUNDERSTORMS TO REDEVELOP LATER TODAY AS ANOTHER UPPER DISTURBANCE HEADS TOWARD THE PANHANDLES ON NORTHWEST FLOW ALOFT. EXPECT STORMS TO GENERATE LATER THIS AFTERNOON AND COVERED THIS POSSIBILITY WITH A PROB GROUP OUT TO 03Z AT ALL THREE TERMINALS. STILL A POSSIBILITY FOR MORE SHOWERS AND THUNDERSTORMS BEYOND THIS PERIOD HOWEVER CONFIDENCE IS LOW SO JUST INSERTED CB REMARKS FOR NOW. CLK PREV DISCUSSION... /ISSUED 604 AM CDT WED AUG 13 2008/ UPDATE... UPON FURTHER REVIEW...WE BELIEVE THAT THERE IS A HEAVY RAIN THREAT THURSDAY THROUGH FRIDAY GIVEN THE POTENTIAL FOR STORMS TRAINING ALONG THE FRONTAL BOUNDARY. WEATHER GRIDS AND HAZARDOUS WEATHER OUTLOOK WERE UPDATED TO MATCH LATEST THINKING. NUNEZ PREV DISCUSSION... /ISSUED 501 AM CDT WED AUG 13 2008/ DISCUSSION... FORECAST STARTS OFF WITH SHOWERS AND THUNDERSTORMS OVER MUCH OF THE PANHANDLES EARLY THIS MORNING AS A WEATHER DISTURBANCE SLIDES DOWN THE NORTHWEST FLOW ALOFT. THERE MAY BE A BRIEF LULL IN THE ACTION LATER THIS MORNING BEFORE SURFACE HEATING DESTABILIZES THE ATMOSPHERE THIS AFTERNOON AND EVENING. ANOTHER WEATHER DISTURBANCE APPEARS TO BE LOCATED NEAR THE UT AND CO BORDER AT THIS TIME...TRACKING TOWARDS THE SOUTH CENTRAL U.S. AND SHOULD TAP INTO THE MOIST AND CONDITIONALLY UNSTABLE AIRMASS...PRIMARILY OVER THE WESTERN AND CENTRAL PARTS OF THE PANHANDLES. A COLD FRONT WILL ENHANCE THE RAINFALL OPPORTUNITIES WHEN IT ARRIVES THURSDAY NIGHT. POPS WERE RAISED INTO THE LIKELY CATEGORY AS A RESULT. THE WEATHER PATTERN BECOMES INTERESTING BY THE WEEKEND WHEN A LOW PRESSURE SYSTEM DRIFTS INTO THE SOUTHERN HIGH PLAINS. RAIN CHANCES WILL REMAIN GOOD WHILE THE PANHANDLES REMAIN POSITIONED ON THE SOUTHERN AND EASTERN SECTORS EARLY. BY MONDAY HOWEVER...THE CENTER OF THE UPPER LOW WILL TRACK SLOWLY EAST ACROSS SRN KS/NRN OK. THIS COURSE WILL CREATE A DOWNSLOPE COMPONENT OVER THE WESTERN PARTS OF THE PANHANDLES...EVENTUALLY SPREADING EAST ACROSS THE AREA WHILE THE UPPER LOW EDGES EAST. THEREFORE...RAIN CHANCES WILL DECREASE FROM WEST TO EAST THOUGH THE EAST MAY BE FAVORED AT THE END OF THE EXTENDED FORECAST. NUNEZ FIRE WEATHER... FIRE WEATHER CONDITIONS WILL REMAIN LOW WHILE PERIODS OF SHOWERS AND THUNDERSTORMS DEVELOP THROUGH THE WEEKEND. NUNEZ && .AMA WATCHES/WARNINGS/ADVISORIES... TX...NONE. OK...NONE. && $$ 03/15 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 1238 PM CDT WED AUG 13 2008 .DISCUSSION...SEE AVIATION DISCUSSION. && .AVIATION...ANOTHER WEAK BOUNDARY STRETCHING FROM LAREDO-ALICE-REFUGIO IS PUSHING SOUTHWARD. THIS BOUNDARY WILL MEET UP WITH THE SEA BREEZE MAINLY NORTHEAST OF CORPUS CHRISTI FOR ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS. MVFR/IFR CIGS/VSBYS WILL ACCOMPANY THE STRONGER STORMS. VFR CIGS WILL BE FOUND ACROSS MUCH OF THE REST OF THE AREA. VFR CONDITIONS WILL PREVAIL ACROSS THE ENTIRE REGION AFTER 03Z, HOWEVER PATCHY MVFR/IFR CIGS/VSBYS WILL DEVELOP ACROSS THE COASTAL PLAINS FROM ALICE TO VICTORIA AFTER 09Z TONIGHT. && .PREV DISCUSSION... /ISSUED 1024 AM CDT WED AUG 13 2008/ DISCUSSION...THOUGH NOT SHOWN WELL IN SURFACE OBSERVATIONS, A WEAK ELONGATED BOUNDARY IS EVIDENT IN SATELLITE IMAGERY AND KCRP DOPPLER RADAR DATA. THIS BOUNDARY IS STRUNG ROUGHLY ALONG A ZAPATA-CORPUS CHRISTI-REFUGIO LINE AND APPEARS TO SLOWLY BE SAGGING SOUTH AND EASTWARD. THE BOUNDARY WILL ACT AS A FOCUSING MECHANISM FOR SHOWERS/THUNDERSTORMS TODAY, ESPECIALLY WHEN IT COMES IN CONTACT WITH THE SEA BREEZE. BOUNDARY INTERACTION SHOULD BE BEST OVER THE COASTAL BEND NORTHEAST OF CORPUS CHRISTI. THE 12Z CORPUS CHRISTI SOUNDING SHOWED PRECIPITABLE WATER VALUES AROUND 2.35 INCHES WITH SOME COOLING SHOWN IN THE 900-750 MILLIBAR LAYER SINCE THIS SAME TIME YESTERDAY. MUCH HIGHER PWATS AND THE IDENTIFIED COOLING SHOULD ALSO HELP TO GET CONVECTION GOING. CURRENT FORECASTS FOR TODAY HAVE AT LEAST SLIGHT CHANCES OF PRECIPITATION ACROSS THE ENTIRE REGION AND THIS LOOKS GOOD SO WILL NOT MAKE ANY CHANGES TO THINGS AT THIS TIME. PREV DISCUSSION... /ISSUED 631 AM CDT WED AUG 13 2008/ DISCUSSION...UPDATED FOR AVIATION DISCUSSION BELOW. AVIATION...MAIN ISSUE TODAY WILL BE THE SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE AREA. CONVERGENCE ALONG A BOUNDARY LOCATED ACROSS THE NORTHERN COASTAL BEND HAS TRIGGERED SOME ACTIVITY ALREADY THIS MORNING. AS DAYTIME HEATING COMMENCES AND THE SEABREEZE COMES INTO PLAY...ACTIVITY IS EXPECTED TO INCREASE DURING THE LATE MORNING/EARLY AFTERNOON HOURS...GENERALLY ACROSS THE EASTERN CWA AFFECTING KALI...KCRP AND KVCT. VFR CONDITIONS WILL GENERALLY PREVAIL TODAY...EXCEPT IN THE VICINITY OF ANY THUNDERSTORMS WHEN MVFR VSBYS/CIGS WILL BE POSSIBLE. PREV DISCUSSION... /ISSUED 519 AM CDT WED AUG 13 2008/ DISCUSSION...BASED ON RADAR TRENDS...SENT OUT A QUICK UPDATE TO ACCOUNT FOR SHOWERS THAT HAVE FORMED ACROSS THE INLAND COASTAL PLAINS. AS PER RADAR/SATELLITE/RUC ANALYSIS...AN OLD BOUNDARY IS SITUATED ACROSS THE NORTHERN COASTAL BEND AND IS PROVIDING ENOUGH CONVERGENCE TO TRIGGER SOME SHOWERS IN A REGION WHERE THE DEWPOINTS ARE WELL INTO THE 70S. UPDATED PRODUCTS ARE OUT. PREV DISCUSSION... /ISSUED 301 AM CDT WED AUG 13 2008/ SHORT TERM (TODAY THROUGH THURSDAY)...MAIN ISSUE DURING THE SHORT TERM WILL BE THE POP FORECAST AS MODELS CONTINUE TO INDICATE PRECIP AREAWIDE...HOWEVER MODELS CONTINUE TO INITIALIZE TOO WET SO CONFIDENCE IN PRECIP IS DIMINISHED. ALSO AM EXPECTING THE BOUNDARY LAYER TO REMAIN RELATIVELY WARM...SIMILAR TO PAST COUPLE OF DAYS AND THIS COULD HELP LIMIT CONVECTION. HOWEVER...AMPLE MOISTURE IS STILL IN PLACE ACROSS THE REGION...WITH THE 00Z CRP SOUNDING COMING IN WITH A 2.20 INCH PRECIPITABLE WATER VALUE. ALSO MODELS CONTINUE TO INDICATE PWAT VALUES ABOVE TWO INCHES THROUGH AT LEAST TODAY. WITH ALL THIS IN MIND...DECIDED TO GO BELOW GUIDANCE WITH RESPECT TO POPS AND AM ONLY EXPECTING ISOLATED TO SCATTERED (AT BEST) SEABREEZE CONVECTION TODAY. BY THURSDAY...AM ONLY EXPECTING ISOLATED SEABREEZE CONVECTION AS MOISTURE VALUES ARE PROGGED TO DECREASE SLIGHTLY. TEMPS WILL BE NEAR TO SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD. MARINE...SEAS FELL BELOW 6 FEET EARLY THIS MORNING AND BOTH WINDS/SEA WILL REMAIN BELOW HEADLINE CRITERIA THROUGH THE PERIOD. LONG TERM (THURSDAY NIGHT THROUGH TUESDAY)...THE MAIN FCST PROBLEM WL REMAIN WHAT TO DO WITH POPS THROUGH THE PD. THE OVERALL ASSESSMENT IS THAT THE MODELS REMAIN A BIT ON THE MOIST SIDE AS SEEN IN THE INITIALIZATION. GIVEN THE CURRENT WARM TROPOSPHERIC COLUMN CURRENTLY ACROSS SOUTH TX AND THE OVERALL LACK OF FOCUS OF CONVECTION (OTHER THAN THE SEABREEZE AND A POSSIBLE OUTFLOW)...BLV IT WL BE BEST TO BE CONSERVATIVE WITH POPS AND GO WITH SLIGHT CHC AT THIS TIME. THE MAIN DYNAMICS AND POOLING OF MOISTURE WL REMAIN TO OUR NORTH THROUGH THE PD AND SO THIS WL ALSO PLAY IN THE CONSERVATIVE POPS AS WELL. TEMPS WL AVERAGE AT OR SLIGHTLY ABV NORMAL. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 76 94 79 93 78 / 10 20 10 10 10 VICTORIA 74 99 77 95 76 / 10 20 10 10 10 LAREDO 79 102 81 103 80 / 10 10 10 10 10 ALICE 76 99 77 98 77 / 10 20 10 10 10 ROCKPORT 80 93 82 91 81 / 10 10 10 10 10 COTULLA 76 101 77 101 77 / 10 10 10 10 10 KINGSVILLE 77 96 78 96 77 / 10 20 10 10 10 NAVY CORPUS 80 92 81 90 81 / 10 10 10 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ JAR/19...SHORT TERM/AVIATION tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 1024 AM CDT WED AUG 13 2008 .DISCUSSION...THOUGH NOT SHOWN WELL IN SURFACE OBSERVATIONS, A WEAK ELONGATED BOUNDARY IS EVIDENT IN SATELLITE IMAGERY AND KCRP DOPPLER RADAR DATA. THIS BOUNDARY IS STRUNG ROUGHLY ALONG A ZAPATA-CORPUS CHRISTI-REFUGIO LINE AND APPEARS TO SLOWLY BE SAGGING SOUTH AND EASTWARD. THE BOUNDARY WILL ACT AS A FOCUSING MECHANISM FOR SHOWERS/THUNDERSTORMS TODAY, ESPECIALLY WHEN IT COMES IN CONTACT WITH THE SEA BREEZE. BOUNDARY INTERACTION SHOULD BE BEST OVER THE COASTAL BEND NORTHEAST OF CORPUS CHRISTI. THE 12Z CORPUS CHRISTI SOUNDING SHOWED PRECIPITABLE WATER VALUES AROUND 2.35 INCHES WITH SOME COOLING SHOWN IN THE 900-750 MILLIBAR LAYER SINCE THIS SAME TIME YESTERDAY. MUCH HIGHER PWATS AND THE IDENTIFIED COOLING SHOULD ALSO HELP TO GET CONVECTION GOING. CURRENT FORECASTS FOR TODAY HAVE AT LEAST SLIGHT CHANCES OF PRECIPITATION ACROSS THE ENTIRE REGION AND THIS LOOKS GOOD SO WILL NOT MAKE ANY CHANGES TO THINGS AT THIS TIME. && .PREV DISCUSSION... /ISSUED 631 AM CDT WED AUG 13 2008/ DISCUSSION...UPDATED FOR AVIATION DISCUSSION BELOW. AVIATION...MAIN ISSUE TODAY WILL BE THE SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE AREA. CONVERGENCE ALONG A BOUNDARY LOCATED ACROSS THE NORTHERN COASTAL BEND HAS TRIGGERED SOME ACTIVITY ALREADY THIS MORNING. AS DAYTIME HEATING COMMENCES AND THE SEABREEZE COMES INTO PLAY...ACTIVITY IS EXPECTED TO INCREASE DURING THE LATE MORNING/EARLY AFTERNOON HOURS...GENERALLY ACROSS THE EASTERN CWA AFFECTING KALI...KCRP AND KVCT. VFR CONDITIONS WILL GENERALLY PREVAIL TODAY...EXCEPT IN THE VICINITY OF ANY THUNDERSTORMS WHEN MVFR VSBYS/CIGS WILL BE POSSIBLE. PREV DISCUSSION... /ISSUED 519 AM CDT WED AUG 13 2008/ DISCUSSION...BASED ON RADAR TRENDS...SENT OUT A QUICK UPDATE TO ACCOUNT FOR SHOWERS THAT HAVE FORMED ACROSS THE INLAND COASTAL PLAINS. AS PER RADAR/SATELLITE/RUC ANALYSIS...AN OLD BOUNDARY IS SITUATED ACROSS THE NORTHERN COASTAL BEND AND IS PROVIDING ENOUGH CONVERGENCE TO TRIGGER SOME SHOWERS IN A REGION WHERE THE DEWPOINTS ARE WELL INTO THE 70S. UPDATED PRODUCTS ARE OUT. PREV DISCUSSION... /ISSUED 301 AM CDT WED AUG 13 2008/ SHORT TERM (TODAY THROUGH THURSDAY)...MAIN ISSUE DURING THE SHORT TERM WILL BE THE POP FORECAST AS MODELS CONTINUE TO INDICATE PRECIP AREAWIDE...HOWEVER MODELS CONTINUE TO INITIALIZE TOO WET SO CONFIDENCE IN PRECIP IS DIMINISHED. ALSO AM EXPECTING THE BOUNDARY LAYER TO REMAIN RELATIVELY WARM...SIMILAR TO PAST COUPLE OF DAYS AND THIS COULD HELP LIMIT CONVECTION. HOWEVER...AMPLE MOISTURE IS STILL IN PLACE ACROSS THE REGION...WITH THE 00Z CRP SOUNDING COMING IN WITH A 2.20 INCH PRECIPITABLE WATER VALUE. ALSO MODELS CONTINUE TO INDICATE PWAT VALUES ABOVE TWO INCHES THROUGH AT LEAST TODAY. WITH ALL THIS IN MIND...DECIDED TO GO BELOW GUIDANCE WITH RESPECT TO POPS AND AM ONLY EXPECTING ISOLATED TO SCATTERED (AT BEST) SEABREEZE CONVECTION TODAY. BY THURSDAY...AM ONLY EXPECTING ISOLATED SEABREEZE CONVECTION AS MOISTURE VALUES ARE PROGGED TO DECREASE SLIGHTLY. TEMPS WILL BE NEAR TO SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD. MARINE...SEAS FELL BELOW 6 FEET EARLY THIS MORNING AND BOTH WINDS/SEA WILL REMAIN BELOW HEADLINE CRITERIA THROUGH THE PERIOD. LONG TERM (THURSDAY NIGHT THROUGH TUESDAY)...THE MAIN FCST PROBLEM WL REMAIN WHAT TO DO WITH POPS THROUGH THE PD. THE OVERALL ASSESSMENT IS THAT THE MODELS REMAIN A BIT ON THE MOIST SIDE AS SEEN IN THE INITIALIZATION. GIVEN THE CURRENT WARM TROPOSPHERIC COLUMN CURRENTLY ACROSS SOUTH TX AND THE OVERALL LACK OF FOCUS OF CONVECTION (OTHER THAN THE SEABREEZE AND A POSSIBLE OUTFLOW)...BLV IT WL BE BEST TO BE CONSERVATIVE WITH POPS AND GO WITH SLIGHT CHC AT THIS TIME. THE MAIN DYNAMICS AND POOLING OF MOISTURE WL REMAIN TO OUR NORTH THROUGH THE PD AND SO THIS WL ALSO PLAY IN THE CONSERVATIVE POPS AS WELL. TEMPS WL AVERAGE AT OR SLIGHTLY ABV NORMAL. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 94 76 94 79 93 / 30 10 20 10 10 VICTORIA 97 74 99 77 95 / 30 10 20 10 10 LAREDO 101 79 102 81 103 / 20 10 10 10 10 ALICE 99 76 99 77 98 / 30 10 20 10 10 ROCKPORT 91 80 93 82 91 / 20 10 10 10 10 COTULLA 99 76 101 77 101 / 20 10 10 10 10 KINGSVILLE 97 77 96 78 96 / 30 10 20 10 10 NAVY CORPUS 90 80 92 81 90 / 20 10 10 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ JAR/19...SHORT TERM/AVIATION tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE AMARILLO TX 650 AM CDT WED AUG 13 2008 .AVIATION... 12 UTC TAFS...MAIN AVIATION FORECAST CONCERN DEALS WITH ONGOING CONVECTION AND THEN CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH THE 24 HOUR TAF PERIOD. WEAK UPPER LEVEL DISTURBANCE AS NOTED PER CURRENT WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSIS HAS PUSHED SOUTH OF THE PANHANDLES EARLY THIS MORNING. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THIS FEATURE CONTINUE TO PUSH SOUTHEAST. RADAR TRENDS SHOW MOST OF THE SHOWERS EAST OF THE TERMINALS ALTHOUGH WILL CARRY A TEMPO GROUP AT AMARILLO THROUGH 14Z FOR STORMS HEADING TOWARD THE TERMINAL. SATELLITE LOOPS SHOW CLEARING TAKING PLACE FURTHER UPSTREAM IN SOUTHEAST COLORADO. CAN SEE SOME THINNING OF THE MID CLOUD DECK...ESPECIALLY AT GUY. HOWEVER EXPECT SHOWERS AND THUNDERSTORMS TO REDEVELOP LATER TODAY AS ANOTHER UPPER DISTURBANCE HEADS TOWARD THE PANHANDLES ON NORTHWEST FLOW ALOFT. EXPECT STORMS TO GENERATE LATER THIS AFTERNOON AND COVERED THIS POSSIBILITY WITH A PROB GROUP OUT TO 03Z AT ALL THREE TERMINALS. STILL A POSSIBILITY FOR MORE SHOWERS AND THUNDERSTORMS BEYOND THIS PERIOD HOWEVER CONFIDENCE IS LOW SO JUST INSERTED CB REMARKS FOR NOW. CLK && .PREV DISCUSSION... /ISSUED 604 AM CDT WED AUG 13 2008/ UPDATE... UPON FURTHER REVIEW...WE BELIEVE THAT THERE IS A HEAVY RAIN THREAT THURSDAY THROUGH FRIDAY GIVEN THE POTENTIAL FOR STORMS TRAINING ALONG THE FRONTAL BOUNDARY. WEATHER GRIDS AND HAZARDOUS WEATHER OUTLOOK WERE UPDATED TO MATCH LATEST THINKING. NUNEZ PREV DISCUSSION... /ISSUED 501 AM CDT WED AUG 13 2008/ DISCUSSION... FORECAST STARTS OFF WITH SHOWERS AND THUNDERSTORMS OVER MUCH OF THE PANHANDLES EARLY THIS MORNING AS A WEATHER DISTURBANCE SLIDES DOWN THE NORTHWEST FLOW ALOFT. THERE MAY BE A BRIEF LULL IN THE ACTION LATER THIS MORNING BEFORE SURFACE HEATING DESTABILIZES THE ATMOSPHERE THIS AFTERNOON AND EVENING. ANOTHER WEATHER DISTURBANCE APPEARS TO BE LOCATED NEAR THE UT AND CO BORDER AT THIS TIME...TRACKING TOWARDS THE SOUTH CENTRAL U.S. AND SHOULD TAP INTO THE MOIST AND CONDITIONALLY UNSTABLE AIRMASS...PRIMARILY OVER THE WESTERN AND CENTRAL PARTS OF THE PANHANDLES. A COLD FRONT WILL ENHANCE THE RAINFALL OPPORTUNITIES WHEN IT ARRIVES THURSDAY NIGHT. POPS WERE RAISED INTO THE LIKELY CATEGORY AS A RESULT. THE WEATHER PATTERN BECOMES INTERESTING BY THE WEEKEND WHEN A LOW PRESSURE SYSTEM DRIFTS INTO THE SOUTHERN HIGH PLAINS. RAIN CHANCES WILL REMAIN GOOD WHILE THE PANHANDLES REMAIN POSITIONED ON THE SOUTHERN AND EASTERN SECTORS EARLY. BY MONDAY HOWEVER...THE CENTER OF THE UPPER LOW WILL TRACK SLOWLY EAST ACROSS SRN KS/NRN OK. THIS COURSE WILL CREATE A DOWNSLOPE COMPONENT OVER THE WESTERN PARTS OF THE PANHANDLES...EVENTUALLY SPREADING EAST ACROSS THE AREA WHILE THE UPPER LOW EDGES EAST. THEREFORE...RAIN CHANCES WILL DECREASE FROM WEST TO EAST THOUGH THE EAST MAY BE FAVORED AT THE END OF THE EXTENDED FORECAST. NUNEZ FIRE WEATHER... FIRE WEATHER CONDITIONS WILL REMAIN LOW WHILE PERIODS OF SHOWERS AND THUNDERSTORMS DEVELOP THROUGH THE WEEKEND. NUNEZ && .AMA WATCHES/WARNINGS/ADVISORIES... TX...NONE. OK...NONE. && $$ 05/08 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 631 AM CDT WED AUG 13 2008 .DISCUSSION...UPDATED FOR AVIATION DISCUSSION BELOW. && .AVIATION...MAIN ISSUE TODAY WILL BE THE SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE AREA. CONVERGENCE ALONG A BOUNDARY LOCATED ACROSS THE NORTHERN COASTAL BEND HAS TRIGGERED SOME ACTIVITY ALREADY THIS MORNING. AS DAYTIME HEATING COMMENCES AND THE SEABREEZE COMES INTO PLAY...ACTIVITY IS EXPECTED TO INCREASE DURING THE LATE MORNING/EARLY AFTERNOON HOURS...GENERALLY ACROSS THE EASTERN CWA AFFECTING KALI...KCRP AND KVCT. VFR CONDITIONS WILL GENERALLY PREVAIL TODAY...EXCEPT IN THE VICINITY OF ANY THUNDERSTORMS WHEN MVFR VSBYS/CIGS WILL BE POSSIBLE. && .PREV DISCUSSION... /ISSUED 519 AM CDT WED AUG 13 2008/ DISCUSSION...BASED ON RADAR TRENDS...SENT OUT A QUICK UPDATE TO ACCOUNT FOR SHOWERS THAT HAVE FORMED ACROSS THE INLAND COASTAL PLAINS. AS PER RADAR/SATELLITE/RUC ANALYSIS...AN OLD BOUNDARY IS SITUATED ACROSS THE NORTHERN COASTAL BEND AND IS PROVIDING ENOUGH CONVERGENCE TO TRIGGER SOME SHOWERS IN A REGION WHERE THE DEWPOINTS ARE WELL INTO THE 70S. UPDATED PRODUCTS ARE OUT. PREV DISCUSSION... /ISSUED 301 AM CDT WED AUG 13 2008/ SHORT TERM (TODAY THROUGH THURSDAY)...MAIN ISSUE DURING THE SHORT TERM WILL BE THE POP FORECAST AS MODELS CONTINUE TO INDICATE PRECIP AREAWIDE...HOWEVER MODELS CONTINUE TO INITIALIZE TOO WET SO CONFIDENCE IN PRECIP IS DIMINISHED. ALSO AM EXPECTING THE BOUNDARY LAYER TO REMAIN RELATIVELY WARM...SIMILAR TO PAST COUPLE OF DAYS AND THIS COULD HELP LIMIT CONVECTION. HOWEVER...AMPLE MOISTURE IS STILL IN PLACE ACROSS THE REGION...WITH THE 00Z CRP SOUNDING COMING IN WITH A 2.20 INCH PRECIPITABLE WATER VALUE. ALSO MODELS CONTINUE TO INDICATE PWAT VALUES ABOVE TWO INCHES THROUGH AT LEAST TODAY. WITH ALL THIS IN MIND...DECIDED TO GO BELOW GUIDANCE WITH RESPECT TO POPS AND AM ONLY EXPECTING ISOLATED TO SCATTERED (AT BEST) SEABREEZE CONVECTION TODAY. BY THURSDAY...AM ONLY EXPECTING ISOLATED SEABREEZE CONVECTION AS MOISTURE VALUES ARE PROGGED TO DECREASE SLIGHTLY. TEMPS WILL BE NEAR TO SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD. MARINE...SEAS FELL BELOW 6 FEET EARLY THIS MORNING AND BOTH WINDS/SEA WILL REMAIN BELOW HEADLINE CRITERIA THROUGH THE PERIOD. LONG TERM (THURSDAY NIGHT THROUGH TUESDAY)...THE MAIN FCST PROBLEM WL REMAIN WHAT TO DO WITH POPS THROUGH THE PD. THE OVERALL ASSESSMENT IS THAT THE MODELS REMAIN A BIT ON THE MOIST SIDE AS SEEN IN THE INITIALIZATION. GIVEN THE CURRENT WARM TROPOSPHERIC COLUMN CURRENTLY ACROSS SOUTH TX AND THE OVERALL LACK OF FOCUS OF CONVECTION (OTHER THAN THE SEABREEZE AND A POSSIBLE OUTFLOW)...BLV IT WL BE BEST TO BE CONSERVATIVE WITH POPS AND GO WITH SLIGHT CHC AT THIS TIME. THE MAIN DYNAMICS AND POOLING OF MOISTURE WL REMAIN TO OUR NORTH THROUGH THE PD AND SO THIS WL ALSO PLAY IN THE CONSERVATIVE POPS AS WELL. TEMPS WL AVERAGE AT OR SLIGHTLY ABV NORMAL. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 94 76 94 79 93 / 30 10 20 10 10 VICTORIA 97 74 99 77 95 / 30 10 20 10 10 LAREDO 101 79 102 81 103 / 20 10 10 10 10 ALICE 99 76 99 77 98 / 30 10 20 10 10 ROCKPORT 91 80 93 82 91 / 20 10 10 10 10 COTULLA 99 76 101 77 101 / 20 10 10 10 10 KINGSVILLE 97 77 96 78 96 / 30 10 20 10 10 NAVY CORPUS 90 80 92 81 90 / 20 10 10 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ KR/97...SHORT TERM KR/97...LONG TERM tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 519 AM CDT WED AUG 13 2008 .DISCUSSION...BASED ON RADAR TRENDS...SENT OUT A QUICK UPDATE TO ACCOUNT FOR SHOWERS THAT HAVE FORMED ACROSS THE INLAND COASTAL PLAINS. AS PER RADAR/SATELLITE/RUC ANALYSIS...AN OLD BOUNDARY IS SITUATED ACROSS THE NORTHERN COASTAL BEND AND IS PROVIDING ENOUGH CONVERGENCE TO TRIGGER SOME SHOWERS IN A REGION WHERE THE DEWPOINTS ARE WELL INTO THE 70S. UPDATED PRODUCTS ARE OUT. && .PREV DISCUSSION... /ISSUED 301 AM CDT WED AUG 13 2008/ SHORT TERM (TODAY THROUGH THURSDAY)...MAIN ISSUE DURING THE SHORT TERM WILL BE THE POP FORECAST AS MODELS CONTINUE TO INDICATE PRECIP AREAWIDE...HOWEVER MODELS CONTINUE TO INITIALIZE TOO WET SO CONFIDENCE IN PRECIP IS DIMINISHED. ALSO AM EXPECTING THE BOUNDARY LAYER TO REMAIN RELATIVELY WARM...SIMILAR TO PAST COUPLE OF DAYS AND THIS COULD HELP LIMIT CONVECTION. HOWEVER...AMPLE MOISTURE IS STILL IN PLACE ACROSS THE REGION...WITH THE 00Z CRP SOUNDING COMING IN WITH A 2.20 INCH PRECIPITABLE WATER VALUE. ALSO MODELS CONTINUE TO INDICATE PWAT VALUES ABOVE TWO INCHES THROUGH AT LEAST TODAY. WITH ALL THIS IN MIND...DECIDED TO GO BELOW GUIDANCE WITH RESPECT TO POPS AND AM ONLY EXPECTING ISOLATED TO SCATTERED (AT BEST) SEABREEZE CONVECTION TODAY. BY THURSDAY...AM ONLY EXPECTING ISOLATED SEABREEZE CONVECTION AS MOISTURE VALUES ARE PROGGED TO DECREASE SLIGHTLY. TEMPS WILL BE NEAR TO SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD. MARINE...SEAS FELL BELOW 6 FEET EARLY THIS MORNING AND BOTH WINDS/SEA WILL REMAIN BELOW HEADLINE CRITERIA THROUGH THE PERIOD. LONG TERM (THURSDAY NIGHT THROUGH TUESDAY)...THE MAIN FCST PROBLEM WL REMAIN WHAT TO DO WITH POPS THROUGH THE PD. THE OVERALL ASSESSMENT IS THAT THE MODELS REMAIN A BIT ON THE MOIST SIDE AS SEEN IN THE INITIALIZATION. GIVEN THE CURRENT WARM TROPOSPHERIC COLUMN CURRENTLY ACROSS SOUTH TX AND THE OVERALL LACK OF FOCUS OF CONVECTION (OTHER THAN THE SEABREEZE AND A POSSIBLE OUTFLOW)...BLV IT WL BE BEST TO BE CONSERVATIVE WITH POPS AND GO WITH SLIGHT CHC AT THIS TIME. THE MAIN DYNAMICS AND POOLING OF MOISTURE WL REMAIN TO OUR NORTH THROUGH THE PD AND SO THIS WL ALSO PLAY IN THE CONSERVATIVE POPS AS WELL. TEMPS WL AVERAGE AT OR SLIGHTLY ABV NORMAL. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 94 76 94 79 93 / 30 10 20 10 10 VICTORIA 97 74 99 77 95 / 30 10 20 10 10 LAREDO 101 79 102 81 103 / 20 10 10 10 10 ALICE 99 76 99 77 98 / 30 10 20 10 10 ROCKPORT 91 80 93 82 91 / 20 10 10 10 10 COTULLA 99 76 101 77 101 / 20 10 10 10 10 KINGSVILLE 97 77 96 78 96 / 30 10 20 10 10 NAVY CORPUS 90 80 92 81 90 / 20 10 10 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ KRR/97...UPDATE tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 415 AM EDT THU AUG 14 2008 .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW LITTLE CHANGE HAS OCCURRED IN THE PATTERN OVER THE LAST 24 HRS. A MIDLEVEL LOW WAS OVER SE SASKATCHEWAN...A MIDLEVEL HIGH WAS OVER NRN MANITOBA...AND A TROF/BROAD MIDLEVEL LOW WAS OVER SE CANADA. THE LOW OVER SE CANADA HAS EXPANDED W A BIT...AND UPPER MI IS NOW UNDER NRLY FLOW ON ITS WRN FRINGE. AROUND THE LOW...A SHORTWAVE WAS ROTATING THRU ERN ONTARIO TOWARD THE UPPER GREAT LAKES. ALTHOUGH SHORTWAVE IS NOT PRODUCING MUCH IN THE WAY OF CLOUD COVER...RADARS IN ONTARIO DO SHOW A FEW -SHRA. ACROSS UPPER MI...WITH THE EXCEPTION OF SOME CLOUDS OVER THE SW THIRD...SKIES ARE CLEAR. && .DISCUSSION... SHORTWAVE ROTATING THRU ERN ONTARIO WILL SWING ACROSS UPPER MI THIS MORNING. HEIGHTS FALL SLIGHTLY OVER THE ERN FCST AREA THRU MID MORNING...AND CORE OF THE 5H COLD POOL BRUSHES THAT AREA...BUT THAT PROBABLY WON`T BE ENOUGH TO GET ANY -SHRA INTO THE ERN FCST AREA. STILL...WILL NEED TO MONITOR RADAR TRENDS DURING THE MORNING TO SEE IF THE ISOLD -SHRA CURRENTLY HEADING SSW TOWARD FAR ERN LAKE SUPERIOR MIGHT CLIP LUCE COUNTY. OTHERWISE...SHORTWAVE PASSAGE WILL BE DRY ACROSS THE FCST AREA SINCE SHORTWAVE WILL BE S OF THE AREA WELL BEFORE PEAK OF THE HEATING CYCLE. STABILIZING N TO NE FLOW OFF LAKE SUPERIOR TO BEGIN THE DAY SUGGESTS LITTLE OR NO CLOUD COVER NEAR THE LAKE TODAY. DIURNAL CU INLAND SHOULD TEND TO DISSIPATE DURING THE AFTN FROM N TO S AS DRIER AIR ARRIVES IN THE WAKE OF SHORTWAVE AND STABILIZING FLOW OFF LAKE SUPERIOR SPREADS WELL INLAND. MIXING TO AROUND 800MB ON FCST SOUNDINGS SUPPORTS MOS GUIDANCE MAX TEMPS IN THE MID/UPPER 70S AWAY FROM LAKE SUPERIOR MODIFICATION. ALONG THE LAKE SUPERIOR SHORE...TEMPS SHOULD TOP OUT IN THE UPPER 60S/AROUND 70F. PROVIDED DEEP MIXING OCCURS...DWPTS WELL AWAY FROM LAKE SUPERIOR SHOULD DROP INTO THE MID 40S PER FCST SOUNDINGS. THIS WILL SEND RH DOWN TO 30-35PCT. CENTER OF SFC HIGH PRES ASSOCIATED WITH UPPER RIDGE EXTENDING FROM SW CANADA TO HUDSON BAY WILL SETTLE S TO NE MN/FAR NW WI BY THU MORNING...SO WRN FCST AREA WILL BE COOLEST TONIGHT. RADIATIONAL COOLING UNDER CLEAR SKIES WILL BE ENHANCED BY DRY AIRMASS WITH PRECIPITABLE WATER AROUND 0.5 INCHES OR AROUND 60PCT OF NORMAL FOR THIS TIME OF YEAR. WILL GO JUST BLO COOLEST MOS GUIDANCE OVER THE INTERIOR W (LOW/MID 40S). FARTHER TO THE E OF THE HIGH...WINDS SHOULD CONTINUE TO STIR A LITTLE OVER THE ERN FCST AREA...AND THERE MAY BE A SOME MIDLEVEL CLOUDS WRAPPING S AROUND THE SE CANADA LOW THRU ERN UPPER MI. WILL STAY CLOSE TO MOS GUIDANCE THERE (UPPER 50S ALONG LAKE SUPERIOR...LOW/MID 50S INLAND). WILL ADD PATCHY FOG OVER THE INTERIOR W HALF WHERE LIGHT/CALM WINDS AND CHILLY AIR OVERNIGHT WILL BE CONDUCIVE TO GROUND FOG DEVELOPMENT AROUND LAKES/STREAMS AND LOW-LYING AREAS (THE LAST FEW NIGHTS HAVE HAD SIMILAR OCCURRENCES). IT`S GETTING TO BE THAT TIME OF YEAR (LATE SUMMER/EARLY FALL) WHERE GROUND FOG OFTEN FORMS AROUND WARM BODIES OF WATER ON QUIET/CHILLY NIGHTS. EWD EXTENT OF UPPER RIDGE WILL SETTLE S INTO THE UPPER LAKES FRI. AT THE SFC...ASSOCIATED HIGH PRES WILL DRIFT VERY SLOWLY S FRI WITH CORE OF DRY AIRMASS OVER THE FCST AREA DURING THE AFTN (PRECIPITABLE WATER FALLS TO AROUND 0.5 INCHES OVER MUCH OF THE AREA). SUNNY SKIES WILL DOMINATE FOR THE MOST PART WITH ANY CU INLAND FROM LAKE SUPERIOR LIMITED TO FEW/SCT COVERAGE. EXPECT DEEP MIXING TO AROUND 750MB UNDER THE DRY AIRMASS. COMPARED TO TODAY...FCST SOUNDINGS SUGGEST MAX TEMPS FRI WILL BE A COUPLE OF DEGREES HIGHER AND DWPTS A COUPLE OF DEGRESS LWR IN MOST PLACES. RH`S COULD FALL TO AROUND 25PCT WELL INLAND FROM LAKE SUPERIOR. FORTUNATELY FOR FIRE WEATHER CONCERNS...WINDS WILL BE RELATIVELY LIGHT WITH HIGH PRES IN THE VCNTY. FRI NIGHT THRU THE WEEKEND...PATTERN WILL FEATURE A BROAD MID/UPPER RIDGE OVER THE W HALF OF THE CONUS/WRN CANADA AND A LOW AMPLITUDE TROF OVER SE CANADA/NEW ENGLAND. WITH THE RESULTING NW FLOW ALOFT INTO THE UPPER LAKES...WOULD TYPICALLY NEED TO CONSIDER CONVECTION. HOWEVER...MAIN UPPER JET IS DISPLACED FAR TO THE N AND NE OF THE FCST AREA (HUDSON BAY VCNTY). SO THIS LOOKS LIKE A TRANQUIL NW FLOW REGIME. THERE WILL BE A SHORTWAVE TRACKING SE THRU FAR NRN ONTARIO TO QUEBEC FRI NIGHT/SAT...BUT THAT WILL BE TOO FAR N TO REQUIRE ANY POPS HERE. WAA REGIME WILL PROBABLY RESULT IN SOME CLOUD COVER THOUGH. DRY WEATHER WILL CONTINUE RIGHT THRU SUN. MAX TEMPS OVER THE WEEKEND SHOULD BE IN THE 80S IN MOST AREAS WITH SUN THE WARMEST DAY (MID 80S COMMON WITH SOME UPPER 80S POSSIBLE IN A FEW SPOTS) AS 850MB THERMAL RIDGE SETTLES OVER THE AREA AHEAD OF COLD FRONT DROPPING S TOWARD THE UPPER LAKES. THERE SHOULD BE ENOUGH HEIGHT FALLS HEADING THRU SE CANADA TO SEND THAT FRONT INTO THE UPPER LAKES MON...PROVIDING THE POSSIBILITY OF A FEW SHRA/TSRA AT THAT TIME. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT PATCHY FOG AND LOW CIGS WITH CONDITIONS GOING TO VLIFR/LIFR THIS MORNING AT BOTH SITES DUE TO MOISTURE AND GOOD RADIATIONAL COOLING. EAST WIND AND WEAK UPSLOPE AT KCMX ALREADY RESULTING IN LIGHT FOG THERE. ALSO RECEIVED REPORT EARLIER FROM CO-WORKER COMING BACK FROM THE U.P. STATE FAIR THAT THERE WAS SOME RADIATIONAL FOG NEAR KSAW. CONDITIONS SHOULD RETURN TO VFR 12Z-14Z TODAY DUE TO INCREASED LOW LEVEL MIXING. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SFC HIGH PRESSURE OVER NORTHWEST ONTARIO SETTLES ACROSS THE GREAT LAKES INTO FRIDAY. EXPECT NORTHEAST WINDS TO 20 KNOTS TODAY OVER FAR WESTERN LAKE SUPERIOR DUE TO CHANNELING BETWEEN MINNESOTA SHORELINE AND APOSTLE ISLANDS. THE HIGH PRESSURE RIDGE MOVES SOUTH OF THE AREA SATURDAY AND SUNDAY. STRONGER WINDS...UP TO 25 KNOTS...SEEM POSSIBLE ON SATURDAY IN TIGHTER PRESSURE GRADIENT ON THE NORTH SIDE OF THE RIDGE. OTHERWISE...WINDS WILL REMAIN 20 KNOTS OR LESS THROUGH NEXT MONDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/DISCUSSION...ROLFSON AVIATION...JLA MARINE...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 103 AM EDT THU AUG 14 2008 .AVIATION... DESPITE FAIRLY DECENT LOW LEVEL MOISTURE...PERIODIC MID/HIGH LEVEL CLOUDINESS THIS MORNING WILL BE A LIMITING FACTOR FOR DENSE FOG DEVELOPMENT. RECENT SATELLITE TRENDS HOWEVER SUGGEST ENOUGH BREAKS IN THE CLOUDS TO WARRANT A TEMPO GROUP THIS MORNING FOR MVFR VSBY IN FOG. THIS IS MORE LIKELY AT MBS AND FNT WHERE CURRENT TEMP/DEWPOINT SPREADS ARE LOWER. A MID LEVEL SHORT WAVE WILL DROP INTO THE GREAT LAKES REGION FROM CANADA THIS AFTERNOON. THE ASSOCIATED MID LEVEL DESTABILIZATION WILL LEAD TO A BKN VFR CU FIELD BY AFTERNOON...WITH SCATTERED SHOWERS AND TSTMS POSSIBLE BY LATE AFTN/EARLY EVENING. && .PREV DISCUSSION...ISSUED 1005 PM EDT WED AUG 13 2008 UPDATE... FOR THE MOST PART SHOWERS HAVE DIMINISHED ACROSS THE FORECAST AREA. PLAN TO ISSUE AN UPDATE TO REMOVE PRECIP WORDING FROM THE REST OF THIS EVENINGS FORECAST BASED ON RADAR TRENDS. THE LOW LEVEL MOISTURE PROFILE ON THE 00Z DTX SOUNDING AND THE CURRENT UPPER 50 SFC DEWPOINTS SUGGEST A MENTION OF PATCHY FOG OVERNIGHT IS STILL JUSTIFIED. AREAS OF MID AND HIGH CLOUDS UPSTREAM HOWEVER WILL LIMIT THE DEGREE OF RADIATIONAL COOLING OVERNIGHT. SO DO NOT ANTICIPATE COVERAGE OF FOG TO BE ANYTHING MORE THAN PATCHY. PREV DISCUSSION...ISSUED 405 PM EDT WED AUG 13 2008 SHORT TERM...THIS AFTERNOON AND EVENING THUNDERSTORM BEHAVIOR THIS AFTERNOON SUPPORTS THE NOTION OF A MARGINAL INSTABILITY/WEAK SHEAR ENVIRONMENT. SURFACE BASED CAPES IN THE LATEST RUC ANALYSIS/BUFKIT SOUNDINGS ARE LESS THAN 1000 J/KG UNDER EXTREMELY MEAGER ENVIRONMENTAL LAPSE RATES (ABOVE 500MB). A COMPOSITE LAKE/CONVECTIVE THERMAL GRADIENT HAS ESTABLISHED FROM ROUGHLY PORT HURON TO BAY CITY. MODELS INDICATE A PUSH OF THE BOUNDARY SOUTHWESTWARD THROUGH THE CWA TONIGHT AS DIURNAL HEATING IS LOST AND WEAK MIDLEVEL ENERGY PUSHES IN BEHIND. WITH THE WEAKLY CAPPED ENVIRONMENT...ADDITIONAL DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG THIS FEATURE UNTIL A SURFACE INVERSION GROWS THIS EVENING. SEVERE WEATHER IS NOT ANTICIPATED THIS AFTERNOON OR EVENING...BUT A STORM OR TWO MAY BECOME STRONG ALONG ANY BOUNDARY INTERSECTIONS AND OR CELL MERGERS. GIVEN WEAK MEAN LAYER FLOW OF 5-10 KNOTS...THE MAIN THREAT WILL BE HEAVY RAINFALL UNDER SLOW MOVING/STALLED THUNDERSTORMS. HAIL TO HALF INCH AND FREQUENT LIGHTNING MAY ALSO BE EXPERIENCED. WITH AN INFILTRATING MARINE AIRMASS AND WEAK FLOW HAVE ADDED PATCHY FOG FOR AREAS OUTSIDE OF THE METRO...WITH ANY DENSE SPOTS REMAINING ISOLATED. LOWS TONIGHT WILL SETTLE INTO THE LOWER 50S NORTH TO LOWER 60S SOUTH. LONG TERM...THURSDAY THROUGH NEXT WEDNESDAY THE NEXT IN THE SERIES OF WAVES ROTATING AROUND THE LARGE EASTERN UPPER LOW IS ON SATELLITE MOVING INTO NORTHERN ONTARIO AND WILL AFFECT SE MICHIGAN ON THURSDAY. THIS WILL KEEP A CHANCE OF SHOWERS AND EVEN AN ISOLATED THUNDERSTORM POSSIBLE BY AFTERNOON. THE PROBLEM IS THAT THE SYSTEM FROM TODAY IS NOT EXPECTED TO SCOUR OUT ENOUGH MOISTURE BELOW 850 MB TO REDUCE THE EFFECTIVENESS OF SUPPORT FROM THE WAVE. DEEP CYCLONIC FLOW, AND THE ASSOCIATED DYNAMIC FORCING, WILL BE ACCOMPANIED BY TEMPERATURES DROPPING TO BETWEEN -14C AND -17C. THIS WILL COMBINE WITH A SURFACE PARCEL IN THE UPPER 70S/UPPER 50S TO PRODUCE POCKETS OF CAPE AROUND 1000 J/KG. THE 12Z MODELS ARE NOT GREATLY IMPRESSED WITH THE AMOUNT OF SURFACE PRESSURE REFLECTION BUT A PATTERN SIMILAR TO TODAY SEEMS LIKE A REASONABLE EXPECTATION, WHICH INCLUDES LAKE BOUNDARY CONTRIBUTIONS AS WELL AS WEAK SYNOPTIC CONTRIBUTIONS. THIS WAVE WILL DO A BETTER JOB OF SCOURING OUT THE MOISTURE IN THE LOW LEVELS BUT THERE WILL BE SOME LINGERING INFLUENCE OF THE SYSTEM DURING FRIDAY. CYCLONIC FLOW IN THE MID AND UPPER LEVELS, AND LINGERING COLD POOL ALOFT, WILL PROVIDE FOR AN ISOLATED SHOWER. THE LARGER STORY WILL BE YET ANOTHER SURGE OF COOL AIR ATTEMPTING TO TAKE 850 MB TEMPERATURES DOWN INTO THE SINGLE DIGITS AND LIMITING HIGH TEMPERATURES TO THE 70S. THE 12Z MODEL RUNS THEN LOOK REASONABLE IN MAINTAINING DRY CONDITIONS OVER SE MICHIGAN ON SATURDAY. THIS WILL BE ACCOMPLISHED BY DRY NW FLOW ALOFT COMBINED WITH SURFACE HIGH PRESSURE CENTERED TO OUR SOUTH. WESTERLY FLOW ON SUNDAY WILL REPRESENT A WARM ADVECTION PATTERN AHEAD OF A WAVE IN CENTRAL CANADA. THIS IS PART OF A TREND IN THE GLOBAL MODEL SOLUTIONS TOWARD A MORE ACTIVE NW UPPER LEVEL FLOW. THIS TREND LOOKS GOOD AFTER CONSIDERING THE FLOW WILL BE FORCED BY RELIABLE DEPICTIONS OF THE HIGHLY AMPLIFIED LONG WAVE PATTERN THROUGHOUT THE WESTERN HEMISPHERE. CONFIDENCE IS ON THE HIGH SIDE THAT THIS LARGE SCALE PATTERN WILL KEEP A LONG WAVE RIDGE ANCHORED OVER WESTERN NORTH AMERICA AND GUIDE THE WESTERLIES FROM CENTRAL CANADA INTO THE NORTHERN GREAT LAKES WHILE THE CUT OFF LOW LUMBERS AROUND OVER THE SOUTHERN PLAINS STATES. WE EXPECT THE WARM ADVECTION PATTERN OVER THE GREAT LAKES WILL BE TOO DRY FOR PRECIPITATION BUT SOME CLOUDS AND NORMAL TO SLIGHTLY ABOVE NORMAL TEMPERATURES LOOK LIKE A GOOD BET. GIVEN THAT A STRONGER NW FLOW ALOFT IS EXPECTED OVER THE GREAT LAKES, A REASONABLE SCENARIO FOR EARLY NEXT WEEK INCLUDES A COLD FRONT SETTLING INTO LOWER MICHIGAN DURING THE MONDAY AND TUESDAY PERIOD. AT THE SAME TIME, THE GLOBAL MODELS DRAW SOME MOISTURE INTO THE FRONTAL ZONE FROM THE CUT OFF LOW THAT IS STILL DRIFTING IN THE PLAINS. PREDICTABILITY IS RATHER LOW IN THIS ASPECT OF THE FORECAST CONSIDERING HOW MUCH VARIABILITY WILL BE INVOLVED IN THE POSITION OF THE LOW AND THE ASSOCIATED DEFORMATION AXIS. ONCE THE FRONT MOVES THROUGH, TUESDAY AND WEDNESDAY COULD END UP DRY AS THE UPPER LOW DRIFTS WESTWARD AND AWAITS THE NEXT PACIFIC COAST TROUGH BEFORE LIFTING BACK INTO THE WESTERLY FLOW. EITHER WAY, COOLER TEMPERATURES DO APPEAR TO BE A MORE SOLID PART OF THE FORECAST DURING THE MID WEEK PERIOD AS HIGH PRESSURE SETTLES INTO QUEBEC. MARINE... NORTHEAST WINDS WILL BECOME ESTABLISHED OVER THE REGION TONIGHT AS LOW PRESSURE MOVES TO OUR SOUTH AND HIGH PRESSURE MOVES INTO NORTHERN ONTARIO. WIND SPEED WILL BE MODEST BUT THE LONG NE FETCH OF WIND DIRECTION WILL KEEP WAVES ON THE HIGH SIDE ON THE BAY AND LAKE HURON WATERS BUT A SMALL CRAFT ADVISORY IS NOT PLANNED AT THIS TIME. THE NE WINDS WILL LAST THROUGH THURSDAY AND DRIVE THE CHANCE OF THUNDERSTORMS MORE OVER INLAND AREAS DURING THE AFTERNOON. THE WILL BE FOLLOWED BY A SLOW BACKING OF THE WIND TOWARD THE SW BY SATURDAY. FAVORABLE WIND AND WAVE CONDITIONS ARE THEN EXPECTED FOR THE WEEKEND. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....KURIMSKI UPDATE.......SC SHORT TERM...CB LONG TERM....BT MARINE.......BT YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE). mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 845 AM PDT THU AUG 14 2008 .SYNOPSIS...THE AIR MASS IS MOIST AND UNSTABLE ENOUGH FOR A CHANCE OF THUNDERSTORMS ACROSS ALL OF SOUTHWEST CALIFORNIA THROUGH THIS EVENING. HOWEVER ON FRIDAY AND SATURDAY...THE THUNDERSTORMS SHOULD BE CONFINED TO THE MOUNTAIN AND DESERT AREAS. HIGH PRESSURE REBUILDING OVER THE AREA SUNDAY THROUGH TUESDAY WILL BRING A DRYING TREND AND A MORE STABLE AIR MASS. THE MARINE LAYER AND ONSHORE FLOW WILL BRING AREAS OF CLOUDS AND FOG DURING THE NIGHTS AND MORNINGS TO THE COASTS AND LOWER WESTERN VALLEYS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .NEAR TERM...TODAY AND TONIGHT... THE MORNING SOUNDING FROM KNKX SHOWS THE AIR MASS IS MORE UNSTABLE AND WETTER...AND A MAJOR CHANGE FROM YESTERDAY IS THE ABSENCE OF SUPPRESSING CONVECTIVE DEBRIS CLOUDS OVER THE AREA. THE LEADING EDGE OF THE NEXT SURGE OF MONSOON MOISTURE IS ADVANCING ACROSS EASTERN RIVERSIDE COUNTY...IMPERIAL COUNTY...AND NORTHEAST BAJA CALIFORNIA THIS MORNING AND IS PROGGED TO MOVE ACROSS SOUTHWEST CALIFORNIA MID DAY THROUGH TONIGHT. USING BOTH THE LATEST RUC13 MODEL AND THE NAM12 MODEL TO DETERMINE THE MOST FAVORED AREAS OF CONVECTION DURING THIS PERIOD...THE STRONGEST SURFACE CONVERGENCE/300-200 MB DIVERGENCE COUPLET AND 850-500MB UPWARD VERTICAL VELOCITY FOR THIS MORNING IS OVER SE SAN DIEGO COUNTY. BY LATE MORNING THIS SHIFTS NORTHWARD TO THE SW SAN BERNARDINO COUNTY...ROUGHLY BETWEEN THE 10000 FOOT RIDGE AND JOHNSON VALLEY. FOR THE EARLY AND MID AFTERNOON HOURS ITS OVER ALL MOUNTAINS AND DESERT AREAS...AND FOR THE LATE AFTERNON AND EVENING HOURS...OVER THE EAST SIDE OF THE ANZA BORREGO DESERT AND SOUTHERN END OF THE COACHELLA VALLEY. OVER THE COASTS AND INLAND VALLEY AREAS AS WELL AS THE COASTAL WATERS...THROUGHOUT THE DAY THE MODELS SHOW WEAK DOWNWARD VERTICAL VELOCITY IN THE MID LEVELS BUT THIS MAY BE OVER DONE DUE TO THE MODEL TERRAIN AND THE SOUTHEAST FLOW ACROSS THE MOUNTAINS. THERE IS ALSO WEAK UPPER LEVEL DIVERGENCE OVER THESE AREAS THAT WOULD OFFSET THE DOWNWARD MOTION...SO THE AIR MASS WILL BE CONDITIONALLY UNSTABLE AND RECEPTIVE TO THUNDERSTORMS THAT FORM OVER THE MOUNTAINS AND ARE CARRIED WEST TO NORTHWEST ACROSS THE INLAND VALLEYS/COASTS...PLUS THE MID LEVEL VERTICAL VELOCITY BECOMES UPWARD OVER THE COASTS AND VALLEYS THIS EVENING. DID SOME MODIFICATION TO THE POPS/WX/SKY AND QPF GRIDS TO REFLECT ALL OF THIS. .REMAINDER OF SHORT TERM...FRIDAY THROUGH SATURDAY... AIR MASS REMAINS MOIST AND CONDITIONALLY UNSTABLE. HOWEVER THE 850-700 MB LAYER STREAMLINES ARE ADVERTISED TO BE FROM THE SOUTH ON FRIDAY AND TO THE SOUTHWEST ON SATURDAY. FOR FRIDAY THIS SHOULD CONFINE THE THUNDERSTORMS TO THE MOUNTAINS AND DESERTS. THEY ARE LIKELY TO BE JUST AS OR MORE NUMEROUS THAN TODAY AND HAVE LITTLE MOVEMENT. THIS RAISES THE THREAT OF FLASH FLOODING AND MAY ISSUE A A FLASH FLOOD WATCH FOR THESE AREAS FOR FRIDAY...HOWEVER WILL MAKE THAT DECISION AROUND NOON AFTER REVIEWING GFS MODEL AND COORDINATING WITH NEIGHBORING OFFICES. ON SATURDAY THUNDERSTORMS SHOULD BE LESS NUMEROUS AND END EARLIER...AS WELL AS DRIFT OFF TO THE NORTHWEST. THERE MAY STILL BE A THREAT OF FLASH FLOODING FOR THE DESERT AREAS. .LONG TERM...SUNDAY THROUGH WEDNESDAY... FROM PREVIOUS DISCUSSION...AN UPPER LEVEL TROUGH APPROACHING FROM THE NW WILL BRING A GRADUAL COOLING TEND WITH A DEEPENING MARINE LAYER WITH WEAK...DRY...WESTERLY FLOW ALOFT....HENCE NO MENTION OF THUNDERSTORMS AFTER SATURDAY EVENING. && .AVIATION... 141500Z...12Z NKX SOUNDING SHOWS MARINE LAYER DEPTH AROUND 1200 FT ASL. STRATUS HAS ALREADY CLEARED AT THE COASTAL AIRPORTS BUT SHOULD REMAIN OVER THE OCEAN TODAY. A BAND OF THUNDERSTORMS IS CURRENTLY MOVING WEST INTO EASTERN IMPERIAL AND RIVERSIDE COUNTIES. THESE STORMS ARE EXPECTED TO CONTINUE TO MOVE WEST AND MAY MAKE IT INTO THE SAN DIEGO COUNTY DESERTS LATER THIS MORNING. BASES SHOULD BE AROUND 8-10K FT WITH TOPS NEAR 40K FT. THERE IS A CHANCE OF THUNDERSTORMS DEVELOPING OVER THE MOUNTAINS AND DESERTS...MAINLY AFTER 18Z. THESE STORMS MAY DRIFT INTO THE VALLEY AND COASTAL AREAS AND CAN CAUSE LOCALLY HEAVY RAIN...HAIL AND STRONG GUSTY WINDS. MID LEVEL CLOUDS NEAR 15K FT WILL ALSO MOVE OVER THE AREA LATER THIS MORNING. MARINE LAYER WILL RETURN TO THE COASTAL AND WRN VALLEY AREAS TONIGHT. EXPECT STRATUS TO REACH THE COASTAL AIRPORTS BETWEEN 08 AND 10Z. BASES WILL BE NEAR 1200 FT ASL. LOCAL VISIBILITIES 3-5SM IN HAZE NEAR SUNRISE. SS/MM && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE AT THIS TIME. PZ...NONE. && $$ PUBLIC...BALFOUR AVIATION/MARINE...SULLIVAN/MM WARNING/NOWCASTS...PG NWS ON THE WEB AT WEATHER.GOV/SANDIEGO ca AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 735 AM EDT THU AUG 14 2008 UPDATED AVIATION DISCUSSION FOR 12Z TAFS .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW LITTLE CHANGE HAS OCCURRED IN THE PATTERN OVER THE LAST 24 HRS. A MIDLEVEL LOW WAS OVER SE SASKATCHEWAN...A MIDLEVEL HIGH WAS OVER NRN MANITOBA...AND A TROF/BROAD MIDLEVEL LOW WAS OVER SE CANADA. THE LOW OVER SE CANADA HAS EXPANDED W A BIT...AND UPPER MI IS NOW UNDER NRLY FLOW ON ITS WRN FRINGE. AROUND THE LOW...A SHORTWAVE WAS ROTATING THRU ERN ONTARIO TOWARD THE UPPER GREAT LAKES. ALTHOUGH SHORTWAVE IS NOT PRODUCING MUCH IN THE WAY OF CLOUD COVER...RADARS IN ONTARIO DO SHOW A FEW -SHRA. ACROSS UPPER MI...WITH THE EXCEPTION OF SOME CLOUDS OVER THE SW THIRD...SKIES ARE CLEAR. && .DISCUSSION (415 AM EDT)... SHORTWAVE ROTATING THRU ERN ONTARIO WILL SWING ACROSS UPPER MI THIS MORNING. HEIGHTS FALL SLIGHTLY OVER THE ERN FCST AREA THRU MID MORNING...AND CORE OF THE 5H COLD POOL BRUSHES THAT AREA...BUT THAT PROBABLY WON`T BE ENOUGH TO GET ANY -SHRA INTO THE ERN FCST AREA. STILL...WILL NEED TO MONITOR RADAR TRENDS DURING THE MORNING TO SEE IF THE ISOLD -SHRA CURRENTLY HEADING SSW TOWARD FAR ERN LAKE SUPERIOR MIGHT CLIP LUCE COUNTY. OTHERWISE...SHORTWAVE PASSAGE WILL BE DRY ACROSS THE FCST AREA SINCE SHORTWAVE WILL BE S OF THE AREA WELL BEFORE PEAK OF THE HEATING CYCLE. STABILIZING N TO NE FLOW OFF LAKE SUPERIOR TO BEGIN THE DAY SUGGESTS LITTLE OR NO CLOUD COVER NEAR THE LAKE TODAY. DIURNAL CU INLAND SHOULD TEND TO DISSIPATE DURING THE AFTN FROM N TO S AS DRIER AIR ARRIVES IN THE WAKE OF SHORTWAVE AND STABILIZING FLOW OFF LAKE SUPERIOR SPREADS WELL INLAND. MIXING TO AROUND 800MB ON FCST SOUNDINGS SUPPORTS MOS GUIDANCE MAX TEMPS IN THE MID/UPPER 70S AWAY FROM LAKE SUPERIOR MODIFICATION. ALONG THE LAKE SUPERIOR SHORE...TEMPS SHOULD TOP OUT IN THE UPPER 60S/AROUND 70F. PROVIDED DEEP MIXING OCCURS...DWPTS WELL AWAY FROM LAKE SUPERIOR SHOULD DROP INTO THE MID 40S PER FCST SOUNDINGS. THIS WILL SEND RH DOWN TO 30-35PCT. CENTER OF SFC HIGH PRES ASSOCIATED WITH UPPER RIDGE EXTENDING FROM SW CANADA TO HUDSON BAY WILL SETTLE S TO NE MN/FAR NW WI BY THU MORNING...SO WRN FCST AREA WILL BE COOLEST TONIGHT. RADIATIONAL COOLING UNDER CLEAR SKIES WILL BE ENHANCED BY DRY AIRMASS WITH PRECIPITABLE WATER AROUND 0.5 INCHES OR AROUND 60PCT OF NORMAL FOR THIS TIME OF YEAR. WILL GO JUST BLO COOLEST MOS GUIDANCE OVER THE INTERIOR W (LOW/MID 40S). FARTHER TO THE E OF THE HIGH...WINDS SHOULD CONTINUE TO STIR A LITTLE OVER THE ERN FCST AREA...AND THERE MAY BE A SOME MIDLEVEL CLOUDS WRAPPING S AROUND THE SE CANADA LOW THRU ERN UPPER MI. WILL STAY CLOSE TO MOS GUIDANCE THERE (UPPER 50S ALONG LAKE SUPERIOR...LOW/MID 50S INLAND). WILL ADD PATCHY FOG OVER THE INTERIOR W HALF WHERE LIGHT/CALM WINDS AND CHILLY AIR OVERNIGHT WILL BE CONDUCIVE TO GROUND FOG DEVELOPMENT AROUND LAKES/STREAMS AND LOW-LYING AREAS (THE LAST FEW NIGHTS HAVE HAD SIMILAR OCCURRENCES). IT`S GETTING TO BE THAT TIME OF YEAR (LATE SUMMER/EARLY FALL) WHERE GROUND FOG OFTEN FORMS AROUND WARM BODIES OF WATER ON QUIET/CHILLY NIGHTS. EWD EXTENT OF UPPER RIDGE WILL SETTLE S INTO THE UPPER LAKES FRI. AT THE SFC...ASSOCIATED HIGH PRES WILL DRIFT VERY SLOWLY S FRI WITH CORE OF DRY AIRMASS OVER THE FCST AREA DURING THE AFTN (PRECIPITABLE WATER FALLS TO AROUND 0.5 INCHES OVER MUCH OF THE AREA). SUNNY SKIES WILL DOMINATE FOR THE MOST PART WITH ANY CU INLAND FROM LAKE SUPERIOR LIMITED TO FEW/SCT COVERAGE. EXPECT DEEP MIXING TO AROUND 750MB UNDER THE DRY AIRMASS. COMPARED TO TODAY...FCST SOUNDINGS SUGGEST MAX TEMPS FRI WILL BE A COUPLE OF DEGREES HIGHER AND DWPTS A COUPLE OF DEGRESS LWR IN MOST PLACES. RH`S COULD FALL TO AROUND 25PCT WELL INLAND FROM LAKE SUPERIOR. FORTUNATELY FOR FIRE WEATHER CONCERNS...WINDS WILL BE RELATIVELY LIGHT WITH HIGH PRES IN THE VCNTY. FRI NIGHT THRU THE WEEKEND...PATTERN WILL FEATURE A BROAD MID/UPPER RIDGE OVER THE W HALF OF THE CONUS/WRN CANADA AND A LOW AMPLITUDE TROF OVER SE CANADA/NEW ENGLAND. WITH THE RESULTING NW FLOW ALOFT INTO THE UPPER LAKES...WOULD TYPICALLY NEED TO CONSIDER CONVECTION. HOWEVER...MAIN UPPER JET IS DISPLACED FAR TO THE N AND NE OF THE FCST AREA (HUDSON BAY VCNTY). SO THIS LOOKS LIKE A TRANQUIL NW FLOW REGIME. THERE WILL BE A SHORTWAVE TRACKING SE THRU FAR NRN ONTARIO TO QUEBEC FRI NIGHT/SAT...BUT THAT WILL BE TOO FAR N TO REQUIRE ANY POPS HERE. WAA REGIME WILL PROBABLY RESULT IN SOME CLOUD COVER THOUGH. DRY WEATHER WILL CONTINUE RIGHT THRU SUN. MAX TEMPS OVER THE WEEKEND SHOULD BE IN THE 80S IN MOST AREAS WITH SUN THE WARMEST DAY (MID 80S COMMON WITH SOME UPPER 80S POSSIBLE IN A FEW SPOTS) AS 850MB THERMAL RIDGE SETTLES OVER THE AREA AHEAD OF COLD FRONT DROPPING S TOWARD THE UPPER LAKES. THERE SHOULD BE ENOUGH HEIGHT FALLS HEADING THRU SE CANADA TO SEND THAT FRONT INTO THE UPPER LAKES MON...PROVIDING THE POSSIBILITY OF A FEW SHRA/TSRA AT THAT TIME. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... HIGH PRESSURE OVER ONTARIO BUILDS IN FOR NEXT 24 HOURS WITH VFR CIGS/VSBY EXPECTED. FOG POSSIBLE TONIGHT DUE TO LIGHT WINDS AND RADIATIONAL COOLING. DECIDED TO LEAVE ANY MENTION OUT THOUGH SINCE FOG LAST TWO NIGHTS AT ANY GIVEN SITE HAS BEEN HIGHLY VARIABLE BOTH IN SPACE AND IN TIME. BEST CHANCE FOR THE FOG WOULD BE AFTER 06Z. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SFC HIGH PRESSURE OVER NORTHWEST ONTARIO SETTLES ACROSS THE GREAT LAKES INTO FRIDAY. EXPECT NORTHEAST WINDS TO 20 KNOTS TODAY OVER FAR WESTERN LAKE SUPERIOR DUE TO CHANNELING BETWEEN MINNESOTA SHORELINE AND APOSTLE ISLANDS. THE HIGH PRESSURE RIDGE MOVES SOUTH OF THE AREA SATURDAY AND SUNDAY. STRONGER WINDS...UP TO 25 KNOTS...SEEM POSSIBLE ON SATURDAY IN TIGHTER PRESSURE GRADIENT ON THE NORTH SIDE OF THE RIDGE. OTHERWISE...WINDS WILL REMAIN 20 KNOTS OR LESS THROUGH NEXT MONDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/DISCUSSION...ROLFSON AVIATION...JLA MARINE...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 642 AM CDT THU AUG 14 2008 .UPDATE... ADDED AVIATION DISCUSSION FOR 12Z TAFS BELOW... && .DISCUSSION... LCL AREAS OF REDUCED VSBY IN FOG WITH AREAS OF MID CLOUDS KEEPING MORE WIDESPREAD FOG AT BAY. FEW -SHRA AND ISOL TSTMS ROAMING THE E DKTS SHOULD WORK INTO WC MN ERLY THIS MORNING AS WEAK UPPER TROF SLOWLY MOVES ACRS DKTS. WEAK UPPER TROF ROTATING AROUND UPPER LOW OVER E CANADA WILL LEND SOME SUPPORT TO A FEW AFTERNOON THUNDERSTORMS OVER EASTERN AREAS. VERY WEAK SURFACE PATTERN IN PLACE MAKES IT DIFFICULT TO DETERMINE MOST LIKELY AREAS OF CONVECTION. MODELS SHOWING AREAS OF 500-1000 J/KG SBCAPE DURING THE AFTERNOON WITH FAIRLY COOL MID LEVEL TEMPERATURES PROVIDING FAIRLY UNSTABLE LAPSE RATES. 0-6KM SHEAR WEAK...GENERALLY LESS THAN 20 KTS. MAX TEMPERATURES THIS AFTERNOON SLIGHTLY COOLER THAN YESTERDAY WITH DEVELOPING NELY FLOW BRINGING IN SLIGHT COOLER AIRMASS. DRIER CANADIAN HIGH PRESSURE BUILDS SOUTH INTO AREA TONIGHT AND FRIDAY BRINGING LOWER DEWPOINTS AND AN END TO CONVECTION. MIN TEMPERATURES THE NEXT COUPLE OF MORNINGS WILL BE A BIT ON THE CHILLY SIDE...ESPECIALLY IN CENTRAL MN AND WI. THE WEEKEND IS SHAPING UP TO BE A NICE ONE WITH HIGH PRESSURE AT THE SURFACE AND WEAK NWLY FLOW ALOFT. UPPER LOW DROPPING INTO THE PLAINS OVER THE WEEKEND MAY BEGIN TO BECOME A PLAYER AGAIN WITH SHOWER CHANCES EARLY TO MID WEEK. .AVIATION.../12Z TAF ISSUANCE/ MAIN FORECAST CONCERNS ARE FOG THROUGH MID MORNING AND THEN SHRA/TSRA DEVELOPMENT AND COVERAGE THIS THROUGH LATE AFTERNOON. WEAK PRESSURE PATTERN CONTINUES TO PROVIDE LIGHT SFC WINDS TO THE AREA THIS MORNING AND. LOWEST VISIBILITY IS ACROSS MUCH OF SOUTHERN MINNESOTA WITH SOME SITES SEEING LESS THAN 1/4SM. A SERIES OF UPPER LEVEL WAVES CONTINUE TO BRING MID LEVEL CLOUDS ALONG THE MN/WI BORDER AND INTO WEST CENT WI WITH VIS ON THE FRINGE OF THIS DECK DROPPING TO A MILE OR LESS. SPOTTY SHOWERS ARE OCCURRING UNDER THE CLOUD DECK. VIS WILL START IMPROVING BETWEEN NOW AND 14Z. BIG UPPER TROUGH IS DROPPING INTO THE WESTERN DAKOTAS FROM CANADA THIS MORNING AND IS SENDING WARM AIR ALOFT INTO THE EASTERN DAKOTAS ALONG WITH SEVERAL SHORTWAVES. SHOWERS ASSOCIATED WITH THESE AREAS OF FORCING ARE HAVING A TOUGH TIME MAKING IT PAST THE DAKS/MN BORDER AND IT APPEARS THAT THIS TREND WILL CONTINUE AT LEAST THROUGH THE MORNING. OF MORE CONCERN IS A SECOND SHORTWAVE DIVING SOUTHWARD ALONG THE MN/WI BORDER BY EARLY AFTERNOON. SHORT TERM RUC MODEL INDICATES THAT THIS WAVE WILL TRACK FURTHER WEST THAN THE CURRENT WAVE SUGGESTING THAT SCT SHRA/ISOLD TSRA WILL BE FURTHER WEST AND MOVE ACROSS EAST CENT MN AND WEST CENT WI. HAVE INCLUDED VCSH AND A CB AT KMSP/KSTC/KRNH FOR EARLY/MID AFTERNOON TO ACCOUNT FOR THE POTENTIAL BUT POTENTIAL AND EXPECTED COVERAGE IS LOWER THAN YESTERDAY. WILL STICK WITH PRECIP MENTION KRWF AS WELL AS A WEAK SFC BOUNDARY WILL BE IN THAT AREA ONCE AGAIN. KRNH MAY SEE A PROLONGED PERIOD OF SCATTERED SHOWERS THROUGH THE MORNING AS THE FIRST SHORTWAVE EXITS AND THE NEXT APPROACHES. DRY AIR RAPIDLY PUSHES IN FROM THE NORTHEAST TONIGHT BRINGING AN END TO THE PRECIP BUT ALSO ANOTHER POSSIBLE ROUND OF FOG. FRIDAY WILL BE VFR ONCE ANY MORNING VIS RESTRICTIONS CLEAR. ..MDB.. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ BAP/MDB mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAND FORKS ND 1046 AM CDT THU AUG 14 2008 .UPDATE... FOCUS THIS AFTN IS ALONG INVERTED TROUGH LOCATED JUST WEST OF THE RED RIVER. UPPER LOW OVER ERN MT WILL NOT HAVE TOO MUCH IMPACT ON OUR WX AS CLOUDS AND SHOWERS WITH IT REMAIN OVER ERN MT AND FAR WRN ND. HOWEVER...SFC LOW IN ECNTRL SD SOUTH OF ABERDEEN IS ASSOC WITH UPR LOW AND HAS INVERTED TROUGH JUST WEST OF FARGO-GRAND FORKS-HALLOCK LATE THIS MORNING. WITH UPPER LOW DROPPING SOUTH EXPECT LITTLE CHANGE TO TROUGH POSITION. LOW TO MID 60 DEW PTS ALONG THE BOUNDARY LATE THIS MORNING WILL REMAIN IN PLACE THIS AFTN WITH LOCAL AREAS NR 70 AS FULLY MATURE CROPS AND WET GROUND IN MANY AREAS ADD TO WATER TO THE LOWER ATMOSPHERE. THESE DEW PTS CAPTURED BEST BY 12Z RUC WHILE 12Z NAM IS WAY LOW WITH ITS 50S. 06Z GFS SEEMS A BIT BETTER BUT A TAD LOW STILL. NET EFFECT WILL BE TO HAVE HIGHER CAPES PER 12Z RUC OVER THE VALLEY THIS AFTN THAN EARLIER THOUGHT WITH 12Z RUC SHOWING 2000-2500 J/KG CAPES BY 00Z IN THE VALLEY PROPER. WITH POSITION OF INVERTED TROUGH AND HIGHEST CAPES IN THE VALLEY AREA WILL UP POPS A BIT AND HIGHLIGHT HVY RAIN THREAT. DVL REGION LOOKS TO BE ON THE DRIER SIDE OF THE TROUGH AND NOT AS MUCH AFFECTED SO REMOVED HVY RAIN THREAT. SOME DRIER AIR TOO FEEDING FROM ONTARIO HIGH INTO BDE-BJI AREAS THIS AFTN SO THREAT FOR CONVECTION AND HVY RAIN THERE TOO IS WEAKER. NO CHANGES TO HIGH TEMPS MADE AS MID 70S OR LOWER 80S REASONABLE. && .AVIATION... IFR CIGS AT BJI IMPROVED TO MVFR AT 1530Z AND LOOK FOR SLOW IMPROVEMENT THRU 17Z AS AREA OF LOW CLDS FROM ROSEAU TO BJI NARROWS AND GRADUALLY BREAKS UP. OTHERWISE VFR TODAY WITH BEST THREAT FOR CONVECTION MIDDAY THRU LATE AFTN NEAR GFK/FAR SITES. LEAST THREAT ATTM SEEMS TO BE FOR DVL REGION WHERE WINDS WILL BE NORTHERLY AND AIRMASS A BIT DRIER. && .PREV DISCUSSION... /ISSUED 314 AM CDT THU AUG 14 2008/ DISCUSSION... THE MAIN CHALLENGE FOR THIS PACKAGE WILL BE CONVECTIVE CHANCES EARLY...THEN TEMPS. MODELS CONTINUE IN REASONABLE AGREEMENT...WITH A SLIGHT TREND TO THE WEST WITH THE UPPER LOW DROPPING SOUTH FROM CANADA. THE MAV GUIDANCE HAS A BETTER HANDLE ON MOS TEMPS...WITH THE NAM MODEL HANDLING INSTABILITY FIELDS A BIT BETTER. THEREFORE A MODEL BLEND IS PREFERRED THIS MORNING. FOR TODAY...SOME PATCHY MORNING FOG WILL PERSIST MAINLY EAST OF THE VALLEY THROUGH 14Z. SOME AREAS COULD GET LOCALLY DENSE IF ENOUGH CLEARING OCCURS...BUT THERE ARE SOME MID CLOUDS AND FEW ISOLATED SHOWERS THAT WILL PRECLUDE A WIDESPREAD FOG THREAT. WE WILL CONTINUE TO MONITOR THIS THREAT THOUGH AND ISSUE NOWCASTS AS NEEDED. FOR THIS AFTERNOON/EVENING...A WEAK SFC TROUGH WILL BE IN PLACE ALONG AND WEST OF THE VALLEY. THE BEST MOISTURE CONVERGENCE IN THE LOWEST 2KM WILL RESIDE IN SOUTHEAST ND TO AROUND GFK...WHERE PWATS WILL APPROACH 1.25 INCHES. THERE WILL ALSO BE ABOUT 1500 J/KG OF SFC BASED CAPE...AND CONVECTIVE TEMPS AROUND 81 SHOULD BE REACHED. WITH SOME UPPER SUPPORT FROM THE WAVE TO THE WEST...EXPECT SOME STORMS WITH LOCALLY HEAVY RAIN ALONG AND WEST OF THE VALLEY. STORM MOTION IS NEAR 0...SO THIS MAY NEED TO BE WATCHED THIS AFTERNOON. THE LACK OF SUSTAINED FORCING AND ONLY ABOUT 10KT OF LLJ SHOULD PRECLUDE A WIDESPREAD FLOOD THREAT...BUT WITH WET SOILS IN MOST AREAS IT IS SOMETHING TO KEEP IN MIND. ON FRI...RIDGING AND DRYING WILL BUILD IN FROM THE NORTH. THIS WILL BRING ANY CONVECTIVE CHANCES TO AN END. TEMPS WILL BE SIMILAR TO THU HIGHS...WITH LIGHT WINDS. FOR SAT-MON...EXPECT A WARMING TREND WITH THE MERCURY CLIMBING ABOVE NORMAL. WITH UPPER RIDGING AND NO INSTABILITY...A DRY PERIOD IS EXPECTED. TUE-WED...SOME MOISTURE MAY RETURN TO OUR EASTERN AREAS ON WED...AS THE CLOSED LOW THAT IS CURRENTLY MOVING OUT OF CANADA BECOMES CAPTURED BY THE NORTHERN STREAM. PWATS ARE PROGGED TO GO OVER 1.5 INCHES IN THE EAST ON WED...ALONG WITH CAPES APPROACHING 1500 J/KG. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ DK/RIDDLE nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 1102 AM EDT THU AUG 14 2008 .SYNOPSIS... A SERIES OF UPPER LEVEL DISTURBANCES WILL MOVE AROUND A CLOSED UPPER LOW CENTERED IN EASTERN CANADA. THIS WILL BRING A CHANCE OF SHOWERS AND THUNDERSTORMS TODAY INTO TONIGHT. HIGH PRESSURE WILL BUILD INTO THE AREA FRIDAY...BRINGING MOSTLY CLEAR SKIES AND DRIER WEATHER THROUGH THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE LATEST H5 RUC ANALYSIS INDICATES A TROF OVER ERN CANADA WITH ITS AXIS EXTENDING SWWD INTO THE GREAT LAKES AND INTO IN/IL. A WEAK VORT MAX IS ALONG CENTRL IN/IL. A NWRLY FLOW ACROSS THE OHIO VALLEY REMAINS IN PLACE. AT THE SURFACE...THE REGION IS UNDER A BROAD PRESSURE GRADIENT BETWEEN A LOW OFF THE MID-ATLANTIC STATES AND HIGH PRESSURE OVER THE OZARKS. SCATTERED SHOWERS AND THUNDERSTORMS KICKED OFF BY THE SHORT WAVE OVER IN/IL ARE MOVING EWD ACROSS SERN INDIANA AND INTO OUR WRN CWA THIS MORNING. THIS AFTERNOON...SCATTERED CONVECTION IS EXPECTED ACROSS THE CWA AS THE H5 VORT MAX MOVES FROM CTNRL INDIANA AND WEAKENS AS IT MOVES INTO NE KENTUCKY. INCREASED INSTABILITY IS EXPECTED THIS AFTERNOON WITH GFS FORECAST CAPE VALUES NEAR 1500 J/KG...HOWEVER WITH WEAK SHEAR STORMS ARE EXPECTED TO REMAIN BELOW SEVERE LIMITS. ADJUSTED POP AND SKY GRIDS TO ACCOUNT FOR DEVELOPING SHOWERS AND THUNDERSTORMS TO THE WEST. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... EXPECT A DRYING TREND TONIGHT AS THE UPPER TROUGH AXIS PASSES TO THE EAST. WENT WITH A DRY FORECAST FOR FRIDAY WITH GFS AND ECMWF KEEPING PRECIP EAST OF THE ILN AREA. HIGH PRESSURE WILL THEN PROVIDE DRY WEATHER THROUGH THE REST OF THE PERIOD ACCORDING TO ALL MODEL GUIDANCE. TEMPERATURES WILL NOT CHANGE MUCH WITH HIGHS IN THE LOWER 80S AND LOWS IN THE MID TO UPPER 50S. A SLIGHT WARMING TREND MAY OCCUR ON SATURDAY IN WARM ADVECTION ASSOCIATED WITH THE HIGH. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... MODELS HAVE ARE IN DECENT AGREEMENT WITH SPREADING SPRAWLING SFC HI PRES ACRS THE NRN PLAINS AND INTO THE OH VLY FOR MUCH OF THE WEEKEND AS REGION BECOMES SANDWICHED BTWN SLOWLY DEPARTING UPR TROF OVER ERN CANADA...AND EVEN SLOWER EVOLVING UPR LO CUTOFF FROM MEAN FLOW AND SETTLING IN THE LEE OF THE CNTRL ROCKIES. MODEL SOUNDINGS INDCG FAIR AMOUNT OF SUBSIDENCE ASSOCD WITH SFC HI WHICH SHOULD TRANSLATE INTO MSTLY CLR SKIES SAT/SAT NIGHT. WITH LIGHT NE FLO...HAVE UNDERCUT MOS GUID AGAIN WITH HIGHS GENERALLY IN THE L80S. SOME DIFFERENCES THEN DVLP WRT MOVEMENT AND EFFECTS OF UPR LO OVER THE CNTRL PLAINS THRU REMAINDER OF EXTENDED. IT IS BECMG INCREASINGLY APPARENT THAT THIS FEATURE MAY IN FACT NEVER GET TO THE OH VLY...AND REMAIN IN THE CNTRL PLAINS BEFORE BECMG PICKED UP BY THE DEEPENING UPR TROF OVER THE WRN CONUS BY LATE NEXT WEEK. ECMWF CONTINUES TO INDCG REX BLOCK LIKE PATTERN DVLPG WITH UPR TROF HOLDING ACRS CANADIAN MARITIMES AND UPR LO STALLING IN THE CNTRL PLAINS. WRN ATLC UPR RIDGE GETS SQUEEZED NORTH INTO REGION BY MIDWEEK WITH TROPICAL SYSTEM MOVING INTO FLORIDA. THIS IS AN OVERALL DRIER AND LESS STORMY SOLN FOR OH VLY. OP GFS/GFS ENSEMBLE MEAN ON OTHER HAND ARE LESS DRAMATIC WITH ALL OF THESE FEATURES...NAMELY THE TROPICAL SYSTEM AND THE RIDGING DVLPG INTO OH VLY BY MIDWEEK. THIS CONSENSUS SOLN IS ALSO SUGGESTIVE OF MAINTAINING ENHANCED SRLY FLO FROM THE GULF BTWN THE UPR LO AND THE RIDGE...ALLOWING AN INCREASINGLY MOIST HUMID AIRMASS TO INVADE THE REGION DURING FIRST HALF OF THE WEEK. PREFER MORE UNSETTLED OP GFS/GFS ENSEMBLE SOLN FOR NEXT WEEK AND WILL CONTINUE TO INDCG MODEST CONVECTIVE CHANCES MON-WED. HAVE MADE SOME MINOR ADJUSTMENTS TO FOCUS BEST PCPN CHANCES ON TUES AS WARM FRONT LIFTS NORTH THRU REGION. TEMPS WILL REMAIN GENERALLY AT OR SLIGHTLY BELOW NORMAL THRU THE EXTENDED. MEX GUID CONTINUES TO BE TOO WARM WITH AFTN HIGHS. UNDERCUT GUID TEMPS THRU MUCH OF THE PERIOD...KEEPING HIGHS IN THE L80S THRU TUES...POSSIBLY REMAINING IN THE U70S MON/TUES IF MORE WIDESPREAD CONVECTION IS REALIZED. WILL ALLOW FOR WARMEST TEMPS WED AS WARM FRONT PROGGED TO BE NORTH OF REGION OVER GRT LKS. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... UPPER LEVEL LOW OVER SOUTHEAST CANADA TO SETTLE INTO THE EASTERN GREAT LAKES TODAY. A SERIES OF WEAK SHORT WAVES WILL ROTATE AROUND THE PERIPHERY OF THIS LOW THRU THE OHIO VALLEY. INITIAL S/W WHICH WAS RESPONSIBLE FOR SCT SHOWERS LAST NIGHT HAS PUSHED EAST OF THE TAF SITES TAKING PRECIP AND CLOUDS WITH IT. CLOUDS HAVE SCATTERED OUT BEING IN BETWEEN SHORTWAVES AND SOME BRIEF MVFR VSBY RESTRICTIONS WL BE OBSERVED EARLY. NEXT S/W TO DROP INTO OHIO TDA. FORCING IS WEAK AND MSTR CONTINUES TO BE LIMITED. GFS IS DEVELOPING LOW END MODERATE INSTABILITY BUT APPEARS OVERDONE WITH SFC DEW POINTS. PREFER NAM SOLN WITH ONLY MARGINAL INSTBY DEVELOPING THIS AFTN. HAVE A MENTION OF VCSH AND CB FOR A PERIOD TODAY (MAINLY AFTN AND EARLY EVENING) AT ALL TAF SITES BECAUSE OF THE EXPECTED LIMITED COVERAGE. WITH MARGINAL INSTBY EXPECTED CAN NOT RULE OUT A STRAY THUNDERSTORM BUT CHC/S ARE TOO LOW TO MENTION IN THE TAFS. WITH CLOUDS SCATTERING OUT TONIGHT AND LIGHT NORTHERLY WINDS...THE DEVELOPMENT OF FOG WILL BE POSSIBLE. AT THIS TIME HAVE A MENTION OF MVFR VSBY RESTRICTION LATE IN THE TAF PERIOD. OUTLOOK...TSTMS POSSIBLE MONDAY AND TUESDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...CONIGLIO NEAR TERM...WOODRUM SHORT TERM...CONIGLIO LONG TERM...RYAN AVIATION...AR oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 355 PM EDT THU AUG 14 2008 .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A FAIRLY AMPLIFIED PATTERN OVER NOAM. A BROAD MID-LVL RIDGE WAS OVER SW CANADA AND MUCH OF THE WRN CONUS WHILE A TROF WAS OVER ERN CANADA INTO THE CENTRAL/ERN GREAT LAKES. A CLOSED LOW HAS MOVED FROM SRN SASK INTO NE MT AND WILL HAVE LTL EFFECT ON OUR WX HERE. A SHORTWAVE AND ASSOC COLD POOL MOVING THROUGH THE BASE OF THE TROF HAS TRIGGERED SOME CONVECTION OVER FAR ERN UPR MI AS NOTED ON RADAR. LOOKS LIKE MAY EVEN ALTHOUGH SHORTWAVE IS NOT PRODUCING MUCH IN THE WAY OF CLOUD COVER...RADARS IN ONTARIO DO SHOW A FEW -SHRA. ACROSS UPPER MI...WITH THE EXCEPTION OF SOME CLOUDS OVER THE SW THIRD...SKIES ARE CLEAR. && .SHORT TERM (TONIGHT AND FRIDAY)... SOME LOCALIZED CONVERGENCE ALONG DEVELOPING LAKE BREEZE BOUNDARY MAY EVEN POP UP A SHOWER OVER SRN SCHOOLCRAFT COUNTY LATE THIS AFTERNOON BUT ANY SHOWER WOULD BE SHORT-LIVED AS MODEL SNDGS A SHARP INCREASE IN MID-LVL SUBSIDENCE TOWARD 00Z THIS EVENING IN THE WAKE OF THE SHORTWAVE. MODELS INDICATE CENTER OF SFC HIGH PRES ASSOCIATED WITH UPPER RIDGE WL MOVE FROM NRN ONTARIO INTO NRN MN BY THU MORNING SO WOULD EXPECT THE WRN FCST AREA TO BE COOLEST TONIGHT. RADIATIONAL COOLING UNDER CLEAR SKIES WILL ALSO BE ENHANCED BY DRY AIRMASS WITH PRECIPITABLE WATER VALUES AROUND 0.5 INCHES OR UNDER 60PCT OF NORMAL FOR THIS TIME OF YEAR. WILL CONTINUE TO GO BLO COOLEST MOS GUIDANCE OVER THE INTERIOR W (LOW/MID 40S) PER GOING FCST. FARTHER TO THE E OF THE HIGH...WINDS SHOULD MIX SOME OVER THE ERN FCST AREA...AND THERE MAY BE A SOME MIDLEVEL CLOUDS WRAPPING S AROUND LOW OVER SE CANADA LOW. WILL STAY CLOSE TO MOS GUIDANCE THERE WITH UPPER 50S ALONG LAKE SUPERIOR AND LOW TO MID 50S INLAND. KEPT IN PATCHY FOG OVER THE INTERIOR W HALF WHERE LIGHT/CALM WINDS AND CHILLY AIR OVERNIGHT COULD GENERATE GROUND FOG AROUND INLAND LAKES/STREAMS AND LOW-LYING AREAS. UPR RDG AXIS WILL SETTLE S INTO THE UPPER LAKES ON FRI. AT THE SFC...ASSOCIATED HIGH PRES WILL DRIFT SLOWLY S BY LATE FRI AS THE CORE OF THE DRY AIRMASS MOVES OVER THE FCST AREA DURING THE AFTN PRECIPITABLE WATER VALUES FALL TO AROUND 0.5 INCHES OVER MUCH OF THE AREA. EXPECT SUNNY SKIES TO DOMINATE FOR THE MOST PART WITH VERY LIMITED CU OVER INLAND AREAS. EXPECT DEEP MIXING TO AROUND 750MB UNDER THE DRY AIRMASS. FCST SOUNDINGS INDICATE MAX TEMPS FRI WILL BE A COUPLE OF DEGREES HIGHER AND DWPTS A COUPLE OF DEGRESS LWR AS DRIER/WARMER AIR MIXES TO THE SFC. RH`S VALUES COULD FALL TO AROUND 25PCT WELL INLAND FROM LAKE SUPERIOR WHICH COULD BE A CONCERN FOR WILDFIRE POTENTIAL. FORTUNATELY WINDS WILL BE RELATIVELY LIGHT WITH HIGH PRES IN THE VCNTY. .LONG TERM...FRIDAY NIGHT AND LATER A BROAD MID LEVEL RIDGE REMAINS OVER THE WEST HALF OF THE CONUS AND WESTERN CANADA AND A LONGWAVE TROUGH OVER SE CANADA/NEW ENGLAND. MAIN UPPER JET IS OVER HUDSON BAY. A WEAK SHORTWAVE WILL TRACK SOUTHEAST THROUGH NORTHERN ONTARIO TO QUEBEC ON SATURDAY. WARM AIR ADVECTION WILL RESULT IN SOME CLOUD COVER THOUGH. DRY WEATHER WILL CONTINUE RIGHT THRU SUNDAY. MAX TEMPS OVER THE WEEKEND SHOULD BE IN THE 80S IN MOST AREAS WITH SUNDAY BEING THE WARMEST DAY (IN THE MID 80S) AS 850MB THERMAL RIDGE SETTLES OVER THE AREA AHEAD OF COLD FRONT WHICH WILL DROP SOUTH TOWARD THE UPPER GREAT LAKES. THERE SHOULD BE ENOUGH HEIGHT FALLS HEADING THROUGH SOUTHEAST CANADA TO SEND THAT FRONT INTO THE UPPER GREAT LAKES ON MONDAY...PROVIDING THE POSSIBILITY OF A FEW SHRA/TSRA AT THAT TIME. A BROAD RIDGE WILL CONTINUE TO BUILD OVER THE WEST HALF OF THE CONUS SUNDAY NIGHT AND MONDAY...WHILE A LONGWAVE TROUGH STRETCHES FROM NORTHEAST QUEBEC SOUTHWEST INTO EAST CENTRAL ONTARIO. A WEAK SHORTWAVE WILL SWEEP THROUGH EASTERN ONTARIO. A COLD FRONT WILL SHIFT SOUTH ACROSS THE FORECAST AREA. A SURFACE RIDGE WILL BUILD BEHIND THE FRONT OVER MANITOBA AND NORTHERN ONTARIO. MOST OF THE INSTABILITY AND LOW LEVEL MOISTURE WILL BE OVER EASTERN ONTARIO. WITH THE SURFACE INSTABILITY FROM THE FRONT AND WEAK SHORTWAVE ENERGY EAST WILL NOT RULE OUT COMPLETELY A CHANCE OF SHOWERS AND THUNDERSTORMS...SO WILL CALL FOR A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS MAINLY OVER LAKE SUPERIOR. THE BROAD RIDGE AND LONGWAVE TROUGH WILL REMAIN IN PLACE THROUGH TUESDAY NIGHT. THE SURFACE RIDGE WILL PUSH INTO THE FORECAST AREA MONDAY NIGHT AND TUESDAY AS THE FRONT WORKS INTO SOUTHERN LOWER MICHIGAN BRINGING DRY AIR TO THE REGION. UNDER DRY STABLE AIR...CONDITIONS WILL REMAIN DRY. A WEAK WARM FRONT WILL SWEEP INTO THE FORECAST AREA ON WEDNESDAY. ECMWF IS CALLING FOR A WEAK SHORTWAVE ENTERING THE AREA AS WELL. MOISTURE WILL REMAIN RATHER LIMITED. THUS WILL KEEP JUST A SLIGHT CHANGE OF SHOWERS AND THUNDERSTORMS FOR WEDNESDAY. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... HIGH PRESSURE OVER ONTARIO BUILDS IN FOR NEXT 24 HOURS WITH VFR CIGS/VSBY EXPECTED. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... SFC HIGH PRESSURE OVER NORTHWEST ONTARIO IS EXPECTED TO SETTLE OVER THE WRN GREAT LAKES LATE TONIGHT INTO FRIDAY. EXPECT NORTHEAST WINDS TO OVER FAR WESTERN LAKE SUPERIOR TO GRADUALLY DIMINISH IN INTENSITY LATER THIS EVENING (BLO 15 KT) AS THE SFC HIGH BECOMES MORE CENTERED OVER THE REGION. AS THE HIGH PRESSURE RIDGE MOVES SOUTH OF THE AREA SATURDAY AND SUNDAY. STRONGER WINDS...UP NEAR 25 KNOTS...SEEM POSSIBLE ON SATURDAY IN THE TIGHTER PRESSURE GRADIENT ON THE NORTH SIDE OF THE RIDGE. OTHERWISE...WINDS WILL REMAIN 20 KNOTS OR LESS INTO EARLY NEXT WEEK. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JV LONG TERM...DLG AVIATION...JV MARINE...JV mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 103 PM EDT THU AUG 14 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAFS .SYNOPSIS... WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW LITTLE CHANGE HAS OCCURRED IN THE PATTERN OVER THE LAST 24 HRS. A MIDLEVEL LOW WAS OVER SE SASKATCHEWAN...A MIDLEVEL HIGH WAS OVER NRN MANITOBA...AND A TROF/BROAD MIDLEVEL LOW WAS OVER SE CANADA. THE LOW OVER SE CANADA HAS EXPANDED W A BIT...AND UPPER MI IS NOW UNDER NRLY FLOW ON ITS WRN FRINGE. AROUND THE LOW...A SHORTWAVE WAS ROTATING THRU ERN ONTARIO TOWARD THE UPPER GREAT LAKES. ALTHOUGH SHORTWAVE IS NOT PRODUCING MUCH IN THE WAY OF CLOUD COVER...RADARS IN ONTARIO DO SHOW A FEW -SHRA. ACROSS UPPER MI...WITH THE EXCEPTION OF SOME CLOUDS OVER THE SW THIRD...SKIES ARE CLEAR. && .DISCUSSION (415 AM EDT)... SHORTWAVE ROTATING THRU ERN ONTARIO WILL SWING ACROSS UPPER MI THIS MORNING. HEIGHTS FALL SLIGHTLY OVER THE ERN FCST AREA THRU MID MORNING...AND CORE OF THE 5H COLD POOL BRUSHES THAT AREA...BUT THAT PROBABLY WON`T BE ENOUGH TO GET ANY -SHRA INTO THE ERN FCST AREA. STILL...WILL NEED TO MONITOR RADAR TRENDS DURING THE MORNING TO SEE IF THE ISOLD -SHRA CURRENTLY HEADING SSW TOWARD FAR ERN LAKE SUPERIOR MIGHT CLIP LUCE COUNTY. OTHERWISE...SHORTWAVE PASSAGE WILL BE DRY ACROSS THE FCST AREA SINCE SHORTWAVE WILL BE S OF THE AREA WELL BEFORE PEAK OF THE HEATING CYCLE. STABILIZING N TO NE FLOW OFF LAKE SUPERIOR TO BEGIN THE DAY SUGGESTS LITTLE OR NO CLOUD COVER NEAR THE LAKE TODAY. DIURNAL CU INLAND SHOULD TEND TO DISSIPATE DURING THE AFTN FROM N TO S AS DRIER AIR ARRIVES IN THE WAKE OF SHORTWAVE AND STABILIZING FLOW OFF LAKE SUPERIOR SPREADS WELL INLAND. MIXING TO AROUND 800MB ON FCST SOUNDINGS SUPPORTS MOS GUIDANCE MAX TEMPS IN THE MID/UPPER 70S AWAY FROM LAKE SUPERIOR MODIFICATION. ALONG THE LAKE SUPERIOR SHORE...TEMPS SHOULD TOP OUT IN THE UPPER 60S/AROUND 70F. PROVIDED DEEP MIXING OCCURS...DWPTS WELL AWAY FROM LAKE SUPERIOR SHOULD DROP INTO THE MID 40S PER FCST SOUNDINGS. THIS WILL SEND RH DOWN TO 30-35PCT. CENTER OF SFC HIGH PRES ASSOCIATED WITH UPPER RIDGE EXTENDING FROM SW CANADA TO HUDSON BAY WILL SETTLE S TO NE MN/FAR NW WI BY THU MORNING...SO WRN FCST AREA WILL BE COOLEST TONIGHT. RADIATIONAL COOLING UNDER CLEAR SKIES WILL BE ENHANCED BY DRY AIRMASS WITH PRECIPITABLE WATER AROUND 0.5 INCHES OR AROUND 60PCT OF NORMAL FOR THIS TIME OF YEAR. WILL GO JUST BLO COOLEST MOS GUIDANCE OVER THE INTERIOR W (LOW/MID 40S). FARTHER TO THE E OF THE HIGH...WINDS SHOULD CONTINUE TO STIR A LITTLE OVER THE ERN FCST AREA...AND THERE MAY BE A SOME MIDLEVEL CLOUDS WRAPPING S AROUND THE SE CANADA LOW THRU ERN UPPER MI. WILL STAY CLOSE TO MOS GUIDANCE THERE (UPPER 50S ALONG LAKE SUPERIOR...LOW/MID 50S INLAND). WILL ADD PATCHY FOG OVER THE INTERIOR W HALF WHERE LIGHT/CALM WINDS AND CHILLY AIR OVERNIGHT WILL BE CONDUCIVE TO GROUND FOG DEVELOPMENT AROUND LAKES/STREAMS AND LOW-LYING AREAS (THE LAST FEW NIGHTS HAVE HAD SIMILAR OCCURRENCES). IT`S GETTING TO BE THAT TIME OF YEAR (LATE SUMMER/EARLY FALL) WHERE GROUND FOG OFTEN FORMS AROUND WARM BODIES OF WATER ON QUIET/CHILLY NIGHTS. EWD EXTENT OF UPPER RIDGE WILL SETTLE S INTO THE UPPER LAKES FRI. AT THE SFC...ASSOCIATED HIGH PRES WILL DRIFT VERY SLOWLY S FRI WITH CORE OF DRY AIRMASS OVER THE FCST AREA DURING THE AFTN (PRECIPITABLE WATER FALLS TO AROUND 0.5 INCHES OVER MUCH OF THE AREA). SUNNY SKIES WILL DOMINATE FOR THE MOST PART WITH ANY CU INLAND FROM LAKE SUPERIOR LIMITED TO FEW/SCT COVERAGE. EXPECT DEEP MIXING TO AROUND 750MB UNDER THE DRY AIRMASS. COMPARED TO TODAY...FCST SOUNDINGS SUGGEST MAX TEMPS FRI WILL BE A COUPLE OF DEGREES HIGHER AND DWPTS A COUPLE OF DEGRESS LWR IN MOST PLACES. RH`S COULD FALL TO AROUND 25PCT WELL INLAND FROM LAKE SUPERIOR. FORTUNATELY FOR FIRE WEATHER CONCERNS...WINDS WILL BE RELATIVELY LIGHT WITH HIGH PRES IN THE VCNTY. FRI NIGHT THRU THE WEEKEND...PATTERN WILL FEATURE A BROAD MID/UPPER RIDGE OVER THE W HALF OF THE CONUS/WRN CANADA AND A LOW AMPLITUDE TROF OVER SE CANADA/NEW ENGLAND. WITH THE RESULTING NW FLOW ALOFT INTO THE UPPER LAKES...WOULD TYPICALLY NEED TO CONSIDER CONVECTION. HOWEVER...MAIN UPPER JET IS DISPLACED FAR TO THE N AND NE OF THE FCST AREA (HUDSON BAY VCNTY). SO THIS LOOKS LIKE A TRANQUIL NW FLOW REGIME. THERE WILL BE A SHORTWAVE TRACKING SE THRU FAR NRN ONTARIO TO QUEBEC FRI NIGHT/SAT...BUT THAT WILL BE TOO FAR N TO REQUIRE ANY POPS HERE. WAA REGIME WILL PROBABLY RESULT IN SOME CLOUD COVER THOUGH. DRY WEATHER WILL CONTINUE RIGHT THRU SUN. MAX TEMPS OVER THE WEEKEND SHOULD BE IN THE 80S IN MOST AREAS WITH SUN THE WARMEST DAY (MID 80S COMMON WITH SOME UPPER 80S POSSIBLE IN A FEW SPOTS) AS 850MB THERMAL RIDGE SETTLES OVER THE AREA AHEAD OF COLD FRONT DROPPING S TOWARD THE UPPER LAKES. THERE SHOULD BE ENOUGH HEIGHT FALLS HEADING THRU SE CANADA TO SEND THAT FRONT INTO THE UPPER LAKES MON...PROVIDING THE POSSIBILITY OF A FEW SHRA/TSRA AT THAT TIME. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... HIGH PRESSURE OVER ONTARIO BUILDS IN FOR NEXT 24 HOURS WITH VFR CIGS/VSBY EXPECTED. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SFC HIGH PRESSURE OVER NORTHWEST ONTARIO SETTLES ACROSS THE GREAT LAKES INTO FRIDAY. EXPECT NORTHEAST WINDS TO 20 KNOTS TODAY OVER FAR WESTERN LAKE SUPERIOR DUE TO CHANNELING BETWEEN MINNESOTA SHORELINE AND APOSTLE ISLANDS. THE HIGH PRESSURE RIDGE MOVES SOUTH OF THE AREA SATURDAY AND SUNDAY. STRONGER WINDS...UP TO 25 KNOTS...SEEM POSSIBLE ON SATURDAY IN TIGHTER PRESSURE GRADIENT ON THE NORTH SIDE OF THE RIDGE. OTHERWISE...WINDS WILL REMAIN 20 KNOTS OR LESS THROUGH NEXT MONDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/DISCUSSION...ROLFSON AVIATION...VOSS MARINE...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SPRINGFIELD MO 215 PM CDT THU AUG 14 2008 .DISCUSSION... PRECIPITATION OVER NORTHEAST KANSAS AND NORTHWEST MISSOURI WAS OCCURRING IN RESPONSE TO AN UPPER LEVEL SHORTWAVE THAT EXISTED OVER NORTHEAST KANSAS. 310K ISENTROPIC SURFACE INDICATED 15 TO 20 KNOT PARCEL FLOW OVER A MESO-SCALE BAND OF BAROCLINICITY ACROSS EASTERN KANSAS. THE EVOLUTION AND MOVEMENT OF THIS AREA OF PRECIPITATION WAS THE INITIAL FORECAST CHALLENGE. OTHER CHALLENGES EXTENDED INTO FRIDAY AND FRIDAY NIGHTS PERIOD...AS ADDITIONAL SHOWER AND THUNDERSTORM CHANCES WERE WARRANTED. SHORT TERM (TONIGHT - FRIDAY NIGHT)... I`M GOING TO MAKE A LAST MINUTE CALL ON TONIGHTS PRECIPITATION CHANCES. WILL WAIT AND SEE HOW THE ONGOING CONVECTIVE CLUSTER IN NORTHERN MISSOURI IS TRENDING ON RADAR. ULTIMATELY NOT A SINGLE COMPUTER MODEL HAS A SNIFF ABOUT WHATS GOING ON RIGHT NOW...LET ALONE IN THE FUTURE. BASED ON RADAR AND MOISTURE CHANNEL IMAGERY TRENDS...PRECIPITATION CHANCES WILL NEED TO BE INCREASED FOR TONIGHTS PERIOD. ALSO HAVE SOME CONCERNS REGARDING INSTABILITY TRENDS OVER EASTERN KANSAS/WESTERN MISSOURI. RUC MIXED LAYER CAPE INDICATES VALUES OF AROUND 1500 J/KG WITH NO CAP. FORCING FROM THE NE KANSAS UPPER LOW INTERACTING WITH THIS CAPE COULD YIELD ANOTHER CONVECTIVE CLUSTER THATS NOT INDICATED BY THE MODELS. FRIDAYS PRECIP CHANCES ARE TOTALLY DEPENDENT UPON HOW TONIGHTS CONVECTION EVOLVES. THEREFORE HAVE LEFT CHANCE TO LIKELY POPS IN FOR FRIDAYS DAY PERIOD. RAIN CHANCES WILL END FRIDAY NIGHT AS A MUCH DRIER AND MORE STABLE AIRMASS SPREADS IN FROM THE UPPER MIDWEST. HAVE DECREASED FRIDAY NIGHTS RAIN CHANCES. LONG TERM (SATURDAY - WEDNESDAY)... MADE SOME SERIOUS ADJUSTMENTS WITH SATURDAY - TUESDAYS POPS. THE MAIN SYNOPTIC UPPER LOW IS TRACKING SOUTHWARD ACROSS THE NORTHERN PLAINS...AND WILL LIKELY STALL OUT OVER THE HIGH PLAINS OF COLORADO/KANSAS. THIS POSITIONING WILL BE TOO FAR WEST FOR HIGH PRECIPITATION CHANCES IN MISSOURI. AS A MATTER OF FACT...I DECIDED TO COMPLETELY TAKE OUT POPS FOR THESE PERIODS...AS THE ENTIRE WEEKEND SHOULD BE DRY FOR EXTREME SOUTHEAST KANSAS AND THE MISSOURI OZARKS. AS THE UPPER LOW WEAKENS HEADING INTO EARLY TO MID NEXT WEEK...THE SHEAR AXIS IS PROGGED TO REMAIN WEST OF THE CWA. THIS WOULD ALLOW TROPICAL AIR TO SPREAD BACK IN A RETURN OF RAIN CHANCES IN THE FORECAST WILL BE NEEDED BY TUESDAY NIGHT OR WEDNESDAY OR NEXT WEEK. REGARDING TEMPERATURES...CLOUD COVER ALONG WITH THE CHANGE IN AIRMASS WILL LIMIT READINGS FROM WARMING OUT OF THE LOW TO MID 80S FOR BOTH SATURDAY AND SUNDAY. WARMER TEMPERATURES WILL BE ON TAP FOR NEXT WEEK AS THE GULF AIRMASS FILTERS IN. CRAMER && .AVIATION... FOR THE 18Z TAFS...UPPER LEVEL LOW WILL MOVE SOUTH DURING THE NEXT 24 HOURS WHICH WILL IMPACT THE AVIATION WEATHER OVERNIGHT. CURRENT MODELS ARE NOT HANDLING THE PRECIPITATION WELL...HOWEVER...THE REGION WILL SEE SOME RAINFALL THROUGH FRIDAY AFTERNOON. CURRENT THOUGHTS ARE THAT SHOWERS AND A FEW THUNDERSTORMS WILL BEGIN TO IMPACT THE TAF SITES AROUND 00Z AND CONTINUE THROUGH THE TAF PERIOD. OVERALL CONDITIONS SHOULD REMAIN VFR EXCEPT IN THE NEAR VICINITY OF ANY CONVECTIVE CELLS. WILL NEED TO KEEP AN EYE ON THE TRACK OF THE LOW OVER THE PLAINS. IF IT MOVES FARTHER EAST INSTEAD OF PASSING SOUTHWEST OF THE OZARKS...AS INDICATED BY THE MODELS...THEN TERMINAL CONDITIONS COULD DETERIORATE. HATCH && .SGF WATCHES/WARNINGS/ADVISORIES... MO...NONE. KS...NONE. && $$ mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BILLINGS MT 317 PM MDT THU AUG 14 2008 .SHORT TERM...VALID FOR FRI AND SAT... SHOWER AND TSTM ACTIVITY CONTINUES TO DEVELOP ACROSS THE EASTERN TWO THIRDS OF THE FORECAST AREA...AS UPPER LOW AND COLD POOL ALOFT IN NE MONTANA MOVES VERY SLOWLY TO THE SOUTH SOUTHWEST. CONVECTION IS BEGINNING TO SHIFT WEST IN RESPONSE TO THIS LOWS MOVEMENT...AND AS WINDS HAVE TURNED MORE NORTHERLY...IE SHIFTING THE DOWNSLOPING OFF THE SNOWY MTNS FURTHER WEST. WILL KEEP NUMEROUS TO CATEGORICAL WORDING GOING INTO THIS EVENING ACROSS THE EAST AND SOUTH. CURRENT TRENDS AND RUC SUGGEST WINDS WILL VEER ENOUGH FOR ACTIVITY TO REACH THE BEARTOOTH FOOTHILLS...AND HAVE RAISED POPS IN THIS AREA AS WELL. BRIEF HEAVY RAIN AND VERY SMALL HAIL REPORTED IN THE HEAVIER SHOWERS...WHICH ARE MOVING QUITE FAST FROM NNW TO SSE WITH THE MID LEVEL FLOW. FOCUS OF PCPN WILL SHIFT SOUTH LATE TONIGHT INTO FRIDAY. UPPER LOW WILL DRIFT TO CENTRAL AND SOUTHERN WYOMING ON FRIDAY...AND AS IT DOES THE ACTIVITY IN OUR AREA WILL DIMINISH. DESPITE THE DRYING...DEEP UPSLOPE FLOW WILL KEEP TEMPS RELATIVELY COOL WITH HIGHS TOMORROW MAINLY IN THE 70S. THINK UPSLOPE FLOW AND LOW LEVEL MOISTURE WILL RESULT IN SOME CLOUD COVER MOST PARTS THROUGH AT LEAST FRIDAY MORNING...WITH INCREASED SUN AS THE DAY WEARS ON. DID CONSIDER THE POSSIBILITY OF FOG TONIGHT GIVEN THE COOL AND WET AIRMASS...BUT IT APPEARS BOUNDARY LAYER WILL REMAIN FAIRLY MIXED...WITH CLOUD COVER AROUND. EVENING SHIFT WILL HAVE TO KEEP WATCH FOR THIS...COULD BE SOME UPSLOPE LOW CLOUD OR FOG ALONG THE FOOTHILLS IF ENOUGH PCPN FALLS THIS EVENING. ANOTHER COOL NIGHT FRIDAY NIGHT...THEN WARMER ON SATURDAY AS UPPER RIDGE BUILDS IN FROM THE NW. HEIGHTS ASSOCIATED WITH THIS RIDGE ALONG THE PACIFIC NORTHWEST ARE ALREADY QUITE HIGH IN THE LOW 590S. DESPITE THIS...PERSISTENT EAST FLOW WITH FILLING LOW TO OUR SOUTH WILL KEEP WARM UP FROM HAPPENING TOO DRAMATICALLY. HIGHS ON SATURDAY SHOULD BE SOMEWHERE NEAR NORMAL WITH 850MB TEMPS IN THE LOWER TO MID 20S...IE HIGHS IN THE 80S. JKL .LONG TERM...VALID FOR SUN...MON...TUE...WED...THU... MADE JUST A FEW CHANGES TO GOING EXTENDED FORECAST. MODELS WERE IN GOOD AGREEMENT IN PLACING UPPER RIDGE OVER THE FORECAST AREA THROUGH EARLY NEXT WEEK UNDER FAIRLY DRY AIRMASS. RIDGE PROGGED TO BREAK DOWN A BIT ON TUE AS SW FLOW INCREASES OVER THE AREA. GFS DID BRING SOME HIGH LEVEL MOISTURE INTO THE WESTERN MOUNTAINS MON NIGHT THROUGH TUE NIGHT. POPS WERE ALREADY IN SW MOUNTAINS BUT ADDED SLIGHT CHANCE TO NW MOUNTAINS AS WELL. A COLD FRONT WAS STILL FORECAST TO MOVE E INTO THE AREA MON NIGHT AND REMAIN STATIONARY OVER THE AREA THROUGH THE PERIOD. THE ABOVE NORMAL TEMPS WERE IN GOOD SHAPE. ONLY CHANGE WAS TO RAISE MINS TOWARD BIAS CORRECTED MEX FOR MON NIGHT WITH FRONT MOVING INTO AREA. GFS/ECMWF BRING PACIFIC TROUGH TOWARD THE AREA ON WED. POPS WERE IN GOOD SHAPE ALTHOUGH 700 MB TEMPS WERE QUITE HIGH WHICH COULD RESULT IN CENTRAL PART OF AREA BEING CAPPED. CAN ADJUST POPS AT LATER TIME IF ENVIRONMENT CONTINUES TO LOOK CAPPED. COLD FRONT PROGGED TO MOVE INTO THE AREA ON WED NIGHT ACCOMPANIED BY BETTER CHANCES OF PRECIPITATION. RAISED TEMPS ON WED IN PREFRONTAL ENVIRONMENT TOWARD THE GFS 700 MB MIX DOWN TEMPS. EXPANDED POPS FOR THU INTO THU NIGHT AS BOTH GFS/ECMWF BROUGHT UPPER TROUGH OVER THE AREA. ADJUSTED TEMPS THU TO RAISE THEM A BIT IN THE E. INCREASING DYNAMICS DURING THIS PERIOD MAY RESULT IN SEVERE WEATHER. WILL WATCH FUTURE MODEL RUNS FOR THIS POSSIBILITY. ARTHUR && .AVIATION... MVFR AND IFR CONDITIONS WILL OCCUR WITH SHOWERS AND THUNDERSTORMS THIS EVENING. THE BEST CHANCES FOR PRECIPITATION WILL BE FROM KBIL TO THE NE BIG HORNS EAST...AND OVER THE RED LODGE AND BEARTOOTH FOOTHILLS. GUSTY N WINDS WILL DIMINISH BY SUNSET. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL PERSIST OVER EASTERN AND SOUTHERN PORTIONS OF THE REGION OVERNIGHT WITH MVFR CONDITIONS. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WITH MVFR/IFR CONDITIONS WILL CONTINUE OVER THE SE AND S PORTIONS OF THE AREA ON FRI. EXPECT MOUNTAIN OBSCURATION OVER THE NE BIG HORNS TONIGHT WITH AREAS OF OBSCURATION ON FRI. ARTHUR && .PRELIMINARY POINT TEMP/POPS... FRI SAT SUN MON TUE WED THU ----------------------------------------------------------- BIL 051/075 053/086 058/092 058/092 062/093 061/092 058/087 51/B 00/U 00/U 00/U 00/U 02/T 22/T LVM 042/077 044/087 049/091 052/092 053/088 050/087 050/086 21/N 00/U 00/U 01/B 10/B 02/T 22/T HDN 050/076 050/087 056/093 057/096 060/093 059/094 058/090 72/T 10/U 00/U 00/U 00/U 01/U 21/U MLS 052/079 054/087 058/091 060/094 065/093 062/094 061/091 62/T 10/U 00/U 00/U 00/U 01/U 21/U 4BQ 050/076 051/084 055/088 058/093 059/090 060/094 059/089 83/T 10/U 00/U 00/U 00/U 01/U 21/B BHK 050/079 051/085 056/087 058/092 058/089 057/093 058/089 62/T 10/U 00/U 00/U 00/U 01/U 21/U SHR 047/071 046/082 051/089 052/090 055/089 054/093 054/088 84/T 10/U 00/U 00/U 00/U 02/T 21/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...NONE. WY...NONE. && $$ WEATHER.GOV/BILLINGS mt AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE OMAHA/VALLEY NE 338 PM CDT THU AUG 14 2008 .DISCUSSION... RECENT NWP HAS MOVED THE PROJECTED POSITION OF THE MAIN CUT OFF LOW MUCH FARTHER WEST AND SOUTH THAN WAS ORIGINALLY FORECAST...THEREFORE WE HAVE SIGNIFICANTLY REDUCED POPS THROUGH THE ENTIRE FORECAST. .SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT. LATEST WATER VAPOR IMAGERY AND RUC 500MB ANALYSIS SHOW CUT OFF LOW CENTERED OVER THE MT/ND/CANADIAN BORDER WITH A FEW WAVES MOVING THRU THE NW FLOW INTO THE CNTRL PLAINS. MAIN SHORTWAVE OF INTEREST IS CURRENTLY PUSHING EAST INTO WESTERN NEBRASKA AND HAS SPARKED A FEW THUNDERSTORMS OVER NORTH CENTRAL NEBRASKA WHERE ML CAPES HAVE RISEN TO NEAR 2500J/KG WITH VERY LITTLE CINH TO HOLD ANYTHING BACK. AS WAVE CONTINUES TO PUSH EWD...TSTM CHANCES INCREASE ACROSS THE CWA HOWEVER...INSTABILITY IS RELATIVELY WEAK DUE TO BLOW OFF CLOUD COVER FROM CONVECTIVE ACTIVITY TO OUR SOUTH. BULK SHEAR REMAINS VERY WEAK ACROSS THE AREA AND ONLY GENERAL THUNDER IS EXPECTED OVERNIGHT. SMALL TSTM CHANCES WILL CONTINUE INTO FRIDAY AS LOBES OF SHORTWAVE ENERGY EJECT OUT OF CUT OFF LOW THAT IS FORECAST TO DROP SOUTH INTO SRN WY/NRN CO. AS MENTIONED ABOVE...THIS PATH IS MUCH FARTHER WEST THAN ORIGINALLY FORECAST SO HAVE BUMPED POPS DOWN TO ACCOUNT FOR THIS. SFC HIGH PRESSURE WILL BUILD OVER THE FORECAST AREA THIS WEEKEND. HAVE REMOVED ALL MENTION OF POPS FOR THE WEEKEND AS THE CUT OFF LOW IS SLOWLY EXPECTED TO SPIN INTO SERN CO BY EARLY NEXT WEEK...KEEPING UPPER DYNAMICS FAR TO OUR WEST. SLIGHTLY COOLER THAN NORMAL TEMPS ARE EXPECTED WITH LOWS IN THE UPPER 50S TO LOW 60S AND HIGHS IN THE LOW 80S. .LONG TERM... LOOKING AT THE LONGTERM...A CUTOFF LOW SITUATED OVER COLORADO SUNDAY EVENING WILL CONTINUE A SOUTHEASTERLY TRACK THROUGH THE SOUTH CENTRAL PLAINS...EVENTUALLY SCOOTING BACK TO THE NORTHEAST AND SITUATED SOUTH OF OUR AREA BY THURSDAY. THE GFS AND RECENT EURO RUNS STAY CONSISTENT WITH THE TRACK OF THE LOW THROUGH NEXT THURSDAY. KEPT A SLIGHT CHANCE OF PRECIP AND SOME ISOLATED THUNDER THROUGH MUCH OF THE EXTENDED. EXPECT A BETTER CHANCE FOR PRECIP THROUGH THE END OF THE PERIOD DUE TO THE POSITION OF THE LOW...SO RAISED POPS JUST A BIT THROUGH THE END OF THURSDAY. HIGHS THROUGH NEXT WEEK SHOULD BE IN THE LOW TO MID 80S AND LOWS ARE FORECAST TO BE IN THE LOW TO MID 60S. && .AVIATION... FOR TAF SITES KOMA/KLNK/KOFK THROUGH 16/00Z. AREA OF CONVECTION OVER NORTHEAST KANSAS AND NORTHWEST MISSOURI WILL CONTINUE MOVING AWAY FROM EASTERN NEBRASKA. LINGERING MID AND HIGH CLOUDINESS SHOULD EXIT ALL TAF SITE BY 00Z. ANOTHER SYSTEM DROPPING SOUTH THROUGH WESTERN NEBRASKA WILL BRING THUNDERSTORM CHANCES WELL WEST OF THE TAF SITES...MAINTAINING VFR CONDITIONS OVER EASTERN NEBRASKA. HOWEVER...ISOLATED THUNDERSTORMS ARE POSSIBLE IN EASTERN NEBRASKA...ESPECIALLY FRIDAY AFTERNOON...BUT COVERAGE EXPECTED TO BE ISOLATED ENOUGH TO PRECLUDE MENTION IN TAFS. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ GRIFFIS/DERGAN/KURTZ ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 235 PM CDT THU AUG 14 2008 .SYNOPSIS... THE 6.7 MICRON WATER VAPOR IMAGERY SHOWED A TROUGH DIGGING TO THE WEST SOUTHWEST INTO LAKE SUPERIOR AND THE MINNESOTA ARROWHEAD REGION. A MATURING UPPER CYCLONE WAS INDICATED OVER THE NORTHERN HIGH PLAINS IN NORTHEAST MONTANA...AND ANOTHER WAS INDICATED OVER THE GULF OF ALASKA. A PLUME OF MID-LEVEL PACIFIC MOISTURE WAS BEING PULLED DOWN BY THE MONTANA VORTEX FROM BRITISH COLUMBIA ACROSS THE CENTRAL ROCKIES AND INTO THE DAKOTAS AND WESTERN NEBRASKA. ANALYSIS OF 18Z MSL DATA SHOWED A WEAK BOUNDARY ACROSS SOUTH DAKOTA AND EASTERN NEBRASKA AND ANOTHER FROM NORTHEAST TO SOUTH CENTRAL KANSAS AND WEST TO THE OKLAHOMA PANHANDLE. VISIBLE SATELLITE IMAGERY AND RADAR HINTED AT ANOTHER BOUNDARY THAT HAS SLIPPED INTO NORTH CENTRAL AND NORTHWEST NEBRASKA. && .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT. FOR TONIGHT...THE RUC AND NAM12 BOTH SHOWED PRECIPITABLE WATER VALUES INCREASING TO GREATER THAT AND INCH. LOW LEVEL WIND PROFILERS AND SATELLITE DERIVED PRECIPITABLE WATER SUPPORTS THE INCREASE AS THE HIGHER VALUES WRAP AROUND FROM THE EAST AND NORTHEAST INTO SOUTHWEST NEBRASKA. HOWEVER...THE MODEL GENERATED PRECIPITATION FORECASTS DO NOT SUPPORT EXCESSIVE RAINFALL. STILL...WITH ENHANCED LIFT FROM THE HIGH PLAINS UPPER ATMOSPHERIC CYCLONE...RAINFALL AMOUNTS OF ONE TO TWO INCHES ARE NOT OUT OF THE RANGE OF POSSIBILITY. THE THREE-HOUR BASIN RUNOFF GUIDANCE ARE AT OR BELOW TWO INCHES OVER EASTERN LINCOLN COUNTY... SOUTHWEST CUSTER COUNTY...AND ALL OF FRONTIER AND HAYES COUNTIES. FOR THE RED WILLOW AND BLACKWOOD CREEKS...THE GUIDANCE VALUES ARE LESS THAN AN INCH. AS A RESULT...WE ARE RELUCTANT TO CANCEL OR CURTAIL THE CURRENT FLASH FLOOD WATCH... THOUGH LAST MINUTE ADJUSTMENTS MAY BE REQUIRED. THE SLOW MOVEMENT OF THE UPPER LOW SUPPORTS THE POSSIBILITY OF HEAVY RAIN IN WESTERN NEBRASKA AGAIN FRIDAY...AND THE MODEL PRODUCED QPF SUPPORTS THAT SCENARIO IN THE WEST. AS THE UPPER LOW CONTINUES TO SPIN OVER THE CENTRAL ROCKIES... THE POTENTIAL FOR HEAVY RAIN IN THE WEST IS LIKELY TO CONTINUE SATURDAY. BASED ON THE ABOVE REASONING...WE WILL KEEP 50-70 PERCENT PROBABILITY IN THE WEST FRIDAY AND SATURDAY. FOR TONIGHT...WE WILL HAVE 35-50 PERCENT THIS EVENING IN THE WEST AND SOUTHWEST AND 55-65 PERCENT AFTER MIDNIGHT. IN THE CENTRAL AND NORTH CENTRAL PARTS... 55-70 PERCENT IS APPROPRIATE THROUGH THE NIGHT. .LONG TERM...SUNDAY THROUGH THURSDAY. PERIOD CONTINUES TO LOOK SOMEWHAT UNSETTLED...WITH LARGE UPPER LEVEL LOW TO MIGRATE SLOWLY NORTHEASTWARD THROUGH THE SOUTHERN AND CENTRAL PLAINS. BOTH THE ECMWF AND GFS NOW DROP THE UPPER LOW A BIT FURTHER SOUTH FROM YESTERDAYS RUN...THIS TRACK STILL PLACES AT LEAST THE SOUTHERN PORTIONS OF WESTERN AND NORTH CENTRAL NEBRASKA IN A FAVORABLE REGION TO RECEIVE PRECIPITATION. PRECIPITATION SEEMS MOST LIKELY ON SUNDAY INTO MONDAY...WITH TUESDAY AND BEYOND LOOKING MAINLY DRY FOR NOW AS THE UPPER LEVEL LOW FILLS AND WEAKENS. TEMPERATURES SOMEWHAT BELOW NORMAL SUNDAY AND MONDAY...WITH A RETURN TO NEAR NORMAL READING FOR TUESDAY AND BEYOND. && .AVIATION... VISUAL FLIGHT RULES EXPECTED THROUGH 15/00Z AT TERMINALS KLBF AND KVTN. SCATTERED THUNDERSTORMS WILL CONTINUE TO DEVELOP ALONG THE BOUNDARY WITH STORMS EXPECTED TO INCREASE IN COVERAGE AS BOUNDARY SHIFTS SOUTH TONIGHT. THE PRIMARY CONCERN OVERNIGHT WILL BE HOW FAST CEILING AND VISIBILITIES WILL LOWER BEYOND 06Z TO MVFR AT BOTH TERMINALS AS UPGLIDE WINDS HELP TO SATURATE BOUNDARY LAYER WITH MVFR CONDITIONS THROUGH 15Z FRIDAY. THUNDERSTORMS WILL BE SLOW MOVERS THAT WILL INCREASE RAINFALL RATES WITH THE POTENTIAL FOR VISIBILITY TO DROP LOWER THAN CURRENTLY INDICATED IN TERMINAL FORECASTS BEYOND 10Z. && .LBF WATCHES/WARNINGS/ADVISORIES... NEZ038-059-070-071...FLASH FLOOD WATCH THROUGH 12Z. && $$ SPRINGER/TAYLOR/KECK ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND FORKS ND 248 PM CDT THU AUG 14 2008 .SHORT TERM... MAIN CONCERN THIS EVENING IS CONVECTION. SO FAR NOT TOO MUCH GOING ON WITH ISOLD CELLS MOVING JUST EAST OF THE RED RIVER...WITH ONE AREA NEAR MOORHEAD AND THE OTHER NEAR HALLOCK. THE ACTIVITY IN THE NORTH WAS MOVING SLOWLY NORTHWARD WHILE THE ACTIVITY IN THE SOUTHERN VALLEY WAS MOVING SLOWLY EAST. CORES OF THESE STORMS ARE VERY SMALL AND THUS HEAVY RAINFALL VERY LIMITED AND VERY BRIEF. SFC MAP STILL SHOWS WEAK INVERTED TROUGH IN PLACE FROM NEAR HALLOCK TO JUST WEST OF GRAN DFORKS THEN TO NEAR LISBON THEN TO LOW PRESSURE NR HURON SD AMD MITCHELL SD. THE UPPER LOW WAS MOVING SOUTHWARD THRU ERN MT WITH MOST OF ITS CONVECTION ON THE SOUTH SIDE OF THE SYSTEM OVER SE MT INTO NE WY/NW SD. RUC STILL HANDLING POOL OF HIGHER DEW PTS IN THE LOW TO MID 60S ALONG THE SFC TROUGH IN THE VALLEY BETTER THAN 12Z NAM AND GFS. FOR LATE AFTN AND EARLY EVENING...WITH TROUGH AND WEAK SFC CONVERGENCE IN THE VALLEY WILL MAINTAIN IDEA OF SCT CONVECTION AND FROM RADAR AND SATELLITE BEST AREA WOULD BE FROM THE IMMEDIATE RED RIVER EASTWARD ABOUT 40-50 MILES TO NR ROX-TVF-FSE-FFM AREAS. FARTHER EAST TOWARD BEMIDJI DRIER AIR FROM HIGH PRESSURE IN ONTARIO IS FEEDING IN AND TO THE WEST OF THE VALLEY DRIER AIR ON BACKSIDE OF TROUGH IS IN PLACE. EXPECT CONVECTION TO DIE OFF SLOWLY RIGHT NEAR TROUGH TONIGHT BY 06Z...AS UPPER LOW MOVES SOUTH TOWARD NE WYOMING AND ASSOC SFC LOW IN SRN SD CONTINUES TO MOVE SOUTH. ALSO WINDS WILL DIMINISH TO NEAR CALM AFTER MIDNIGHT MAKING SFC CONVERGENCE MINIMAL. SOME CONCEN FOR PATCHY FOG LATE TONIGHT IN OVER PARTS OF MINNESOTA TREE COUNTRY AS LIGHT WINDS AND MAINLY CLEAR SKY IN THAT AREA ALLOW FOR MAX RADITIONAL COOLING AND LESS LOW LEVEL MIXING. FOR FRIDAY...HIGH PRESSURE IN ONTARIO WILL SLIDE SOUTH TOWARD NRN MINNESOTA PUSHING MORE STABLE AND SLIGHTLY LOWER DEW PT AIRMASS INTO THE AREA. A 500 MB UPPER RIDGE WILL BUILD TO THE NORTH OF THE UPPER LOW THIS WEEKEND OVER SRN CANADA AND THE NRN PLAINS WHILE THE SFC HIGH SLIPS SOUTHEAST THROUGH THE SOUTHERN GREAT LAKES. SUNNY SKIES WILL BE THE RULE THIS WEEKEND WITH WARMING TEMPERATURES BY SUNDAY TO ABOVE NORMAL LEVELS AS THE RIDGE ALOFT SUPRESSES MUCH CLOUD DEVELOPMENT AND DEW PTS REMAIN REALTIVELY LOW. .LONG TERM (SUN-THU)... MODELS INITIALIZED WELL AND ARE IN GENERAL AGREEMENT...SO WILL GO WITH A BLENDED SOLUTION ATTM. MODELS SHOW A FAIRLY STAGNANT PATTERN INITIALLY AS THE MEAN UPPER LEVEL RIDGE IS IN PLACE OVER THE HIGH PLAINS. CORRESPONDING SFC RIDGE WILL REMAIN IN PLACE RESULTING IN SCATTERED SKIES AND WARM TEMPERATURES. THE UPPER RIDGE IS EXPECTED TO SLOWLY SHIFT EAST BY DAY 6 WITH A SFC LOW DEVELOPING OVER THE HIGH PLAINS AND MOVING EAST. LOOKING FOR SOUTHERLY FLOW AT THE SFC BEHIND RETREATING HIGH PRESSURE INCREASING TEMPS AND MOISTURE AHEAD OF THE LOW. UPPER LEVEL ENERGY WILL SHIFT OVER THE AREA IN SW FLOW ALOFT BRINGING A CHANCE FOR SHOWERS/TSTMS BY THE END OF PERIOD. OTHERWISE...NO SIGNIFICANT CHANGES ARE ANTICIPATED ATTM. && .AVIATION... VFR CONDITIONS WITH SPOTTY MVFR EARLY IN THE PERIOD ASSOCIATED WITH SHOWERS/TSTMS COINCIDING WITH SFC TROF/SOLAR HEATING OVER THE RED RIVER VALLEY. WINDS MAY BE ERRATIC IN VCNTY OF STRONGER STORMS. .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ RIDDLE/HOPKINS nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 421 PM EDT THU AUG 14 2008 .SYNOPSIS... A SERIES OF UPPER LEVEL DISTURBANCES WILL ROTATE AROUND A CLOSED UPPER LOW CENTERED OVER SOUTHEAST CANADA THROUGH FRIDAY. SURFACE HIGH PRESSURE WILL BUILD INTO THE AREA FRIDAY NIGHT...AND WILL REMAIN ACROSS THE REGION THROUGH THE UPCOMING WEEKEND. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... HAVE TAKEN A BLEND OF THE LATEST RUC...NAM-WRF AND GFS FOR THE NEAR TERM FORECAST. VORT MAX ACRS S CNTRL INDIANA THIS AFTN WILL DRIFT SE ACRS NRN KY THROUGH THE EARLY MORNING HOURS. MEANWHILE...A WEAK SFC BOUNDARY...COMBINED WITH WEAK 700 MB DEFORMATION...WILL MOVE ACRS THE NRN CWFA THROUGH THE EARLY MORNING HOURS. THESE FEATURES...COMBINED WITH DAYTIME HEATING...HAVE RESULTED IN SCATTERED SHOWERS AND THUNDERSTORMS. AS THESE SYSTEMS DRIFT OFF TO THE EAST OVERNIGHT...AND THE AIRMASS STABILIZES...PCPN SHOULD DWINDLE DOWN TO JUST A SLIGHT CHANCE OF SHOWERS ACRS THE ERN AND SRN ZONES. OVERNIGHT LOWS WILL RANGE FROM THE MID 50S TO NEAR 60. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... MODELS ARE IN GOOD AGREEMENT THAT THE CLOSED UPPER LEVEL LOW OVER SE CANADA WILL MOVE EAST AWAY FROM THE REGION BY FRIDAY NIGHT...ALLOWING SFC HIGH PRESSURE TO BUILD INTO OUR REGION FROM THE NORTHWEST. BEFORE THEN...A TANDEM OF VORT LOBES ARE FCST TO ROTATE SE ACRS THE FORECAST AREA FRIDAY AFTN AND EARLY EVENING. DESPITE LACK OF LOW LEVEL FORCING...THERE SHOULD BE ENOUGH MOISTURE AND DAYTIME INSTABILITY TO POP A SHOWER OR THUNDERSTORM ACRS THE FAR ERN AND SRN ZONES. THUS...WILL MENTION A SLIGHT CHANCE IN THESE LOCALES. ANY SHOWER OR THUNDERSTORM WILL COME TO AN END QUICKLY FRIDAY EVENING AS VORT LOBE MOVES AWAY...THE AIRMASS STABILIZES...AND SFC HIGH PRESSURE BRINGS DRIER AIR TO THE REGION. HIGH PRESSURE WILL SET UP RESIDENCE ACROSS THE OHIO VALLEY ON SATURDAY...PROVIDING A DRY...MOSTLY SUNNY DAY AND A MOSTLY CLEAR NIGHT. TEMPERATURES THROUGH THE PERIOD...ESPECIALLY AT NIGHT...WILL CONTINUE TO AVERAGE BELOW NORMAL FOR MID AUGUST. && .LONG TERM /SUNDAY THROUGH THURSDAY/... BULK OF THE EXTENDED MODEL GUID HAS SHIFTED TO THE DRIER SOLN FIRST INDICATED BY THE 12Z ECMWF ON WED. THIS HAS REQUIRED SVRL CHANGES TO THE PREV LONG TERM FCST...MAINLY REMOVING A GOOD DEAL OF PCPN CHANCES AND ALLOWING FOR SLIGHTLY WARMER TEMPS. HIGHLY AMPLIFIED FLO PERSISTS ACRS MUCH OF THE CONUS AS OH VLY WILL REMAIN STUCK BTWN PERSISTENT UPR TROF OVER CANADIAN MARITIMES AND STAGNANT UPR LO CUTOFF FROM MEAN FLO OVER THE CNTRL ROCKIES/HIGH PLAINS. WRN ATLC UPR RIDGE WILL SLOWLY PULL NORTH THRU THE PERIOD INTO THE SE CONUS AND OH/TN VLYS BY MIDWEEK. SFC HI PRES WILL REMAIN ACRS THE REGION SUN. MID LVL S/WV SWINGING AROUND BASE OF ERN CANADA TROF WILL PASS THRU OH VLY SUN AFTN BUT AM ONLY EXPECTING AN INCREASE IN MID/HI LVL CLOUDS WITH FAIRLY DRY ATMOSPHERE IN PLACE. A COLD FRONT WILL DROP SOUTH THRU THE GRT LKS AND INTO THE REGION TUES AS UPR TROF RELOADS AND AMPLIFIES TO THE NORTHEAST. FRONT LOOKS ESPECIALLY STARVED FOR MOISTURE...AS ADJUSTMENT IN OVERALL PATTERN DESCRIBED ABV ESSENTIALLY WILL TAKE AWAY ANY SIGNIFICANT INFLUENCE OF GULF MOISTURE. WILL MAINTAIN LO CHC POPS FOR TUES INTO ERLY WED HOWEVER WITH FRNTL BNDRY INVOF REGION. DRY WX EXPECTED FOR REMAINDER OF THE WEEK AS HI PRES AT THE SFC AND ALOFT ESTABLISH ACRS THE OH VLY. MEX GUID CONTINUES TO BE TOO WARM WITH AFTN HIGHS...AND IS SUGGESTIVE OF AFTN TEMPS NEAR 90 DEG BY TUES/WED. UNDERCUT GUID TEMPS THRU MUCH OF THE PERIOD...KEEPING HIGHS IN THE 80 TO 85 RANGE SUN/MON...WITH PREDOMINANTLY M80S BEYOND. LOWS WILL LARGELY REMAIN IN THE L/M60S THRU THE PERIOD. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... SHOWERS AND THUNDERSTORMS IN THE VICINITY OF THE TERMINALS THIS AFTN WILL BE THE LARGEST CONCERN THROUGHOUT THE FCST PERIOD AS AN UPPER LEVEL DISTURBANCE SWINGS ACROSS THE OHIO VALLEY. WENT WITH PREVAILING VCSH AND TEMPO GROUPS FOR EVERYWHERE EXCEPT CMH AND LCK TO ACCOUNT FOR SCTD TSRA WITH MVFR VSBYS FOR THE LATE AFTERNOON ACROSS THE TRI-STATE AREA. THIS ALSO ACCOUNTS FOR THE MORE ORGANIZED CONVECTION MOVING SEWD FROM CNTRL INDIANA. VCTS EXPECTED AT CMH AND LCK AS ISOLATED CONVECTION DEVELOPS THIS AFTN. CONVECTION FOR THE MAJORITY SHOULD BE CLEARED OUT OF THE TERMINALS BY 00Z. OVERNIGHT...WITH SFC MOISTURE IN PLACE FROM EVENING CONVECTION AND LIGHT WINDS OVERNIGHT SOME MVFR FOG CAN BE EXPECTED EVERYWHERE EXCEPT LCK/CMH. WENT WITH TEMPO GROUPS DURING EARLY MORNING HRS WITH IFR VSBYS AT LUK. OUTLOOK...NO SIGNIFICANT WEATHER EXPECTED. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HICKMAN NEAR TERM...HICKMAN SHORT TERM...HICKMAN LONG TERM...RYAN AVIATION...WOODRUM oh