AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 137 PM MST WED AUG 20 2008 SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA FORECAST DISCUSSION .UPDATE...UPDATED AVIATION DISCUSSION. && .SYNOPSIS... A RELATIVELY DRY WESTERLY FLOW ALOFT WILL REMAIN IN PLACE ACROSS THE DESERT SOUTHWEST THE NEXT SEVERAL DAYS. THIS WILL PRECLUDE ANY THREAT OF SHOWERS AND THUNDERSTORMS ACROSS THE AREA UNTIL LATE IN THE WEEKEND...WITH SUNNY SKIES EXPECTED UNTIL THEN. AFTERNOON TEMPERATURES WILL GENERALLY BE ABOVE LATE AUGUST NORMALS...WITH PLEASANTLY MILD NIGHTS. && .DISCUSSION... LATEST RUC HAS ANALYZED A CLEARLY DEFINED MID-LEVEL TROUGH MOVING THROUGH THE MOJAVE DESERT...THOUGH THIS SYSTEM WILL WEAKEN AND IS NOT EXPECTED TO HAVE ANY IMPACT ON THE FORECAST AREA. INSTEAD...CONDITIONS WILL REMAIN RELATIVELY QUIET...WITH ABOVE AVERAGE TEMPERATURES AND MOSTLY SUNNY SKIES. FORECAST SOUNDINGS YIELD NO CAPE THIS AFTERNOON AND WITH A WESTERLY/NORTHWESTERLY STEERING FLOW...CONFIDENCE IS HIGH THAT ANY THUNDERSTORMS THAT DEVELOP ACROSS THE HIGHER TERRAIN WILL REMAIN WELL OUTSIDE OF THE FORECAST AREA. PREVIOUS DISCUSSION... EARLY MORNING SATELLITE PIX SHOWED A BAND OF HIGH CLOUDS TRAVERSING ACROSS NRN AZ...REPRESENTING A WEAK UPPER LEVEL TROUGH PASSING BY THE REGION IN THE WLYS. THIS TROUGH IS THE SRN EXTENT OF A MUCH LARGER LOW PRESSURE SYSTEM THAT IS PUSHING TOWARDS THE WRN COAST OF CANADA. AS THIS TROUGH MOVES EWD AND ACROSS THE EXTREME NRN TIER OF STATES THE NEXT COUPLE OF DAYS...IT WILL BE RESPONSIBLE FOR KEEPING THE MONSOON RIDGE SUPPRESSED TO THE S. THIS POSITION WILL ALLOW FOR NO FURTHER INTRUSION OF SIGNIFICANT MONSOON MOISTURE FOR THE NEXT FEW DAYS. MODEL FORECAST SOUNDINGS FROM BOTH THE NAM AND GFS REFLECT THIS DRY SITUATION NICELY...WITH LITTLE TO NO THREAT OF DAILY STORMS ANYWHERE WITHIN THE CWA OVER THE NEXT SEVERAL DAYS. MEANWHILE...SURFACE DEWPOINTS ARE QUITE A BIT LOWER MOST PLACES THIS MORNING...REFLECTING THE DRY AIR INFILTRATING THE AREA. THESE LOWER DEWPOINTS WILL ALLOW FOR COOLER NIGHTS...AND HAVE TRENDED INHERITED MIN T GRIDS DOWN A COUPLE DEGREES AS A RESULT. MAX TEMPS WILL BE ABLE TO WARM UP QUITE EFFECTIVELY WITH THE DRY AIR...GENERALLY AVGG SEVERAL DEGREES ABOVE SEASONAL NORMALS. HOW LONG WILL THIS DRY...EXTENDED BREAK IN THE MONSOON LAST? WELL... ACCORDING TO LATEST GFS ENSEMBLE MEANS...RIDGE WILL STAY SUPPRESSED SWD THE NEXT SEVEN DAYS...ALTHO IT COULD ATTEMPT TO MAKE A NWD SHIFT FOR A TIME OVER THE WEEKEND. HOWEVER...FCST SOUNDINGS HOLD OUT VERY LITTLE HOPE THAT ANY SIGNIFICANT INCURSION OF MOISTURE IS IN THE OFFING INTO EARLY NEXT WEEK. HAVE THEREFORE LIMITED SLIGHT CHANCE TSTMS TO HIGHER TERRAIN OF ZONE 24 BEGINNING ABOUT SUNDAY AFTN THRU TUESDAY. LOOKING FOR AFTN TEMPS TO MAX OUT AROUND SUN/MON TIME FRAME. && .AVIATION... SOUTH-CENTRAL ARIZONA...KPHX/KIWA AND SURROUNDING AIRFIELDS...AND SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA...KNYL/KBLH AND KIPL... NO AVIATION CONCERNS EXPECTED. MOSTLY CLEAR SKIES AND LIGHT DIURNAL SURFACE WINDS WILL CONTINUE ACROSS THE AREA THROUGH AT LEAST 00 UTC FRIDAY. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... THURSDAY THROUGH MONDAY... A DRIER AIR MASS OVER THE AREA WILL KEEP MINIMUM HUMIDITY LEVELS IN THE TEENS ACROSS THE SOUTHWEST ARIZONA DESERTS...DIPPING DOWN INTO THE SINGLE DIGITS ACROSS PORTIONS OF SOUTHEAST CALIFORNIA AND JTNP. OVERNIGHT RECOVERY ACROSS SOUTHEAST CALIFORNIA WILL REMAIN POOR THROUGH FRIDAY MORNING...AND POSSIBLY INTO THE WEEKEND. EXPECT UPSLOPE WINDS...GUSTY AT TIMES WITH PEAK HEATING OF THE DAY...AND WEAK DRAINAGE FLOWS AT NIGHT. MOVING EAST...THE HIGHER TERRAIN OF SOUTHERN GILA COUNTY WILL HOLD ON TO HIGHER HUMIDITY LEVELS...WITH A SLIGHT CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS BY SUNDAY. EXPECT A BETTER RECOVERY TREND...AND LIGHT DIURNAL WINDS FAVORING WEST DURING THE DAY. MOISTURE LEVELS TREND UPWARD ACROSS THE REGION BY LATE SATURDAY. THE MOISTURE COULD LEAD TO THE RETURN OF SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF EASTERN ARIZONA BY SUNDAY...WITH MOISTURE SPREADING WESTWARD INTO THE LOWER DESERTS EARLY NEXT WEEK. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT WEATHER.GOV/PHOENIX DISCUSSION...HIRSCH/ESTLE AVIATION...WANEK FIRE WEATHER...MEYERS az AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LITTLE ROCK AR 955 PM CDT WED AUG 20 2008 .UPDATE... BULK OF RAINFALL HAS SHIFTED INTO NRN AR ATTM. THE UPR LOW WAS NOTED OVR NERN OK EARLY THIS EVENING...WITH A SHRTWV VCNTY OF SWRN AR. SCTD SHRA/ISOLD TSRA HAS PERSISTED OVR PARTS OF SWRN AR AND EXPECT THIS ACTIVITY TO SLOLY LIFT NWD OVERNIGHT AS THE UPR SHRTWV LIFTS ACRS THE FA. BASED ON LATEST RUC/NAM DATA...FCST QPF AMOUNTS NOT AS HVY AS PREV INDCD...SO HAVE OPTED TO CANCEL THE FF WATCH. UPDATED HRLY TEMPS TO REFLECT CURRENT TRENDS. MIN TEMP FCST ON TRACK. NO OTHER CHGS TO GOING FCST. ALL UPDATES ARE OUT. /44/ && .PREV DISCUSSION... /ISSUED 641 PM CDT WED AUG 20 2008/ AVIATION... FIRST ROUND OF RAINFALL MOVING ACROSS THE NORTHEAST...WITH THE NEXT ROUND ACROSS THE SOUTHWEST. CONDITIONS WILL REMAIN MVFR TO IFR THROUGH THE NIGHT...WITH LIFR CONDITIONS TOWARDS SUNRISE. AS THE SYSTEM BEGINS TO MOVE NORTHEAST THURSDAY...CONDITIONS WILL GRADUALLY IMPROVE AFTER 15Z THURSDAY. && .LZK WATCHES/WARNINGS/ADVISORIES...NONE. && $$ ar AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE POCATELLO ID 740 PM MDT TUE AUG 19 2008 .DISCUSSION...MID-LEVEL CLOUDS MOVING OVER THE FORECAST AREA THIS EVENING HAVE REDUCED THE OVERALL MIXING AND WIND SPEEDS THROUGHOUT THE SNAKE RIVER PLAIN AND HENCE THE LAKE WIND ADVISORY HAS BEEN CANCELLED. CONVECTIVE POTENTIAL HAS ALSO WEAKENED AND THIS WELL SUPPORTED BY LATEST RUC13 RUN WHICH HAS NOW BACKED AWAY FROM CONVECTION 00-03Z THIS EVENING ACROSS THE SRN HIGHLANDS. UPDATES TO PRODUCTS COMING SOON. SEE PREVIOUS DISCUSSION BELOW. HUSTON CONVECTION IS DEVELOPING OVER THE NORTHERN HALF OF THE CENTRAL MOUNTAINS THIS AFTERNOON. THIS IS IN RESPONSE TO A BROAD UPPER LEVEL TROUGH THAT IS ADVANCING INTO THE REGION. NAM SHOWS MOST OF THE CONVECTION STAYING IN THIS AREA THIS AFTERNOON AND EVENING...BUT ALSO HINTS AT AN ISOLATED STORM OR TWO DEVELOPING OVER THE SNAKE PLAIN AND SOUTHERN HIGHLANDS...DRIFTING EASTWARD THROUGHOUT THE EVENING. THUNDERSTORMS CHANCES HANG AROUND WEDNESDAY AND THURSDAY AS THE UPPER TROUGH MOVES THROUGH THE AREA. THE BETTER DYNAMICS WILL BE NORTH OF THE REGION CONSEQUENTLY EXPECT THE BETTER RAIN CHANCES TO BE NORTH OF TH AREA. THIS TROUGH WILL BE BRINGING IN COOLER TEMPERATURES AS WELL. DRY WEATHER AND GRADUALLY WARMING TEMPERATURES ARE EXPECTED FOR THE WEEKEND AND BEYOND AS A RIDGE OF HIGH PRESSURE REESTABLISHES ITSELF. VALLE && .AVIATION...VFR CONDITIONS WILL CONTINUE THROUGH WEDNESDAY. MID TO HIGH LEVEL CLOUDS WILL CONTINUE TO INCREASE THROUGH THE NEXT 24 HOURS. ISOLATED THUNDERSTORMS ARE POSSIBLE IN THE CENTRAL MOUNTAINS THIS EVENING AND AGAIN WEDNESDAY AFTERNOON. HANKO && .FIRE WEATHER...THE MAIN AREA OF THUNDERSTORM ACTIVITY HAS MOVED NORTHEAST INTO MONTANA. NO LIGHTING HAS BEEN OBSERVED IN SOUTHEAST IDAHO FOR THE LAST HOUR...THEREFORE THE RED FLAG WARNING FOR THE SALMON-CHALLIS NATIONAL FOREST AREA WILL BE CANCELLED. WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TO REDEVELOP ON WEDNESDAY FOR THE FAR NORTHERN EXTENT OF THE CENTRAL MOUNTAINS...MAINLY NORTH OF STANLEY. A COLD FRONT PASSAGE ON THURSDAY WILL BRING STRONG WINDS TO MUCH OF THE AREA...ALONG WITH COOLER TEMPERATURES. HANKO/SURVICK && .PIH WATCHES/WARNINGS/ADVISORIES...NONE. && $$ id AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1245 PM EDT TUE AUG 19 2008 .UPDATE/AVIATION... HIGH PRESSURE CENTERED OVER SRN ONTARIO BUILDING SEWD TODAY WITH CU/WIND FIELD SUGGESTING BACKDOOR CDFNT EXTENDING THROUGH FWA/SBN AT 16Z. LAKE BREEZE ALSO PUSHING INLAND FROM SE LM SHOULD ENHANCE CONVERGENCE ALONG THIS BOUNDARY PSBLY RESULTING IN ISOLATED SHOWER/TSTM THIS AFTN. LIMITING FACTOR APPEARS TO BE INSTABILITY AS CURRENT LAPS/SPC ANALYSIS SUGGEST CAPES CONSIDERABLY LOWER THAN AT THIS TIME YDAY MAINLY DUE TO MID LEVEL WARMING AS UPPER TROF OVER ERN U.S. CONTS TO MOVE SLOWLY AWAY FROM OUR AREA. UPDATED ZFP TO FRESHEN WORDING AND FOR MINOR CHANGES INCLUDING MOVG THIS AFTN`S SCHC POPS W-SW CLOSER TO BOUNDARY LOCATION AND TO LOWER HIGH TEMPS SLIGHTLY ACROSS THE NE. AS FOR TAFS...APPEARS MVFR DECK UPSTREAM IS MIXING OUT AND IS NOT EXPECTED TO REACH THE TERMINALS. CONTD WITH SCT CU THIS AFTN/EVE WITH VFR CONDITIONS THROUGH THE PD AS A LITTLE TIGHTER PRES GRADIENT TONIGHT ALONG WITH SOMEWHAT DRIER AIR MOVG IN FROM THE EAST SHOULD LIMIT FOG DEVELOPMENT OVERNIGHT. && .PREV DISCUSSION... UPDATE/AVIATION... WILL UPDATE ZONES/HWO TO REMOVE FOG MENTION AS NO SGFNT REDUCTIONS TO VSBYS NOTED WITH LATEST OBS WITH JUST A TEMPO MVFR GROUP FIRST HOUR OF NEW TAFS. BACKDOOR CDFNT MOVG THROUGH AREA THIS MORNING. DAYTIME HEATING/DESTABILIZATION MAY LEAD TO A FEW SHRA/TS ALONG FRONT OVER NRN INDIANA THIS AFTN AS CONVERGENCE BECOMES ENHANCED BY LAKE BREEZE. OTRWS...VFR CONDITIONS EXPECTED THROUGH THE PD AS HIGH PRESSURE DROPS SE INTO THE LWR GRTLKS. PRES GRADIENT OVER THE CWA WILL BE A LITTLE STRONGER TOMORROW MORNING DUE TO PROXIMITY OF THIS HIGH...SO NO RESTRICTIONS TO VSBY DUE TO FOG FCST AT TERMINALS IN THESE TAFS. SHORT TERM... TODAY THROUGH WEDNESDAY BACKDOOR COLD FRONT CONTINUES TO DROP SSW ACROSS THE GREAT LAKES. PRECIP HAS ALL BUT DIMINISHED...SAVE A FEW SHOWERS IN SE MI. TROUGH AXIS AS OF 07Z WAS LOCATED FROM BIV EAST TO DTW. OTHERWISE...MASSIVE ROCKIES RIDGING CONTINUES WITH TROUGHING IN PLACE OVER SE CANADA...A TYPICAL SYNOPTIC PATTERN THIS SUMMER. ACROSS THE FA...WINDS WERE LIGHT TO CALM UNDER CLEAR SKIES. AREAS OF FG CONTINUE TO DEVELOP WITH EXCELLENT RADIATIONAL COOLING IN PLACE. WILL HIGHLIGHT FOG MENTION IN ZONES WITH PATCHY DENSE MENTION. HAVE UTILIZED A BLEND OF THE NAM/GFS/RUC13/SREF/AND UKMET FOR SYNOPTIC AND MESOSCALE EVOLUTION THIS FORECAST PERIOD...RELYING ON THE STRENGTHS OF EACH INDIVIDUAL MODEL. TODAY...BACKDOOR COLD FRONT WILL SAG SW INTO THE FA...SLOWING IN THE PROCESS AS MAIN UPPER LEVEL SUPPORT WILL SHIFT WELL NE OF THE GREAT LAKES. WEAK SFC CONVERGENCE WILL BE IN PLACE ALONG THE FRONTAL BOUNDARY. BY AFTERNOON...LK MI LAKE BREEZE IS EXPECTED TO DEVELOP AND PUSH WELL INLAND AIDED BY LONG FETCH TRAJECTORIES AND UP-LK PRESSURE RISES. WIND SHIFT ASSOCIATED WITH THIS FEATURE COMBINE WITH FRONTAL CONVERGENCE/MOISTURE POOLING AND DAYTIME HEATING WILL SUPPORT CONVECTIVE CU DEVELOPMENT. WEAK MID LEVEL COOLING UPSTREAM INDICATED BY RUC13 PROGS COMBINED WITH AFOREMENTIONED DYNAMICS MAY JUST BE ENOUGH TO FORCE A SH/TS...WITH SBCAPE PROGS IN THE 700 TO 1000 J/KG. NAM/NMM/GFS/RUC13 PROGS ALL HIGHLIGHT THE SAME AREA IN NORTHERN IN/SE LOWER MI FOR ISOLATED CONVECTION THIS AFTERNOON. HAVE ADDED SLT CH POPS FOR THIS. ANY CONVECTION SHOULD WAIN AFTER SUNRISE...WITH A FEW LINGER SH POSSIBLE ON OLD OUTFLOW BOUNDARIES. FOG WILL BE POSSIBLE AGAIN...BUT QUESTIONS STILL LINGER ON COVERAGE AND THICKNESS POTENTIAL GIVEN SFC PRESSURE GRADIENT IN PLACE. WILL WORD PATCHY FOG AT THIS TIME...TRENDING TOWARD MOS NUMBERS. WEDNESDAY...HIGH PRESSURE WILL RESIDE EAST OF THE FA...DOMINATING THE WX FOR MUCH OF THE GREAT LAKES. EXPECTING PT CLOUDY CONDITIONS WITH DEEP MIXING PER DRYING BL. HAVE GONE ABOVE GUIDANCE FOR HIGHS GIVEN DRY SOIL CONDITIONS/AMPLE SUN/AND H85 TEMPS. DRY AIR IN PLACE COMBINED WITH MOSTLY CLEAR SKIES WILL SUPPORT LARGE DIURNAL SWINGS WITH TEMPS LIKELY FALLING INTO THE LOW TO MID 50S WED NIGHT...COOLEST READINGS IN OUTLYING AREAS. HAVE OPTED FOR COOLEST GUIDANCE PROGS GIVEN DRY CONDITIONS IN PLACE. WANDERING CUT OFF LOW WILL EDGE TOWARD THE REGION...POSSIBLY SPREADING SOME CIRRUS INTO THE SOUTH OVERNIGHT. LONG TERM (THURSDAY TROUGH MONDAY) MAJOR CONCERNS FOR THE LONG TERM CONTINUE TO BE MOISTURE RETURN/FRONTAL PASSAGE FOR LATE WEEK AND WEEKEND. MAJOR FEATURES OF THE WEEK LARGELY UNCHANGED WITH CWA UNDER INFLUENCE OF STRONG HIGH PRESSURE RIDGE AS CUT OFF LOW OVER TEXAS FINALLY MOVES NE AHEAD OF AN UPSTREAM TROF CENTERED OVER SOUTHERN CANADA. TIMING OF LOW AND ASSOC MOISTURE RETURN NOW IN BETTER AGREEMENT BETWEEN GFS/EC WITH THE MAIN AXIS OF INSTABILITY REMAINING JUST TO OUR WEST...ALTHOUGH THE GFS IS STILL SLIGHTLY FURTHER EASTWARD AND THE ENSEMBLE MEAN PRODUCES PRECIP OVER THE CWA FRIDAY AFTERNOON. WILL ONCE MORE FOLLOW THE EC WHICH HAS HAD GOOD RUN TO RUN CONTINUITY AND LEAVE GRIDS DRY THROUGH FRIDAY FOR THIS PACKAGE. GFS/EC BOTH BRING FRONTAL BOUNDARY TO OUT DOORSTEP BY SATURDAY NIGHT BUT THE EC THEN SLOWS DOWN PROGRESSION LARGELY DUE TO THE HANDLING OF TS FAY REMNANTS WHICH IT PULLS NORTHWESTWARD INTO ALABAMA/TENNESSEE...WHEREAS THE GFS STILL HAS FAY OUT OF PLAY OVER THE GULF. EVEN WITH THIS UNCERTAINTY THE OVERALL PICTURE UP TO THIS POINT IS IN GOOD AGREEMENT AND LIKE THE SLOWER EC TIMING WITH STRONG RIDGING IN PLACE AHEAD OF THE BNDRY SO HAVE ELECTED TO ONCE AGAIN LEAVE THE WEEKEND OUTLOOK UNCHANGED WHILE NOTING THE FASTER GFS WOULD IMPLY A QUICKER END TO POPS ON SUNDAY SHOULD IT COME TO FRUITION. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...CHAMBERLAIN LONG TERM...LUDINGTON AVIATION/UPDATE...JT in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 800 AM EDT TUE AUG 19 2008 .UPDATE/AVIATION... WILL UPDATE ZONES/HWO TO REMOVE FOG MENTION AS NO SGFNT REDUCTIONS TO VSBYS NOTED WITH LATEST OBS WITH JUST A TEMPO MVFR GROUP FIRST HOUR OF NEW TAFS. BACKDOOR CDFNT MOVG THROUGH AREA THIS MORNING. DAYTIME HEATING/DESTABILIZATION MAY LEAD TO A FEW SHRA/TS ALONG FRONT OVER NRN INDIANA THIS AFTN AS CONVERGENCE BECOMES ENHANCED BY LAKE BREEZE. OTRWS...VFR CONDITIONS EXPECTED THROUGH THE PD AS HIGH PRESSURE DROPS SE INTO THE LWR GRTLKS. PRES GRADIENT OVER THE CWA WILL BE A LITTLE STRONGER TOMORROW MORNING DUE TO PROXIMITY OF THIS HIGH...SO NO RESTRICTIONS TO VSBY DUE TO FOG FCST AT TERMINALS IN THESE TAFS. && .PREV DISCUSSION... SHORT TERM... TODAY THROUGH WEDNESDAY BACKDOOR COLD FRONT CONTINUES TO DROP SSW ACROSS THE GREAT LAKES. PRECIP HAS ALL BUT DIMINISHED...SAVE A FEW SHOWERS IN SE MI. TROUGH AXIS AS OF 07Z WAS LOCATED FROM BIV EAST TO DTW. OTHERWISE...MASSIVE ROCKIES RIDGING CONTINUES WITH TROUGHING IN PLACE OVER SE CANADA...A TYPICAL SYNOPTIC PATTERN THIS SUMMER. ACROSS THE FA...WINDS WERE LIGHT TO CALM UNDER CLEAR SKIES. AREAS OF FG CONTINUE TO DEVELOP WITH EXCELLENT RADIATIONAL COOLING IN PLACE. WILL HIGHLIGHT FOG MENTION IN ZONES WITH PATCHY DENSE MENTION. HAVE UTILIZED A BLEND OF THE NAM/GFS/RUC13/SREF/AND UKMET FOR SYNOPTIC AND MESOSCALE EVOLUTION THIS FORECAST PERIOD...RELYING ON THE STRENGTHS OF EACH INDIVIDUAL MODEL. TODAY...BACKDOOR COLD FRONT WILL SAG SW INTO THE FA...SLOWING IN THE PROCESS AS MAIN UPPER LEVEL SUPPORT WILL SHIFT WELL NE OF THE GREAT LAKES. WEAK SFC CONVERGENCE WILL BE IN PLACE ALONG THE FRONTAL BOUNDARY. BY AFTERNOON...LK MI LAKE BREEZE IS EXPECTED TO DEVELOP AND PUSH WELL INLAND AIDED BY LONG FETCH TRAJECTORIES AND UP-LK PRESSURE RISES. WIND SHIFT ASSOCIATED WITH THIS FEATURE COMBINE WITH FRONTAL CONVERGENCE/MOISTURE POOLING AND DAYTIME HEATING WILL SUPPORT CONVECTIVE CU DEVELOPMENT. WEAK MID LEVEL COOLING UPSTREAM INDICATED BY RUC13 PROGS COMBINED WITH AFOREMENTIONED DYNAMICS MAY JUST BE ENOUGH TO FORCE A SH/TS...WITH SBCAPE PROGS IN THE 700 TO 1000 J/KG. NAM/NMM/GFS/RUC13 PROGS ALL HIGHLIGHT THE SAME AREA IN NORTHERN IN/SE LOWER MI FOR ISOLATED CONVECTION THIS AFTERNOON. HAVE ADDED SLT CH POPS FOR THIS. ANY CONVECTION SHOULD WAIN AFTER SUNRISE...WITH A FEW LINGER SH POSSIBLE ON OLD OUTFLOW BOUNDARIES. FOG WILL BE POSSIBLE AGAIN...BUT QUESTIONS STILL LINGER ON COVERAGE AND THICKNESS POTENTIAL GIVEN SFC PRESSURE GRADIENT IN PLACE. WILL WORD PATCHY FOG AT THIS TIME...TRENDING TOWARD MOS NUMBERS. WEDNESDAY...HIGH PRESSURE WILL RESIDE EAST OF THE FA...DOMINATING THE WX FOR MUCH OF THE GREAT LAKES. EXPECTING PT CLOUDY CONDITIONS WITH DEEP MIXING PER DRYING BL. HAVE GONE ABOVE GUIDANCE FOR HIGHS GIVEN DRY SOIL CONDITIONS/AMPLE SUN/AND H85 TEMPS. DRY AIR IN PLACE COMBINED WITH MOSTLY CLEAR SKIES WILL SUPPORT LARGE DIURNAL SWINGS WITH TEMPS LIKELY FALLING INTO THE LOW TO MID 50S WED NIGHT...COOLEST READINGS IN OUTLYING AREAS. HAVE OPTED FOR COOLEST GUIDANCE PROGS GIVEN DRY CONDITIONS IN PLACE. WANDERING CUT OFF LOW WILL EDGE TOWARD THE REGION...POSSIBLY SPREADING SOME CIRRUS INTO THE SOUTH OVERNIGHT. LONG TERM (THURSDAY TROUGH MONDAY) MAJOR CONCERNS FOR THE LONG TERM CONTINUE TO BE MOISTURE RETURN/FRONTAL PASSAGE FOR LATE WEEK AND WEEKEND. MAJOR FEATURES OF THE WEEK LARGELY UNCHANGED WITH CWA UNDER INFLUENCE OF STRONG HIGH PRESSURE RIDGE AS CUT OFF LOW OVER TEXAS FINALLY MOVES NE AHEAD OF AN UPSTREAM TROF CENTERED OVER SOUTHERN CANADA. TIMING OF LOW AND ASSOC MOISTURE RETURN NOW IN BETTER AGREEMENT BETWEEN GFS/EC WITH THE MAIN AXIS OF INSTABILITY REMAINING JUST TO OUR WEST...ALTHOUGH THE GFS IS STILL SLIGHTLY FURTHER EASTWARD AND THE ENSEMBLE MEAN PRODUCES PRECIP OVER THE CWA FRIDAY AFTERNOON. WILL ONCE MORE FOLLOW THE EC WHICH HAS HAD GOOD RUN TO RUN CONTINUITY AND LEAVE GRIDS DRY THROUGH FRIDAY FOR THIS PACKAGE. GFS/EC BOTH BRING FRONTAL BOUNDARY TO OUT DOORSTEP BY SATURDAY NIGHT BUT THE EC THEN SLOWS DOWN PROGRESSION LARGELY DUE TO THE HANDLING OF TS FAY REMNANTS WHICH IT PULLS NORTHWESTWARD INTO ALABAMA/TENNESSEE...WHEREAS THE GFS STILL HAS FAY OUT OF PLAY OVER THE GULF. EVEN WITH THIS UNCERTAINTY THE OVERALL PICTURE UP TO THIS POINT IS IN GOOD AGREEMENT AND LIKE THE SLOWER EC TIMING WITH STRONG RIDGING IN PLACE AHEAD OF THE BNDRY SO HAVE ELECTED TO ONCE AGAIN LEAVE THE WEEKEND OUTLOOK UNCHANGED WHILE NOTING THE FASTER GFS WOULD IMPLY A QUICKER END TO POPS ON SUNDAY SHOULD IT COME TO FRUITION. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...CHAMBERLAIN LONG TERM...LUDINGTON AVIATION/UPDATE...JT in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 359 AM EDT TUE AUG 19 2008 .SHORT TERM... TODAY THROUGH WEDNESDAY BACKDOOR COLD FRONT CONTINUES TO DROP SSW ACROSS THE GREAT LAKES. PRECIP HAS ALL BUT DIMINISHED...SAVE A FEW SHOWERS IN SE MI. TROUGH AXIS AS OF 07Z WAS LOCATED FROM BIV EAST TO DTW. OTHERWISE...MASSIVE ROCKIES RIDGING CONTINUES WITH TROUGHING IN PLACE OVER SE CANADA...A TYPICAL SYNOPTIC PATTERN THIS SUMMER. ACROSS THE FA...WINDS WERE LIGHT TO CALM UNDER CLEAR SKIES. AREAS OF FG CONTINUE TO DEVELOP WITH EXCELLENT RADIATIONAL COOLING IN PLACE. WILL HIGHLIGHT FOG MENTION IN ZONES WITH PATCHY DENSE MENTION. HAVE UTILIZED A BLEND OF THE NAM/GFS/RUC13/SREF/AND UKMET FOR SYNOPTIC AND MESOSCALE EVOLUTION THIS FORECAST PERIOD...RELYING ON THE STRENGTHS OF EACH INDIVIDUAL MODEL. TODAY...BACKDOOR COLD FRONT WILL SAG SW INTO THE FA...SLOWING IN THE PROCESS AS MAIN UPPER LEVEL SUPPORT WILL SHIFT WELL NE OF THE GREAT LAKES. WEAK SFC CONVERGENCE WILL BE IN PLACE ALONG THE FRONTAL BOUNDARY. BY AFTERNOON...LK MI LAKE BREEZE IS EXPECTED TO DEVELOP AND PUSH WELL INLAND AIDED BY LONG FETCH TRAJECTORIES AND UP-LK PRESSURE RISES. WIND SHIFT ASSOCIATED WITH THIS FEATURE COMBINE WITH FRONTAL CONVERGENCE/MOISTURE POOLING AND DAYTIME HEATING WILL SUPPORT CONVECTIVE CU DEVELOPMENT. WEAK MID LEVEL COOLING UPSTREAM INDICATED BY RUC13 PROGS COMBINED WITH AFOREMENTIONED DYNAMICS MAY JUST BE ENOUGH TO FORCE A SH/TS...WITH SBCAPE PROGS IN THE 700 TO 1000 J/KG. NAM/NMM/GFS/RUC13 PROGS ALL HIGHLIGHT THE SAME AREA IN NORTHERN IN/SE LOWER MI FOR ISOLATED CONVECTION THIS AFTERNOON. HAVE ADDED SLT CH POPS FOR THIS. ANY CONVECTION SHOULD WAIN AFTER SUNRISE...WITH A FEW LINGER SH POSSIBLE ON OLD OUTFLOW BOUNDARIES. FOG WILL BE POSSIBLE AGAIN...BUT QUESTIONS STILL LINGER ON COVERAGE AND THICKNESS POTENTIAL GIVEN SFC PRESSURE GRADIENT IN PLACE. WILL WORD PATCHY FOG AT THIS TIME...TRENDING TOWARD MOS NUMBERS. WEDNESDAY...HIGH PRESSURE WILL RESIDE EAST OF THE FA...DOMINATING THE WX FOR MUCH OF THE GREAT LAKES. EXPECTING PT CLOUDY CONDITIONS WITH DEEP MIXING PER DRYING BL. HAVE GONE ABOVE GUIDANCE FOR HIGHS GIVEN DRY SOIL CONDITIONS/AMPLE SUN/AND H85 TEMPS. DRY AIR IN PLACE COMBINED WITH MOSTLY CLEAR SKIES WILL SUPPORT LARGE DIURNAL SWINGS WITH TEMPS LIKELY FALLING INTO THE LOW TO MID 50S WED NIGHT...COOLEST READINGS IN OUTLYING AREAS. HAVE OPTED FOR COOLEST GUIDANCE PROGS GIVEN DRY CONDITIONS IN PLACE. WANDERING CUT OFF LOW WILL EDGE TOWARD THE REGION...POSSIBLY SPREADING SOME CIRRUS INTO THE SOUTH OVERNIGHT. && .LONG TERM (THURSDAY TROUGH MONDAY) MAJOR CONCERNS FOR THE LONG TERM CONTINUE TO BE MOISTURE RETURN/FRONTAL PASSAGE FOR LATE WEEK AND WEEKEND. MAJOR FEATURES OF THE WEEK LARGELY UNCHANGED WITH CWA UNDER INFLUENCE OF STRONG HIGH PRESSURE RIDGE AS CUT OFF LOW OVER TEXAS FINALLY MOVES NE AHEAD OF AN UPSTREAM TROF CENTERED OVER SOUTHERN CANADA. TIMING OF LOW AND ASSOC MOISTURE RETURN NOW IN BETTER AGREEMENT BETWEEN GFS/EC WITH THE MAIN AXIS OF INSTABILITY REMAINING JUST TO OUR WEST...ALTHOUGH THE GFS IS STILL SLIGHTLY FURTHER EASTWARD AND THE ENSEMBLE MEAN PRODUCES PRECIP OVER THE CWA FRIDAY AFTERNOON. WILL ONCE MORE FOLLOW THE EC WHICH HAS HAD GOOD RUN TO RUN CONTINUITY AND LEAVE GRIDS DRY THROUGH FRIDAY FOR THIS PACKAGE. GFS/EC BOTH BRING FRONTAL BOUNDARY TO OUT DOORSTEP BY SATURDAY NIGHT BUT THE EC THEN SLOWS DOWN PROGRESSION LARGELY DUE TO THE HANDLING OF TS FAY REMNANTS WHICH IT PULLS NORTHWESTWARD INTO ALABAMA/TENNESSEE...WHEREAS THE GFS STILL HAS FAY OUT OF PLAY OVER THE GULF. EVEN WITH THIS UNCERTAINTY THE OVERALL PICTURE UP TO THIS POINT IS IN GOOD AGREEMENT AND LIKE THE SLOWER EC TIMING WITH STRONG RIDGING IN PLACE AHEAD OF THE BNDRY SO HAVE ELECTED TO ONCE AGAIN LEAVE THE WEEKEND OUTLOOK UNCHANGED WHILE NOTING THE FASTER GFS WOULD IMPLY A QUICKER END TO POPS ON SUNDAY SHOULD IT COME TO FRUITION. && .AVIATION.../06Z TAFS/ REMNANT BOUNDARY IN PLACE OVER THE FORECAST AREA HAS ALL BUT WASHED OUT...LEAVING CALM WINDS AND CLEAR SKIES ACROSS THE FA. CALM WINDS AND CLEAR SKIES WITH TEMP-DEWPOINTS SPREADS GROWING SMALLER...IS ALLOWING AREAS OF BR TO DEVELOP. EXPECT THIS TREND TO CONTINUE THROUGH SUNRISE...WITH AREAS OF FOG LIKELY. HAVE ADDED 2SM AT FWA WHERE LL MOISTURE IS SLIGHTLY ELEVATED PER RESIDUAL MOISTURE POOLING FROM YESTERDAYS BOUNDARY PUSH. LEFT THINGS A LITTLE MORE OPTIMISTIC AT SBN WHERE DRIER AIR IS IN PLACE. PATCHY DENSE FOG WILL BE A POSSIBILITY...MAINLY AFTER 08Z...AND COULD VERY WELL AFFECT THE TERMINALS. WILL MONITOR AND AMEND AS NEEDED. FARTHER NORTH OVER MI...A BACK DOOR COLD FRONT CONTINUES TO PUSH SSW TOWARD THE FA AND WILL BE THE MAIN FORECAST CONCERN THIS AFTERNOON. LOOK FOR WINDS TO SHIFT NE BY AFTERNOON NE-SW ACROSS THE FA. THERE IS A SMALL CHANCE FOR A SH/TS...BUT GIVEN WEAK FORCING AND DYNAMICS...COVERAGE WOULD BE MINIMAL..AND THUS HAVE LEFT ANY MENTION OUT OF TERMINALS. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...CHAMBERLAIN LONG TERM...LUDINGTON AVIATION...CHAMBERLAIN in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 145 AM MDT TUE AUG 19 2008 .DISCUSSION... TODAY-THURSDAY NIGHT...WE WILL CONTINUE TO TALK ABOUT THIS PAST WEEKENDS UPPER LOW AS IT REMAINS A FACTOR IN THE FORECAST OVER THE NEXT FEW DAYS. FOR TODAY AND TONIGHT IT WILL NOT BE A FACTOR IN THE WEATHER PICTURE. 850 TEMPERATURES AVERAGE A 3-9F WARM UP (WEST TO EAST) WITH AFTERNOON HIGHS IN THE UPPER 70S FROM FLAGLER SOUTHEAST THROUGH TRIBUNE WITH 80-83 ELSEWHERE ACROSS THE AREA. FOR WEDNESDAY AND WEDNESDAY NIGHT THE UPPER LOW STARTS TO MOVE NORTHEAST INTO PARTS OF EASTERN KANSAS AS A LARGE UPPER LOW ENTERS THE PACIFIC NORTHWEST PUSHING A DOWNSTREAM RIDGE TO THE EAST. WRAPAROUND CLOUDINESS WILL MOSTLY IMPACT THE EASTERN 1/3 OF THE AREA BUT THE EXTENT IS SOMEWHAT IN QUESTION. EITHER WAY IT SHOULD NOT IMPACT TEMPERATURES AND HAVE GONE WITH HIGHS AROUND 80/LOW 80S. SOUTHERLY WINDS WILL INCREASE INTO THE BREEZY CATEGORY DURING THE AFTERNOON HOURS AS WELL. FOR THURSDAY AND THURSDAY NIGHT THE UPPER LOW CONTINUES NORTHEAST AND FINALLY OUT OF THE AREA AS THE PACIFIC NORTHWEST TROUGH DEEPENS BUT REMAINING WELL NORTH/NORTHWEST OF THE AREA. UPPER RIDGING AHEAD OF THIS FEATURE COUPLED WITH BREEZY SOUTH WINDS AT THE SURFACE WILL ALLOW A 10F OR SO WARM UP WITH READINGS IN THE 85-90 DEGREE RANGE...WARMEST ACROSS THE WEST. NO PRECIPITATION EXPECTED THROUGH THURSDAY NIGHT. WILL NEED TO MONITOR FOG POTENTIAL EACH NIGHT AFTER MIDNIGHT GIVEN RECENT RAINFALL. LATEST NAM/GFS SHOW A WIDELY SATURATED BOUNDARY LAYER THURSDAY NIGHT ACROSS ALL BUT FAR EASTERN COLORADO. WILL NEED TO KEEP AN EYE ON THIS FOR A MORE WIDESPREAD FOG POTENTIAL. FRIDAY...COLD FRONT ENTERS THE FORECAST AREA DURING THE MORNING/EARLY AFTERNOON HOURS AS LARGE UPPER AND SURFACE LOW SKIRT JUST NORTH OF THE NORTH DAKOTA/CANADIAN BORDER BEFORE LIFTING NORTHEAST DURING THE NIGHT. AS IT DOES UPPER LEVEL HIGH PRESSURE MOVES TOWARD THE FOUR CORNERS AREA. LITTLE CHANGE MADE TO AFTERNOON TEMPERATURES GIVEN THE ECMWF/GFS 850 TEMPS. WILL KEEP SLIGHT CHANCE/LOW CHANCE POPS FOR FRIDAY NIGHT AS MOISTURE INCREASES ALONG AND BEHIND THE FRONT. SATURDAY-MONDAY...NO CHANGES MADE. DDT && .AVIATION... FOR THE 12Z TAFS AT KGLD AND KMCK...FOR KGLD AM EXPECTING SCT-BKN003-007 DECK TO IMPACT THE SITE BETWEEN 09Z-12Z AND LASTING THROUGH 14Z-15Z PER LATEST RUC AND SATELLITE IMAGERY...OTHERWISE PERHAPS SOME FAIR WEATHER CU DURING THE DAY WITH SKC SHORTLY AFTER DARK. FOR KMCK GENERALLY SKC THROUGH THE PERIOD. DDT && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ WFO GOODLAND ks AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 138 AM EDT WED AUG 20 2008 UPDATED AVIATION DISCUSSION 06Z TAF ISSUANCE .SYNOPSIS... 19Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER RIDGING FROM SOUTH CENTRAL CANADA INTO THE UPPER MIDWEST...TROPICAL STORM FAY CROSSING SE FLORIDA...A 582 DAM LOW NEAR WICHITA FALLS TX...AND A TROUGH OVER THE NE PACIFIC INTO THE PACIFIC NW. UPPER MI LIES ON THE EAST SIDE OF THE UPPER RIDGE...WHICH FAVORS SUBSIDENCE AND HIGH PRESSURE AT THE SFC. CURRENTLY THIS HIGH IS CENTERED ALONG THE ERN LAKE SUPERIOR/ONTARIO SHORELINE. A LOT OF DRY AIR EXISTS NEAR THIS HIGH...NOTED ON TAMDAR SOUNDINGS FROM SAW AND CMX WHICH HAVE 30-40C DEWPOINT DEPRESSIONS BETWEEN 850-700MB. MIXING OF THIS DRY AIR TO THE SURFACE HAS BEEN SOMEWHAT TROUBLESOME...THOUGH...DUE TO THE COLD AIR THAT MOVED IN LAST NIGHT. SOME LOCATIONS LAST NIGHT DROPPED INTO THE 30S...SUCH AS CHATHAM WHICH FELL TO 34. THIS COLD AIR EVEN GENERATED SOME LAKE EFFECT CLOUDS OVER NRN LAKE MI...BUT THESE HAVE SINCE DISSIPATED. TO OUR SW...ANOTHER BAND OF MOISTURE NOTED BY CLOUDS EXTENDS FROM DLH TO GRB. TAMDAR SOUNDING FROM RHI SHOWS THIS WITH A BIT MORE SATURATION BETWEEN 800-900MB. OTHER LOW CLOUDS EXIST DOWN NEAR MILWAUKEE. FARTHER TO THE S...UPPER LEVEL MOISTURE CAN BE SEEN STREAMING NORTHWARD FROM LOUISIANA INTO MISSOURI ON THE EAST SIDE OF THE UPPER LOW. A FEW STORMS ARE ALSO NOTED IN LOUISIANA WHERE DEWPOINTS ARE IN THE 70S. WELL OFF TO THE WEST...STORMS ARE MARCHING ACROSS THE PACIFIC NW WITH THE INCOMING UPPER TROUGH. && .SHORT TERM (TONIGHT THROUGH WED NIGHT)... QUIET WEATHER IS EXPECTED TO PREVAIL THROUGH THIS PERIOD...THANKS TO THE UPPER RIDGE OVER THE UPPER MIDWEST SHIFTING OVER UPPER MI ON WED...RESULTING IN CONTINUED SUBSIDENCE. HOWEVER...THERE ARE A FEW ISSUES TO DEAL WITH...MAINLY CLOUDS AND TEMPS. THIS EVENING SHOULD GENERALLY BE CLEAR ACROSS THE CWA...THEN SOME INCREASING CLOUDS ARE EXPECTED OVER THE WESTERN U.P. AS RETURN FLOW BRINGS THE CLOUDS TO OUR SW INTO THE AREA. WHERE THESE CLOUDS MOVE IN WILL ALSO BE THE SAME AREA WHERE SOUTHERLY WINDS PICK UP TONIGHT...AND THEREFORE FORECAST LOWS ARE SIMILAR TO GUIDANCE. OVER THE EASTERN HALF OF UPPER MI WHERE SKIES ARE CLEAR...THE WINDS ARE GENERALLY LIGHT ALL NIGHT AND PRECIPITABLE WATER STAYS AROUND 0.50 INCH...EXPECTING TEMPS TO GET CHILLY AGAIN. WENT BELOW ALL GUIDANCE GIVEN WHAT HAPPENED LAST NIGHT SINCE SIMILAR CONDITIONS ARE PRESENT...EXCEPT THAT THE AIRMASS HAS MODIFIED SLIGHTLY SINCE YESTERDAY. RETURN FLOW CLOUDS SHOULD CONTINUE SHIFTING INTO THE CENTRAL U.P. ON WED...BUT NOT PREVENT A DECENT AMOUNT OF SUNSHINE FROM OCCURRING. THIS SUNSHINE...COMBINED WITH 850MB TEMPS OF 14C EAST TO 16C WEST WILL BRING HIGHS INTO THE 70S AND 80S...COOLEST ALONG THE LAKE MI SHORE WITH ONSHORE WINDS AND WARMEST IN THE WESTERN U.P. WHERE THE DEEPEST MIXING IS EXPECTED. FOR WED NIGHT...THE GFS/NAM/UKMET ALL DEPICT A SHRTWV MOVING ON TOP OF THE UPPER RIDGE. THIS SHRTWV SHOULD HAVE LITTLE IMPACT GIVEN THE DRY AIR IN PLACE...AND LIKELY ONLY PRODUCING A FEW CLOUDS. THEREFORE A DRY FORECAST REMAINS. A SOUTHERLY BREEZE CONTINUES IN THE WESTERN U.P....SO TEMPS WILL BE ON THE MILD SIDE (FOLLOWED A BLEND OF THE MET/MAV GUIDANCE). FOR THE EASTERN U.P....THERE ARE INDICATIONS THAT WINDS MAY DECOUPLE IN THE INLAND AREAS. HOWEVER...PRECIPITABLE WATER VALUES ARE BETWEEN 0.75 INCHES AND 1 INCH...SUGGESTING THE NIGHT SHOULD NOT BE NEARLY AS COLD AS THE LAST TWO. THEREFORE...HAVE LOWS INLAND DROPPING BELOW GUIDANCE TO AROUND 50. .LONG TERM (THU THROUGH NEXT TUE)... PERIOD BEGINS WITH REGION STILL UNDER THE UPPER RIDGE AND INFLUENCE OF HIGH PRESSURE CENTERED OVER THE NE U.S. FARTHER WEST...LONGWAVE TROUGH WORKING INTO THE PACIFIC NW AT 00Z THURS...WHICH WILL BE THE NEXT WEATHER MAKER FOR THIS AREA AND BRING THE BEST CHANCE OF RAIN IN THE EXTENDED PERIOD. THURS LOOKS TO BE DRY WITH REGION BETWEEN THE SFC LOW OVER CANADIAN ROCKIES AND WARM FRONT STRETCHING EAST ACROSS SRN CANADA...AND UPPER LOW THAT HAS BEEN LINGERING OVER THE SRN PLAINS FOR THE LAST COUPLE OF DAYS. DISTURBANCES COMING OUT OF THE UPPER LOW WILL AFFECT THE REGION AT A COUPLE DIFFERENT TIMES. FIRST WAVE COMES THROUGH EARLY ON THURS AND EXPECTED TO BE DRY...DUE TO LIMITED FORCING AND DRY AIR LINGERING OVER THE AREA FROM THE EXISTING HIGH. MOISTURE LOOKS TO STREAM INTO THE SRN PART OF THE CWA ON THURS AFTN AND CONTINUE ACROSS THE REST OF THE CWA ON THURS NIGHT. THERE ARE SOME DIFFERENCES IN THE 00Z ECMWF AND 00/12Z GFS RUNS...AS TO LIGHT PCPN ACROSS THE SRN PART OF THE CWA FOR THURS NIGHT. THE 00Z ECMWF/GFS DO BRING PCPN TO THE AREA...AS ANOTHER WEAK SHORTWAVE AND H850-700 Q-VECTOR CONVERGENCE MOVES ACROSS THE REGION. BELIEVE THERE SHOULD BE ENOUGH MOISTURE TO SQUEEZE A SOME -SHRA OUT...SO HAVE ADDED SLIGHT CHANCES TO THE SOUTH CENTRAL PART OF THE CWA. FOR FRIDAY...PCPN CHANCES BECOME A LITTLE HARDER TO PINPOINT...AS UPPER LOW CONTINUES TO SHEAR OUT AND LINGERING ENERGY SLIDES NE ACROSS THE ERN PART OF THE CWA. WITH THE MOISTURE ALREADY PRESENT AND WEAK OMEGA/QVECTOR FORCING ON GFS/ECMWF...FELT ADDING SLIGHT CHANCES TO EASTERN HALF OF CWA WAS WARRANTED. AS FOR THE WRN HALF...WITH THE AREA BETWEEN THE WAVE TO THE EAST AND APPROACHING SFC LOW OVER LK WINNIPEG AND SFC COLD FRONT STRETCHING S ALONG THE RED RIVER VALLEY AND S TO KFSD AND INTO ERN NEB BETWEEN 18Z FRI AND 00Z SAT...DONT REALLY SEE MUCH CHANCE OF PCPN AND MORE LIKELY JUST PARTLY SUNNY SKIES. THEREFORE...ADDED SLIGHT CHANCES FOR THE WRN THIRD DUE TO APPROACHING FRONT. WINDS WILL BE A LITTLE GUSTY FROM THE SOUTH AHEAD OF THE FRONT ON FRI...WHICH MAY CREATE A FEW MARINE HEADLINES. FORTUNATELY...GULF MOISTURE WORKING NORTH WITH THE WINDS SHOULD LIMIT ANY FIRE WX ISSUES WITH THE DRY WX OF LATE. COLD FRONT MOVES THROUGH THE REGION FAIRLY QUICKLY ON FRI NIGHT AND INTO SAT. INSTABILITY INCREASES ON FRI OVER THE WRN HALF OF THE CWA...WITH MLCAPES AROUND 500-700 J/KG BY FRI EVENING. WITH THE STRONG H850 JET...AROUND 40-45KTS AHEAD OF THE FRONT...AND 6-7C H700-500 LAPSE RATES...EXPECT SOME RUMBLES OF THUNDER AS THE FRONT MOVES THROUGH. 0-6KM BULK SHEAR VALUES ARE EXPECTED TO BE AROUND 35-40KTS...BUT WITH CAPE DIMINISHING DURING THE OVERNIGHT HOURS...DOWN TO 200-400 J/KG AND VERY TALL/SKINNY...DONT REALLY EXPECT ANYTHING SEVERE. BIGGEST THREAT WILL BE SOME GUSTY WINDS IF PCPN LOADING CAN BRING SOME OF THE WINDS ALOFT DOWN. OVERALL...WITH PWAT VALUES AROUND 1.5...WE SHOULD SEE SOME MUCH NEEDED RAIN ACROSS MOST OF THE REGION. SAT NIGHT THROUGH TUES...EXTENDED MODELS IN PRETTY GOOD AGREEMENT ON HIGH PRESSURE DROPPING SOUTH ACROSS REGION. AS THE UPPER LOW SHIFTS ACROSS THE AREA ON SUN...SHOULD PROBABLY SEE SOME LOW/MID CLOUDS ACROSS LK SUPERIOR AND OVER LAND LOCATIONS NEAR LK SUPERIOR. GFS HAS BEEN HINTING THAT A FEW SHOWERS MAY DEVELOP OVER THE FAR ERN PART OF THE CWA ON SUN...WHICH WOULDNT BE SURPRISING GIVEN THE AMOUNT OF MOISTURE AND PROXIMITY TO UPPER LOW...BUT DIDNT HAVE ENOUGH CONFIDENCE TO PUT IT IN RIGHT NOW. DRIER AIR THEN WORKS INTO THE AREA FOR SUN NIGHT THROUGH TUES...AS HIGH MOVES FROM THE ARROWHEAD OF MN ON SUN...TO THE NE U.S. ON TUES. WITH LIMITED CLOUD COVER...SUBSIDING WINDS...AND PWAT VALUES EXPECTED TO BE ABOUT 50 PERCENT OF NORMAL...COULD SEE SOME COLD NIGHTS UNDER THE HIGH ON SUN/MON NIGHT. HAVE TRENDED THE LOWS DOWN INTO THE MID 40S FOR INTERIOR LOCATIONS...BUT EXPECT THE TRADITIONAL COLD SPOTS TO BE EVEN COLDER. FUTURE SHIFTS WILL PROBABLY NEED TO ADJUST THE TEMPS DOWN FURTHER. HIGHS ON MON/TUES SHOULD BE NEAR TO SLIGHTLY BELOW NORMAL WITH H850 TEMPS IN THE 10-12C RANGE. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... EXPECT VFR CONDITIONS/LGT WINDS TO PREVAIL THIS FCST PD WITH HI PRES RDG/DRY AIRMASS REMAINING DOMINANT. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE OVER SE QUEBEC WILL SHIFT EAST OVER THE NORTHEAST U.S. ON THURSDAY...ALLOWING WINDS TO SHIFT TO THE SOUTH AND INCREASE THROUGH FRIDAY. THIS IS DUE TO AN APPROACHING LOW PRESSURE SYSTEM OVER CANADA AND ASSOCIATED COLD FRONT OVER THE NRN PLAINS ON FRIDAY. WINDS ARE EXPECTED TO GET A LITTLE GUSTY ON FRIDAY...WITH GUSTS TO 25KTS OVER EASTERN LAKE SUPERIOR AND LAKE MICHIGAN. WITH THE FRONTAL PASSAGE LATE FRIDAY NIGHT AND SATURDAY...WINDS WILL BECOME GUSTY FROM THE WEST NORTHWEST UP TO 25 KNOTS. HIGH PRESSURE THEN MOVES OVER THE REGION FOR SUNDAY THROUGH TUESDAY AND KEEP WINDS LESS THAN 20KTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...SRF AVIATION...KC MARINE...SRF mi AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE MARQUETTE MI 725 PM EDT TUE AUG 19 2008 UPDATED FOR 00Z TAF ISSUANCE .SYNOPSIS... 19Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER RIDGING FROM SOUTH CENTRAL CANADA INTO THE UPPER MIDWEST...TROPICAL STORM FAY CROSSING SE FLORIDA...A 582 DAM LOW NEAR WICHITA FALLS TX...AND A TROUGH OVER THE NE PACIFIC INTO THE PACIFIC NW. UPPER MI LIES ON THE EAST SIDE OF THE UPPER RIDGE...WHICH FAVORS SUBSIDENCE AND HIGH PRESSURE AT THE SFC. CURRENTLY THIS HIGH IS CENTERED ALONG THE ERN LAKE SUPERIOR/ONTARIO SHORELINE. A LOT OF DRY AIR EXISTS NEAR THIS HIGH...NOTED ON TAMDAR SOUNDINGS FROM SAW AND CMX WHICH HAVE 30-40C DEWPOINT DEPRESSIONS BETWEEN 850-700MB. MIXING OF THIS DRY AIR TO THE SURFACE HAS BEEN SOMEWHAT TROUBLESOME...THOUGH...DUE TO THE COLD AIR THAT MOVED IN LAST NIGHT. SOME LOCATIONS LAST NIGHT DROPPED INTO THE 30S...SUCH AS CHATHAM WHICH FELL TO 34. THIS COLD AIR EVEN GENERATED SOME LAKE EFFECT CLOUDS OVER NRN LAKE MI...BUT THESE HAVE SINCE DISSIPATED. TO OUR SW...ANOTHER BAND OF MOISTURE NOTED BY CLOUDS EXTENDS FROM DLH TO GRB. TAMDAR SOUNDING FROM RHI SHOWS THIS WITH A BIT MORE SATURATION BETWEEN 800-900MB. OTHER LOW CLOUDS EXIST DOWN NEAR MILWAUKEE. FARTHER TO THE S...UPPER LEVEL MOISTURE CAN BE SEEN STREAMING NORTHWARD FROM LOUISIANA INTO MISSOURI ON THE EAST SIDE OF THE UPPER LOW. A FEW STORMS ARE ALSO NOTED IN LOUISIANA WHERE DEWPOINTS ARE IN THE 70S. WELL OFF TO THE WEST...STORMS ARE MARCHING ACROSS THE PACIFIC NW WITH THE INCOMING UPPER TROUGH. && .SHORT TERM (TONIGHT THROUGH WED NIGHT)... QUIET WEATHER IS EXPECTED TO PREVAIL THROUGH THIS PERIOD...THANKS TO THE UPPER RIDGE OVER THE UPPER MIDWEST SHIFTING OVER UPPER MI ON WED...RESULTING IN CONTINUED SUBSIDENCE. HOWEVER...THERE ARE A FEW ISSUES TO DEAL WITH...MAINLY CLOUDS AND TEMPS. THIS EVENING SHOULD GENERALLY BE CLEAR ACROSS THE CWA...THEN SOME INCREASING CLOUDS ARE EXPECTED OVER THE WESTERN U.P. AS RETURN FLOW BRINGS THE CLOUDS TO OUR SW INTO THE AREA. WHERE THESE CLOUDS MOVE IN WILL ALSO BE THE SAME AREA WHERE SOUTHERLY WINDS PICK UP TONIGHT...AND THEREFORE FORECAST LOWS ARE SIMILAR TO GUIDANCE. OVER THE EASTERN HALF OF UPPER MI WHERE SKIES ARE CLEAR...THE WINDS ARE GENERALLY LIGHT ALL NIGHT AND PRECIPITABLE WATER STAYS AROUND 0.50 INCH...EXPECTING TEMPS TO GET CHILLY AGAIN. WENT BELOW ALL GUIDANCE GIVEN WHAT HAPPENED LAST NIGHT SINCE SIMILAR CONDITIONS ARE PRESENT...EXCEPT THAT THE AIRMASS HAS MODIFIED SLIGHTLY SINCE YESTERDAY. RETURN FLOW CLOUDS SHOULD CONTINUE SHIFTING INTO THE CENTRAL U.P. ON WED...BUT NOT PREVENT A DECENT AMOUNT OF SUNSHINE FROM OCCURRING. THIS SUNSHINE...COMBINED WITH 850MB TEMPS OF 14C EAST TO 16C WEST WILL BRING HIGHS INTO THE 70S AND 80S...COOLEST ALONG THE LAKE MI SHORE WITH ONSHORE WINDS AND WARMEST IN THE WESTERN U.P. WHERE THE DEEPEST MIXING IS EXPECTED. FOR WED NIGHT...THE GFS/NAM/UKMET ALL DEPICT A SHRTWV MOVING ON TOP OF THE UPPER RIDGE. THIS SHRTWV SHOULD HAVE LITTLE IMPACT GIVEN THE DRY AIR IN PLACE...AND LIKELY ONLY PRODUCING A FEW CLOUDS. THEREFORE A DRY FORECAST REMAINS. A SOUTHERLY BREEZE CONTINUES IN THE WESTERN U.P....SO TEMPS WILL BE ON THE MILD SIDE (FOLLOWED A BLEND OF THE MET/MAV GUIDANCE). FOR THE EASTERN U.P....THERE ARE INDICATIONS THAT WINDS MAY DECOUPLE IN THE INLAND AREAS. HOWEVER...PRECIPITABLE WATER VALUES ARE BETWEEN 0.75 INCHES AND 1 INCH...SUGGESTING THE NIGHT SHOULD NOT BE NEARLY AS COLD AS THE LAST TWO. THEREFORE...HAVE LOWS INLAND DROPPING BELOW GUIDANCE TO AROUND 50. .LONG TERM (THU THROUGH NEXT TUE)... PERIOD BEGINS WITH REGION STILL UNDER THE UPPER RIDGE AND INFLUENCE OF HIGH PRESSURE CENTERED OVER THE NE U.S. FARTHER WEST...LONGWAVE TROUGH WORKING INTO THE PACIFIC NW AT 00Z THURS...WHICH WILL BE THE NEXT WEATHER MAKER FOR THIS AREA AND BRING THE BEST CHANCE OF RAIN IN THE EXTENDED PERIOD. THURS LOOKS TO BE DRY WITH REGION BETWEEN THE SFC LOW OVER CANADIAN ROCKIES AND WARM FRONT STRETCHING EAST ACROSS SRN CANADA...AND UPPER LOW THAT HAS BEEN LINGERING OVER THE SRN PLAINS FOR THE LAST COUPLE OF DAYS. DISTURBANCES COMING OUT OF THE UPPER LOW WILL AFFECT THE REGION AT A COUPLE DIFFERENT TIMES. FIRST WAVE COMES THROUGH EARLY ON THURS AND EXPECTED TO BE DRY...DUE TO LIMITED FORCING AND DRY AIR LINGERING OVER THE AREA FROM THE EXISTING HIGH. MOISTURE LOOKS TO STREAM INTO THE SRN PART OF THE CWA ON THURS AFTN AND CONTINUE ACROSS THE REST OF THE CWA ON THURS NIGHT. THERE ARE SOME DIFFERENCES IN THE 00Z ECMWF AND 00/12Z GFS RUNS...AS TO LIGHT PCPN ACROSS THE SRN PART OF THE CWA FOR THURS NIGHT. THE 00Z ECMWF/GFS DO BRING PCPN TO THE AREA...AS ANOTHER WEAK SHORTWAVE AND H850-700 Q-VECTOR CONVERGENCE MOVES ACROSS THE REGION. BELIEVE THERE SHOULD BE ENOUGH MOISTURE TO SQUEEZE A SOME -SHRA OUT...SO HAVE ADDED SLIGHT CHANCES TO THE SOUTH CENTRAL PART OF THE CWA. FOR FRIDAY...PCPN CHANCES BECOME A LITTLE HARDER TO PINPOINT...AS UPPER LOW CONTINUES TO SHEAR OUT AND LINGERING ENERGY SLIDES NE ACROSS THE ERN PART OF THE CWA. WITH THE MOISTURE ALREADY PRESENT AND WEAK OMEGA/QVECTOR FORCING ON GFS/ECMWF...FELT ADDING SLIGHT CHANCES TO EASTERN HALF OF CWA WAS WARRANTED. AS FOR THE WRN HALF...WITH THE AREA BETWEEN THE WAVE TO THE EAST AND APPROACHING SFC LOW OVER LK WINNIPEG AND SFC COLD FRONT STRETCHING S ALONG THE RED RIVER VALLEY AND S TO KFSD AND INTO ERN NEB BETWEEN 18Z FRI AND 00Z SAT...DONT REALLY SEE MUCH CHANCE OF PCPN AND MORE LIKELY JUST PARTLY SUNNY SKIES. THEREFORE...ADDED SLIGHT CHANCES FOR THE WRN THIRD DUE TO APPROACHING FRONT. WINDS WILL BE A LITTLE GUSTY FROM THE SOUTH AHEAD OF THE FRONT ON FRI...WHICH MAY CREATE A FEW MARINE HEADLINES. FORTUNATELY...GULF MOISTURE WORKING NORTH WITH THE WINDS SHOULD LIMIT ANY FIRE WX ISSUES WITH THE DRY WX OF LATE. COLD FRONT MOVES THROUGH THE REGION FAIRLY QUICKLY ON FRI NIGHT AND INTO SAT. INSTABILITY INCREASES ON FRI OVER THE WRN HALF OF THE CWA...WITH MLCAPES AROUND 500-700 J/KG BY FRI EVENING. WITH THE STRONG H850 JET...AROUND 40-45KTS AHEAD OF THE FRONT...AND 6-7C H700-500 LAPSE RATES...EXPECT SOME RUMBLES OF THUNDER AS THE FRONT MOVES THROUGH. 0-6KM BULK SHEAR VALUES ARE EXPECTED TO BE AROUND 35-40KTS...BUT WITH CAPE DIMINISHING DURING THE OVERNIGHT HOURS...DOWN TO 200-400 J/KG AND VERY TALL/SKINNY...DONT REALLY EXPECT ANYTHING SEVERE. BIGGEST THREAT WILL BE SOME GUSTY WINDS IF PCPN LOADING CAN BRING SOME OF THE WINDS ALOFT DOWN. OVERALL...WITH PWAT VALUES AROUND 1.5...WE SHOULD SEE SOME MUCH NEEDED RAIN ACROSS MOST OF THE REGION. SAT NIGHT THROUGH TUES...EXTENDED MODELS IN PRETTY GOOD AGREEMENT ON HIGH PRESSURE DROPPING SOUTH ACROSS REGION. AS THE UPPER LOW SHIFTS ACROSS THE AREA ON SUN...SHOULD PROBABLY SEE SOME LOW/MID CLOUDS ACROSS LK SUPERIOR AND OVER LAND LOCATIONS NEAR LK SUPERIOR. GFS HAS BEEN HINTING THAT A FEW SHOWERS MAY DEVELOP OVER THE FAR ERN PART OF THE CWA ON SUN...WHICH WOULDNT BE SURPRISING GIVEN THE AMOUNT OF MOISTURE AND PROXIMITY TO UPPER LOW...BUT DIDNT HAVE ENOUGH CONFIDENCE TO PUT IT IN RIGHT NOW. DRIER AIR THEN WORKS INTO THE AREA FOR SUN NIGHT THROUGH TUES...AS HIGH MOVES FROM THE ARROWHEAD OF MN ON SUN...TO THE NE U.S. ON TUES. WITH LIMITED CLOUD COVER...SUBSIDING WINDS...AND PWAT VALUES EXPECTED TO BE ABOUT 50 PERCENT OF NORMAL...COULD SEE SOME COLD NIGHTS UNDER THE HIGH ON SUN/MON NIGHT. HAVE TRENDED THE LOWS DOWN INTO THE MID 40S FOR INTERIOR LOCATIONS...BUT EXPECT THE TRADITIONAL COLD SPOTS TO BE EVEN COLDER. FUTURE SHIFTS WILL PROBABLY NEED TO ADJUST THE TEMPS DOWN FURTHER. HIGHS ON MON/TUES SHOULD BE NEAR TO SLIGHTLY BELOW NORMAL WITH H850 TEMPS IN THE 10-12C RANGE. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... EXPECT VFR CONDITIONS/LGT WINDS TO PREVAIL THIS FCST PD WITH HI PRES RDG/DRY AIRMASS REMAINING DOMINANT. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE OVER SE QUEBEC WILL SHIFT EAST OVER THE NORTHEAST U.S. ON THURSDAY...ALLOWING WINDS TO SHIFT TO THE SOUTH AND INCREASE THROUGH FRIDAY. THIS IS DUE TO AN APPROACHING LOW PRESSURE SYSTEM OVER CANADA AND ASSOCIATED COLD FRONT OVER THE NRN PLAINS ON FRIDAY. WINDS ARE EXPECTED TO GET A LITTLE GUSTY ON FRIDAY...WITH GUSTS TO 25KTS OVER EASTERN LAKE SUPERIOR AND LAKE MICHIGAN. WITH THE FRONTAL PASSAGE LATE FRIDAY NIGHT AND SATURDAY...WINDS WILL BECOME GUSTY FROM THE WEST NORTHWEST UP TO 25 KNOTS. HIGH PRESSURE THEN MOVES OVER THE REGION FOR SUNDAY THROUGH TUESDAY AND KEEP WINDS LESS THAN 20KTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...SRF AVIATION...KC MARINE...SRF mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 330 PM EDT TUE AUG 19 2008 .SYNOPSIS... 19Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED UPPER RIDGING FROM SOUTH CENTRAL CANADA INTO THE UPPER MIDWEST...TROPICAL STORM FAY CROSSING SE FLORIDA...A 582 DAM LOW NEAR WICHITA FALLS TX...AND A TROUGH OVER THE NE PACIFIC INTO THE PACIFIC NW. UPPER MI LIES ON THE EAST SIDE OF THE UPPER RIDGE...WHICH FAVORS SUBSIDENCE AND HIGH PRESSURE AT THE SFC. CURRENTLY THIS HIGH IS CENTERED ALONG THE ERN LAKE SUPERIOR/ONTARIO SHORELINE. A LOT OF DRY AIR EXISTS NEAR THIS HIGH...NOTED ON TAMDAR SOUNDINGS FROM SAW AND CMX WHICH HAVE 30-40C DEWPOINT DEPRESSIONS BETWEEN 850-700MB. MIXING OF THIS DRY AIR TO THE SURFACE HAS BEEN SOMEWHAT TROUBLESOME...THOUGH...DUE TO THE COLD AIR THAT MOVED IN LAST NIGHT. SOME LOCATIONS LAST NIGHT DROPPED INTO THE 30S...SUCH AS CHATHAM WHICH FELL TO 34. THIS COLD AIR EVEN GENERATED SOME LAKE EFFECT CLOUDS OVER NRN LAKE MI...BUT THESE HAVE SINCE DISSIPATED. TO OUR SW...ANOTHER BAND OF MOISTURE NOTED BY CLOUDS EXTENDS FROM DLH TO GRB. TAMDAR SOUNDING FROM RHI SHOWS THIS WITH A BIT MORE SATURATION BETWEEN 800-900MB. OTHER LOW CLOUDS EXIST DOWN NEAR MILWAUKEE. FARTHER TO THE S...UPPER LEVEL MOISTURE CAN BE SEEN STREAMING NORTHWARD FROM LOUISIANA INTO MISSOURI ON THE EAST SIDE OF THE UPPER LOW. A FEW STORMS ARE ALSO NOTED IN LOUISIANA WHERE DEWPOINTS ARE IN THE 70S. WELL OFF TO THE WEST...STORMS ARE MARCHING ACROSS THE PACIFIC NW WITH THE INCOMING UPPER TROUGH. && .SHORT TERM (TONIGHT THROUGH WED NIGHT)... QUIET WEATHER IS EXPECTED TO PREVAIL THROUGH THIS PERIOD...THANKS TO THE UPPER RIDGE OVER THE UPPER MIDWEST SHIFTING OVER UPPER MI ON WED...RESULTING IN CONTINUED SUBSIDENCE. HOWEVER...THERE ARE A FEW ISSUES TO DEAL WITH...MAINLY CLOUDS AND TEMPS. THIS EVENING SHOULD GENERALLY BE CLEAR ACROSS THE CWA...THEN SOME INCREASING CLOUDS ARE EXPECTED OVER THE WESTERN U.P. AS RETURN FLOW BRINGS THE CLOUDS TO OUR SW INTO THE AREA. WHERE THESE CLOUDS MOVE IN WILL ALSO BE THE SAME AREA WHERE SOUTHERLY WINDS PICK UP TONIGHT...AND THEREFORE FORECAST LOWS ARE SIMILAR TO GUIDANCE. OVER THE EASTERN HALF OF UPPER MI WHERE SKIES ARE CLEAR...THE WINDS ARE GENERALLY LIGHT ALL NIGHT AND PRECIPITABLE WATER STAYS AROUND 0.50 INCH...EXPECTING TEMPS TO GET CHILLY AGAIN. WENT BELOW ALL GUIDANCE GIVEN WHAT HAPPENED LAST NIGHT SINCE SIMILAR CONDITIONS ARE PRESENT...EXCEPT THAT THE AIRMASS HAS MODIFIED SLIGHTLY SINCE YESTERDAY. RETURN FLOW CLOUDS SHOULD CONTINUE SHIFTING INTO THE CENTRAL U.P. ON WED...BUT NOT PREVENT A DECENT AMOUNT OF SUNSHINE FROM OCCURRING. THIS SUNSHINE...COMBINED WITH 850MB TEMPS OF 14C EAST TO 16C WEST WILL BRING HIGHS INTO THE 70S AND 80S...COOLEST ALONG THE LAKE MI SHORE WITH ONSHORE WINDS AND WARMEST IN THE WESTERN U.P. WHERE THE DEEPEST MIXING IS EXPECTED. FOR WED NIGHT...THE GFS/NAM/UKMET ALL DEPICT A SHRTWV MOVING ON TOP OF THE UPPER RIDGE. THIS SHRTWV SHOULD HAVE LITTLE IMPACT GIVEN THE DRY AIR IN PLACE...AND LIKELY ONLY PRODUCING A FEW CLOUDS. THEREFORE A DRY FORECAST REMAINS. A SOUTHERLY BREEZE CONTINUES IN THE WESTERN U.P....SO TEMPS WILL BE ON THE MILD SIDE (FOLLOWED A BLEND OF THE MET/MAV GUIDANCE). FOR THE EASTERN U.P....THERE ARE INDICATIONS THAT WINDS MAY DECOUPLE IN THE INLAND AREAS. HOWEVER...PRECIPITABLE WATER VALUES ARE BETWEEN 0.75 INCHES AND 1 INCH...SUGGESTING THE NIGHT SHOULD NOT BE NEARLY AS COLD AS THE LAST TWO. THEREFORE...HAVE LOWS INLAND DROPPING BELOW GUIDANCE TO AROUND 50. .LONG TERM (THU THROUGH NEXT TUE)... PERIOD BEGINS WITH REGION STILL UNDER THE UPPER RIDGE AND INFLUENCE OF HIGH PRESSURE CENTERED OVER THE NE U.S. FARTHER WEST...LONGWAVE TROUGH WORKING INTO THE PACIFIC NW AT 00Z THURS...WHICH WILL BE THE NEXT WEATHER MAKER FOR THIS AREA AND BRING THE BEST CHANCE OF RAIN IN THE EXTENDED PERIOD. THURS LOOKS TO BE DRY WITH REGION BETWEEN THE SFC LOW OVER CANADIAN ROCKIES AND WARM FRONT STRETCHING EAST ACROSS SRN CANADA...AND UPPER LOW THAT HAS BEEN LINGERING OVER THE SRN PLAINS FOR THE LAST COUPLE OF DAYS. DISTURBANCES COMING OUT OF THE UPPER LOW WILL AFFECT THE REGION AT A COUPLE DIFFERENT TIMES. FIRST WAVE COMES THROUGH EARLY ON THURS AND EXPECTED TO BE DRY...DUE TO LIMITED FORCING AND DRY AIR LINGERING OVER THE AREA FROM THE EXISTING HIGH. MOISTURE LOOKS TO STREAM INTO THE SRN PART OF THE CWA ON THURS AFTN AND CONTINUE ACROSS THE REST OF THE CWA ON THURS NIGHT. THERE ARE SOME DIFFERENCES IN THE 00Z ECMWF AND 00/12Z GFS RUNS...AS TO LIGHT PCPN ACROSS THE SRN PART OF THE CWA FOR THURS NIGHT. THE 00Z ECMWF/GFS DO BRING PCPN TO THE AREA...AS ANOTHER WEAK SHORTWAVE AND H850-700 Q-VECTOR CONVERGENCE MOVES ACROSS THE REGION. BELIEVE THERE SHOULD BE ENOUGH MOISTURE TO SQUEEZE A SOME -SHRA OUT...SO HAVE ADDED SLIGHT CHANCES TO THE SOUTH CENTRAL PART OF THE CWA. FOR FRIDAY...PCPN CHANCES BECOME A LITTLE HARDER TO PINPOINT...AS UPPER LOW CONTINUES TO SHEAR OUT AND LINGERING ENERGY SLIDES NE ACROSS THE ERN PART OF THE CWA. WITH THE MOISTURE ALREADY PRESENT AND WEAK OMEGA/QVECTOR FORCING ON GFS/ECMWF...FELT ADDING SLIGHT CHANCES TO EASTERN HALF OF CWA WAS WARRANTED. AS FOR THE WRN HALF...WITH THE AREA BETWEEN THE WAVE TO THE EAST AND APPROACHING SFC LOW OVER LK WINNIPEG AND SFC COLD FRONT STRETCHING S ALONG THE RED RIVER VALLEY AND S TO KFSD AND INTO ERN NEB BETWEEN 18Z FRI AND 00Z SAT...DONT REALLY SEE MUCH CHANCE OF PCPN AND MORE LIKELY JUST PARTLY SUNNY SKIES. THEREFORE...ADDED SLIGHT CHANCES FOR THE WRN THIRD DUE TO APPROACHING FRONT. WINDS WILL BE A LITTLE GUSTY FROM THE SOUTH AHEAD OF THE FRONT ON FRI...WHICH MAY CREATE A FEW MARINE HEADLINES. FORTUNATELY...GULF MOISTURE WORKING NORTH WITH THE WINDS SHOULD LIMIT ANY FIRE WX ISSUES WITH THE DRY WX OF LATE. COLD FRONT MOVES THROUGH THE REGION FAIRLY QUICKLY ON FRI NIGHT AND INTO SAT. INSTABILITY INCREASES ON FRI OVER THE WRN HALF OF THE CWA...WITH MLCAPES AROUND 500-700 J/KG BY FRI EVENING. WITH THE STRONG H850 JET...AROUND 40-45KTS AHEAD OF THE FRONT...AND 6-7C H700-500 LAPSE RATES...EXPECT SOME RUMBLES OF THUNDER AS THE FRONT MOVES THROUGH. 0-6KM BULK SHEAR VALUES ARE EXPECTED TO BE AROUND 35-40KTS...BUT WITH CAPE DIMINISHING DURING THE OVERNIGHT HOURS...DOWN TO 200-400 J/KG AND VERY TALL/SKINNY...DONT REALLY EXPECT ANYTHING SEVERE. BIGGEST THREAT WILL BE SOME GUSTY WINDS IF PCPN LOADING CAN BRING SOME OF THE WINDS ALOFT DOWN. OVERALL...WITH PWAT VALUES AROUND 1.5...WE SHOULD SEE SOME MUCH NEEDED RAIN ACROSS MOST OF THE REGION. SAT NIGHT THROUGH TUES...EXTENDED MODELS IN PRETTY GOOD AGREEMENT ON HIGH PRESSURE DROPPING SOUTH ACROSS REGION. AS THE UPPER LOW SHIFTS ACROSS THE AREA ON SUN...SHOULD PROBABLY SEE SOME LOW/MID CLOUDS ACROSS LK SUPERIOR AND OVER LAND LOCATIONS NEAR LK SUPERIOR. GFS HAS BEEN HINTING THAT A FEW SHOWERS MAY DEVELOP OVER THE FAR ERN PART OF THE CWA ON SUN...WHICH WOULDNT BE SURPRISING GIVEN THE AMOUNT OF MOISTURE AND PROXIMITY TO UPPER LOW...BUT DIDNT HAVE ENOUGH CONFIDENCE TO PUT IT IN RIGHT NOW. DRIER AIR THEN WORKS INTO THE AREA FOR SUN NIGHT THROUGH TUES...AS HIGH MOVES FROM THE ARROWHEAD OF MN ON SUN...TO THE NE U.S. ON TUES. WITH LIMITED CLOUD COVER...SUBSIDING WINDS...AND PWAT VALUES EXPECTED TO BE ABOUT 50 PERCENT OF NORMAL...COULD SEE SOME COLD NIGHTS UNDER THE HIGH ON SUN/MON NIGHT. HAVE TRENDED THE LOWS DOWN INTO THE MID 40S FOR INTERIOR LOCATIONS...BUT EXPECT THE TRADITIONAL COLD SPOTS TO BE EVEN COLDER. FUTURE SHIFTS WILL PROBABLY NEED TO ADJUST THE TEMPS DOWN FURTHER. HIGHS ON MON/TUES SHOULD BE NEAR TO SLIGHTLY BELOW NORMAL WITH H850 TEMPS IN THE 10-12C RANGE. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... VFR CONDITIONS EXPECTED FOR BOTH TAF SITES THROUGH THE NEXT 24 HOURS WITH HIGH PRESSURE IN CONTROL. THERE ARE TWO ITEMS OF SOME CONCERN. THE FIRST IS POTENTIAL FOR LLWS AT CMX BTWN 06-12Z...BUT WITH SFC WINDS INCREASING THROUGH THE NIGHT AND THE MAX WIND SPEED WITH THE SHEAR BTWN 25-30 KT...HAVE DISCOUNTED MENTIONING IT FOR NOW. THE SECOND ITEM OF CONCERN IS IF ANY LAKE EFFECT CLOUDS OVER NRN LAKE MI WILL HOLD TOGETHER THE REST OF THE AFTN...THEN UPSLOPE INTO SAW AROUND MIDNIGHT. RIGHT NOW HAVE DISCOUNTED THE IDEA SINCE THE LAKE EFFECT CLOUDS ARE IN THE PROCESS OF DISSIPATING. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... HIGH PRESSURE OVER SE QUEBEC WILL SHIFT EAST OVER THE NORTHEAST U.S. ON THURSDAY...ALLOWING WINDS TO SHIFT TO THE SOUTH AND INCREASE THROUGH FRIDAY. THIS IS DUE TO AN APPROACHING LOW PRESSURE SYSTEM OVER CANADA AND ASSOCIATED COLD FRONT OVER THE NRN PLAINS ON FRIDAY. WINDS ARE EXPECTED TO GET A LITTLE GUSTY ON FRIDAY...WITH GUSTS TO 25KTS OVER EASTERN LAKE SUPERIOR AND LAKE MICHIGAN. WITH THE FRONTAL PASSAGE LATE FRIDAY NIGHT AND SATURDAY...WINDS WILL BECOME GUSTY FROM THE WEST NORTHWEST UP TO 25 KNOTS. HIGH PRESSURE THEN MOVES OVER THE REGION FOR SUNDAY THROUGH TUESDAY AND KEEP WINDS LESS THAN 20KTS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...SRF AVIATION...AJ MARINE...SRF mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 128 PM EDT TUE AUG 19 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAFS .SYNOPSIS... (ISSUED AT 420 AM EDT) IR SATELLITE AND RUC ANALYSIS SHOW AN UPPER TROUGH OVER THE NORTHEASTERN UNITED STATES...WITH ZONAL FLOW ACROSS THE MID-ATLANTIC STATES. UPPER LEVEL RIDGING DOMINATES THE CENTRAL UNITED STATES EXCEPT FOR A CUTOFF LOW OVER THE OK-TX PANHANDLES. A SECOND TROUGH IS JUST OFFSHORE THE WESTERN UNITED STATES. AT THE SURFACE...LOW PRESSURE MOVING OVER THE ST LAWRENCE RIVER VALLEY HAS A COLD FRONT EXTENDING ACROSS THE EASTERN GREAT LAKES INTO LOWER MICHIGAN. THIS COLD FRONT BROUGHT SHARPLY COLDER TEMPERATURES AND LITTLE PRECIPITATION TO OUR AREA YESTERDAY...BUT WAS RESPONSIBLE FOR SOME ISOLATED WIND AND HAIL REPORTS IN NEW YORK AND NEW ENGLAND YESTERDAY AFTERNOON AND EVENING. HIGH PRESSURE NORTH OF LAKE SUPERIOR IS SLOWLY DRIFTING SOUTH AND EXTENDING INTO THE WESTERN GREAT LAKES. TROPICAL STORM FAY IS SLOWLY MOVING NORTH IN THE GULF OF MEXICO...BETWEEN THE FLORIDA PENINSULA AND KEYS. && .DISCUSSION... (ISSUED AT 420 AM EDT) QUIET PATTERN WITH HIGH PRESSURE OVERHEAD THROUGH THE WEEK RESULTS IN ONLY MINOR CHANGES TO THE FORECAST. LESS CONFIDENT ABOUT LOW TEMPERATURES TONIGHT ACROSS THE WEST AS MODELS ARE NOW SHOWING VARYING AMOUNTS OF MOISTURE FOR THAT PORTION OF THE FORECAST AREA. LOW TO MID LEVEL MOISTURE THAT WAS PREVIOUSLY SHOWN MOVING INTO THE AREA DURING THAT TIME PERIOD IS NOT AS PREVALENT IN THE GFS...ALTHOUGH THE NAM STILL HAS THIS MOISTURE PRESENT. DECIDED TO NUDGE LOWS DOWN A LITTLE IN THE WEST IN CASE CONDITIONS ARE MORE DRY THAN ORIGINALLY FORECAST AND RADIATIONAL COOLING CAN OCCUR. MOSTLY CLEAR SKIES SHOULD THEN DOMINATE WED AND THURS...WITH TEMPERATURES REMAINING AT OR SLIGHTLY ABOVE NORMAL. UPPER LEVEL LOW CURRENTLY OVER TEXAS IS EXPECTED TO REMAIN NEARLY STATIONARY OVER THE NEXT TWO DAYS BEFORE SLOWLY DRIFTING NORTH AND SHEARING APART ON FRIDAY. ONE SHORTWAVE IS EXPECTED TO ROTATE THROUGH THE AREA ON THURSDAY MORNING...BUT WITH DRY AIR ENTRENCHED NO PRECIPITATION IS EXPECTED. HOWEVER...A SECOND SHORTWAVE MOVING OUT FROM THE UPPER LOW SHOULD MOVE THROUGH THE AREA LATE THURSDAY NIGHT INTO FRIDAY. MOISTURE FROM THE GULF OF MEXICO IS EXPECTED TO ACCOMPANY THIS SHORTWAVE...AND THIS COULD ALLOW FOR SOME PRECIPITATION IN ADVANCE OF THE APPROACHING UPPER TROUGH FROM THE WEST. ADDED SLIGHT CHANCE POPS TO THE WEST HALF OF UPPER MI FOR FRIDAY MORNING TO ACCOUNT FOR THIS FEATURE. GOING FORECAST FOR POPS WITH THE TROUGH MOVING THROUGH THE AREA FRIDAY AFTERNOON INTO SATURDAY STILL APPEAR FINE. WAS TEMPTED TO INCREASE POPS FOR FRIDAY EVENING...BUT FORCING REMAINS A POTENTIAL LIMITING FACTOR WITH THE SYSTEM. GFS AND ECMWF SHOW STRONG Q-VECTOR CONVERGENCE AND 500MB VORTICITY ACROSS THE NORTHERN PLAINS FRIDAY MORNING...BUT SHOW THESE QUANTITIES DIMINISHING AS THE SYSTEM PASSES OVER THE AREA. BEST CHANCE FOR PRECIPITATION FRIDAY NIGHT MAY LIKELY END UP OVER LAKE SUPERIOR OR FARTHER TO THE NORTH. PRECIPITATION CHANCES WILL THEN COME TO AN END SATURDAY AFTERNOON AS THE DRY SLOT MOVES THROUGH. 00Z GFS IS A TOUCH MORE PROGRESSIVE WITH THE TIMING OF THE FRONTAL PASSAGE...BUT WILL NOT CHANGE THE END TIME OF PRECIPITATION CHANCES IN THE FORECAST AT THIS TIME. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... VFR CONDITIONS EXPECTED FOR BOTH TAF SITES THROUGH THE NEXT 24 HOURS WITH HIGH PRESSURE IN CONTROL. THERE ARE TWO ITEMS OF SOME CONCERN. THE FIRST IS POTENTIAL FOR LLWS AT CMX BTWN 06-12Z...BUT WITH SFC WINDS INCREASING THROUGH THE NIGHT AND THE MAX WIND SPEED WITH THE SHEAR BTWN 25-30 KT...HAVE DISCOUNTED MENTIONING IT FOR NOW. THE SECOND ITEM OF CONCERN IS IF ANY LAKE EFFECT CLOUDS OVER NRN LAKE MI WILL HOLD TOGETHER THE REST OF THE AFTN...THEN UPSLOPE INTO SAW AROUND MIDNIGHT. RIGHT NOW HAVE DISCOUNTED THE IDEA SINCE THE LAKE EFFECT CLOUDS ARE IN THE PROCESS OF DISSIPATING. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... AS HIGH PRES JUST N OF LAKE SUPERIOR MOVES TO THE LOWER GREAT LAKES BY WED MORNING...ERLY WINDS THIS MORNING WILL VEER SRLY BY WED MORNING. SPEEDS WILL GENERALLY BE IN THE 10-20KT RANGE THOUGH THERE WILL BE GUSTS TO AROUND 25KT...MAINLY OVER FAR WRN LAKE SUPERIOR. S TO SE WINDS WILL THEN PERSIST THRU FRI AS THE HIGH SHIFTS TO THE E COAST AND LOW PRES ORGANIZES OVER THE NORTHERN PLAINS. WINDS OF 10-20KT WITH GUSTS TO AROUND 25KT ARE EXPECTED DURING THIS TIME WITH THE HIGHEST SPEEDS OVER EASTERN LAKE SUPERIOR. AHEAD OF AN APPROACHING COLD FRONT...WIND GUSTS COULD REACH UP TO 30 KT FRI/FRI NIGHT OVER EASTERN LAKE SUPERIOR. IN THE WAKE OF THE COLD FRONT SAT...MUCH OF LAKE SUPERIOR SHOULD SEE WEST WIND GUSTS UP TO 25 KT...ESPECIALLY OVER THE WEST HALF OF THE LAKE. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS...TAG DISCUSSION...TAG AVIATION...AJ MARINE...ROLFSON mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 735 AM EDT TUE AUG 19 2008 UPDATED AVIATION DISCUSSION FOR 12Z TAFS .SYNOPSIS... (ISSUED AT 420 AM EDT) IR SATELLITE AND RUC ANALYSIS SHOW AN UPPER TROUGH OVER THE NORTHEASTERN UNITED STATES...WITH ZONAL FLOW ACROSS THE MID-ATLANTIC STATES. UPPER LEVEL RIDGING DOMINATES THE CENTRAL UNITED STATES EXCEPT FOR A CUTOFF LOW OVER THE OK-TX PANHANDLES. A SECOND TROUGH IS JUST OFFSHORE THE WESTERN UNITED STATES. AT THE SURFACE...LOW PRESSURE MOVING OVER THE ST LAWRENCE RIVER VALLEY HAS A COLD FRONT EXTENDING ACROSS THE EASTERN GREAT LAKES INTO LOWER MICHIGAN. THIS COLD FRONT BROUGHT SHARPLY COLDER TEMPERATURES AND LITTLE PRECIPITATION TO OUR AREA YESTERDAY...BUT WAS RESPONSIBLE FOR SOME ISOLATED WIND AND HAIL REPORTS IN NEW YORK AND NEW ENGLAND YESTERDAY AFTERNOON AND EVENING. HIGH PRESSURE NORTH OF LAKE SUPERIOR IS SLOWLY DRIFTING SOUTH AND EXTENDING INTO THE WESTERN GREAT LAKES. TROPICAL STORM FAY IS SLOWLY MOVING NORTH IN THE GULF OF MEXICO...BETWEEN THE FLORIDA PENINSULA AND KEYS. && .DISCUSSION... (ISSUED AT 420 AM EDT) QUIET PATTERN WITH HIGH PRESSURE OVERHEAD THROUGH THE WEEK RESULTS IN ONLY MINOR CHANGES TO THE FORECAST. LESS CONFIDENT ABOUT LOW TEMPERATURES TONIGHT ACROSS THE WEST AS MODELS ARE NOW SHOWING VARYING AMOUNTS OF MOISTURE FOR THAT PORTION OF THE FORECAST AREA. LOW TO MID LEVEL MOISTURE THAT WAS PREVIOUSLY SHOWN MOVING INTO THE AREA DURING THAT TIME PERIOD IS NOT AS PREVALENT IN THE GFS...ALTHOUGH THE NAM STILL HAS THIS MOISTURE PRESENT. DECIDED TO NUDGE LOWS DOWN A LITTLE IN THE WEST IN CASE CONDITIONS ARE MORE DRY THAN ORIGINALLY FORECAST AND RADIATIONAL COOLING CAN OCCUR. MOSTLY CLEAR SKIES SHOULD THEN DOMINATE WED AND THURS...WITH TEMPERATURES REMAINING AT OR SLIGHTLY ABOVE NORMAL. UPPER LEVEL LOW CURRENTLY OVER TEXAS IS EXPECTED TO REMAIN NEARLY STATIONARY OVER THE NEXT TWO DAYS BEFORE SLOWLY DRIFTING NORTH AND SHEARING APART ON FRIDAY. ONE SHORTWAVE IS EXPECTED TO ROTATE THROUGH THE AREA ON THURSDAY MORNING...BUT WITH DRY AIR ENTRENCHED NO PRECIPITATION IS EXPECTED. HOWEVER...A SECOND SHORTWAVE MOVING OUT FROM THE UPPER LOW SHOULD MOVE THROUGH THE AREA LATE THURSDAY NIGHT INTO FRIDAY. MOISTURE FROM THE GULF OF MEXICO IS EXPECTED TO ACCOMPANY THIS SHORTWAVE...AND THIS COULD ALLOW FOR SOME PRECIPITATION IN ADVANCE OF THE APPROACHING UPPER TROUGH FROM THE WEST. ADDED SLIGHT CHANCE POPS TO THE WEST HALF OF UPPER MI FOR FRIDAY MORNING TO ACCOUNT FOR THIS FEATURE. GOING FORECAST FOR POPS WITH THE TROUGH MOVING THROUGH THE AREA FRIDAY AFTERNOON INTO SATURDAY STILL APPEAR FINE. WAS TEMPTED TO INCREASE POPS FOR FRIDAY EVENING...BUT FORCING REMAINS A POTENTIAL LIMITING FACTOR WITH THE SYSTEM. GFS AND ECMWF SHOW STRONG Q-VECTOR CONVERGENCE AND 500MB VORTICITY ACROSS THE NORTHERN PLAINS FRIDAY MORNING...BUT SHOW THESE QUANTITIES DIMINISHING AS THE SYSTEM PASSES OVER THE AREA. BEST CHANCE FOR PRECIPITATION FRIDAY NIGHT MAY LIKELY END UP OVER LAKE SUPERIOR OR FARTHER TO THE NORTH. PRECIPITATION CHANCES WILL THEN COME TO AN END SATURDAY AFTERNOON AS THE DRY SLOT MOVES THROUGH. 00Z GFS IS A TOUCH MORE PROGRESSIVE WITH THE TIMING OF THE FRONTAL PASSAGE...BUT WILL NOT CHANGE THE END TIME OF PRECIPITATION CHANCES IN THE FORECAST AT THIS TIME. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... SHALLOW MOISTURE IN ERLY UPSLOPE FLOW OFF LAKE SUPERIOR WILL RESULT IN OCCASIONAL MVFR CIGS AT KCMX FOR THE NEXT COUPLE OF HRS. OTHERWISE...DRYING AIRMASS AIDED BY DIURNAL HEATING/MIXING WILL ENSURE VFR CONDITIONS TODAY AT KCMX/KSAW. VFR CONDITIONS WILL THEN PERSIST THRU THE END OF THIS FCST PERIOD. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... AS HIGH PRES JUST N OF LAKE SUPERIOR MOVES TO THE LOWER GREAT LAKES BY WED MORNING...ERLY WINDS THIS MORNING WILL VEER SRLY BY WED MORNING. SPEEDS WILL GENERALLY BE IN THE 10-20KT RANGE THOUGH THERE WILL BE GUSTS TO AROUND 25KT...MAINLY OVER FAR WRN LAKE SUPERIOR. S TO SE WINDS WILL THEN PERSIST THRU FRI AS THE HIGH SHIFTS TO THE E COAST AND LOW PRES ORGANIZES OVER THE NORTHERN PLAINS. WINDS OF 10-20KT WITH GUSTS TO AROUND 25KT ARE EXPECTED DURING THIS TIME WITH THE HIGHEST SPEEDS OVER EASTERN LAKE SUPERIOR. AHEAD OF AN APPROACHING COLD FRONT...WIND GUSTS COULD REACH UP TO 30 KT FRI/FRI NIGHT OVER EASTERN LAKE SUPERIOR. IN THE WAKE OF THE COLD FRONT SAT...MUCH OF LAKE SUPERIOR SHOULD SEE WEST WIND GUSTS UP TO 25 KT...ESPECIALLY OVER THE WEST HALF OF THE LAKE. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS...TAG DISCUSSION...TAG AVIATION...ROLFSON MARINE...ROLFSON mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 420 AM EDT TUE AUG 19 2008 .SYNOPSIS... IR SATELLITE AND RUC ANALYSIS SHOW AN UPPER TROUGH OVER THE NORTHEASTERN UNITED STATES...WITH ZONAL FLOW ACROSS THE MID-ATLANTIC STATES. UPPER LEVEL RIDGING DOMINATES THE CENTRAL UNITED STATES EXCEPT FOR A CUTOFF LOW OVER THE OK-TX PANHANDLES. A SECOND TROUGH IS JUST OFFSHORE THE WESTERN UNITED STATES. AT THE SURFACE...LOW PRESSURE MOVING OVER THE ST LAWRENCE RIVER VALLEY HAS A COLD FRONT EXTENDING ACROSS THE EASTERN GREAT LAKES INTO LOWER MICHIGAN. THIS COLD FRONT BROUGHT SHARPLY COLDER TEMPERATURES AND LITTLE PRECIPITATION TO OUR AREA YESTERDAY...BUT WAS RESPONSIBLE FOR SOME ISOLATED WIND AND HAIL REPORTS IN NEW YORK AND NEW ENGLAND YESTERDAY AFTERNOON AND EVENING. HIGH PRESSURE NORTH OF LAKE SUPERIOR IS SLOWLY DRIFTING SOUTH AND EXTENDING INTO THE WESTERN GREAT LAKES. TROPICAL STORM FAY IS SLOWLY MOVING NORTH IN THE GULF OF MEXICO...BETWEEN THE FLORIDA PENINSULA AND KEYS. && .DISCUSSION... QUIET PATTERN WITH HIGH PRESSURE OVERHEAD THROUGH THE WEEK RESULTS IN ONLY MINOR CHANGES TO THE FORECAST. LESS CONFIDENT ABOUT LOW TEMPERATURES TONIGHT ACROSS THE WEST AS MODELS ARE NOW SHOWING VARYING AMOUNTS OF MOISTURE FOR THAT PORTION OF THE FORECAST AREA. LOW TO MID LEVEL MOISTURE THAT WAS PREVIOUSLY SHOWN MOVING INTO THE AREA DURING THAT TIME PERIOD IS NOT AS PREVALENT IN THE GFS...ALTHOUGH THE NAM STILL HAS THIS MOISTURE PRESENT. DECIDED TO NUDGE LOWS DOWN A LITTLE IN THE WEST IN CASE CONDITIONS ARE MORE DRY THAN ORIGINALLY FORECAST AND RADIATIONAL COOLING CAN OCCUR. MOSTLY CLEAR SKIES SHOULD THEN DOMINATE WED AND THURS...WITH TEMPERATURES REMAINING AT OR SLIGHTLY ABOVE NORMAL. UPPER LEVEL LOW CURRENTLY OVER TEXAS IS EXPECTED TO REMAIN NEARLY STATIONARY OVER THE NEXT TWO DAYS BEFORE SLOWLY DRIFTING NORTH AND SHEARING APART ON FRIDAY. ONE SHORTWAVE IS EXPECTED TO ROTATE THROUGH THE AREA ON THURSDAY MORNING...BUT WITH DRY AIR ENTRENCHED NO PRECIPITATION IS EXPECTED. HOWEVER...A SECOND SHORTWAVE MOVING OUT FROM THE UPPER LOW SHOULD MOVE THROUGH THE AREA LATE THURSDAY NIGHT INTO FRIDAY. MOISTURE FROM THE GULF OF MEXICO IS EXPECTED TO ACCOMPANY THIS SHORTWAVE...AND THIS COULD ALLOW FOR SOME PRECIPITATION IN ADVANCE OF THE APPROACHING UPPER TROUGH FROM THE WEST. ADDED SLIGHT CHANCE POPS TO THE WEST HALF OF UPPER MI FOR FRIDAY MORNING TO ACCOUNT FOR THIS FEATURE. GOING FORECAST FOR POPS WITH THE TROUGH MOVING THROUGH THE AREA FRIDAY AFTERNOON INTO SATURDAY STILL APPEAR FINE. WAS TEMPTED TO INCREASE POPS FOR FRIDAY EVENING...BUT FORCING REMAINS A POTENTIAL LIMITING FACTOR WITH THE SYSTEM. GFS AND ECMWF SHOW STRONG Q-VECTOR CONVERGENCE AND 500MB VORTICITY ACROSS THE NORTHERN PLAINS FRIDAY MORNING...BUT SHOW THESE QUANTITIES DIMINISHING AS THE SYSTEM PASSES OVER THE AREA. BEST CHANCE FOR PRECIPITATION FRIDAY NIGHT MAY LIKELY END UP OVER LAKE SUPERIOR OR FARTHER TO THE NORTH. PRECIPITATION CHANCES WILL THEN COME TO AN END SATURDAY AFTERNOON AS THE DRY SLOT MOVES THROUGH. 00Z GFS IS A TOUCH MORE PROGRESSIVE WITH THE TIMING OF THE FRONTAL PASSAGE...BUT WILL NOT CHANGE THE END TIME OF PRECIPITATION CHANCES IN THE FORECAST AT THIS TIME. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... AS LLVL FLOW VEERS TO MORE ESE ARND HI PRES BLDG INTO ERN LK SUP... EXPECT SOME LO CLDS WITH MVFR/IFR CIGS AND PSBLY SOME FOG TO DVLP AT CMX WITH UPSLOPE WIND COMPONENT UNDER LO INVRN SHOWN ON 00Z TAMDAR SDNG AT SAW. KEPT SAW VFR WITH POSSIBLE MVFR UNDER NOT SO FVRBL ELY WIND. DRYING AIRMASS/DIURNAL HTG TDAY WL ENSURE VFR CONDITIONS THRU THIS EVNG AFT ANY LO CLD AT CMX DSPTS THIS MRNG. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... AS HIGH PRES JUST N OF LAKE SUPERIOR MOVES TO THE LOWER GREAT LAKES BY WED MORNING...ERLY WINDS THIS MORNING WILL VEER SRLY BY WED MORNING. SPEEDS WILL GENERALLY BE IN THE 10-20KT RANGE THOUGH THERE WILL BE GUSTS TO AROUND 25KT...MAINLY OVER FAR WRN LAKE SUPERIOR. S TO SE WINDS WILL THEN PERSIST THRU FRI AS THE HIGH SHIFTS TO THE E COAST AND LOW PRES ORGANIZES OVER THE NORTHERN PLAINS. WINDS OF 10-20KT WITH GUSTS TO AROUND 25KT ARE EXPECTED DURING THIS TIME WITH THE HIGHEST SPEEDS OVER EASTERN LAKE SUPERIOR. AHEAD OF AN APPROACHING COLD FRONT...WIND GUSTS COULD REACH UP TO 30 KT FRI/FRI NIGHT OVER EASTERN LAKE SUPERIOR. IN THE WAKE OF THE COLD FRONT SAT...MUCH OF LAKE SUPERIOR SHOULD SEE WEST WIND GUSTS UP TO 25 KT...ESPECIALLY OVER THE WEST HALF OF THE LAKE. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS...TAG DISCUSSION...TAG AVIATION...KC MARINE...ROLFSON mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1234 PM CDT WED AUG 20 2008 .AVIATION... /18Z TAF ISSUANCE/ HIGH PRESSURE CENTERED OVER THE GREAT LAKES WILL MOVE ONLY A LITTLE TO THE EAST DURING THE TAF PERIOD. SOUTHERLY SURFACE WINDS ON THE BACK SIDE OF THE HIGH WILL INCREASE INTO THE 15 TO 25 KNOT RANGE OVER WESTERN MN THIS AFTERNOON AS THE PRESSURE GRADIENT TIGHTENS AHEAD OF A COLD FRONT OVER MT/WY. THE GRADIENT WILL BECOME EVEN STRONGER ON THURSDAY WITH SOUTHERLY WINDS OF 20 TO 30 KNOTS LIKELY BY LATE MORNING FOR KAXN AND KRWF WITH 10 TO 20 KNOTS ELSEWHERE. STRATUS THAT SPREAD ACROSS WEST CENTRAL WI OVERNIGHT HAS DIMINISHED AT KRNH AND SHOULD BE BREAKING UP AT KEAU AT THE START OF THE TAF. HOWEVER...CU RULE IS NEGATIVE THIS AFTERNOON AND BKN VFR CUMULUS IS FORECAST. && .PREV DISCUSSION... /ISSUED 345 AM CDT WED AUG 20 2008/ PRIMARY FORECAST CONCERN IS CHANCE FOR MORE WIDESPREAD SHRA/TSRA ACTIVITY RETURNING TO THE AREA THURSDAY AFTERNOON THROUGH FRIDAY AS TWO SEPARATE DISTURBANCES IMPACT THE REGION. LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES SHOW BOTH OF THESE FEATURES QUITE WELL. THE FIRST ITEM OF CONCERN IS THE UPPER LOW ROTATING NEAR THE TX/OK BORDER... WHICH IS PROGGED TO LIFT NORTH OVER THE NEXT 36 HOURS... WORKING INTO THE SOUTHERN AND EASTERN CWFA THURSDAY AFTERNOON AND EVENING. THE SECOND FEATURE OF INTEREST IS THE VIGOROUS UPPER LOW APPROACHING THE PACIFIC NORTHWEST... WHICH IS EXPECTED TO PUSH EASTWARD AND WORK INTO THE WESTERN CWFA ON FRIDAY. THE 00Z GFS AND NAM ARE IN REMARKABLY GOOD AGREEMENT ON THE GENERAL EVOLUTION AND TIMING OF THINGS THROUGH THE PERIOD... AND THE SREF ALSO MATCHED THINGS FAIRLY WELL... SO ESSENTIALLY USED A BLEND OF GFS AND NAM FOR THE FORECAST. HAD A BIT OF A SURPRISE WITH A FEW SHRA/TSRA OVER THE CENTRAL PORTION OF THE AREA YESTERDAY... WHERE MLCAPES OF 1000-1500 J/KG COMBINED WITH SOME DECENT LOW LEVEL CONVERGENCE TO GET SOME CONVECTION GOING. ALTHOUGH TEMPERATURES AND DEWPOINTS WILL BE SIMILAR TODAY... AND THE NAM SUGGESTS MLCAPES OF 500-1000 J/KG OVER PARTS OF THE SOUTHERN AND EASTERN FORECAST AREA... THERE DOES NOT APPEAR TO BE AS WELL DEFINED OF A CONVERGENCE AXIS EITHER IN THE CURRENT OBSERVATIONS OR THE FORECAST WIND FIELDS. SO... WILL STICK WITH THE GOING DRY FORECAST FOR TODAY. IF SOMETHING WERE TO DEVELOP... IT APPEARS THE BEST CHANCE WOULD BE OVER WEST CENTRAL WISCONSIN WHICH WILL BE IN CLOSER PROXIMITY TO THE DEWPOINT GRADIENT AND HAVE THE BEST CHANCE TO SEE SOME LOW LEVEL ANOMALIES IN THE WIND FIELDS. THE GFS AND NAM ALSO SHOW BETTER LOW LEVEL MOISTURE AND LESS CAPPING IN THAT AREA... SO THE DAY SHIFT MAY NEED TO AT LEAST KEEP AN EYE OUT FOR A STRAY SHRA DURING THE AFTERNOON IN THAT AREA. OTHERWISE... RIDGING AND A GENERALLY DRY PROFILE LOOK TO REIGN TODAY THROUGH THURSDAY MORNING... WITH WARM AND DRY WEATHER EXPECTED. BY THURSDAY AFTERNOON THE GFS AND NAM SUGGEST THE UPPER LOW OVER THE SOUTHERN PLAINS WILL BE LIFTING NORTH TOWARD SOUTHEAST MINNESOTA. A FAIRLY SUBSTANTIAL JUMP IN PRECIPITABLE WATER VALUES IS ADVERTISED AS THIS SYSTEM MOVES INTO THE AREA... ALONG WITH THE ATTENDANT HEIGHT FALLS AND 925-700MB WARM ADVECTION. INCLUDED CHANCE POPS OVER THE SOUTHERN AND EASTERN PORTION OF THE AREA FROM THURSDAY AFTERNOON INTO THURSDAY NIGHT AS THIS SYSTEM LIFTS NORTH THROUGH THE AREA. LATE THURSDAY NIGHT THROUGH FRIDAY EVENING EYES TURN TOWARD THE STRONG SHORTWAVE THAT WILL BE APPROACHING FROM THE NORTHERN PLAINS. THIS FEATURE WILL DRIVE A ROBUST COLD FRONT THROUGH THE REGION FRIDAY AND FRIDAY EVENING... BRINGING WITH IT A CHANCE FOR SHOWERS AND THUNDERSTORMS AS IT DOES SO. INCLUDING SOME LOW POPS OVER THE NORTHWEST FOR LATE FRIDAY NIGHT... THEN SHIFTED THESE EASTWARD FRIDAY THROUGH FRIDAY NIGHT. GIVEN THE GOOD MODEL AGREEMENT AND STRONG FORCING EXPECTED... INCLUDED 50 POPS OVER THE EASTERN PORTION OF THE AREA FRIDAY EVENING AS THE FRONT SWINGS THROUGH THE AREA. INITIATION MAY TAKE A BIT OF TIME TO GET GOING GIVEN PROGGED 700MB TEMPERATURES NEAR 12C OVER THE WESTERN CWFA AHEAD OF THE FRONT FRIDAY MORNING AND AFTERNOON... HENCE KEPT POPS A BIT LOWER THERE. THERE STILL APPEARS TO BE SOME POTENTIAL FOR SEVERE WEATHER AS THE SHORTWAVE AND COLD FRONT MOVE THROUGH THE AREA FRIDAY AFTERNOON AND EVENING. THE LIMITING FACTOR AT THIS POINT APPEARS TO BE INSTABILITY... WITH THE GFS AND NAM BOTH SHOWING MLCAPES OF 500-1500 J/KG AHEAD OF THE FRONT. HOWEVER... WIND FIELDS ARE FORECAST TO BE FAIRLY STRONG WITH DEEP LAYER SHEAR VALUES OF AROUND 40KT ALONG AND AHEAD OF THE FRONT... AND 0-2KM SHEAR OF AROUND 25KT. AT THIS POINT... IT WOULD APPEAR THAT THE MAIN SEVERE WEATHER THREAT WOULD BE WIND WITH THE POSSIBILITY OF A LINE OF STORMS DEVELOPING... ALTHOUGH LARGE HAIL COULD ALSO BE POSSIBLE GIVEN THE FORECAST DEEP LAYER SHEAR VALUES AND THE POTENTIAL FOR ROTATING UPDRAFTS... PARTICULARLY EARLY ON BEFORE THINGS POSSIBLY BECOME LINEAR IN NATURE. THINGS WILL BEAR SOME WATCHING OVER THE NEXT DAY OR SO AS THIS SYSTEM TAKES SHAPE. MADE MINOR ADJUSTMENTS TO THE POPS INTO SATURDAY MORNING TO ACCOUNT FOR LATEST FRONTAL TIMING FROM THE MODELS... BUT GENERALLY MADE ONLY MINIMAL CHANGES BEYOND FRIDAY EVENING. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ RAH/TRH mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 628 AM CDT WED AUG 20 2008 .DISCUSSION... PRIMARY FORECAST CONCERN IS CHANCE FOR MORE WIDESPREAD SHRA/TSRA ACTIVITY RETURNING TO THE AREA THURSDAY AFTERNOON THROUGH FRIDAY AS TWO SEPARATE DISTURBANCES IMPACT THE REGION. LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES SHOW BOTH OF THESE FEATURES QUITE WELL. THE FIRST ITEM OF CONCERN IS THE UPPER LOW ROTATING NEAR THE TX/OK BORDER... WHICH IS PROGGED TO LIFT NORTH OVER THE NEXT 36 HOURS... WORKING INTO THE SOUTHERN AND EASTERN CWFA THURSDAY AFTERNOON AND EVENING. THE SECOND FEATURE OF INTEREST IS THE VIGOROUS UPPER LOW APPROACHING THE PACIFIC NORTHWEST... WHICH IS EXPECTED TO PUSH EASTWARD AND WORK INTO THE WESTERN CWFA ON FRIDAY. THE 00Z GFS AND NAM ARE IN REMARKABLY GOOD AGREEMENT ON THE GENERAL EVOLUTION AND TIMING OF THINGS THROUGH THE PERIOD... AND THE SREF ALSO MATCHED THINGS FAIRLY WELL... SO ESSENTIALLY USED A BLEND OF GFS AND NAM FOR THE FORECAST. HAD A BIT OF A SURPRISE WITH A FEW SHRA/TSRA OVER THE CENTRAL PORTION OF THE AREA YESTERDAY... WHERE MLCAPES OF 1000-1500 J/KG COMBINED WITH SOME DECENT LOW LEVEL CONVERGENCE TO GET SOME CONVECTION GOING. ALTHOUGH TEMPERATURES AND DEWPOINTS WILL BE SIMILAR TODAY... AND THE NAM SUGGESTS MLCAPES OF 500-1000 J/KG OVER PARTS OF THE SOUTHERN AND EASTERN FORECAST AREA... THERE DOES NOT APPEAR TO BE AS WELL DEFINED OF A CONVERGENCE AXIS EITHER IN THE CURRENT OBSERVATIONS OR THE FORECAST WIND FIELDS. SO... WILL STICK WITH THE GOING DRY FORECAST FOR TODAY. IF SOMETHING WERE TO DEVELOP... IT APPEARS THE BEST CHANCE WOULD BE OVER WEST CENTRAL WISCONSIN WHICH WILL BE IN CLOSER PROXIMITY TO THE DEWPOINT GRADIENT AND HAVE THE BEST CHANCE TO SEE SOME LOW LEVEL ANOMALIES IN THE WIND FIELDS. THE GFS AND NAM ALSO SHOW BETTER LOW LEVEL MOISTURE AND LESS CAPPING IN THAT AREA... SO THE DAY SHIFT MAY NEED TO AT LEAST KEEP AN EYE OUT FOR A STRAY SHRA DURING THE AFTERNOON IN THAT AREA. OTHERWISE... RIDGING AND A GENERALLY DRY PROFILE LOOK TO REIGN TODAY THROUGH THURSDAY MORNING... WITH WARM AND DRY WEATHER EXPECTED. BY THURSDAY AFTERNOON THE GFS AND NAM SUGGEST THE UPPER LOW OVER THE SOUTHERN PLAINS WILL BE LIFTING NORTH TOWARD SOUTHEAST MINNESOTA. A FAIRLY SUBSTANTIAL JUMP IN PRECIPITABLE WATER VALUES IS ADVERTISED AS THIS SYSTEM MOVES INTO THE AREA... ALONG WITH THE ATTENDANT HEIGHT FALLS AND 925-700MB WARM ADVECTION. INCLUDED CHANCE POPS OVER THE SOUTHERN AND EASTERN PORTION OF THE AREA FROM THURSDAY AFTERNOON INTO THURSDAY NIGHT AS THIS SYSTEM LIFTS NORTH THROUGH THE AREA. LATE THURSDAY NIGHT THROUGH FRIDAY EVENING EYES TURN TOWARD THE STRONG SHORTWAVE THAT WILL BE APPROACHING FROM THE NORTHERN PLAINS. THIS FEATURE WILL DRIVE A ROBUST COLD FRONT THROUGH THE REGION FRIDAY AND FRIDAY EVENING... BRINGING WITH IT A CHANCE FOR SHOWERS AND THUNDERSTORMS AS IT DOES SO. INCLUDING SOME LOW POPS OVER THE NORTHWEST FOR LATE FRIDAY NIGHT... THEN SHIFTED THESE EASTWARD FRIDAY THROUGH FRIDAY NIGHT. GIVEN THE GOOD MODEL AGREEMENT AND STRONG FORCING EXPECTED... INCLUDED 50 POPS OVER THE EASTERN PORTION OF THE AREA FRIDAY EVENING AS THE FRONT SWINGS THROUGH THE AREA. INITIATION MAY TAKE A BIT OF TIME TO GET GOING GIVEN PROGGED 700MB TEMPERATURES NEAR 12C OVER THE WESTERN CWFA AHEAD OF THE FRONT FRIDAY MORNING AND AFTERNOON... HENCE KEPT POPS A BIT LOWER THERE. THERE STILL APPEARS TO BE SOME POTENTIAL FOR SEVERE WEATHER AS THE SHORTWAVE AND COLD FRONT MOVE THROUGH THE AREA FRIDAY AFTERNOON AND EVENING. THE LIMITING FACTOR AT THIS POINT APPEARS TO BE INSTABILITY... WITH THE GFS AND NAM BOTH SHOWING MLCAPES OF 500-1500 J/KG AHEAD OF THE FRONT. HOWEVER... WIND FIELDS ARE FORECAST TO BE FAIRLY STRONG WITH DEEP LAYER SHEAR VALUES OF AROUND 40KT ALONG AND AHEAD OF THE FRONT... AND 0-2KM SHEAR OF AROUND 25KT. AT THIS POINT... IT WOULD APPEAR THAT THE MAIN SEVERE WEATHER THREAT WOULD BE WIND WITH THE POSSIBILITY OF A LINE OF STORMS DEVELOPING... ALTHOUGH LARGE HAIL COULD ALSO BE POSSIBLE GIVEN THE FORECAST DEEP LAYER SHEAR VALUES AND THE POTENTIAL FOR ROTATING UPDRAFTS... PARTICULARLY EARLY ON BEFORE THINGS POSSIBLY BECOME LINEAR IN NATURE. THINGS WILL BEAR SOME WATCHING OVER THE NEXT DAY OR SO AS THIS SYSTEM TAKES SHAPE. MADE MINOR ADJUSTMENTS TO THE POPS INTO SATURDAY MORNING TO ACCOUNT FOR LATEST FRONTAL TIMING FROM THE MODELS... BUT GENERALLY MADE ONLY MINIMAL CHANGES BEYOND FRIDAY EVENING. && .AVIATION.../12Z TAF ISSUANCE/ SFC HIGH PRESSURE MOVING GRADUALLY EAST OVER ERN WI...WITH STRATUS-CONTAMINATED RETURN FLOW IN WRN WI AND SE MN. STRATUS DOWN TO LIFR IN PLACES OF SW WI AND NE IA....WITH IFR/MVFR BEING MORE COMMON. AS IT MOVES NORTHWARD...THE STRATUS FIELD SHOULD BEGIN TO RETREAT SLIGHTLY IN AREAL COVERAGE...LIFT...AND SCATTER AFTER 13Z. TEMPORARY BROKEN CIGS ARE POSSIBLE AS IT DOES THIS AT WI TAF SITES. LOCAL HIGH RES MODEL 950MB RH FIELD MATCHES UP WELL WITH CURRENT DEPICTION OF LOW CLOUDS AND THIS DOES NOT ADVECT HIGH RH LEVELS INTO MSP THIS MORNING. BUT SOME FRINGE FEW-SCT 2.5 TO 3.5 KFT STRATOCU SEEM PLAUSIBLE DURING THE MID TO LATE MORNING. WIND ARE THE OTHER CONCERN IN THE TAFS TODAY. THESE SRLY WINDS WILL BE ON THE CLIMB FAIRLY QUICKLY AT WRN MN TAF SITES THANKS TO THE GRADIENT ALREADY IN PLACE AND MOSTLY SUNNY SKIES TO START MIXING. AT OTHER SITES...WIND SPEEDS MAY BE SLOW TO GO AT FIRST BUT BY AFTN 10 KT PLUS WINDS ARE EXPECTED AT ALL SITES...WITH GUSTINESS AT MN SITES. MPX VAD PROFILE ALREADY INDICATING NEAR 20 KT FLOW AT 2 KFT WHICH SHOULD BE MIXABLE TODAY. SO HAVE BUMPED UP GUSTS THERE AND INCREMENTED UP FOR THE FURTHER WEST STC AND ESPECIALLY RWF AND AXN. GUSTS SHOULD DROP DURING THE EVE BUT SUSTAINED WINDS WILL BE SLOW TO DECREASE AT MN SITES GIVEN THE GRADIENT. LLWS POSSIBLE AT WRN MN TAF SITES TONIGHT...BUT SFC WIND SHOULD BE STRONG ENOUGH TO PREVENT A SHARP VERTICAL PROFILE CHANGE WORTH MENTIONING IN THE AXN AND RWF TAFS. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ TRH/MTF mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1137 PM CDT MON AUG 18 2008 .UPDATE...FOR 06Z AVIATION DISCUSSION BELOW && .DISCUSSION.../ISSUE 230 PM CDT MON AUG 18 2008/ WARM AFTERNOON TEMPERATURES IN WSW FLOW AHEAD OF WEAK BACKDOOR COOL FRONT WHICH HAS BEEN SAGGING INTO CENTRAL MN. STILL LITTLE SIGN OF ANY CUMULUS VICINITY OF FRONT...AND CONVECTIVE TEMPERATURE HAS BEEN REACHED. WV IMAGERY DOES SHW A COUPLE OF VERY WEAK IMPULSES IN NW FLOW. ONE IS NEAR MSP AND THE OTHER NEAR BIS. WILL LEAVE IN THE LOW POPS WE HAVE BEEN CARRYING IN THE GRIDS FOR THE LATE AFTERNOON AND EVENING HOURS AS SURFACE TROUGH DROPS SOUTH. BOUNDARY PROGGED BY RUC/NAM/GFS TO SETTLE INTO S MN OVERNIGHT AND THEN MOVE BACK NORTH TOMORROW AS FLOW BECOMES MORE SOUTHERLY IN ADVANCE OF TROUGH MOVING INTO MT/WY. RUN OF WARM TEMPERATURES WILL CONTINUE THROUGH MUCH OF WEEK. NEXT CHANCE OF PRECIPITATION WILL BEGIN ON THURSDAY NIGHT. ONE AREA POSSIBLE IN SE AREA AS SLUG OF HIGHER MOISTURES PUSHES OUT OF IOWA AHEAD OF UPPER TROUGH LIFTING OUT OF CENTRAL PLAINS. MAY ALSO SEE A CHANCE LATE IN NW AREAS AHEAD OF TROUGH MOVING OUT OF NORTHERN ROCKIES. HAVE HIGHEST POPS IN FOR FRIDAY AFTERNOON AND NIGHT AS NORTHERN ROCKIES TROUGH MOVES THRU AREA. TRIMMED BACK POPS ON SATURDAY WITH MODELS SHOWING PROGRESSIVE SYSTEM WITH DRIER AIRMASS MOVING IN. SHOULD SEE BIT COOLER TEMPERATURES FOR THE WEEKEND AS CANADIAN HIGH PRESSURE BUILDS INTO AREA. && .AVIATION.../06Z TAF ISSUANCE/ VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD...AS WEAK HIGH PRESSURE AT THE MID LEVELS OF THE ATMOSPHERE DOMINATES. MOSTLY CLEAR SKIES AND LIGHT WINDS WILL PREVAIL OVERNIGHT. SOUTHERLY FLOW WILL DEVELOP ON TUESDAY...AS LOW PRESSURE BEGINS TO DEVELOP OVER THE LEE OF THE ROCKIES. MOSTLY SUNNY SKIES WILL CONTINUE ON TUESDAY. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON MS 901 PM CDT WED AUG 20 2008 .UPDATE...AREA RADARS HAVE SHOWN A DEFINITE DIMINISHING TREND IN THE SHRA/TSRA ACTIVITY AND BOTH RUC/LOCAL WRFS NOT DEVELOPING MUCH MORE THAN LIGHT SHRA OVERNIGHT...MAINLY W OF MS RIVER TOWARD MORNING. HAVE ALREADY UPDATED TO CANCEL FFA AND LOWER POPS FOR MOST AREAS THE REST OF TONIGHT. PRIMARY UPPER LOW SPINNING NNE THROUGH WRN AR CURRENTLY AND ROTATING A DRY SLOT TOWARD SERN AR/NERN LA./40/ PORTIONS OF THE PREVIOUS DISCUSSION FOLLOW: LESS UPPER LEVEL FORCING FOR PRECIPITATION AND CLOUD COVER SHOULD EXIST IN OUR REGION THURSDAY AND THIS SHOULD ALLOW TEMPERATURES TO GENERALLY GET A LITTLE WARMER THAN THE PAST FEW DAYS. AN ASSOCIATED INCREASE IN INSTABILITY DUE TO THE WARMER TEMPS SHOULD OFFSET LESS FAVORABLE "SYNOPTICS" TO GET ADDITIONAL SHOWERS AND STORMS INSTIGATED BY THE AFTERNOON. DESPITE POTENTIALLY HIGHER AVAILABLE INSTABILITY...STILL DOES NOT LOOK LIKELY STRONG TO SEVERE STORMS SHOULD BE MUCH OF A THREAT...BUT WE WILL HAVE TO WATCH FOR LOCALLY HEAVY RAIN AS PRECIPITABLE WATER VALUES WILL LIKELY RUN AT OR ABOVE 2 INCHES AGAIN. BEYOND THURSDAY...THE PREVIOUS UPPER LEVEL LOW TO OUR WEST WILL EVOLVE INTO AN UPPER LEVEL WEAKNESS IN THE VICINITY THAT WILL VAGUELY AID IN THUNDERSTORM DEVELOPMENT FRIDAY AFTERNOON AND POSSIBLY INTO SATURDAY AFTERNOON. BUT BY LATE SATURDAY OUR WEATHER WILL HAVE THE POTENTIAL TO BE INCREASINGLY AFFECTED BY TROPICAL STORM FAY (OR WHATEVER FORM FAY HAPPENS TO BE IN). THERE IS SOME POTENTIAL FOR SATURDAY TO BE DRIER AND WARMER THAN CURRENTLY FORECAST IF FAY IS TAKING A CERTAIN TRAJECTORY TOWARD THE REGION AT THAT TIME...BUT THE IDEA THAT CONVERGING EASTERLY FLOW FROM FAY COULD ENHANCE RAIN POTENTIAL IS ALSO AT LEAST SOMEWHAT VALID AT THIS POINT. I DID DEBATE RAISING OUR POPS A LITTLE ON SUNDAY...BUT THERE IS STILL MUCH UNCERTAINTY WITH WHERE FAY WILL BE AT THAT TIME AND EVEN FOLLOWING THE EXPLICIT CENTERLINE OF NHC`S FORECAST COULD RESULT IN LIMITED RAINFALL FOR MY CWA ON SUNDAY. BUT...I WILL ADD THAT IT IS WELL WITHIN NHC`S CONE OF TRACK UNCERTAINTY (AND ECHOES A FEW AVAILABLE MODEL SOLUTIONS)...TO HAVE PORTIONS OF EASTERN MISSISSIPPI IN OUR CWA UNDER THE THREAT OF SOME GUSTY WINDS AND HEAVY RAINS COME SUNDAY OR MONDAY. /BB/ .LONG TERM...FRIDAY THROUGH NEXT WEDNESDAY...BEGINNING LATE IN THE UPCOMING WEEKEND...CONFIDENCE ON THE MID AND EXTENDED PORTIONS OF THE FORECAST REMAINS LOW. THE UPPER TROUGH TO THE WEST THAT`S BEEN RESPONSIBLE FOR THE WIDESPREAD RAINFALL OVER THE REGION THE PAST FEW DAYS...WILL SLOWLY PULL OFF TO THE NORTHEAST ACROSS THE MID MISSISSIPPI RIVER VALLEY ON FRIDAY. THIS WILL ALLOW THE FORECAST AREA TO BECOME MORE UNDER THE INFLUENCE OF AN UPPER LEVEL RIDGE THAT WEDGES ITSELF SOUTHWEST INTO THE LOWER MISSISSIPPI RIVER VALLEY. WITH A CONTINUED WARM...MOIST...AND UNSTABLE AIRMASS OVER THE AREA...LOOK FOR RAIN CHANCES THROUGH AT LEAST THE FIRST HALF OF THE WEEKEND TO MAINLY BE IN THE FORM OF TYPICAL SUMMER TIME DIURNAL CONVECTION. AFTER THAT THE QUESTION BECOMES WHERE IS FAY...OR THE TROPICAL SYSTEM FORMALLY KNOWN AS FAY...GOING AND WHAT AFFECTS...IF ANY...WILL SHE POTENTIALLY HAVE ON THE FORECAST AREA? YES MOST EYES WILL BE FIXED UPON FAY THROUGH THE WEEKEND AND INTO THE FIRST HALF OF NEXT WEEK AS TO WHERE SHE`LL END UP./19/ LATEST NHC/MODEL GUIDANCE TAKING FAY REMNANTS INTO ERN MS EARLY SUNDAY MORNING AND THEN TOWARD FAR NWRN MS. THIS TRACK WOULD BEGIN INCREASING OUR RAINS FROM THE E ON SATURDAY WITH MODERATE WIND FIELDS ARRIVING SATURDAY NIGHT THROUGH SUNDAY WITH EVEN HEAVIER RAINFALL POTENTIAL. WE WILL OBVIOUSLY HAVE TO MONITOR THESE TRENDS VERY CLOSELY DUE TO THE LARGE DISPLACEMENT SPREADS IN THE GUIDANCE FOR THIS SYSTEM./40/ && .AVIATION...SKIES HAVE BEEN CLEARING OUT TEMPORARILY AFTER SUNDOWN. EXPECT THE POSSIBILITY FOR LIGHT PATCHY FOG AND/OR STRATUS TO AGAIN DEVELOP EARLY THURSDAY MORNING MAINLY BETWEEN 09-14Z. OTHERWISE...VFR FLIGHT CATEGORIES WILL PREVAIL. SCATTERED SHRA AND TSRA WILL AGAIN BE POSSIBLE FOR PORTIONS OF THE REGION ON THURSDAY GENERALLY AFTER 17Z FOR SITES GENERALLY ALONG AND WEST OF THE INTERSTATE 55 CORRIDOR./40/ && .PRELIMINARY POINT TEMPS/POPS... JACKSON 69 89 69 93 / 40 58 26 27 MERIDIAN 68 92 69 92 / 32 48 27 28 VICKSBURG 70 88 69 92 / 42 63 28 29 HATTIESBURG 69 93 71 94 / 19 36 22 25 NATCHEZ 71 87 70 91 / 41 55 26 30 GREENVILLE 70 87 70 92 / 70 65 35 42 GREENWOOD 69 88 71 92 / 71 64 35 43 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...NONE. LA...NONE. AR...NONE. && $$ ms AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GLASGOW MT 901 PM MDT WED AUG 20 2008 .SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY... SWATH OF MID LEVEL CLOUDS IN ADVANCE OF TOMORROW/S STORM HAS OVERSPREAD THE REGION WITH A FEW SHOWERS AND STORMS NOTED OVER THE WESTERN ZONES. A COUPLE STRONGER STORMS MANAGED TO DEVELOP JUST EAST OF SIDNEY EARLIER THIS EVENING NEAR A MODIFIED FRONT/SURFACE TROF...BUT 00Z UPPER AIR OBSERVATIONS AND RUC REVEAL THE LLJ AND 700MB THERMAL RIDGE STRUCTURES ARE POISED JUST EAST OF THE MT/ND BORDER...SO DO NOT EXPECT ANYTHING ORGANIZED IN OUR CWA THIS EVENING. ONLY UPDATES WERE TO TAILOR WINDS AND SKY COVER INTO TONIGHT. MCZ PREVIOUS SHORT TERM DISCUSSION... UPPER LOW/VORTEX MOVES ONSHORE OVER BRITISH COLUMBIA/WASHINGTON STATE THIS EVENING. THIS SYSTEM WILL CONTINUE TO SEND WEAK WAVES/IMPULSES OUT ACROSS THE FORECAST AREA TONIGHT AND THURSDAY IN THE SOUTHWEST UPPER FLOW. THERE IS SOME INSTABILITY ASSOCIATED WITH THESE WAVES SO COULD GENERATE THUNDER ANY TIME. THE UPPER SYSTEM WILL THEN SEND A STRONGER COLD FRONT ACROSS NE MT THURSDAY AFTERNOON. MORE MOISTURE WILL BE ASSOCIATED WITH THIS FRONT BUT CAPE VALUES WILL BE VERY WEAK...SO EXPECT ONLY ISOLATED LIGHTNING STRIKES AROUND THE FRONT. UPPER TROUGH THEN PASSES OVER THE AREA THURSDAY NIGHT THROUGH FRIDAY MORNING INCREASING THE CHANCE FOR SHOWERS. MOST INSTABILITY WILL BE TO THE EAST OF CWA SO EXPECT STRONGER STORMS TO STAY EAST. HOWEVER SPC CURRENTLY HAS AN AREA OF SLIGHT RISK FOR SEVERE WX IN NORTH DAKOTA THURSDAY AFTERNOON AND EVENING VERY CLOSE TO THE EASTERN BORDER OF MT. AS AREA OF INSTABILITY MOVES FARTHER EAST REMOVED MENTION OF THUNDER FROM WESTERN ZONES THURSDAY NIGHT AND FRIDAY. COOLER AIR BEHIND THE COLD FRONTS THROUGH THURSDAY AFTERNOON WILL LOWER TMAX CLOSER TO NORMAL THURSDAY. THEN NORTHWEST UPPER FLOW BEHIND THE TROUGH WILL BRING EVEN COOLER AIR FRIDAY DROPPING TEMPERATURES BELOW NORMAL WITH MAV/MET MOS GUIDANCE SUGGESTING HIGHS IN THE 70S FRIDAY. BASED ON BUFKIT INVERTED V SOUNDINGS...GUSTY WINDS ARE POSSIBLE THIS EVENING OVER WESTERN ZONES AS A COLD FRONT NUDGES IN. SURFACE WINDS WILL BE MORE SOUTHWESTERLY THROUGH THURSDAY MORNING. THEN SURFACE TROUGH HEADS EAST LEAVING A STRONG PRESSURE GRADIENT ACROSS THE AREA LATE THURSDAY AND FRIDAY. THIS WILL BE REINFORCED BY UPPER LEVEL NORTHWEST WINDS MIXING DOWN FOR GUSTY NORTHWEST SURFACE WINDS OF AROUND 20 KTS. IT IS LIKELY A LAKE WIND ADVISORY FOR FORT PECK LAKE WILL BE NEEDED FRIDAY. HOWEVER WITH COOLER TEMPERATURES AND HIGHER RH VALUES DO NOT EXPECT ANY FIRE WX CONCERNS. SCT .LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY... EUROPEAN AND GFS MODELS AGREE REASONABLY WELL ON THE MAIN FEATURES OF THE LONG TERM FORECAST WITH WARMING SATURDAY AS THE NEXT RIDGE MOVES IN AND WARM AND CLEAR CONDITIONS SATURDAY THROUGH MONDAY FOLLOWED BY A CHANCE OF RAIN AND COOLER IN THE TUESDAY THROUGH WEDNESDAY PERIOD AS THE NEXT TROUGH MOVES THROUGH. WJM PREVIOUS LONG TERM DISCUSSION.... LACK OF ANY BLOCKING RIDGES WILL KEEP THE FLOW QUITE PROGRESSIVE THROUGH THE EXTENDED SENDING TEMPERATURES ON A SEESAW RIDE. VERY WINDY CONDITIONS BEHIND A DEEPENING LOW FRIDAY WILL BEGIN ABATING FRIDAY EVENING AS HIGH PRESSURE NESTLES INTO THE REGION. CONSEQUENTLY...LOW TEMPS FRIDAY NIGHT COULD BE THE COOLEST THUS FAR FOR THE MONTH WITH MOST LOCALES DROPPING WELL INTO THE 40S. STRONG HEIGHT GAINS BEHIND FRIDAY`S LOW WILL THEN PROMOTE SUBSTANTIAL THICKNESS GAINS THROUGH THE WEEKEND BEFORE HIGH TEMPS TAP VALUES WELL ABOVE NORMAL MONDAY UNDERNEATH AN IMPRESSIVE 700MB THERMAL RIDGE. LATEST ECWMF WOULD RATHER KEEP THIS FEATURE MUCH FARTHER WEST...ALTHOUGH THIS IS A SERIOUS BREAK IN CONTINUITY WITH ITS PREVIOUS RUN SO AM NOT INCLINED TO BUY THIS YET. GFS AND ITS ENSEMBLES MEANWHILE SHOW BETTER AGREEMENT IN A FASTER EVOLUTION PUSHING THE NEXT COLD FRONT THROUGH THE CWA MONDAY NIGHT. THE TROF DRIVING THIS FRONT DOESN`T APPEAR AS IMPRESSIVE AS THE ONE FROM THE SHORT TERM PACKAGE...ALTHOUGH PATTERN RECOGNITION WOULD STILL SUPPORT SOME LOW POPS MOSTLY IN THE POST-FRONTAL ENVIRONMENT. MODELS AND ENSEMBLES DO AGREE QUITE WELL IN DEVELOPING A FAST ZONAL FLOW IN THE WAKE OF THIS TROF...SO KEPT SOME SLIGHT CHANCE POPS INTACT GOING INTO MIDWEEK. TEMPS WITHIN THIS FLOW SHOULD BE KEPT WELL IN CHECK WITH NO THREAT OF WELL ABOVE NORMAL MAX TEMPS. MCZ && .AVIATION... CLEAR AND VFR CONDITIONS THIS EVENING WITH SOME HIGHER CLOUDS MOVING-IN FROM THE WEST OVER NIGHT. THERE IS A SLIGHT CHANCE OF A SHOWER THURSDAY MORNING AND A BETTER CHANCE IN THE AFTERNOON...ESPECIALLY NORTHWEST OF GLASGOW. SHOWER ACTIVITY THURSDAY COULD LEAD TO SOME LOCALLY MVFR CONDITIONS AND LOCALLY GUSTY WINDS FROM STORM OUTFLOWS. OTHERWISE...WINDS ARE EXPECTED TO BE AROUND 10 KTS FROM THE WEST TO NORTHWEST. WJM && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ WEATHER.GOV/GLASGOW mt AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 745 PM EDT WED AUG 20 2008 .SYNOPSIS... A RIDGE OF HIGH PRESSURE WILL BUILD NORTH OF THE AREA AND PERSIST THROUGH THE WEEKEND. TROPICAL STORM FAY WILL REMAIN SOUTH OF THE REGION...AND EVENTUALLY WEAKEN OVER THE DEEP SOUTH. OTHERWISE... CONDITIONS WILL REMAIN MOSTLY DRY WITH SEASONAL TEMPERATURES THROUGH THE PERIOD. && .NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM WEDNESDAY...FORECAST DILEMMA WILL CONTINUE TO BE THE AREA OF LOW LEVEL CONVERGENCE AND ASSOCIATED SHOWERS THAT HAVE BASICALLY SET UP JUST OFF THE SE COAST OF BRUNSWICK COUNTY AND EXTENDING BACK TO THE SOUTHWEST THROUGH GEORGETOWN AND WILLIAMSBURG COUNTIES. THE ACTIVITY HAS DECREASED A BIT THE PAST FEW MINUTES...AND LOOKING AT RUC LOW LEVEL CONVERGENCE AT 925MB...IT APPEARS TO HAVE A HANDLE ON THINGS. THE TREND IS FOR THIS AREA TO CONTINUE TO DISSIPATE AS THE CONVERGENCE DISAPPEARS. THIS TREND IS REFLECTED IN THE POP GRIDS/FORECAST THROUGH THE EVENING HOURS. AFTER 0600 UTC...USED A MORE BROAD BASED APPROACH WITH THE LOW LEVEL CONVERGENCE INCREASING ONCE AGAIN VIA THE GFS. POPS REMAIN LOW WITH THE BEST CHANCES ACROSS THE SOUTH AND EAST OVER THE COASTAL WATERS. GENERALLY USED A BLEND OF GUIDANCE REGARDING OVERNIGHT LOWS. DO EXPECT WINDS TO KEEP THE BOUNDARY LAYER AT LEAST PARTIALLY MIXED...WITH WINDS OF 5-10 MPH COMMON WITH SLIGHTLY HIGHER VALUES ALONG THE COAST. THIS SHOULD MITIGATE THE FOG THREAT AS WELL...ALTHOUGH MY THOUGHTS THIS TIME YESTERDAY WERE SIMILAR. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 3 PM...H5 RIDGE WILL BECOME CENTERED OVER VA DURING THURSDAY AND LINGER THROUGH FRIDAY NIGHT. DEEPER MOISTURE WILL BE AVAILABLE ACROSS THE SOUTHERN ZONES WITH STRONGER EASTERLY LOW-LEVEL INFLOW IN PLACE. LOW-LEVEL MOISTURE IS A LITTLE MORE LIMITED ACROSS THE NORTHERN AREAS PER TIME HEIGHT CROSS SECTIONS. SPEED CONVERGENCE WILL PERSIST ALONG THE COAST WITH FAY TO THE SOUTH AND HIGH PRESSURE RIDGING IN FROM THE NORTH. THE SPEED CONVERGENCE ALONG WITH MARGINAL INSTABILITY WILL SUPPORT WIDELY SCATTERED TO SCATTERED SHOWERS/TSTMS...WITH THE BEST CHANCES SETTING UP ACROSS ILM/S SOUTHERN ZONES THIS PERIOD. OTHERWISE...EXPECT BREEZY/WINDY CONDITIONS THURSDAY AND FRIDAY WITH MIXING OF STRONGER EASTERLY LOW-LEVEL FLOW A GOOD BET EACH DAY. WINDS EXPECTED TO BE HIGHEST ACROSS THE COASTAL SC ZONES. AS FOR TEMPS....CONTINUE TO FAVOR A BLEND TOWARD THE COOLER MET NUMBERS FOR THE HIGHS...AND A STRAIGHT BLEND FOR THE LOWS. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 3 PM...LARGE UPPER RIDGE ELONGATED FROM SW TO NE WILL STRETCH ACROSS MOST OF THE EASTERN U.S. BY SATURDAY. FORECAST SOUNDINGS SHOW VERY DRY AIR ABOVE ABOUT 600MB ON ACCOUNT OF THIS FEATURE. DESPITE THE FACT THAT MOST OF THE FLOW BELOW 500MB WILL BE EASTERLY LITTLE MORE THAN A FEW TROPICAL-LIKE SHOWERS SHOULD BE ABLE TO MAKE IT ONSHORE. SINCE MOST OF THEM WILL NOT BE MEASURABLE POPS HAVE BEEN KEPT IN THE SLIGHT CHANCE RANGE. NOT MUCH CHANGES INTO SUNDAY...THE LOW LEVEL EASTERLY FLOW MAY BECOME EVEN SHALLOWER WHILE THE MID AND UPPER DRY AIR PERSISTS. OVER THE WEEKEND AS FAYS CIRCULATION MOVES FARTHER WEST A TREMENDOUSLY LONG EASTERLY FETCH AROUND ATLANTIC HIGH PRESSURE DEVELOPS. THIS IS PROGGED TO BRING INCREASING SWELL ENERGY TO AREA BEACHES OVER THE WEEKEND AND INTO MONDAY. THIS SHOULD PROLONG/ENHANCE THE RIP CURRENT THREAT. THE RIDGING WILL WEAKEN MONDAY THROUGH WEDNESDAY AT THE MID LEVELS. THIS SHOULD DECREASE THE CAPPING AND MID LVL DRYNESS LEADING TO BETTER BUT STILL QUITE SMALL RAIN CHANCES ACROSS THE REGION AS BOTH THE SEA BREEZE AND A WEAK PIEDMONT TROUGH SERVE AS CONVECTIVE FOCI. FCST SOUNDINGS STILL SHOW PRETTY WEAK LAPSE RATES SO ANY STORMS THAT DO DEVELOP MAY NOT BE SIGNIFICANT RAINMAKERS. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... ALL TERMINALS ARE CURRENTLY VFR. MOST SHOWERS MOVING ONSHORE SOUTH OF MYR...BUT ISOLATED SHOWERS STILL DEVELOPING OFFSHORE EAST OF THE TERMINAL. SHOWERS SHOULD REMAIN SOUTH OF MYR FOR THE MOST PART THROUGH THE EVENING...BUT WILL BE CLOSE ENOUGH TO WARRANT VCSH IN THE MYR TAF. SHOWERS SHOULD BE TOO ISOLATED TO TO MENTION IN THE CRE TAF. REMAINING TERMINALS SHOULD REMAIN DRY OVERNIGHT. TEMPO MVFR CEILINGS POSSIBLE BY 10Z AT FLO/LBT BUT CONFIDENCE IS LOW. THINK THE COASTAL TERMINALS WILL REMAIN VFR THROUGH THE OVERNIGHT PERIOD. SHOULD BE NO DENSE FOG PROBLEMS TONIGHT ALTHOUGH LBT COULD HAVE TEMPO MVFR VSBYS AFTER 10Z WHERE WINDS WILL BE LIGHTEST. VFR EXPECTED THURSDAY WITH EAST WINDS GUSTING TO 20-25 KNOTS. WINDS SHOULD SUBSIDE BY AFTERNOON. OUTLOOK THOUGH MONDAY...ISOLATED THUNDERSTORMS THROUGH THE PERIOD...EXCEPT FOR SCATTERED THUNDERSTORMS FRIDAY. && .MARINE... NEAR TERM /THROUGH TONIGHT/... AS OF 3 PM WEDNESDAY...STILL EXPECTING SMALL CRAFT CONDITIONS TO DEVELOP ACROSS OUR SOUTHERN WATERS...ZONE 256...THIS EVENING VIA SIX FOOT SEAS. THESE SEAS WILL DEVELOP FROM A COMBINATION OF WIND WAVES WITH THE INCREASED GRADIENT AND SWELL ALREADY DEVELOPING FROM FAY. IF ANYTHING THE WAVEWATCH GUIDANCE IS LAGGING A BIT WITH THE INCREASE AS 41004 IS REPORTING SIX FOOTERS CURRENTLY. WINDS HOWEVER INITIATED A BIT HIGH AND THIS SHOULD KEEP A 6:00 PM/2200 UTC START FOR SMALL CRAFT CONDITIONS ON TRACK. STILL EXPECTING A RANGE OF 20-25 KNOTS BY THURSDAY MORNING ACROSS ALL WATERS...INCREASING FROM 15-20 KNOTS THIS AFTERNOON. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 3 PM...EASTERLY FETCH WILL PERSIST ACROSS THE COASTAL WATERS WITH FAY TO THE SOUTH AND A RIDGE BUILDING IN FROM THE NORTH. THIS PATTERN WILL LEAD TO A CONTINUATION OF ROUGH SEAS...AND THE SMALL CRAFT ADVISORY WILL REMAIN IN PLACE FOR ALL OF THE COASTAL WATERS. REEFCAST PLOTS AND THE LATEST WNA OUTPUT BOTH SHOW SEAS BUILDING INTO THE 6-8 FT RANGE THROUGH THE PERIOD. LONG TERM /SATURDAY THROUGH MONDAY/... AS OF 3 PM...PERIOD WILL BE CHARACTERIZED BY AN UNUSUALLY LONG EASTERN FETCH AROUND LARGE ATLANTIC HIGH PRESSURE. NEARSHORE VS OFFSHORE RANGE IN SIGNIFICANT WAVE HEIGHT WILL BE A BIT LOWER THAN NORMAL FOR AUGUST AS SEAS WILL BE PUSHED DIRECTLY TOWARDS THE COAST. WIND WAVES AVERAGING 2 TO 4 FT WITH AN APPROXIMATE PD OF 7 SECONDS WILL BE ACCOMPANIED BY A 1 TO 2 FT SWELL IN THE 12-14 SECOND RANGE. && .RIP CURRENTS... WAVEWATCH GUIDANCE NOT ADVERTISING ANY LONG-PERIOD SWELL...BUT AM STILL CONCERNED ABOUT RIP CURRENT RISK THRU THIS PERIOD. THE LONG EASTERLY FETCH IS A PATTERN THAT FAVORS RIPS...AND ANY SWELL GENERATED BY FAY WOULD END UP AT A RIGHT ANGLE TO WIND WAVE ACTION. EVEN WITH FAY NO LONGER OVER WATER BY THE WEEKEND...SAT/SUN WILL BE DAYS 4 AND 5 OF A CONTINUOUS AND SOMETIMES FRISKY ONSHORE FLOW...A PATTERN THAT LENDS ITSELF TO INCREASED RIP CURRENT THREATS. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 AM EDT SATURDAY FOR AMZ256. SMALL CRAFT ADVISORY FROM 2 AM THURSDAY TO 6 AM EDT SATURDAY FOR AMZ250-252-254. && $$ SYNOPSIS...SRP NEAR TERM...HEDEN SHORT TERM...SRP LONG TERM...MBB AVIATION...MR nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND FORKS ND 820 PM CDT WED AUG 20 2008 .SHORT TERM... WINDS HAVE SUFFICIENTLY DIMINISHED TO ALLOW WIND ADVISORY TO EXPIRE. STILL LOOKING AT BREEZY TO WINDY CONDITIONS TO CONTINUE ALTHOUGH RUC SOUNDINGS GRADUALLY ERODE MIXED LAYER WHICH SHOULD KEEP 40-45KT LOW LEVEL JET WINDS FROM MIXING DOWN. WITH MIXING WINDS WILL LIMIT COOLING OVERNIGHT AND CURRENT MINIMUMS SEEM REASONABLE. ADDITIONAL CHANGES TO CURRENT FORECAST MINOR. && .AVIATION... VFR...CAVOK HOWEVER GUSTY WINDS TO CONTINUE OVERNIGHT AND KICK UP AGAIN THURSDAY. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ VOELKER nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 1041 AM EDT TUE AUG 19 2008 .SYNOPSIS... A WEAK COLD FRONT WILL SLIDE SOUTH THROUGH THE OHIO VALLEY AND MID ATLANTIC REGION TODAY. HIGH PRESSURE OVER SOUTHERN ONTARIO WILL THEN MOVE SOUTHEAST TO THE MID ATLANTIC COAST THROUGH FRIDAY...AS AN UPPER RIDGE BUILDS ACROSS THE EASTERN U.S. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A WEAK FRONT OVER THE LOWER GREAT LAKES WILL PUSH TOWARD THE OHIO RIVER TODAY AS HIGH PRESSURE BUILDS IN FROM THE NORTH. MORNING SOUNDING AND RUC FORECAST SOUNDINGS ARE INDICATING 500-1000 J/KG OF CAPE OVER THE REGION THIS AFTERNOON. MAY SEE ENOUGH CONVERGENCE ALONG THE WEAK FRONT TO SQUEEZE OUT ONE OR TWO SHOWERS/THUNDERSTORMS... MAINLY IN THE NORTHERN CWA...BUT WENT ONLY SLIGHT CHANCE DUE TO LACK OF CONFIDENCE IN ANY WELL DEFINED FORCING. WENT CLOSE TO A MAV/MET BLEND FOR TEMPS. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... HIGH PRESSURE SLIDING FROM THE GREAT LAKES TO THE EAST COAST WILL BE THE DOMINANT FEATURE THROUGH THE SHORT TERM PERIOD. THIS WILL KEEP DRY WEATHER IN PLACE...WITH A GRADUAL WARMING TREND AS WINDS RETURN FROM THE SOUTH LATER IN THE WORK WEEK. WENT WITH WARMER END OF GUIDANCE AND EVEN A BIT ABOVE GUIDANCE BY THURSDAY GIVEN PROGGED 850 MB TEMPS AND STRENGTH OF THE UPPER RIDGING AND SUBSIDENCE. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... EXTENDED MODELS CONTINUE TO SHOW LARGE SPREADS IN TRACK OF FAY...WHICH LEADS TO VERY LOW CONFIDENCE IN THE EXTENDED FORECAST. LAST FEW RUNS OF THE GFS...TAKES T.S. FAY ACROSS FL INTO THE ATLANTIC...THEN WWD BACK ACRS FL INTO THE GULF OF MEXICO. FOR THE 12Z GFS THIS OCCURS FRI INTO SAT. THE 12Z GFS THEN TAKES FAY TO NEW ORLEANS BY THE END OF THE PERIOD. THE 00Z ECMWF ALSO TAKES FAY ACRS FL INTO THE ATLANTIC...BUT THEN INTO GA ON SAT. THE REMAINS OF FAY ARE THEN PULLED N AND COMBINE WITH A CDFNT SUN INTO MON. MORE OF THE CDFNT LATER. OFFICIAL TRACK OF FAY FROM HPC MEANWHILE TAKES FAY UP THRU FL TO THE SE GA COAST...THEN BACK NW TO WRN NC BY SAT MRNG. HPC THEN MEANDERS IT AROUND THE SE U.S. BEFORE BEGINNING TO PULL IT N AHEAD OF THE CDFNT. GENERAL FEELING IS THAT MODELS...GFS IN PARTICULAR...ARE TOO STRONG WITH SFC RIDGING OVER NEW ENGLAND...THEREFORE FAY WILL BE ABLE TO WORK NWD. WITH ALL THAT GOING ON...FILLING H5 LOW OVER THE PLAINS TRIES TO PULL NWD. GFS SPREADS QPF INTO THE WRN OH VLY THU NGT INTO FRI...DROPPING SOME LIGHT PCPN IN INDIANA. ECMWF IS A LITTLE WEAKER AND FARTHER W WITH ITS PCPN. GFS AND ECMWF DIFFER ON STRENGTH OF LOW. GENERALLY THE WEAKER ECMWF IS PREFERRED. GFS AND ECMWF DO AGREE THAT AN H5 S/W WILL SWING THRU SC CANADA LATE IN THE WEEK...PUSHING A CDFNT THRU THE UPPER MS VLY INTO THE REGION. SHOULD SEE SOME CONVECTION AHEAD OF FNT SAT AND SUN. DEPENDING ON WHERE FAY GOES...TROPICAL MOISTURE COULD WORK INTO THE REGION AHEAD OF THE FNT...AND THE PCPN COULD BE HEAVIER AND MORE WIDESPREAD. THE GFS IS QUICKER IN PUSHING FNT THRU THE REGION...HAVING FROPA ON SUN. THE ECMWF...WITH FAY FARTHER N...LINGERS FROPA TIL SUN NGT INTO MONDAY. HOWEVER...ECMWF STALLS FNT IN THE APPALACHIANS AND BRINGS REMAINS OF FAY UP THE FNT ON MONDAY. WITH ALL THAT SAID...THREW OUT THE GFS AND ECMWF RUNS INDIVIDUALLY AND HAD TO GO BLEND OF THE TWO...ALONG WITH ADDING TPC AND HPC FCSTS OF FAY. KEPT THU NGT AND FRI DRY...FOLLOWING THE ECMWF WEAKER REPRESENTATION OF THE EJECTING H5 LOW. BROUGHT SCT TRW AHEAD OF FNT SAT AND SUN. WENT WITH THE SLOWER ECMWF FROPA...BUT DIDNT BRING THE HEAVIER PCPN AS THE ECMWF DID. TEMPS WERE ALSO A BLEND OF LATEST MEX AND HPC GUID. THOUGHT HPC WAS TOO WARM FOR TEMPS THU NGT INTO SAT. WENT BETWEEN THE TWO SET THOSE PERIODS. GRADUALLY BLENDED INTO HPC BY THE END OF THE PERIOD. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... WEAK BOUNDARY WILL SAG DOWN INTO THE AREA THROUGH THIS AFTERNOON. AHEAD OF IT...MARGINAL INSTABILITY WILL DEVELOP AND THIS COMBINED WITH SOME WEAK LOW LEVEL FORCING...MAY BE ENOUGH TO PRODUCE AN ISOLATED SHOWER OR THUNDERSTORM. HOWEVER...CHANCE STILL APPEARS LOW ENOUGH TO HOLD OFF ON ANY MENTION IN THE TAFS. DIURNAL CU AND ANY SHOWER ACTIVITY SHOULD DISSIPATE QUICKLY WITH LOSS OF DAYTIME HEATING...LEAVING MAINLY CLEAR SKIES OVERNIGHT. OUTLOOK...NO SIGNIFICANT WEATHER EXPECTED. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HAWBLITZEL LONG TERM...SITES AVIATION...JGL oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 251 AM EDT TUE AUG 19 2008 .SYNOPSIS... A COLD FRONT WILL DROP SOUTHEASTWARD ACROSS THE COMMONWEALTH TODAY... BRINGING A NORTHWEST FLOW OF COOLER AIR THROUGH MIDWEEK. SOME LOCATIONS ACROSS THE NORTHERN TIER WILL BE IN THE LOW 40S WEDNESDAY MORNING. HIGH PRESSURE WILL THEN BUILD ACROSS THE REGION...BRINGING MODERATING TEMPERATURES AND MAINLY DRY WEATHER FOR THE LATER PART OF THE WORK WEEK. THE REMAINS OF TROPICAL STORM FAY COULD PLAY A ROLE IN THE LOCAL WEATHER BY THE WEEKEND. && .NEAR TERM /UNTIL 11 AM THIS MORNING/... SHOWERS AND THUNDERSTORMS CONTINUE ALONG THE COLD FRONT CURRENTLY ARCING FROM THE EASTERN LAKESHORE OF LAKE ONTARIO TO SE MICHIGAN. BEST CONVERGENCE AND MAINTENANCE OF CONVECTIVE ACTIVITY REMAINS FROM THE FINGLERLAKES REGION NORTHEASTWARD TO LAKE CHAMPLAIN THIS MORNING... WITH ACTIVITY DWINDLING TO THE WEST OF A JAMESTOWN TO BUFFALO LINE ALONG THE FRONTAL BOUNDARY. EXPECT THIS TREND TO CONTINUE PROVIDING THE NORTHERN TIER THE HIGHEST POPS IN THE PREDAWN HOURS WITH LITTLE IN THE WAY OF SHOWER ACTIVITY REACHING SOUTH OF I-80 AS SFC DEWPOINTS AND DYNAMICS UNFAVORABLE FOR THEIR MAINTENANCE. BY DAWN...FRONTAL BOUNDARY SHOULD BE DRAPED ACROSS NORTHWEST SECTIONS AND CONTINUE SLOWLY MOVING SOUTHEASTWARD. ISOLATED SHOWER ACTIVITY SHOULD PREDOMINATE AT THAT TIME...AGAIN MAINLY NORTH OF I-80...BUT AS THE MORNING PROGRESSES AND SFC HEATING COMMENCES ACROSS THE SOUTHERN HALF OF PA...MAY SEE ISOLD TO SCT ACTIVITY REDEVELOP AHEAD OF THE FRONT AS IT DROPS SOUTH OF I-80 INTO THE CENTRAL MOUNTAINS. HAVE THEREFORE MAINTAINED SLGT-CHC POPS FOR THE MORNING. && .SHORT TERM /11 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... THERMODYNAMIC SUPPORT STILL THERE FOR SOME POTENTIALLY STRONG HAIL PRODUCING STORMS ACROSS THE MID SUSQ. RIVER VALLEY LATER THIS MORNING INTO EARLY AFTERNOON AS THE FRONT DROPS SOUTHWARD. PLUMES CONTINUE TO INDICATE A WIDE SPREAD OF CAPE SOLUTIONS...AND GIVEN CURRENT MOVEMENT OF FRONT BELIEVE THE FRONT WILL BE SLOW ENOUGH TO ALLOW AT LEAST PARTIAL DAYTIME HEATING TO MAKE THINGS INTERESTING OVER MY SOUTHEAST COUNTIES LATER THIS MORNING. IN PARTICULAR...A SHARP GRADIENT IN THE WET BULB ZERO HEIGHTS BETWEEN 14 AND 19Z SUGGESTS ISOLATED SUPERCELLS/POTENTIALLY LARGE HAILERS MAY BE POSSIBLE WITH ANY CONVECTION THAT INTENSIFIES ALONG AND AHEAD OF THE FRONT MID TO LATE MORNING. THIS WILL NEED TO BE WATCHED CLOSELY TODAY. THE WINDOW OF OPPORTUNITY TIMEWISE IS FAIRLY NARROW...AS BY EARLY AFTERNOON...CONVERGENCE ALONG FRONT IS GONE...AND DYNAMICS LIFT AWAY FROM THE AREA. ISOLD EARLY AFTERNOON STORMS...SOME OF WHICH COULD PRODUCE LARGE HAIL...SHOULD EXIT MY EASTERN ZONES BY MID AFTERNOON. COOLER AND DRIER AIR OVERSPREADS THE AREA TONIGHT AND WEDNESDAY FOR A RETURN TO QUITE COMFORTABLE AIR FOR AUGUST...WITH SOME CHILLY MORNING READINGS POTENTIALLY REACHING THE UPPER 30S ACROSS THE NORTHERN TIER EARLY WEDNESDAY REMINDING US THAT AUTUMN IS NOT FAR AWAY. HAVE KEPT MINS AROUND 40 AGAIN FOR THIS PACKAGE. LARGE AIR/WATER TEMP DIFFERENTIALS WILL LIKELY RESULT IN LOCALLY DENSE VALLEY FOG OVR THE NCENT MTNS. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... SFC RIDGE FCST TO STRENGTHEN TO +2-3SD PER GEFS WILL SLOWLY SLIDE OFF THE MID ATLC COAST BY WEEK`S END...PROVIDING DRY AND TRANQUIL WEATHER THROUGH THE END OF THE WORK WEEK THE LATEST SUITE OF GLOBAL MODELS /ECMWF/GFS/UKMET/CMC/ ALONG WITH THE GFS ENS /GEFS/ APPEAR TO HAVE REACHED A GENERAL CONSENSUS IN HOLDING THE STG MID ATLC RIDGE IN PLACE THRU AT LEAST SAT. THEREFORE...HAVE DELAYED POPS MAINLY UNTIL SUN AS IT APPEARS /AT LEAST ATTM/ THAT MOST OF THE DEEPER MSTR /PRIMARILY ASSOC WITH TS FAY/ WILL STAY FURTHER TO THE SOUTH AND WEST. ALTHOUGH THERE IS STILL PLENTY OF UNCERTAINTY WITH REGARD TO THE TRACK OF TS FAY IN THE MEDIUM TO LONG RANGE...CONCEPTUAL MODELS WOULD SUGGEST THAT ANY REMNANT MSTR WOULD EVENTUALLY GET FUNNELED NEWD AHEAD OF AN UPR GRT LKS TROF/ASSOC CLD FNT MOVG THRU THE OH VLY BY LATE IN THE WEEKEND/EARLY NEXT WEEK. GEFS PLUMES ALSO SUGGEST THE BEST CHC FOR RNFL TO BE AFT 25/00Z. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... REGIONAL RADARS SHOWING A FAIRLY SOLID BAND OF SHWRS/TSTMS ASSOCIATED WITH COLD FRONT OVR UPSTATE NEW YORK ATTM. WANING UPPER LVL SUPPORT...COMBINED WITH NEGATIVE DIURNAL INFLUENCE...SHOULD RESULT IN A DISSIPATING LINE OF CONVECTION AS COLD FRONT PUSHES INTO NORTHERN PA LATER THIS MORNING. FOR NOW...WILL HANDLE WITH CB APPENDAGE TO THE BFD TAF BTWN 06Z-11Z. POST FRONTAL MVFR STRATOCU CURRENTLY OBSERVED IN VICINITY OF LK ONTARIO...AND FEEL QUITE CERTAIN THAT BFD WILL EXPERIENCE AT LEAST MVFR CIG /POSS IFR/ BEHIND FROPA. LATEST RUC13 DATA SUGGESTS REDUCED CIGS AT BFD BTWN 11Z- 15Z. FURTHER SOUTH...SHWRS WILL BE HARD TO COME BY AS FROPA OCCURS DURING DIURNAL MINIMUM AND UPPER LVL SUPPORT PASSES TO THE NORTH. MAIN AFFECT ACROSS CENTRAL/SOUTHERN PA WILL BE A WIND SHIFT TO THE NORTH AS COLD PASSES THRU BTWN 12Z-17Z. HAVE LOWERED WIND SPEEDS A BIT...AS LATEST ENS SOUNDING DATA ONLY SUPPORTS WINDS NR 10KTS WITH GUSTS ARND 15KTS LATER TDY. A LARGE HI PRES SYSTEM WILL BUILD INTO PENNSYLVANIA WED...BRINGING A STRETCH OF FAIR WX AND LIGHT WINDS THAT SHOULD LAST THRU SATURDAY. PATCHY EARLY MORNING DENSE FOG IS LIKELY WED/THU IN THE DEEP RIVER/STREAM VALLEYS OF THE ALLEGHENIES. AIRMASS WILL BE QUITE DRY...SO THE ONLY TAF SITES THAT MIGHT BE AFFECTED BY THE AM FOG WOULD BE BFD AND IPT...WHERE LOCAL TOPOGRAPHY IS MORE FAVORABLE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...STEINBUGL AVIATION...FITZGERALD pa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 127 AM EDT TUE AUG 19 2008 .SYNOPSIS... A COLD FRONT WILL MOVE SOUTHWARD THROUGH THE STATE LATE TONIGHT AND EARLY TUESDAY. A NORTHWEST FLOW OF MUCH COOLER AIR WILL FOLLOW. SOME LOCATIONS ACROSS THE NORTHERN TIER WILL BE IN THE LOW 40S WEDNESDAY MORNING. HIGH PRESSURE WILL THEN BUILD ACROSS THE REGION...BRINGING MODERATING TEMPERATURES AND MAINLY DRY WEATHER FOR THE LATER PART OF THE WORK WEEK. THE REMAINS OF TROPICAL STORM FAY COULD PLAY A ROLE IN THE LOCAL WEATHER BY THE WEEKEND. && .NEAR TERM /UNTIL 7 AM THIS MORNING/... STORMS ALONG THE FRONT IN LOWER ONTARIO SHOULD WEAKEN AS THEY MOVE THROUGH WRN NY STATE TOWARD THE NRN TIER LATER TONIGHT...AS TIMING DURING THE DAY IS POOR AND THE DYNAMICS ARE BETTER TO OUR NE. ALSO INFLOW AIR IS NOT THAT MOIST - WITH ONLY A THIN RIBBON OF BETTER- THAN 60F DEW POINT AIR RIGHT AHEAD OF THE FRONT. MOST DEWPOINTS LOCALLY WERE INTO THE LOW 50S EARLIER THIS AFTN. HIGHEST CHANCE FOR SHOWERS WILL BE IN && .SHORT TERM /7 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... STILL HAVE SOME CONCERN FOR ISOLATED STRONG STORMS TUE MORNING... ACROSS THE MIDDLE SUSQUEHANNA VALLEY...AS EDGE OF STRONGER DYNAMICS BRUSH OUR AREA. MODELS HAVE BEEN HINTING THE LAST FEW DAYS THAT DEWPOINTS PEAK OUT AROUND 15Z. WIDE SPREAD IN CAPE VALUES ON PLUME DIAGRAMS. BY EARLY AFTERNOON...CONVERGENCE ALONG FRONT IS GONE...AND DYNAMICS LIFT AWAY FROM THE AREA. ISOLD STORMS ARE STILL POSSIBLE ACROSS THE EASTERN ZONES THROUGH EARLY AFTN. WE HAD A CASE LIKE THIS LAST YEAR...WHERE THE DRIER AIR WAS SLOW COMING IN...AND ISOLATED SUPERCELLS FORMED JUST SE OF IPT...AND PRODUCED A DAMAGING HAIL EVENT. WEATHER CONDITIONS LATELY HAVE BEEN MORE LIKE LATE AUGUST AND EARLY SEPT. THE FRONT ON TUESDAY IS QUITE SHARP...WITH 40S NOTED THIS MORNING TO THE NORTH OF THE FRONT. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... STRONG COLD ADVECTION IN THE WAKE OF THE CLD FNT SHOULD RAPIDLY DRY THINGS OUT TUE EVE...AND TEMPS MAY EVEN LEVEL OFF SOME. AN UNSEASONABLY STRONG SFC HIGH ACCOMPANIED BY RATHER COOL AND ANOMALOUSLY DRY AIR WILL MOVE INTO THE REGION FROM THE NORTH LATE TUES NIGHT INTO WED. LOW TEMPS WILL BE RATHER CHILLY ACROSS THE NRN TIER TUES NGT/WED MORNING. A STRAIGHT MOS BLEND WOULD YIELD MID TO UPPER 30S FOR MINS /SOME 13-15F BELOW CLIMATOLOGICAL VALUES/...WHICH IS NOT OUT OF THE QUESTION GIVEN IDEAL RAD COOLING AND PW VALUES FALLING TO -2 TO -3SD BTWN 06-12Z. HAVE KEPT MINS AROUND 40-41F FOR THE TIME BEING...BUT COULD EASILY SEE GOING LOWER WITH THE NEXT PACKAGE. LARGE AIR/WATER TEMP DIFFERENTIALS WILL LIKELY RESULT IN LOCALLY DENSE VALLEY FOG OVR THE NCENT MTNS. THIS HIGH /WHICH IS ACTUALLY FCST TO STRENGTHEN TO +2-3SD PER THE LATEST GEFS/ WILL SLOWLY SLIDE OFF THE MID ATLC COAST BY WEEK`S END...PROVIDING DRY AND TRANQUIL WEATHER THROUGH THE END OF THE WORK WEEK THE LATEST SUITE OF GLOBAL MODELS /ECMWF/GFS/UKMET/CMC/ ALONG WITH THE GFS ENS /GEFS/ APPEAR TO HAVE REACHED A GENERAL CONSENSUS IN HOLDING THE STG MID ATLC RIDGE IN PLACE THRU AT LEAST SAT. THEREFORE...HAVE DELAYED POPS MAINLY UNTIL SUN AS IT APPEARS /AT LEAST ATTM/ THAT MOST OF THE DEEPER MSTR /PRIMARILY ASSOC WITH TS FAY/ WILL STAY FURTHER TO THE SOUTH AND WEST. ALTHOUGH THERE IS STILL PLENTY OF UNCERTAINTY WITH REGARD TO THE TRACK OF TS FAY IN THE MEDIUM TO LONG RANGE...CONCEPTUAL MODELS WOULD SUGGEST THAT ANY REMNANT MSTR WOULD EVENTUALLY GET FUNNELED NEWD AHEAD OF AN UPR GRT LKS TROF/ASSOC CLD FNT MOVG THRU THE OH VLY BY LATE IN THE WEEKEND/EARLY NEXT WEEK. GEFS PLUMES ALSO SUGGEST THE BEST CHC FOR RNFL TO BE AFT 25/00Z. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... REGIONAL RADARS SHOWING A FAIRLY SOLID BAND OF SHWRS/TSTMS ASSOCIATED WITH COLD FRONT OVR UPSTATE NEW YORK ATTM. WANING UPPER LVL SUPPORT...COMBINED WITH NEGATIVE DIURNAL INFLUENCE...SHOULD RESULT IN A DISSIPATING LINE OF CONVECTION AS COLD FRONT PUSHES INTO NORTHERN PA LATER THIS MORNING. FOR NOW...WILL HANDLE WITH CB APPENDAGE TO THE BFD TAF BTWN 06Z-11Z. POST FRONTAL MVFR STRATOCU CURRENTLY OBSERVED IN VICINITY OF LK ONTARIO...AND FEEL QUITE CERTAIN THAT BFD WILL EXPERIENCE AT LEAST MVFR CIG /POSS IFR/ BEHIND FROPA. LATEST RUC13 DATA SUGGESTS REDUCED CIGS AT BFD BTWN 11Z- 15Z. FURTHER SOUTH...SHWRS WILL BE HARD TO COME BY AS FROPA OCCURS DURING DIURNAL MINIMUM AND UPPER LVL SUPPORT PASSES TO THE NORTH. MAIN AFFECT ACROSS CENTRAL/SOUTHERN PA WILL BE A WIND SHIFT TO THE NORTH AS COLD PASSES THRU BTWN 12Z-17Z. HAVE LOWERED WIND SPEEDS A BIT...AS LATEST ENS SOUNDING DATA ONLY SUPPORTS WINDS NR 10KTS WITH GUSTS ARND 15KTS LATER TDY. A LARGE HI PRES SYSTEM WILL BUILD INTO PENNSYLVANIA WED...BRINGING A STRETCH OF FAIR WX AND LIGHT WINDS THAT SHOULD LAST THRU SATURDAY. PATCHY EARLY MORNING DENSE FOG IS LIKELY WED/THU IN THE DEEP RIVER/STREAM VALLEYS OF THE ALLEGHENIES. AIRMASS WILL BE QUITE DRY...SO THE ONLY TAF SITES THAT MIGHT BE AFFECTED BY THE AM FOG WOULD BE BFD AND IPT...WHERE LOCAL TOPOGRAPHY IS MORE FAVORABLE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO/MARTIN NEAR TERM...DANGELO/MARTIN SHORT TERM...DANGELO/MARTIN LONG TERM...STEINBUGL AVIATION...FITZGERALD pa AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 910 PM MDT WED AUG 20 2008 .DISCUSSION...CURRENT RADAR IMAGERY SHOWS SHOWERS AND ISOLATED THUNDERSTORMS MOVING ACROSS THE BLACK HILLS. GUSTY WINDS TO AROUND 40 MPH ARE EXPECTED AHEAD OF THE SHOWERS AND STORMS. THE SHOWERS AND STORMS SHOULD END BEFORE MIDNIGHT. GUSTY SOUTH TO SOUTHWEST WINDS WILL DEVELOP ACROSS THE EASTERN BLACK HILLS TONIGHT. WITH SOME DOWNSLOPING...EXPECT TEMPERATURES TO REMAIN MILD WITH LOWS ONLY DROPPING INTO THE UPPER 60S. SOME LOCATIONS IN THE EASTERN FOOTHILLS MAY NOT DROP BELOW THE LOWER 70S TONIGHT. HAVE RAISED LOWS ACROSS THE EASTERN FOOTHILLS. HAVE ALSO INCREASED WINDS AS A PRESSURE GRADIENT WILL DEVELOP OVER THE BLACK HILLS THIS EVENING CREATING GUSTY SOUTH TO SOUTHWEST WINDS OF 15 TO 25 MPH WITH GUSTS TO AROUND 35 MPH. THE REST OF THE FORECAST IS ON TRACK. && PREV DISCUSSION... /ISSUED 220 PM MDT WED AUG 20 2008/ DISCUSSION...SKIES REMAIN MOSTLY SUNNY ACROSS THE CWA TODAY. SURFACE ANALYSIS PLACES A STATIONARY SURFACE TROUGH/DRYLINE ACROSS NORTHWEST SOUTH DAKOTA THROUGH THE BLACK HILLS AND TO THE SOUTH. BREEZY SOUTHERLY FLOW CONTINUES ACROSS THE SOUTH DAKOTA PLAINS TODAY KEEPING DEWPOINTS IN THE 50S. BOTH THE NAM AND RUC ARE STILL IN GOOD AGREEMENT THAT SOME PARTS OF THE SOUTH DAKOTA PLAINS AND THE BLACK HILLS ARE SEEING CAPE VALUES RISING UP TO 1500 J/KG THIS AFTERNOON. VIS SAT SHOWS TOWERING CU DEVELOPING WEST AND SOUTH OF THE CWA ACROSS THE HIGHER TERRAIN OF WYOMING...AND OVER THE BLACK HILLS. RADAR IS NOW SHOWING THUNDERSTORMS DEVELOPING OVER EAST CENTRAL WYOMING...SO WILL LEAVE IN ISOLATED EVENING POPS ACROSS THE HILLS AND ACROSS THE FAR WESTERN SOUTH DAKOTA PLAINS. SHEAR VALUES REMAIN ON THE WEAK SIDE...SO NO ORGANIZED SEVERE WEATHER IS EXPECTED. ANOTHER QUIET DAY IS EXPECTED TOMORROW AS THE UPPER RIDGE WEAKENS AND SHIFTS EAST. WARMER 700 MB TEMPS OF UP TO 16C WILL BRING HIGHER MAX TEMPS...POSSIBLY INTO THE UPPER 90S ACROSS SOME LOCATIONS ACROSS THE PLAINS. CLOUDS WILL BE ON THE RISE AS AN UPPER TROUGH MOVES ACROSS MONTANA. A COLD FRONT WILL SLIDE ACROSS THE CWA TOMORROW NIGHT BRINGING IN MUCH COOLER AIR TO THE CWA ALONG WITH GUSTY NORTHWEST WINDS. OVERALL THE FRONTAL PASSAGE IS NOT EXPECTED TO PRODUCE MUCH IN THE WAY OF PRECIP DUE TO A LACK OF MOISTURE IN THE LOWER LEVELS. AREAS ACROSS FAR NORTHWEST SOUTH DAKOTA AND PARTS OF NORTHEAST WYOMING WILL HAVE THE BEST CHANCES OF SEEING STORMS SINCE THE MAIN UPPER FORCING IS ACROSS NORTH DAKOTA AND EASTERN MONTANA...BUT CHANCES REMAIN SLIM. THE WAVE WILL BEGIN TO MOVE EAST/NORTHEAST OF THE AREA FRIDAY WITH A STRONG UPPER RIDGE BUILDING BACK INTO THE REGION. ANOTHER QUIET DAY IS EXPECTED FRIDAY WITH HIGHS JUST IN THE MID 70S TO MID 80S. EXTENDED...AN UPPER RIDGE BUILDING OVER THE NORTHERN PLAINS WILL LEAD TO WARM AND MAINLY DRY WEATHER THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. AVIATION...A FEW ISOLATED THUNDERSTORMS MAY BE POSSIBLE THIS AFTERNOON AND EARLY EVENING OVER PARTS OF FAR WESTERN SOUTH DAKOTA AND FAR NORTHEAST WYOMING. OTHERWISE...VFR CONDITIONS WILL PREVAIL. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. && $$ WETENKAMP sd AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 626 PM MDT WED AUG 20 2008 .DISCUSSION...CURRENT WATER VAPOR IMAGERY INDICATES BROAD TROUGH OVER THE PACIFIC NORTHWEST. SOUTHWESTERLY FLOW ALOFT WILL REMAIN OVER THE CWA TONIGHT. DRY LINE CURRENTLY POSITIONED OVER FAR EASTERN WYOMING INTO FAR WESTERN SOUTH DAKOTA WILL BE THE FOCUS FOR ISOLATED THUNDERSTORMS THIS EVENING. ISOLATED THUNDERSTORMS HAVE DEVELOPED OVER PORTIONS OF NORTHEAST WYOMING. HAVE TWEAKED THIS EVENINGS FORECAST TO ACCOUNT FOR THUNDERSTORM ACTIVITY. THE REST OF THE FORECAST IS ON TRACK. && .PREV DISCUSSION... /ISSUED 220 PM MDT WED AUG 20 2008/ DISCUSSION...SKIES REMAIN MOSTLY SUNNY ACROSS THE CWA TODAY. SURFACE ANALYSIS PLACES A STATIONARY SURFACE TROUGH/DRYLINE ACROSS NORTHWEST SOUTH DAKOTA THROUGH THE BLACK HILLS AND TO THE SOUTH. BREEZY SOUTHERLY FLOW CONTINUES ACROSS THE SOUTH DAKOTA PLAINS TODAY KEEPING DEWPOINTS IN THE 50S. BOTH THE NAM AND RUC ARE STILL IN GOOD AGREEMENT THAT SOME PARTS OF THE SOUTH DAKOTA PLAINS AND THE BLACK HILLS ARE SEEING CAPE VALUES RISING UP TO 1500 J/KG THIS AFTERNOON. VIS SAT SHOWS TOWERING CU DEVELOPING WEST AND SOUTH OF THE CWA ACROSS THE HIGHER TERRAIN OF WYOMING...AND OVER THE BLACK HILLS. RADAR IS NOW SHOWING THUNDERSTORMS DEVELOPING OVER EAST CENTRAL WYOMING...SO WILL LEAVE IN ISOLATED EVENING POPS ACROSS THE HILLS AND ACROSS THE FAR WESTERN SOUTH DAKOTA PLAINS. SHEAR VALUES REMAIN ON THE WEAK SIDE...SO NO ORGANIZED SEVERE WEATHER IS EXPECTED. ANOTHER QUIET DAY IS EXPECTED TOMORROW AS THE UPPER RIDGE WEAKENS AND SHIFTS EAST. WARMER 700 MB TEMPS OF UP TO 16C WILL BRING HIGHER MAX TEMPS...POSSIBLY INTO THE UPPER 90S ACROSS SOME LOCATIONS ACROSS THE PLAINS. CLOUDS WILL BE ON THE RISE AS AN UPPER TROUGH MOVES ACROSS MONTANA. A COLD FRONT WILL SLIDE ACROSS THE CWA TOMORROW NIGHT BRINGING IN MUCH COOLER AIR TO THE CWA ALONG WITH GUSTY NORTHWEST WINDS. OVERALL THE FRONTAL PASSAGE IS NOT EXPECTED TO PRODUCE MUCH IN THE WAY OF PRECIP DUE TO A LACK OF MOISTURE IN THE LOWER LEVELS. AREAS ACROSS FAR NORTHWEST SOUTH DAKOTA AND PARTS OF NORTHEAST WYOMING WILL HAVE THE BEST CHANCES OF SEEING STORMS SINCE THE MAIN UPPER FORCING IS ACROSS NORTH DAKOTA AND EASTERN MONTANA...BUT CHANCES REMAIN SLIM. THE WAVE WILL BEGIN TO MOVE EAST/NORTHEAST OF THE AREA FRIDAY WITH A STRONG UPPER RIDGE BUILDING BACK INTO THE REGION. ANOTHER QUIET DAY IS EXPECTED FRIDAY WITH HIGHS JUST IN THE MID 70S TO MID 80S. EXTENDED...AN UPPER RIDGE BUILDING OVER THE NORTHERN PLAINS WILL LEAD TO WARM AND MAINLY DRY WEATHER THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. AVIATION...A FEW ISOLATED THUNDERSTORMS MAY BE POSSIBLE THIS AFTERNOON AND EARLY EVENING OVER PARTS OF FAR WESTERN SOUTH DAKOTA AND FAR NORTHEAST WYOMING. OTHERWISE...VFR CONDITIONS WILL PREVAIL. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. && $$ WETENKAMP sd AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 220 PM MDT WED AUG 20 2008 .DISCUSSION...SKIES REMAIN MOSTLY SUNNY ACROSS THE CWA TODAY. SURFACE ANALYSIS PLACES A STATIONARY SURFACE TROUGH/DRYLINE ACROSS NORTHWEST SOUTH DAKOTA THROUGH THE BLACK HILLS AND TO THE SOUTH. BREEZY SOUTHERLY FLOW CONTINUES ACROSS THE SOUTH DAKOTA PLAINS TODAY KEEPING DEWPOINTS IN THE 50S. BOTH THE NAM AND RUC ARE STILL IN GOOD AGREEMENT THAT SOME PARTS OF THE SOUTH DAKOTA PLAINS AND THE BLACK HILLS ARE SEEING CAPE VALUES RISING UP TO 1500 J/KG THIS AFTERNOON. VIS SAT SHOWS TOWERING CU DEVELOPING WEST AND SOUTH OF THE CWA ACROSS THE HIGHER TERRAIN OF WYOMING...AND OVER THE BLACK HILLS. RADAR IS NOW SHOWING THUNDERSTORMS DEVELOPING OVER EAST CENTRAL WYOMING...SO WILL LEAVE IN ISOLATED EVENING POPS ACROSS THE HILLS AND ACROSS THE FAR WESTERN SOUTH DAKOTA PLAINS. SHEAR VALUES REMAIN ON THE WEAK SIDE...SO NO ORGANIZED SEVERE WEATHER IS EXPECTED. ANOTHER QUIET DAY IS EXPECTED TOMORROW AS THE UPPER RIDGE WEAKENS AND SHIFTS EAST. WARMER 700 MB TEMPS OF UP TO 16C WILL BRING HIGHER MAX TEMPS...POSSIBLY INTO THE UPPER 90S ACROSS SOME LOCATIONS ACROSS THE PLAINS. CLOUDS WILL BE ON THE RISE AS AN UPPER TROUGH MOVES ACROSS MONTANA. A COLD FRONT WILL SLIDE ACROSS THE CWA TOMORROW NIGHT BRINGING IN MUCH COOLER AIR TO THE CWA ALONG WITH GUSTY NORTHWEST WINDS. OVERALL THE FRONTAL PASSAGE IS NOT EXPECTED TO PRODUCE MUCH IN THE WAY OF PRECIP DUE TO A LACK OF MOISTURE IN THE LOWER LEVELS. AREAS ACROSS FAR NORTHWEST SOUTH DAKOTA AND PARTS OF NORTHEAST WYOMING WILL HAVE THE BEST CHANCES OF SEEING STORMS SINCE THE MAIN UPPER FORCING IS ACROSS NORTH DAKOTA AND EASTERN MONTANA...BUT CHANCES REMAIN SLIM. THE WAVE WILL BEGIN TO MOVE EAST/NORTHEAST OF THE AREA FRIDAY WITH A STRONG UPPER RIDGE BUILDING BACK INTO THE REGION. ANOTHER QUIET DAY IS EXPECTED FRIDAY WITH HIGHS JUST IN THE MID 70S TO MID 80S. EXTENDED...AN UPPER RIDGE BUILDING OVER THE NORTHERN PLAINS WILL LEAD TO WARM AND MAINLY DRY WEATHER THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. && .AVIATION...A FEW ISOLATED THUNDERSTORMS MAY BE POSSIBLE THIS AFTERNOON AND EARLY EVENING OVER PARTS OF FAR WESTERN SOUTH DAKOTA AND FAR NORTHEAST WYOMING. OTHERWISE...VFR CONDITIONS WILL PREVAIL. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. && $$ CALDERON/SCHILD sd AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 955 AM MDT WED AUG 20 2008 .DISCUSSION...SKIES REMAIN MOSTLY SUNNY ACROSS THE CWA THIS MORNING. SURFACE ANALYSIS PLACES A STATIONARY SURFACE TROUGH/DRYLINE ACROSS NORTHWEST SOUTH DAKOTA SOUTH THROUGH THE BLACK HILLS AND TO THE SOUTH. BREEZY SOUTHERLY FLOW CONTINUES ACROSS THE SOUTH DAKOTA PLAINS TODAY KEEPING DEWPOINTS IN THE 50S TO NEAR 60. BOTH THE NAM AND RUC ARE IN GOOD AGREEMENT THAT SOME PARTS OF THE SOUTH DAKOTA PLAINS AND THE BLACK HILLS COULD SEE CAPE VALUES RISING UP TO 1500 J/KG THIS AFTERNOON WITH THE DIURNAL HEATING. THE QUESTION IS WILL THESE AREA BE ABLE TO BREAK THE CAP. MODELS THINK SO...ESPECIALLY ACROSS THE BLACK HILLS AND SURROUNDING AREAS. HAVE THUS ADDED POPS FOR THIS AFTERNOON AND EVENING MENTIONING ISOLATED THUNDERSTORMS. REST OF THE FORECAST && .PREVIOUS DISCUSSION [300 AM MDT]...CURRENT SURFACE ANALYSIS SHOW LOW PRESSURE OVER SOUTHEAST MT...WITH SURFACE TROUGH EXTENDING INTO CENTRAL WY AND A COLD FRONT FURTHER WEST ACROSS CENTRAL MT. UPPER LEVEL ANALYSIS SHOWS RIDGE AXIS OVER THE UPPER MIDWEST WITH LOW PRESSURE ALONG THE PACIFIC NW COAST. TIGHT SURFACE PRESSURE GRADIENT IN PLACE ACROSS MOST OF THE DAKOTAS. WINDS ARE STRONGEST RIGHT NOW ACROSS PORTIONS OF SOUTHWEST AND CENTRAL SD...WHERE GUSTS TO 30 MPH ARE NOTED. SKIES ARE CLEAR WITH TEMPS MOSTLY IN THE 60S. A COUPLE MORE WARM AND DRY DAYS ARE ON TAP AS FRONT TO THE WEST STALLS OUT ACROSS CENTRAL MT. THE SURFACE TROF WILL MAKE ITS WAY INTO NORTHEAST WY LATER THIS MORNING AND POSSIBLY REACH THE SD BORDER IN THE AFTERNOON. I SUPPOSE IT IS NOT OUT OF THE REALM OF POSSIBILITY THAT A HIGH BASED STORM OR TWO COULD DEVELOP ALONG THE TROF THIS AFTERNOON OR EARLY EVENING...BUT THE ATMOSPHERE JUST LOOKS TOO DRY SO WILL LEAVE CHANCES OUT OF THE FORECAST. FURTHER EAST TOWARD CENTRAL SD...SOUTH-SOUTHEAST WINDS WILL INCREASE LATER THIS MORNING AS BOUNDARY LAYER MIXES OUT. WINDS WILL APPROACH ADVISORY CRITERIA ACROSS SOUTH CENTRAL SD DURING THE LATE MORNING AND AFTERNOON HOURS. NOT SURE WINDS WILL REACH ADVISORY CRITERIA FOR ANY PROLONGED PERIOD OF TIME...SO WILL NOT ISSUE ONE AT THIS TIME. HIGH TEMPS TODAY WILL AGAIN BE MOSTLY IN THE UPPER 80S TO LOWER 90S...POSSIBLY A FEW MID 90S AROUND THE BADLANDS. IT WILL STAY BREEZY ACROSS MUCH OF SOUTH CENTRAL SD TONIGHT AS LOW LEVEL JET REMAINS IN PLACE OVER THE AREA. SURFACE TROF WILL RETREAT A BIT WESTWARD INTO WY TONIGHT. LOWS WILL MOSTLY BE IN THE 60S. UPPER TROF WILL MOVE EAST ACROSS THE CANADIAN ROCKIES ON THURSDAY AND INTO THE NORTHERN HIGH PLAINS THURSDAY NIGHT. THIS WILL FINALLY HELP TO PUSH COLD FRONT EAST ACROSS THE FORECAST AREA THURSDAY NIGHT. BEFORE THAT...ONE MORE VERY WARM DAY IS ON TAP FOR THURSDAY...WITH HIGHS IN THE 90S ACROSS THE PLAINS AND 80S IN THE HILLS. WINDS WILL BE STRONG AGAIN ACROSS CENTRAL SD...WITH SOUTHERLY WINDS NEAR ADVISORY CRITERIA DURING THE DAY. ANY CHANCES FOR SHOWERS AND STORMS SHOULD OFF UNTIL THURSDAY NIGHT AS FRONT CROSSES. MAIN CHANCES FOR PCPN WILL BE ACROSS THE FAR NORTHWESTERN CWA...WHERE BETTER UPPER LEVEL SUPPORT AND MOISTURE WILL BE. THREAT FOR ANY SEVERE STORMS SHOULD BE FURTHER NORTH ACROSS ND. THE SOUTHERN HALF OF THE CWA WILL REMAIN DRY. COOLER AIR WILL FILTER INTO THE AREA LATE THURSDAY NIGHT AND FRIDAY ...WITH TEMPS A GOOD 10 TO 15 DEGREES COOLER FOR MOST AREAS COMPARED TO THURSDAY. GUSTY NORTHWEST WINDS CAN BE EXPECTED ACROSS THE NORTHWEST AND WEST CENTRAL SD PLAINS...ESPECIALLY DURING THE MORNING HOURS. A PLEASANTLY COOL FRIDAY NIGHT IS IN STORE WITH LOWS IN THE MID 40S TO MID 50S. EXTENDED...AN UPPER RIDGE BUILDING OVER THE NORTHERN PLAINS WILL LEAD TO WARM AND DRY WEATHER THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. MODELS SHOWING LL MOISTURE AND INSTABILITY INCREASING WEST OF THE SFC HIGH OVER NORTHEASTERN WYOMING AND SOUTHWESTERN SOUTH DAKOTA ON SUNDAY BUT THE MID LEVELS LOOK WARM ENOUGH KEEP THE CAPPING INVERSION IN PLACE. && .AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH THE AVIATION FORECAST PERIOD. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. && $$ sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 433 AM CDT WED AUG 20 2008 .SHORT TERM...TODAY THROUGH FRIDAY FORECAST CHALLENGES INCLUDE WIND SPEEDS TODAY...ALONG WITH PRECIPITATION CHANCES TONIGHT AND AGAIN THURSDAY NIGHT/FRIDAY...FOLLOWED BY IMPACTS OF AIRMASS CHANGE ON TEMPS FRIDAY IN CAA. CURRENTLY...RETURN FLOW PATTERN CONTINUES IN FULL SWING...WITH A 30 TO 45 KNOT LLJ RAMPING UP ACROSS CENTRAL/NC SODAK...PER THE LATEST RUC ANALYSIS. ANOTHER SCT-BKN MID-LEVEL DECK OF ACCUS HAS DEVELOPED THIS MORNING IN AREAS OF BEST SPEED CONVERGENCE ON THE NOSE OF THE LLJ. TODAY...SOUTH WINDS ARE EXPECTED TO REALLY PICK UP AS PRESSURE GRADIENT TIGHTENS SOMEWHAT...AND STRONG LLJ WINDS BEGIN MIXING OUT WITH DAYTIME HEATING. WIND ADVISORY HOISTED FOR PORTIONS OF THE FORECAST AREA WHERE STRONGEST WINDS LOOK TO HAVE THE BEST CHANCE FOR KNOCKING OUT A COUPLE OF HOURS OF 30 MPH OR GREATER SUSTAINED AND/OR GUSTS TO 45 MPH OR HIGHER. WINDS AS STRONG...IF NOT STRONGER...PROGGED TO SET UP AGAIN ON THURSDAY. MORE SUBSTANTIVE AREAL COVERAGE OF ACCUS THIS MORNING ON THE NOSE OF STRONGER LLJ COMPARED TO LAST NIGHT AT THIS TIME. LATER TONIGHT...TONS MORE LLM/INSTABILITY PROGGED TO BE AROUND /THAN THERE IS NOW/. 700HPA WAA PATTERN STILL SHOWING UP TONIGHT...AND ANOTHER STRONG LLJ OF 35 TO 50 KNOTS WILL BE AROUND TONIGHT AS WELL. WENT AHEAD AND TOSSED IN A SLIGHT CHANCE POP FOR THUNDER WITH WHAT IS EXPECTED TO BE A SOMEWHAT MORE ACTIVE ACCUS FIELD LATER TONIGHT. ONLY MADE MINOR ADJUSTMENTS TO WX/POPS MENTION THURSDAY NIGHT INTO FRIDAY AS MOST ALL OF THE DYNAMICS AND INSTABILITY WILL BE BOTTLED UP ACROSS NORTH DAKOTA. BOTH THE 00Z GFS AND NAM SOLUTIONS AGREE BETTER THIS GO ROUND WITH FROPA TIMING ON FRIDAY...SO WENT AHEAD AND BASICALLY BROUGHT PRECIP MENTION TO AN END BY MID DAY ON FRIDAY...WHEN THE SURFACE TO 850HPA COLD FRONT WILL BE WORKING EAST OUT OF THIS CWA. NO CHANGES MADE TO MAX/MIN T GRIDS THIS MORNING. FRIDAY WILL BE A REAL PICKLE TO FORECAST FOR MAX TEMPS WITH A FROPA IN PROGRESS AND CAA WORKING INTO THE CWA FROM THE NORTHWEST. .LONG TERM...FRIDAY NIGHT THROUGH TUESDAY THE MODELS AND GFS ENSEMBLES ARE IN MORE AGREEMENT WITH THE MAIN WEATHER SYSTEMS AFFECTING THE AREA THROUGH THE LONG TERM. FIRST OFF...THE LOCATION OF THE COLD FRONT COME FRIDAY NIGHT IS PROGGED TO BE TO THE EAST OF THE CWA WITH COOLER AND DRIER NORTHWEST WINDS PREVAILING. THUS...TOOK OUT THE LOW POP FOR NORTHEAST SD AND WEST CENTRAL MN FOR FRIDAY NIGHT. OTHERWISE...A LARGE AREA OF SURFACE HIGH PRESSURE WILL BE SLIDING ACROSS THE REGION THROUGH THE LONG TERM. ON SATURDAY THE SURFACE HIGH PRESSURE AREA WILL BE OVER THE CWA WITH NOT MUCH FOR WINDS...SUNNY SKIES AND COOLER TEMPERATURES. SATURDAY NIGHT SHOULD BE THE COOLEST NIGHT WE HAVE HAD IN WHILE WITH LOWER 50S EAST IN THE CWA AND MAYBE 50 OR LOWER OCCURRING IN THE JAMES VALLEY BY SUNRISE SUNDAY. LOWERED THE TEMPERATURES FOR SATURDAY NIGHT SOME AND MAY HAVE TO LOWER THEM EVEN MORE. WAA RETURNS FOR THE REST OF THE PERIOD AS THE HIGH PRESSURE AREA PUSHES EAST ALONG WITH INCREASING SOUTH WINDS. ANOTHER PACIFIC FRONT WILL AFFECT THE REGION COME TUESDAY AND TUESDAY NIGHT. MAY HAVE TO ADD IN A POP FOR THIS TIME PERIOD IN THE NEXT FORECAST. && .AVIATION... SCT TO BKN 8000 FOOT CLOUDS WILL MOVE OVER THE ABR AND ATY TAF SITES THROUGH 14Z OR SO. OTHERWISE...SKIES WILL BE MOSTLY CLEAR AT ALL TAF SITES LATER THIS MORNING THROUGH TONIGHT. THE ISSUE TODAY INTO THIS EVENING WILL BE THE STRONG SOUTH WINDS IN THE 20 TO 35 KNOT RANGE...ESPECIALLY AT MBG...PIR AND ABR. NO SIGNIFICANT WEATHER OR VISIBILITY RESTRICTIONS ARE EXPECTED AT THE TAF SITES THROUGH TONIGHT. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...WIND ADVISORY UNTIL 10 PM CDT THIS EVENING FOR BROWN-CAMPBELL- CLARK-DAY-EDMUNDS-FAULK-HAND-HYDE-MARSHALL-MCPHERSON-POTTER- SPINK-WALWORTH. WIND ADVISORY UNTIL 1 PM CDT /NOON MDT/ THIS AFTERNOON FOR BUFFALO-DEWEY-HUGHES-JONES-LYMAN-STANLEY-SULLY. MN...NONE. && $$ SHORT TERM...DORN LONG TERM...MOHR AVIATION...MOHR WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE ABERDEEN SD 1048 AM CDT TUE AUG 19 2008 .UPDATE...REST OF TODAY OVERALL...FORECAST FOR TODAY IS ON TRACK WITH ONLY A FEW MINOR CHANGES MADE. FOG/STRATUS HAS DISSIPATED ACROSS THE EXTREME NORTHEASTERN CWA AND LLJ INDUCED MID LEVEL CLOUDS BEGINNING TO ALSO DECREASE ACROSS THE SOUTHWESTERN CWA. HIGH TEMPS ONLY CHANGED A DEGREE OR TWO BASED ON TRENDS THIS MORNING. SKIES WILL BE MOSTLY SUNNY TODAY WITH SOUTHERLY WINDS PICKING UP INTO THE 15 TO 25 MPH RANGE ACROSS CENTRAL/WESTERN SOUTH DAKOTA THIS AFTERNOON. DEWPOINTS ONCE AGAIN HAVING A TOUGH TIME DROPPING AND ARE STAYING UP IN THE MID 60S ACROSS THE EASTERN CWA. HAVE INCREASED DEWPOINTS A BIT HEADING INTO THE AFTERNOON HOURS. && .PREV DISCUSSION... .SHORT TERM...TODAY THROUGH THURSDAY FORECAST CHALLENGES WILL BE WIND SPEEDS AND EXTENT OF MOISTURE RETURN INTO THE AREA THROUGH THURSDAY...ALONG WITH MAX/MIN TEMPS. CURRENTLY...AN EAST-WEST ORIENTED STALLED FRONTAL BOUNDARY BASICALLY BISECTS THE CWA...WITH LIGHT EASTERLY SURFACE WINDS NORTH OF THE BOUNDARY AND LIGHT SOUTHERLY SURFACE WINDS SOUTH OF THE BOUNDARY. SURFACE DEWPOINT DEPRESSIONS HAVE DROPPED DOWN TO LESS THEN 3 DEGREES ALREADY THIS MORNING ACROSS MUCH OF THE EASTERN HALF OF THE CWA...SO CONTINUED THE PATCHY FOG MENTION IN THE GRIDS THROUGH 9 AM CDT. HIGH PRESSURE ALSO RESIDES THROUGHOUT THE REGION SOUTH AND EAST OF THE CWA. DESPITE THE MEAGER 850HPA MOISTURE AVAILABLE TO WORK WITH AND THE LACK OF MID/UPPER LEVEL LIFT/SUPPORT...AN ACCUS CLOUD FIELD HAS FORMED EARLY THIS MORNING FROM SOUTH CENTRAL SODAK THROUGH EASTERN NEBRASKA ALONG THE NOSE OF A DEVELOPING 25 KNOT LLJ MAX /PER LATEST RUC ANALYSIS/. THIS STALLED FRONTAL BOUNDARY WILL RECEDE NORTHWARD TODAY...AS A RETURN FLOW PRESSURE GRADIENT WIND STARTS TO DEVELOP ACROSS THE FORECAST AREA IN RESPONSE TO A DEEPENING LEE-SIDE SURFACE TROF OF LOW PRESSURE. THE RETURN FLOW SOUTHERLY WINDS WILL STICK AROUND THROUGH THURSDAY RESULTING IN BREEZY TO WINDY SOUTHERLY WINDS. AND BREEZY TO WINDY SOUTHERLY WINDS BRING ABOUT SOME CONCERN ON THE FIRE WEATHER SIDE OF THE HOUSE. WILL LIKELY HAVE 25 MPH OR HIGHER GUSTS CRITERIA SATISFIED TODAY THROUGH THURSDAY. FINE FUELS ARE SAID TO BE CURED OR ARE CURING...SO MAY NOT BE MUCH LONGER BEFORE FINE FUELS CRITERIA FOR EXPLOSIVE FIRE GROWTH ARE MET. THE THIRD AND FINAL COMPONENT...LOW RELATIVE HUMIDITY...DOES NOT APPEAR TO BE MET TODAY THROUGH THURSDAY. RANGELAND FIRE DANGER WORKS OUT TO BE MODERATE TO HIGH THIS AFTERNOON ACROSS THE WESTERN MOST FIRE WEATHER FORECAST ZONES. 850HPA THERMAL ADVECTION OFF BOTH THE NAM AND GFS 00Z SOLUTIONS SUGGESTS THAT 850HPA TEMPS BY PEAK HEATING TODAY COULD ACTUALLY BE A DEGREE OR TWO COOLER THAN THEY WERE ON MONDAY AT PEAK HEATING AS THE DEVELOPING RETURN FLOW SOUTHERLY WINDS DRAW RELATIVELY COOLER AIR NORTHWARD OFF OF THE SURFACE HIGH RESIDING ACROSS THE CENTRAL PLAINS. CALL IT NEUTRAL AIR ADVECTION FROM THE SOUTH FOR WEDNESDAY AS WELL...BEFORE THE PREFRONTAL WARMING HAS A CHANCE TO KICK IN ACROSS THE MISSOURI RIVER VALLEY ON THURSDAY. STILL LOOKS LIKE MID TO UPPER 90S IS ACHIEVABLE OUT ACROSS THE WESTERNMOST THIRD OF FORECAST ZONES ON THURSDAY...BUT FURTHER EAST /JAMES RIVER VALLEY AND POINTS EAST/ WILL PROBABLY ONLY BE ABLE TO WARM TO MID/UPPER 80S...AGAIN DUE TO LACK OF DECENT LOW LEVEL WAA. SOUTHERLY LLJ MAXES DEVELOP EACH OF THE NEXT TWO NIGHTS...WITH THE STRONGEST LLJ WINDS PROGGED WEDNESDAY NIGHT BETWEEN 35 AND 45 KNOTS BETWEEN THE GFS AND NAM RESPECTIVELY. SLIGHTLY HIGHER MOISTURE CONTENT AIR WILL BE DRAWN UP INTO THE FORECAST AREA ON THESE LOW LEVEL JETS /PROLLY MORE MOISTURE THAN PROGGED BY THE GFS SINCE LOW LEVEL MOISTURE ADVECTION IS A KNOWN WEAKNESS IN THE GFS MODEL/...AND DESPITE THE LACK OF 250HPA JET LEVEL SUPPORT AND ANY NOTABLE MID-LEVEL SHORTWAVE TROFPAS...AM CONCERNED ABOUT THE LACK OF LATE NIGHT POPS/WX MENTION FOR ACCUS-TYPE ELEVATED SHOWERS AND THUNDERSTORMS THAT MIGHT BE ABLE TO GET GOING JUST BASED OFF THE COMBINATION OF 850HPA MOISTURE ADVECTION/WEAK 700HPA WAA AND CONVERGENCE ALONG THE NOSE OF 850HPA LOW LEVEL JETS EACH OF THE NEXT COUPLE OF NIGHTS. COLLABORATION OVER THIS ISSUE CONCLUDED WITH A CONTINUED DRY FORECAST FOR NOW. BUT WILL NEED TO RE-ASSESS WITH THE NEXT FEW MODEL RUNS. .LONG TERM...THURSDAY NIGHT THROUGH MONDAY THE MODELS AND GFS ENSEMBLES SHOW SOME IMPORTANT DIFFERENCES IN THE LONG TERM WITH THE LOCATION OF THE COLD FRONT AS IT MOVES THROUGH THE REGION. FOR THURSDAY NIGHT AND FRIDAY...THE LAST FORECAST IN THE NAM CYCLE SHOWS THE COLD FRONT JUST MOVING INTO OUR WESTERN CWA WHILE THE GFS SHOWS THE FRONT INTO OUR FAR EASTERN CWA. THE EC WAS BETWEEN THESE TWO MODELS WITH THE COLD FRONTAL LOCATION. WHATEVER OCCURS...BELIEVE A 20 POP AT LEAST IS WARRANTED FOR THURSDAY NIGHT ACROSS THE CWA. DESPITE THE WARM MID LEVELS...A STRONG LLJ...INCREASING DEEP LAYER SHEAR...LIKELY DEWPOINTS IN THE MID TO UPPER 60S...GOOD INSTABILITY...AND GOOD LOW LEVEL LIFT ALONG THE FRONTAL ZONE COULD RESULT IN A LINE OF STORMS DEVELOPING AND SWEEPING ACROSS THE CWA IF THE CAP TURNS OUT TO BE WEAKER AND IS BROKEN. ALSO...IF A SURFACE LOW PRESSURE AREA DEVELOPS ALONG THE FRONT AS WAS SHOWN BY THE NAM...THIS WILL INTENSIFY THE LOW LEVEL CONVERGENCE AND LIFT...INCREASING THE CHANCES OF TSRA DEVELOPMENT. LEFT THE POPS AS IS FOR FRIDAY AND FRIDAY NIGHT FOR THE EASTERN CWA TO ACCOUNT FOR THE POSSIBLE SLOWER SOLUTIONS OF THE NAM AND EC. WILL HAVE TO WAIT AND SEE ON THIS. OTHERWISE...GOOD CAA ON FRIDAY ALONG WITH A DEEP MIXING LAYER WILL RESULT IN COOLER TEMPERATURES ACROSS THE CWA ALONG WITH LIKELY BREEZY CONDITIONS. SURFACE HIGH PRESSURE WILL SLIDE ACROSS THE REGION THROUGH THE WEEKEND WITH A RETURN TO WAA ON SUNDAY INTO MONDAY. EXPECT IT TO REMAIN DRY THROUGH THIS TIME PERIOD. && .AVIATION... LOOK FOR A FEW MID CLOUDS (FEW-SCT080-100) TO DEVELOP OVER ALL THE TERMINAL SITES AFT 18Z. VSBYS EXPECTED TO REMAIN P6SM THROUGH 12Z WEDNESDAY WITH ONLY FEW-SCT MID CLOUDS DOTTING THE SKY. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...TMT SHORT TERM...DORN LONG TERM...MOHR AVIATION...HINTZ WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 322 AM CDT TUE AUG 19 2008 .SHORT TERM...TODAY THROUGH THURSDAY FORECAST CHALLENGES WILL BE WIND SPEEDS AND EXTENT OF MOISTURE RETURN INTO THE AREA THROUGH THURSDAY...ALONG WITH MAX/MIN TEMPS. CURRENTLY...AN EAST-WEST ORIENTED STALLED FRONTAL BOUNDARY BASICALLY BISECTS THE CWA...WITH LIGHT EASTERLY SURFACE WINDS NORTH OF THE BOUNDARY AND LIGHT SOUTHERLY SURFACE WINDS SOUTH OF THE BOUNDARY. SURFACE DEWPOINT DEPRESSIONS HAVE DROPPED DOWN TO LESS THEN 3 DEGREES ALREADY THIS MORNING ACROSS MUCH OF THE EASTERN HALF OF THE CWA...SO CONTINUED THE PATCHY FOG MENTION IN THE GRIDS THROUGH 9 AM CDT. HIGH PRESSURE ALSO RESIDES THROUGHOUT THE REGION SOUTH AND EAST OF THE CWA. DESPITE THE MEAGER 850HPA MOISTURE AVAILABLE TO WORK WITH AND THE LACK OF MID/UPPER LEVEL LIFT/SUPPORT...AN ACCUS CLOUD FIELD HAS FORMED EARLY THIS MORNING FROM SOUTH CENTRAL SODAK THROUGH EASTERN NEBRASKA ALONG THE NOSE OF A DEVELOPING 25 KNOT LLJ MAX /PER LATEST RUC ANALYSIS/. THIS STALLED FRONTAL BOUNDARY WILL RECEDE NORTHWARD TODAY...AS A RETURN FLOW PRESSURE GRADIENT WIND STARTS TO DEVELOP ACROSS THE FORECAST AREA IN RESPONSE TO A DEEPENING LEE-SIDE SURFACE TROF OF LOW PRESSURE. THE RETURN FLOW SOUTHERLY WINDS WILL STICK AROUND THROUGH THURSDAY RESULTING IN BREEZY TO WINDY SOUTHERLY WINDS. AND BREEZY TO WINDY SOUTHERLY WINDS BRING ABOUT SOME CONCERN ON THE FIRE WEATHER SIDE OF THE HOUSE. WILL LIKELY HAVE 25 MPH OR HIGHER GUSTS CRITERIA SATISFIED TODAY THROUGH THURSDAY. FINE FUELS ARE SAID TO BE CURED OR ARE CURING...SO MAY NOT BE MUCH LONGER BEFORE FINE FUELS CRITERIA FOR EXPLOSIVE FIRE GROWTH ARE MET. THE THIRD AND FINAL COMPONENT...LOW RELATIVE HUMIDITY...DOES NOT APPEAR TO BE MET TODAY THROUGH THURSDAY. RANGELAND FIRE DANGER WORKS OUT TO BE MODERATE TO HIGH THIS AFTERNOON ACROSS THE WESTERN MOST FIRE WEATHER FORECAST ZONES. 850HPA THERMAL ADVECTION OFF BOTH THE NAM AND GFS 00Z SOLUTIONS SUGGESTS THAT 850HPA TEMPS BY PEAK HEATING TODAY COULD ACTUALLY BE A DEGREE OR TWO COOLER THAN THEY WERE ON MONDAY AT PEAK HEATING AS THE DEVELOPING RETURN FLOW SOUTHERLY WINDS DRAW RELATIVELY COOLER AIR NORTHWARD OFF OF THE SURFACE HIGH RESIDING ACROSS THE CENTRAL PLAINS. CALL IT NEUTRAL AIR ADVECTION FROM THE SOUTH FOR WEDNESDAY AS WELL...BEFORE THE PREFRONTAL WARMING HAS A CHANCE TO KICK IN ACROSS THE MISSOURI RIVER VALLEY ON THURSDAY. STILL LOOKS LIKE MID TO UPPER 90S IS ACHIEVABLE OUT ACROSS THE WESTERNMOST THIRD OF FORECAST ZONES ON THURSDAY...BUT FURTHER EAST /JAMES RIVER VALLEY AND POINTS EAST/ WILL PROBABLY ONLY BE ABLE TO WARM TO MID/UPPER 80S...AGAIN DUE TO LACK OF DECENT LOW LEVEL WAA. SOUTHERLY LLJ MAXES DEVELOP EACH OF THE NEXT TWO NIGHTS...WITH THE STRONGEST LLJ WINDS PROGGED WEDNESDAY NIGHT BETWEEN 35 AND 45 KNOTS BETWEEN THE GFS AND NAM RESPECTIVELY. SLIGHTLY HIGHER MOISTURE CONTENT AIR WILL BE DRAWN UP INTO THE FORECAST AREA ON THESE LOW LEVEL JETS /PROLLY MORE MOISTURE THAN PROGGED BY THE GFS SINCE LOW LEVEL MOISTURE ADVECTION IS A KNOWN WEAKNESS IN THE GFS MODEL/...AND DESPITE THE LACK OF 250HPA JET LEVEL SUPPORT AND ANY NOTABLE MID-LEVEL SHORTWAVE TROFPAS...AM CONCERNED ABOUT THE LACK OF LATE NIGHT POPS/WX MENTION FOR ACCUS-TYPE ELEVATED SHOWERS AND THUNDERSTORMS THAT MIGHT BE ABLE TO GET GOING JUST BASED OFF THE COMBINATION OF 850HPA MOISTURE ADVECTION/WEAK 700HPA WAA AND CONVERGENCE ALONG THE NOSE OF 850HPA LOW LEVEL JETS EACH OF THE NEXT COUPLE OF NIGHTS. COLLABORATION OVER THIS ISSUE CONCLUDED WITH A CONTINUED DRY FORECAST FOR NOW. BUT WILL NEED TO RE-ASSESS WITH THE NEXT FEW MODEL RUNS. .LONG TERM...THURSDAY NIGHT THROUGH MONDAY THE MODELS AND GFS ENSEMBLES SHOW SOME IMPORTANT DIFFERENCES IN THE LONG TERM WITH THE LOCATION OF THE COLD FRONT AS IT MOVES THROUGH THE REGION. FOR THURSDAY NIGHT AND FRIDAY...THE LAST FORECAST IN THE NAM CYCLE SHOWS THE COLD FRONT JUST MOVING INTO OUR WESTERN CWA WHILE THE GFS SHOWS THE FRONT INTO OUR FAR EASTERN CWA. THE EC WAS BETWEEN THESE TWO MODELS WITH THE COLD FRONTAL LOCATION. WHATEVER OCCURS...BELIEVE A 20 POP AT LEAST IS WARRANTED FOR THURSDAY NIGHT ACROSS THE CWA. DESPITE THE WARM MID LEVELS...A STRONG LLJ...INCREASING DEEP LAYER SHEAR...LIKELY DEWPOINTS IN THE MID TO UPPER 60S...GOOD INSTABILITY...AND GOOD LOW LEVEL LIFT ALONG THE FRONTAL ZONE COULD RESULT IN A LINE OF STORMS DEVELOPING AND SWEEPING ACROSS THE CWA IF THE CAP TURNS OUT TO BE WEAKER AND IS BROKEN. ALSO...IF A SURFACE LOW PRESSURE AREA DEVELOPS ALONG THE FRONT AS WAS SHOWN BY THE NAM...THIS WILL INTENSIFY THE LOW LEVEL CONVERGENCE AND LIFT...INCREASING THE CHANCES OF TSRA DEVELOPMENT. LEFT THE POPS AS IS FOR FRIDAY AND FRIDAY NIGHT FOR THE EASTERN CWA TO ACCOUNT FOR THE POSSIBLE SLOWER SOLUTIONS OF THE NAM AND EC. WILL HAVE TO WAIT AND SEE ON THIS. OTHERWISE...GOOD CAA ON FRIDAY ALONG WITH A DEEP MIXING LAYER WILL RESULT IN COOLER TEMPERATURES ACROSS THE CWA ALONG WITH LIKELY BREEZY CONDITIONS. SURFACE HIGH PRESSURE WILL SLIDE ACROSS THE REGION THROUGH THE WEEKEND WITH A RETURN TO WAA ON SUNDAY INTO MONDAY. EXPECT IT TO REMAIN DRY THROUGH THIS TIME PERIOD. && .AVIATION... VFR MOSTLY CLEAR SKIES ARE EXPECTED THROUGH THIS TAF PERIOD WITH INCREASING SOUTH WINDS BY THIS AFTERNOON. SOME LIGHT FOG IS AGAIN POSSIBLE UNTIL 14Z AT ABR AND ATY. OTHERWISE...NO OTHER SIGNIFICANT WEATHER IS EXPECTED AT THE TAF SITES. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ SHORT TERM...DORN LONG TERM...MOHR AVIATION...MOHR WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BROWNSVILLE TX 300 AM CDT WED AUG 20 2008 .DISCUSSION...THE H5 LOW OVER NORTH TEXAS WILL LINGER NEAR THE RED RIVER TODAY BEFORE TROUGHING OUT AND LIFTING NORTHEAST TONIGHT. THE LACK OF ASSOCIATED ENERGY PULSES MOVING OVER DEEP SOUTH TEXAS MAY PROVIDE A BRIEF RESPITE TO THE ONGOING RAIN SITUATION. HOWEVER...THE LATEST BRO SOUNDING IS EXTREMELY MOIST WITH PWAT AT 2.41...AND IT WILL NOT TAKE MUCH HEATING TO TRIGGER SHOWERS ONCE AGAIN. FORECAST SOUNDINGS REMAIN MOIST WITH OVER TWO INCHES OF PWAT INTO THE WEEKEND BEFORE THINGS DRY OUT SOMEWHAT. THAT HAVING BEEN SAID...MOST OF THE MODELS SEEM TO FOCUS THE HIGHER RAIN CHANCES FOR TODAY OVER THE EASTERN SECTIONS AND THE MARINE AREAS. STORM TOTAL PRECIP ESTIMATES FROM THE LAST THREE DAYS SHOW AREAS AWAY FROM THE COAST TAKING THE BRUNT OF THE RAINFALL...WITH MANY AREAS INDICATING OVER 5 INCHES OF RAIN. COASTAL AREAS HAVE GENERALLY RECEIVED LESS THAN 5 INCHES. FEEL THAT RAINS TODAY WILL TOUCH DIFFERENT AREAS AND WILL BE LOCALIZED...SO WILL DROP THE CURRENT FLASH FLOOD WATCH FOR THE WESTERN COUNTIES. THIS EVENT IS BY NO MEANS OVER HOWEVER...AND ENERGY PULSES ARE PROGGED TO MOVE FROM SOUTHWEST TO NORTHEAST ALONG A MID LEVEL WEAKNESS ABOVE DEEP SOUTH TEXAS ON THURSDAY AND FRIDAY. UNSETTLED WEATHER MAY CONTINUE INTO THE WEEKEND AS WELL...WITH THE FOCUS SHIFTING TO CONVECTION OVER OLD MEXICO...WHICH WILL SPILL OVER INTO DEEP SOUTH TEXAS. WITH THE H5 RIDGE RELOCATED UPSTREAM...THERE IS LITTLE CAP TO PREVENT REGULAR SHOWER ACTIVITY...AND THIS SITUATION IS PROGGED TO PERSIST THROUGH THE FORECAST. CHANCES WILL DIMINISH NEXT WEEK...BUT SHOWERS WILL STILL BE POSSIBLE VIA AT LEAST THE SEA BREEZE. ADDED PATCHY FOG TO THE FORECAST FOR THE EARLY HOURS OF THIS MORNING AS STANDING WATER AND LIGHT WINDS ARE PROMOTING ITS FORMATION. OTHERWISE...DID NOT ALTER THE OTHER GRIDS VERY MUCH. RAIN COOLING AFTER THIS WEEKEND WILL DECREASE AND THE DIURNAL TEMPERATURE SPREAD SHOULD INCREASE AS HIGH TEMPERATURES RISE. && .PREV DISCUSSION...ISSUED AT 843 PM CDT TUE AUG 19 2008...SATELLITE AND RADAR IMAGES INDICATE LESS CONVECTION ACROSS DEEP SOUTH TEXAS AND NORTHEAST MEXICO TONIGHT COMPARED TO LAST NIGHT. RUC80 500MB HEIGHT ANALYSIS AND WATER VAPOR IMAGES INDICATE THE LOW ACROSS THE SOUTHERN PLAINS CONTINUES TO DRAW MOISTURE ACROSS CENTRAL MEXICO INTO THE WESTERN GULF OF MEXICO. PRECIPITABLE WATER VALUES HAVE CHANGED LITTLE ACROSS THE LOWER RIO GRANDE VALLEY SINCE LAST NIGHT SO WILL CONTINUE FLASH FLOOD WATCH FOR THE WESTERN AND SOUTHERN PORTIONS OF THE CWA THROUGH TONIGHT SINCE SURFACE LOW PRESSURE ACROSS SOUTHWEST TX WILL CONTINUE TO PULL MOISTURE OVER THE WESTERN GULF INLAND AND THE 500MB TROUGH AXIS ACROSS THE RIO GRANDE PLAINS SHOULD PROVIDE ENOUGH INSTABILITY ALOFT TO PRODUCE ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE AREA TONIGHT INTO WEDNESDAY. WILL LOWER POPS TONIGHT BASED ON RADAR TRENDS BUT WILL CONTINUE TO MENTION HEAVY RAINFALL WITH STORMS. && .MARINE...BUOY 42020 REPORTED SOUTH WINDS AROUND 10 KNOTS GUSTING TO AROUND 12 KNOTS WITH SEAS AT 2 FEET WITH A PERIOD OF 5 SECONDS AT 01 CDT/06 UTC. BROAD MID-LEVEL LOW PRESSURE WILL PERSIST OVER TEXAS FOR THE NEXT SEVERAL DAYS...PRODUCING ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS OVER THE ADJACENT COASTAL WATERS OF DEEP SOUTH TEXAS. MARINERS CAN ALSO EXPECT LIGHT TO MODERATE WINDS AND LOW TO MODERATE SEAS. && .AVIATION...VFR CONDITIONS WILL PREVAIL OVER THE TRIO OF REGIONAL AIRPORTS THROUGH THE NEXT 24 HOURS...WITH BRIEF MVFR CONDITIONS IN THE VICINITY OF ANY LATE MORNING THROUGH EARLY EVENING THUNDERSTORMS. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW 089 079 090 079 / 050 010 050 020 BROWNSVILLE 090 078 092 078 / 050 010 050 020 FALFURRIAS 093 074 093 076 / 040 020 050 030 HARLINGEN 092 078 093 078 / 050 020 050 020 HEBBRONVILLE 094 074 095 075 / 030 020 050 030 MCALLEN 093 078 095 078 / 040 020 050 020 PORT ISABEL 087 079 088 079 / 050 010 050 020 RIO GRANDE CITY 094 076 095 076 / 040 010 050 030 SOUTH PADRE ISLAND 086 080 086 080 / 050 020 050 020 && .BRO WATCHES/WARNINGS/ADVISORIES...NONE. && $$ 54/66 THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT: HTTP://WWW.WEATHER.GOV/BROWNSVILLE tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BROWNSVILLE TX 843 PM CDT TUE AUG 19 2008 .DISCUSSION...SATELLITE AND RADAR IMAGES INDICATE LESS CONVECTION ACROSS DEEP SOUTH TEXAS AND NORTHEAST MEXICO TONIGHT COMPARED TO LAST NIGHT. RUC80 500MB HEIGHT ANALYSIS AND WATER VAPOR IMAGES INDICATE THE LOW ACROSS THE SOUTHERN PLAINS CONTINUES TO DRAW MOISTURE ACROSS CENTRAL MEXICO INTO THE WESTERN GULF OF MEXICO. PRECIPITABLE WATER VALUES HAVE CHANGED LITTLE ACROSS THE LOWER RIO GRANDE VALLEY SINCE LAST NIGHT SO WILL CONTINUE FLASH FLOOD WATCH FOR THE WESTERN AND SOUTHERN PORTIONS OF THE CWA THROUGH TONIGHT SINCE SURFACE LOW PRESSURE ACROSS SOUTHWEST TX WILL CONTINUE TO PULL MOISTURE OVER THE WESTERN GULF INLAND AND THE 500MB TROUGH AXIS ACROSS THE RIO GRANDE PLAINS SHOULD PROVIDE ENOUGH INSTABILITY ALOFT TO PRODUCE ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE AREA TONIGHT INTO WEDNESDAY. WILL LOWER POPS TONIGHT BASED ON RADAR TRENDS BUT CONTINUE TO MENTION HEAVY RAINFALL WITH STORMS. && .AVIATION...THIS EVENINGS CONV HAS DISSIPATED LEAVING BEHIND ONLY MID AND HIGH CLD DECKS. WILL MAINTAIN VFR CONDITONS FOR THE OVERNIGHT PERIOD...BUT WILL INCLUDE A MENTION OF LOWER CEILINGS AND VSBYS TOMORROW AFTERNOON FOR SOME POSSIBLE DIURNALLY DRIVEN CONV LATER IN THE CURRENT TAF PERIOD. && .MARINE...A LIGHT ONSHORE FLOW WILL PREVAIL ALONG THE LOWER TX COASTLINE THROUGH THE NIGHT MAINTAINING PRETTY BENIGN MARINE CONDITIONS ACROSS THE BAY AND GULF WATERS. NO MAJOR CHANGES EXPECTED FOR THE UPCOMING CWF UPDATE. && .PREV DISCUSSION... /ISSUED ISSUED BY NATIONAL WEATHER SERVICE LAKE CHARLES LA/ UPPER LOW OVER NORTH CENTRAL TEXAS IS FORECAST TO WEAKEN AND BEGIN LIFTING OUT OVER THE NEXT 72 HRS. A WEAK UPPER TROF WILL REMAIN IN PLACE DOWN TO THE BIG BEND...WITH SUBTLE PERTURBATIONS CONTINUING TO SET OFF SHOWERS AND THUNDERSTORMS ACROSS SOUTH TEXAS. CONVECTIVE COVERAGE TODAY HAS BEEN ON THE ISOLATED TO SCATTERED SIDE...AND DEEP MOISTURE AXIS IS EXPECTED TO SHIFT TO THE EAST AND NORTHEAST OVER THE GULF WATERS OVER THE NEXT 24 HRS OR SO. THUS...THE THREAT OF ADDITIONAL FLOODING RAINS WOULD APPEAR TO BE COMING TO AN END. HAVING SAID THIS...WILL LET FLOOD WATCH CONTINUE THROUGH CURRENT 7 PM EXPIRATION TIME AND ALLOW EVENING SHIFT TO FURTHER EVALUATE THE SITUATION. REMAINDER OF INHERITED FORECAST LOOKED ON TARGET WITH RAINFALL CHANCES DROPPING OFF INTO THE SLIGHT CHANCE TO CHANCE CATEGORY TOWARD THE END OF THE WEEK. POPS OVER THE WEEKEND MAY NEED TO BE INCREASED...AS BOTH THE GFS AND ECMWF ARE SHOWING AN INVERTED TROF/LOW DEVELOPING AND TRACKING OVER THE AREA. WILL CONTINUE TO MONITOR TRENDS. AVIATION...VFR WILL GENERALLY PREVAIL FOR THE NEXT 24 HOURS...THOUGH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO AFFECT THE AREA. MARINE...DEEP TROPICAL MOISTURE...IN CONJUNCTION WITH UPPER LEVEL DISTURBANCES MOVING OVERHEAD FROM UPPER LEVEL LOW PRESSURE LOCATED IN NORTHERN TEXAS...WILL KEEP SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS IN THE FORECAST FOR THE NEXT FEW DAYS. WEAK TO MODERATE SOUTHEAST WINDS WILL RESULT IN SEAS OF 2 TO 4 FEET. WINDS AND SEAS WILL BE HIGHER IN AN NEAR ANY THUNDERSTORMS. PRECIPITATION CHANCES WILL DECREASE AROUND THE END OF THE WEEK AS SURFACE HIGH PRESSURE MOVES CLOSER TO THE WESTERN GULF OF MEXICO. LIGHT TO MODERATE WINDS AND LOW SEAS CAN BE EXPECTED THROUGH THE EXTENDED FORECAST. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 78 89 79 90 / 30 50 20 30 BROWNSVILLE 78 90 78 92 / 30 50 20 30 HARLINGEN 77 92 78 93 / 30 50 20 30 MCALLEN 77 93 78 95 / 30 50 20 30 RIO GRANDE CITY 76 94 76 95 / 30 30 10 10 SOUTH PADRE ISLAND 80 86 80 86 / 30 50 20 30 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...FLASH FLOOD WATCH UNTIL 4 AM CDT WEDNESDAY FOR TXZ248-249-252- 253. GM...NONE. && $$ THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT: HTTP://WWW.WEATHER.GOV/BROWNSVILLE PUBLIC/GRIDS...61 AVIATION/MARINE/MESO...60 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN ANGELO TX 120 PM CDT TUE AUG 19 2008 .DISCUSSION... EXPECT VFR CONDITIONS TO DOMINATE WEST CENTRAL TEXAS FOR THE REMAINDER OF TODAY AND MOST OF TONIGHT. SEE AVIATION BELOW FOR DETAILS. && .AVIATION... SHOWERS AND THUNDERSTORMS WILL CONTINUE TO REDEVELOP ACROSS MUCH OF WEST CENTRAL TEXAS THIS AFTERNOON AS AN UPPER-LEVEL LOW MOVES SLOWLY EAST ALONG THE RED RIVER VALLEY NEAR WICHITA FALLS. THE BEST CHANCE FOR THUNDERSTORMS THIS AFTERNOON WILL BE MAINLY ALONG AND NORTHEAST OF A LINE FROM SWEETWATER TO SAN SABA. AFTER MIDNIGHT TONIGHT...LOOK FOR MAINLY RAIN SHOWERS AND MVFR CEILINGS TO DOMINATE WEST CENTRAL TEXAS. BY SUNRISE TOMORROW MORNING...EXPECT MAINLY OVERCAST CEILINGS WITH BASES AROUND 1200 FEET ABOVE GROUND LEVEL TO DOMINATE WEST CENTRAL TEXAS. HOWEVER...SOME AREAS MAY HAVE TEMPORARY IFR CEILINGS WITH BASES AROUND 800 FEET ABOVE GROUND LEVEL. 23/HUBER && .PREV DISCUSSION... /ISSUED 1206 PM CDT TUE AUG 19 2008/ UPDATE... ADJUSTED SKY...WEATHER...POPS...AND QPF GRIDS FOR THE REMAINDER OF TODAY. LATEST ZONE PRODUCT REFLECTS THESE CHANCES. SEE DISCUSSION BELOW FOR DETAILS. DISCUSSION... LATEST WATER VAPOR IMAGERY SHOWS A SIGNIFICANT DRY SLOT OVER ALL BUT OUR BIG COUNTRY COUNTIES. LATEST RUC DOES INDICATE A WEAK 500 VORTICITY MAX WILL MOVE SOUTHEAST ACROSS OUR CENTRAL AND SOUTHERN COUNTIES LATER THIS AFTERNOON. HOWEVER...RUC SOUNDING DATA...CENTERED ON SAN ANGELO...INDICATE PRECIPITABLE WATER VALUES DECREASE THIS AFTERNOON. THUS...DECIDED TO ADJUST POPS ACROSS MAINLY OUR CENTRAL AND SOUTHERN COUNTIES TO REFLECT A CHANCE (30 TO 50 PERCENT) FOR SHOWERS AND THUNDERSTORMS FOR THE REMAINDER OF TODAY. ALSO...BASED ON VISIBLE SATELLITE TRENDS OVER THE LAST COUPLE HOURS...ADJUSTED SKY GRIDS FOR THE REMAINDER OF TODAY. TEMPERATURES LOOKED ON TRACK. 23/HUBER PREV DISCUSSION... /ISSUED 617 AM CDT TUE AUG 19 2008/ UPDATE... SEE AVIATION SECTION FOR 12Z TAFS. AVIATION... STRATUS WITH MVFR/IFR CIGS INCREASE TO VFR BY EARLY AFTERNOON. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MAY BRING CIGS/VISIBILITES BACK INTO IFR/MVFR THIS AFTERNOON FOR SHORT AMOUNTS OF TIME. BEST CHANCES OF RAIN AT KABI AND KBBD. OTHERWISE...LIGHT WINDS WILL BECOME NORTH THIS MORNING...5 TO 10 MPH AS A WEAK COLD FRONT PUSHES THROUGH. LOW LEVEL MOISTURE WILL REMAIN OVER THE REGION TONIGHT AND HAVE STRATUS WITH MVFR CIGS COMING BACK THIS EVENING AT KABI AND TOWARD/AFTER MIDNIGHT FOR THE REST OF THE TAF SITES. PREV DISCUSSION... /ISSUED 340 AM CDT TUE AUG 19 2008/ DISCUSSION... UPPER LEVEL LOW THAT HAS BROUGHT WELCOME RAINFALL TO WEST CENTRAL TEXAS CONTINUES TO CHURN OVER NORTHWEST TEXAS EARLY THIS MORNING. NUMEROUS SHOWERS AND THUNDERSTORMS CONTINUE TO AFFECT SOUTHWESTERN OK...NORTH AND NORTHWEST TEXAS. MOST OF THE ACTIVITY IS EITHER NORTH AND EAST OF THE LOW...OR CONCENTRATED WITHIN THE CORE OF THE PARENT LOW. WEST OF THE LOW IN DRYING NORTH/NORTHWEST FLOW... WIDELY SCATTERED THUNDERSTORMS EARLIER THIS EVENING DISSIPATED AS THEY MADE THEIR WAY INTO THE CWA...AND THIS TREND CAN BE SEEN WITH NEW DEVELOPMENT NORTHWEST OF THE CWA AS WELL. WILL CANCEL THE FFA FOR THE BIG COUNTRY FOR THE REST OF THIS MORNING...WITH MOST OF THE THUNDERSTORM ACTIVITY EXPECTED TO REMAIN JUST NORTH AND EAST OF OUR COUNTIES THROUGH THE REST OF THE MORNING HOURS. HOWEVER...IF THE UPPER LEVEL LOW DRIFTS TO THE SOUTH INSTEAD OF ON ITS PRESENT COURSE TO THE EAST/SOUTHEAST... MORE THUNDERSTORM ACTIVITY WILL TAKE PLACE IN THE BIG COUNTRY. SO...WE WILL CONTINUE TO CLOSELY MONITOR THIS. FOR THE REST OF TODAY...WITH THE EXPECTED TRACK OF THE LOW MAINLY TO THE EAST...THE HEAVIEST RAINFALL SHOULD ALSO REMAIN EAST OF OUR FORECAST AREA. THE CENTER OF THE 500MB LOW MAY BRUSH OUR NORTHERN COUNTIES. THIS SHOULD BRING SCATTERED TO NUMEROUS THUNDERSTORMS INTO THE BIG COUNTRY. STORMS WILL LIKELY TRACK TO THE SOUTH/SOUTHEAST WITH THE BIG COUNTRY JUST WEST OF THE MAIN LOW. WHILE THERE MAY BE LOCALIZED FLOODING...THE EXPECTED MOVEMENT OF STORMS SHOULD MINIMIZE THE THREAT ENOUGH TO PRECLUDE A FLASH FLOOD WATCH. CHANCES ARE LIKELY FOR THUNDERSTORMS ACROSS THE HEARTLAND/NORTHWEST HILL COUNTRY AREAS AS WELL AS A WEAK COLD FRONT MOVES SOUTH THROUGH THE AREA...SPARKING CONVECTION AS DAYTIME HEATING OCCURS LATER. HERE AGAIN...MOVEMENT SHOULD BE ENOUGH TO KEEP THE THREAT OF FLASH FLOODING TO LOCAL AREAS. ELSEWHERE ACROSS THE CWA...ISOLATED TO SCATTERED CONVECTION IS POSSIBLE WITH DAYTIME HEATING AND A SHORTWAVE EXPECTED TO PASS OVER THE AREA. TEMPERATURES SHOULD BE COOLER ACROSS THE BIG COUNTRY THAN THE REST OF THE AREA WITH MORE CLOUDCOVER AND/OR THUNDERSTORMS. COULD SEE QUITE A FEW BREAKS IN THE CLOUDS ACROSS THE SOUTHWESTERN 1/3 OF THE FORECAST AREA AS SLIGHTLY DRIER NORTHWEST FLOW MOVES IN. HAVE GENERALLY GONE JUST WARMER THAN MAV MOS NUMBERS. THE THREAT FOR SHOWERS AND THUNDERSTORMS LINGERS INTO TONIGHT FOR THE EASTERN HALF OF THE FORECAST AREA AS THE UPPER LEVEL LOW WILL BE SLOW TO MOVE NORTHEAST. BUT THE GENERAL TREND WILL BE FOR DECREASING AREAL COVERAGE THROUGH THE NEXT 24 TO 48 HOURS. FOR THE LONG TERM. AFTER THE LOW MOVES AWAY...RIDGING WILL BUILD BACK IN FROM THE WEST AND TEMPERATURES WILL WARM BACK UP TO NEAR NORMAL READINGS BY THURSDAY. WILL HAVE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS IN FOR SUNDAY ACROSS THE NORTHWEST HILL COUNTRY. THE RIDGE MAY BE WEAKENED SOME BY THE REMNANTS OF /FAY/ AS THEY MOVE NORTH THROUGH THE U.S. DEEP SOUTH. WEAK SHORTWAVES MAY ROTATE THROUGH IN NORTHERLY FLOW GIVING OUR SOUTHEASTERN COUNTIES A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS. && .PRELIMINARY POINT TEMPS/POPS... ABILENE 65 85 65 92 70 / 20 20 10 10 0 SAN ANGELO 64 87 64 91 68 / 10 10 10 0 0 JUNCTION 65 88 67 91 70 / 20 10 10 10 0 && .SJT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 23/HUBER tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN ANGELO TX 1206 PM CDT TUE AUG 19 2008 .UPDATE... ADJUSTED SKY...WEATHER...POPS...AND QPF GRIDS FOR THE REMAINDER OF TODAY. LATEST ZONE PRODUCT REFLECTS THESE CHANCES. SEE DISCUSSION BELOW FOR DETAILS. && .DISCUSSION... LATEST WATER VAPOR IMAGERY SHOWS A SIGNIFICANT DRY SLOT OVER ALL BUT OUR BIG COUNTRY COUNTIES. LATEST RUC DOES INDICATE A WEAK 500 VORTICITY MAX WILL MOVE SOUTHEAST ACROSS OUR CENTRAL AND SOUTHERN COUNTIES LATER THIS AFTERNOON. HOWEVER...RUC SOUNDING DATA...CENTERED ON SAN ANGELO...INDICATE PRECIPITABLE WATER VALUES DECREASE THIS AFTERNOON. THUS...DECIDED TO ADJUST POPS ACROSS MAINLY OUR CENTRAL AND SOUTHERN COUNTIES TO REFLECT A CHANCE (30 TO 50 PERCENT) FOR SHOWERS AND THUNDERSTORMS FOR THE REMAINDER OF TODAY. ALSO...BASED ON VISIBLE SATELLITE TRENDS OVER THE LAST COUPLE HOURS...ADJUSTED SKY GRIDS FOR THE REMAINDER OF TODAY. TEMPERATURES LOOKED ON TRACK. 23/HUBER && .PREV DISCUSSION... /ISSUED 617 AM CDT TUE AUG 19 2008/ UPDATE... SEE AVIATION SECTION FOR 12Z TAFS. AVIATION... STRATUS WITH MVFR/IFR CIGS INCREASE TO VFR BY EARLY AFTERNOON. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MAY BRING CIGS/VISIBILITES BACK INTO IFR/MVFR THIS AFTERNOON FOR SHORT AMOUNTS OF TIME. BEST CHANCES OF RAIN AT KABI AND KBBD. OTHERWISE...LIGHT WINDS WILL BECOME NORTH THIS MORNING...5 TO 10 MPH AS A WEAK COLD FRONT PUSHES THROUGH. LOW LEVEL MOISTURE WILL REMAIN OVER THE REGION TONIGHT AND HAVE STRATUS WITH MVFR CIGS COMING BACK THIS EVENING AT KABI AND TOWARD/AFTER MIDNIGHT FOR THE REST OF THE TAF SITES. PREV DISCUSSION... /ISSUED 340 AM CDT TUE AUG 19 2008/ DISCUSSION... UPPER LEVEL LOW THAT HAS BROUGHT WELCOME RAINFALL TO WEST CENTRAL TEXAS CONTINUES TO CHURN OVER NORTHWEST TEXAS EARLY THIS MORNING. NUMEROUS SHOWERS AND THUNDERSTORMS CONTINUE TO AFFECT SOUTHWESTERN OK...NORTH AND NORTHWEST TEXAS. MOST OF THE ACTIVITY IS EITHER NORTH AND EAST OF THE LOW...OR CONCENTRATED WITHIN THE CORE OF THE PARENT LOW. WEST OF THE LOW IN DRYING NORTH/NORTHWEST FLOW... WIDELY SCATTERED THUNDERSTORMS EARLIER THIS EVENING DISSIPATED AS THEY MADE THEIR WAY INTO THE CWA...AND THIS TREND CAN BE SEEN WITH NEW DEVELOPMENT NORTHWEST OF THE CWA AS WELL. WILL CANCEL THE FFA FOR THE BIG COUNTRY FOR THE REST OF THIS MORNING...WITH MOST OF THE THUNDERSTORM ACTIVITY EXPECTED TO REMAIN JUST NORTH AND EAST OF OUR COUNTIES THROUGH THE REST OF THE MORNING HOURS. HOWEVER...IF THE UPPER LEVEL LOW DRIFTS TO THE SOUTH INSTEAD OF ON ITS PRESENT COURSE TO THE EAST/SOUTHEAST... MORE THUNDERSTORM ACTIVITY WILL TAKE PLACE IN THE BIG COUNTRY. SO...WE WILL CONTINUE TO CLOSELY MONITOR THIS. FOR THE REST OF TODAY...WITH THE EXPECTED TRACK OF THE LOW MAINLY TO THE EAST...THE HEAVIEST RAINFALL SHOULD ALSO REMAIN EAST OF OUR FORECAST AREA. THE CENTER OF THE 500MB LOW MAY BRUSH OUR NORTHERN COUNTIES. THIS SHOULD BRING SCATTERED TO NUMEROUS THUNDERSTORMS INTO THE BIG COUNTRY. STORMS WILL LIKELY TRACK TO THE SOUTH/SOUTHEAST WITH THE BIG COUNTRY JUST WEST OF THE MAIN LOW. WHILE THERE MAY BE LOCALIZED FLOODING...THE EXPECTED MOVEMENT OF STORMS SHOULD MINIMIZE THE THREAT ENOUGH TO PRECLUDE A FLASH FLOOD WATCH. CHANCES ARE LIKELY FOR THUNDERSTORMS ACROSS THE HEARTLAND/NORTHWEST HILL COUNTRY AREAS AS WELL AS A WEAK COLD FRONT MOVES SOUTH THROUGH THE AREA...SPARKING CONVECTION AS DAYTIME HEATING OCCURS LATER. HERE AGAIN...MOVEMENT SHOULD BE ENOUGH TO KEEP THE THREAT OF FLASH FLOODING TO LOCAL AREAS. ELSEWHERE ACROSS THE CWA...ISOLATED TO SCATTERED CONVECTION IS POSSIBLE WITH DAYTIME HEATING AND A SHORTWAVE EXPECTED TO PASS OVER THE AREA. TEMPERATURES SHOULD BE COOLER ACROSS THE BIG COUNTRY THAN THE REST OF THE AREA WITH MORE CLOUDCOVER AND/OR THUNDERSTORMS. COULD SEE QUITE A FEW BREAKS IN THE CLOUDS ACROSS THE SOUTHWESTERN 1/3 OF THE FORECAST AREA AS SLIGHTLY DRIER NORTHWEST FLOW MOVES IN. HAVE GENERALLY GONE JUST WARMER THAN MAV MOS NUMBERS. THE THREAT FOR SHOWERS AND THUNDERSTORMS LINGERS INTO TONIGHT FOR THE EASTERN HALF OF THE FORECAST AREA AS THE UPPER LEVEL LOW WILL BE SLOW TO MOVE NORTHEAST. BUT THE GENERAL TREND WILL BE FOR DECREASING AREAL COVERAGE THROUGH THE NEXT 24 TO 48 HOURS. FOR THE LONG TERM. AFTER THE LOW MOVES AWAY...RIDGING WILL BUILD BACK IN FROM THE WEST AND TEMPERATURES WILL WARM BACK UP TO NEAR NORMAL READINGS BY THURSDAY. WILL HAVE A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS IN FOR SUNDAY ACROSS THE NORTHWEST HILL COUNTRY. THE RIDGE MAY BE WEAKENED SOME BY THE REMNANTS OF /FAY/ AS THEY MOVE NORTH THROUGH THE U.S. DEEP SOUTH. WEAK SHORTWAVES MAY ROTATE THROUGH IN NORTHERLY FLOW GIVING OUR SOUTHEASTERN COUNTIES A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS. && .PRELIMINARY POINT TEMPS/POPS... ABILENE 79 65 85 65 92 / 60 20 20 10 10 SAN ANGELO 84 64 87 64 91 / 40 10 10 10 0 JUNCTION 83 65 88 67 91 / 40 20 10 10 10 && .SJT WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 23/HUBER tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE AMARILLO TX 1143 PM CDT MON AUG 18 2008 .AVIATION... BROUGHT IN LOW CLOUDS AND BR TO ALL TAF SITES OVERNIGHT BASED ON CURRENT TRENDS...PLUS WET GROUND AND LIGHT WINDS SHOULD ALSO ASSIST IN PRODUCTION OF FOG. KEPT IN MENTION OF PRECIP BUT TIMING AT ANY ONE SITE IS DIFFICULT SINCE UPPER LOW IS POSITIONED OVER SERN TX PNHDL. LOW CONFIDENCE IN PRECIPITATION. GRADUALLY IMPROVING CONDITIONS LATE IN THE TAF FCST PERIOD AS UPPER LOW MOVES FURTHER E AND S. ANDRADE && .PREV DISCUSSION... /ISSUED 936 PM CDT MON AUG 18 2008/ UPDATE... PLAN ON CONTINUING FLASH FLOOD WATCH THRU 12Z TUESDAY FOR ENTIRE FORECAST AREA AS PRECIP CONTINUES TO PINWHEEL AROUND UPPER LOW WHICH APPEARS TO BE CENTERED IN SERN TX PNHDL. RAISED POPS SOME ACROSS THE BOARD AND REVERTED TO AREAL QUALIFIERS REST OF TONIGHT. UPDATED PRODUCTS OUT AS SOON AS POSSIBLE. ANDRADE PREV DISCUSSION... /ISSUED 608 PM CDT MON AUG 18 2008/ AVIATION... 00 UTC TAFS...MAIN AVIATION CONCERNS CENTER ON CIGS/VISIBILITIES AND PRECIP TRENDS THROUGH THE FORECAST PERIOD. LARGE UPPER LOW WAS OVER THE PANHANDLES. STRONG LIFT ASSOCIATED WITH THIS LOW RESULTED IN SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE PANHANDLES. RADAR LOOPS SHOW STORMS MOVING AROUND THE UPPER LOW WITH ADDITIONAL STORMS EXPECTED THIS EVENING. MVFR AND IFR CIGS AND VISIBILITIES ARE POSSIBLE WITH THE STORMS. THE UPPER LOW SLOWLY HEADS TO THE SOUTH WHICH WILL KEEP PRECIP CHANCES IN AT DHT AND GUY THROUGH LATE MORNING BEFORE VFR CONDITIONS RETURN BY EARLY AFTERNOON. RAIN CHANCES WILL LINGER LONGER AT AMA AS THE LOW SLOWLY LEAVES THE AREA. CLK PREV DISCUSSION... /ISSUED 344 PM CDT MON AUG 18 2008/ DISCUSSION... MAIN FORECAST CONCERNS CENTER ON PRECIP CHANCES IN THE SHORT TERM. LARGE CUTOFF UPPER LOW CENTERED OVER THE TEXAS/OKLAHOMA PANHANDLES PER CURRENT SATELLITE IMAGERY WILL SLOWLY DRIFT TO THE SOUTHEAST. CURRENT RADAR LOOPS SHOW SCATTERED THUNDERSTORMS DEVELOPING IN IN AREAS WHERE THERE WERE SOME BREAKS IN LOW CLOUD DECK AND WHERE INSTABILITY IS A BIT STRONGER. SHOWERS AND THUNDERSTORMS WILL INCREASE IN COVERAGE TONIGHT WITH STRONG LIFT ASSOCIATED WITH UPPER LOW. AMA 12Z SOUNDING INDICATES 25-30 KT WINDS AROUND 400 MB WHICH MAY SUPPORT MARGINALLY SEVERE STORMS THIS EVENING ALTHOUGH SPC RUC MESOSCALE ANAYLSIS SHOWS WEAK MID LEVEL LAPSE RATES. AT ANY RATE... MAIN THREAT FROM THE STORMS WILL BE HEAVY RAINFALL ONCE AGAIN SO HAVE CONTINUED FLASH FLOOD WATCH UNTIL 12Z TUE. MODELS ARE IN GOOD AGREEMENT IN TIMING OF THE UPPER LOW AS IT HEADS TOWARD THE RED RIVER VALLEY TUE AND SLOWLY LIFTS NORTH INTO THE CENTRAL PLAINS TOWARD THE END OF THE WEEK. RETAINED POPS DURING THE DAY AS DEFORMATION BAND SWINGS ACROSS THE CWA. WENT WITH THE COOLER MOS GUIDANCE ON TEMPS TUE DUE TO EXPANSIVE LOW CLOUD DECK WITH HIGHS MAINLY IN THE 70S. WITH THE UPPER LOW LIFTING TO THE NORTH... DRY WEATHER WILL RETURN TO THE CWA WED THROUGH FRI. TEMPS WILL REBOUND BACK INTO THE 80S AND 90S DURING THIS PERIOD AS SURFACE WINDS BACK AROUND TO THE SOUTH. MADE VERY LITTLE CHANGES TO THE REMAINDER OF THE FORECAST AS NEXT SIGNIFICANT UPPER TROUGH SLIDES ACROSS SOUTHERN CANADA. A COLD FRONT WILL PUSH THROUGH THE PANHANDLES FRI NIGHT/SAT MORNING AND CAN BRING THE NEXT CHANCE OF SHOWERS AND THUNDERSTORMS. CLK FIRE WEATHER... BESIDES LIGHTNING FROM THUNDERSTORMS...FIRE WEATHER CONCERNS WILL REMAIN LOW THE NEXT COUPLE OF DAYS DUE TO LIGHT WINDS...HIGH RELATIVE HUMIDITIES AND SATURATED SOILS. CLK && .AMA WATCHES/WARNINGS/ADVISORIES... TX...FLASH FLOOD WATCH UNTIL 7 AM CDT TUESDAY FOR THE FOLLOWING ZONES: ARMSTRONG...CARSON...COLLINGSWORTH...DALLAM...DEAF SMITH...DONLEY...GRAY...HANSFORD...HARTLEY...HEMPHILL... HUTCHINSON...LIPSCOMB...MOORE...OCHILTREE...OLDHAM... POTTER...RANDALL...ROBERTS...SHERMAN...WHEELER. OK...FLASH FLOOD WATCH UNTIL 7 AM CDT TUESDAY FOR THE FOLLOWING ZONES: BEAVER...CIMARRON...TEXAS. && $$ tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SEATTLE WA 300 PM PDT WED AUG 20 2008 .SYNOPSIS...SHOWERY AND BREEZY WEATHER WILL CONTINUE TONIGHT AND THURSDAY MORNING AS A COOL UPPER TROUGH MOVES ACROSS WESTERN WASHINGTON. THE WEATHER WILL IMPROVE GRADUALLY THURSDAY AFTERNOON AS A WEAK UPPER RIDGE MOVES INTO THE OFFSHORE WATERS. DRY WEATHER AND MORE SUNSHINE IS EXPECTED FRIDAY AND SATURDAY AS THE UPPER RIDGE CROSSES THE REGION. A WEAK FRONT WILL ARRIVE SUNDAY OR MONDAY. && .SHORT TERM...SCATTERED SHOWERS CONTINUE ACROSS WESTERN WASHINGTON AS COOL MOIST AIR STREAMS INTO THE AIR BEHIND LAST NIGHT`S COLD FRONT. BREEZY CONDITIONS WILL CONTINUE ACROSS THE AREA AS WELL...AS SURFACE HIGH PRESSURE BUILDS WEAKLY OVER THE REGION. THE PARENT UPPER LOW IS NEAR 50N/131W AND MOVING SLOWLY EAST. THE FRONTAL WAVE THAT DEVELOPED OFF THE NORTH COAST OF OREGON IS LIFTING NORTHEAST INTO THE AREA...AND AN UPPER SHORTWAVE MOVING INTO THE BASE OF THE TROUGH WILL CROSS THE AREA TONIGHT. THE UPPER LOW WILL SWING INLAND LATE TONIGHT. AS IT BEGINS TO MOVE EAST OF THE AREA... ANOTHER UPPER SHORTWAVE ROTATING THROUGH ITS SOUTHWEST QUADRANT WILL DIG ACROSS WESTERN WASHINGTON THURSDAY MORNING. THESE FEATURES WILL KEEP SHOWERY WEATHER OVER THE AREA THROUGH THURSDAY MORNING WITH LIKELY TO CATEGORICAL POPS. THE SNOW LEVEL WILL FALL TO AROUND 6500 FT WITH THE PASSAGE OF THE TROUGH. SHOWERS SO FAR TODAY HAVE ADDED SOME TO THE RAINFALL TOTALS SO FAR...WITH GENERALLY .75 TO 1.50 INCHES ALONG THE COAST AND 1.50 TO 3.00 INCHES OVER MUCH OF THE OLYMPIC MOUNTAINS. AMOUNTS IN THE WESTERN WASHINGTON INTERIOR HAVE MOSTLY RANGED FROM 0.25 TO 1.00 INCH. IN THE CASCADES MOST SITES HAVE RECEIVED 0.75 TO 1.50 INCHES OF PRECIPITATION...BUT THE CASCADES WILL BE THE WETTEST REGION OF THE FORECAST AREA TONIGHT AND THURSDAY AS MOIST WESTERLY FLOW PRODUCES OROGRAPHIC ENHANCEMENT. ANOTHER 0.75 TO 1.75 INCHES IS LIKELY IN THE CASCADES DURING THAT TIME...WITH UP TO ANOTHER INCH OR SO OVER THE WEST SLOPES OF THE OLYMPICS. AS THE UPPER TROUGH HEADS EAST OF THE CASCADES BY MIDDAY THURSDAY... A WEAK UPPER RIDGE WILL MOVE INTO THE OFFSHORE WATERS. HOWEVER SURFACE HIGH PRESSURE BUILDING INTO WESTERN WASHINGTON FROM THE SOUTHWEST WILL PROBABLY RESULT IN A PUGET SOUND CONVERGENCE ZONE. SO SCATTERED SHOWERS CAN BE EXPECTED THURSDAY AFTERNOON ALONG WITH SOME SUN BREAKS AND BELOW NORMAL TEMPERATURES. THE WEAK UPPER RIDGE WILL PROGRESS ACROSS WESTERN WASHINGTON ON FRIDAY...WHICH SHOULD BRING FURTHER IMPROVEMENT. THE DAY WILL LIKELY BEGIN WITH AREAS OF MORNING LOW CLOUDS AND PROBABLY SOME FOG AS WELL. AND THE SOUTH END OF A WEAK WARM FRONT WILL BRUSH THE OFFSHORE WATERS IN THE AFTERNOON...WHICH COULD CONTRIBUTE SOME HIGH CLOUD COVER. EITHER PARTLY SUNNY OR MOSTLY SUNNY LOOKS LIKE THE RIGHT FORECAST FOR FRIDAY. TEMPERATURES WILL BOUNCE BACK SOMEWHAT BUT STILL BE A FEW DEGREES BELOW NORMAL. SATURDAY WILL PROBABLY BE THE WARMEST DAY OF THE NEXT WEEK. THE RIDGE WILL MOVE TO THE EAST...AND THE UPPER LEVEL FLOW WILL BACK TO THE SOUTHWEST. A WEAK COLD FRONT WILL BE SLOWLY MOVING TOWARD THE PACIFIC NORTHWEST BUT REMAIN WELL OFFSHORE. MCDONNAL/DAMICO .LONG TERM...GFS AND EURO IN EXCELLENT AGREEMENT SAGGING THE APPROACHING FRONTAL SYSTEM SATURDAY NIGHT OVER THE WESTERN PORTION OF THE CWA SUNDAY. MONDAY LOOKS POST-FRONTAL WITH SHOWERS AND BELOW NORMAL TEMPERATURES...BUT DISCREPANCIES BEGIN TO CREEP INTO LONG RANGE MODELS AT THIS POINT. UNDER ZONAL FLOW EURO BRINGS A WEAK SURFACE LOW INTO WESTERN WASHINGTON WEDNESDAY MORNING...WHILE GFS DEVELOPS A UPPER LEVEL TROUGH THAT PASSES RIGHT OVER US AND DRIVES SURFACE LOW TOWARDS OREGON LATE TUESDAY. DUE TO DISCREPANCIES...HAVE KEPT TUE-WED DRY AND JUST A BIT ON THE COOL SIDE BUT LATER SHIFTS WILL LIKELY HAVE TO INTRODUCE AT LEAST CHANCE POPS. DAMICO/MCDONNAL && .AVIATION...THE UPPER LEVEL TROF AND SFC TROF WILL WORK EAST THRU WRN WA OVERNIGHT. SHOWERS ALONG THE COAST TODAY WERE PUSHING INTO PUGET SOUND EARLY THIS AFTERNOON...VSBY LCLLY DROPPING TO 2SM IN MDT RAIN. SHOWERS WITH AREAS OF MVFR WILL CONTINUE TO WORK THRU WRN WA THRU EVENING. ONSHORE FLOW SHUD KEEP CONDITIONS FROM IMPROVING MUCH THRU THU MORNING. MTNS OBSCD. 19 KSEA...SHOWERS AT TIMES THRU THU MORNING. CHANCE OF A PSCZ THU AFTERNOON SO WINDS MAY SHIFT FROM BREEZY SLY TONIGHT AND THU MORNING TO NLY THU EVENING. OF NOTE IS THE WLY JETSTREAM ARND 115KT CENTERED OVER SW WA THIS EVENING. A JET STREAK NEAR 50N/140W THIS AFTERNOON ROUNDS THE BASE OF THE TROF AND MOVES OVER WRN WA THU MORNING WITH THE GFS SHOWING WNW 130KT INTO THE SOUTH WA COAST AT 12Z THEN LIFTING NORTH AND WEAKENING A BIT THU AFTERNOON. THE STRONG JETSTREAM MOVES INLAND BY FRIDAY AS THE UPPER TROF MOVES INLAND AND HIGH PRES BUILDS INTO THE REGION. 19 && .MARINE...GRADIENTS WEAKENED INTO MIDDAY TODAY BUT WILL INCREASE THIS EVENING. THE RUC MODEL SHOWS PDX-BLI OF JUST +2MB GETTING BACK TO ARND +4.5MB AT 6PM THIS EVENING AS THE TROF WORKS OVER WRN WA. WLY SWELL WILL BE COMING UP COASTAL WATERS AND WEST ENTRANCE TO THE STRAIT TONIGHT...SO THE SMALL CRAFT ADVISORIES FOR BREEZY SLIES WILL PROBABLY BE REPLACED WITH AN ADVISORY FOR HAZARDOUS SEAS ON THU. 19 && .SEW WATCHES/WARNINGS/ADVISORIES... .SMALL CRAFT ADVISORY FOR ALL WATERS EXCEPT CENTRAL STRAIT. .SMALL CRAFT ADVISORY FOR ROUGH/SEVERE BAR CONDITIONS GRAYS HARBOR BAR. $$ wa AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 257 PM CDT WED AUG 20 2008 .SHORT TERM...TONIGHT THROUGH SATURDAY MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES THURSDAY INTO SATURDAY. LATEST WATER VAPOR SATELLITE IMAGERY INDICATING UPPER LEVEL CUT-OFF LOW OVER THE SOUTHERN PLAINS AND MOISTURE STREAMING SLOWLY NORTHWARD INTO THE CENTRAL PLAINS STATES. LATEST VISIBLE SATELLITE IMAGERY INDICATING STRATUS DECK OVER WESTERN...CENTRAL AND EASTERN WISCONSIN DISSIPATING...AS DAYTIME HEATING HAS ALLOWED INVERSION TO WEAKEN AND MIX OUT PER LATEST RUC SOUNDINGS. LATEST 19Z SURFACE ANALYSIS INDICATING HIGH PRESSURE OVER EASTERN MICHIGAN. LATEST 20.12Z GFS AND NAM ARE IN VERY GOOD AGREEMENT IN LIFTING AND WEAKENING UPPER LEVEL CUT-OFF LOW NORTHWARD INTO THE UPPER MIDWEST BY 00Z FRIDAY. THOUGH BOTH MODELS INDICATING A SLIGHTLY FASTER MOVEMENT NORTHWARD WITH UPPER LEVEL LOW THAN PREVIOUS RUNS. THIS IS EVIDENT IN CLOUD TRENDS PER LATEST VISIBLE SATELLITE AND BOTH THE 20.12Z GFS AND NAM MOISTURE FIELDS HANDLING THE MOISTURE ADVECTION WELL. BOTH MODELS IN DECENT AGREEMENT WITH OVERALL UPPER LEVEL PATTERN THROUGH PERIOD...AS UPPER LEVEL TROUGH OVER PACIFIC NORTHWEST BREAKS DOWN UPPER LEVEL RIDGE AND MOVES INTO THE UPPER MIDWEST AND GREAT LAKES REGION BY 00Z SATURDAY. WITH NO REAL SIGNIFICANT DIFFERENCES SEEN IN EITHER MODEL...CONFIDENCE THROUGH FORECAST IS MODERATE. TONIGHT...MOISTURE ON NORTHERN PERIPHERY OF UPPER LEVEL LOW OVER THE CENTRAL PLAINS WILL CONTINUE TO ADVECT NORTHWARD INTO THE SOUTHERN FORECAST AREA THIS EVENING AND INTO TONIGHT. BOTH MODELS HANDLING MOISTURE WELL AND ARE MUCH FASTER IN LIFTING MOISTURE INTO FORECAST AREA OVERNIGHT THAN PREVIOUS RUNS. HAVE INCREASED SKY CONDITION... ESPECIALLY ACROSS SOUTHERN FORECAST AREA. BOTH THE 20.12Z GFS AND NAM CONTINUE TO PHASE UPPER LEVEL LOW INTO THE NORTHERN STREAM BY 06Z FRIDAY. BOTH MODELS INDICATE UPPER LEVEL LOW TO WEAKEN AS IT MOVES NORTH INTO THE UPPER MIDWEST AND GREAT LAKES REGION. THOUGH...MODELS CONTINUE TO INDICATE DECENT MOISTURE CONVERGENCE AND THETA E CONVERGENCE AT 850MB IN ASSOCIATION WITH UPPER LEVEL LOW. WITH THE PROGRESSION UPPER LEVEL LOW SLIGHTLY FASTER THAN PREVIOUS RUNS...HAVE INCREASED PRECIPITATION CHANCES ACROSS MUCH OF FORECAST AREA DURING THE DAY THURSDAY. THE 20.12Z GFS AND NAM CONTINUE TO INDICATE LIMITED INSTABILITY WITH 300 TO 400 J/KG MOST UNSTABLE CAPE IN THE 0-6 KM LAYER. WILL CONTINUE WITH PREVIOUS FORECAST MENTION OF ISOLATED THUNDERSTORMS THURSDAY INTO THURSDAY NIGHT. AS UPPER LEVEL LOW MOVES NORTH...UPPER LEVEL TROUGH OVER PACIFIC NORTHWEST BREAKS DOWN RIDGE AND TRACKS INTO THE NORTHERN PLAINS BY 12Z FRIDAY. WITH BEST LIFT AND MOISTURE CONVERGENCE MOVING NORTH WITH UPPER LEVEL LOW...HAVE REMOVED PRECIPITATION CHANCES IN THE 12- 18Z FRIDAY TIMEFRAME ACROSS MUCH OF THE FORECAST AREA. SURFACE COLD FRONT IN ASSOCIATION WITH UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST MOVES ACROSS FORECAST AREA BY 18Z SATURDAY. BOTH MODELS INDICATE PRECIPITABLE WATER VALUES INCREASING TO 1.5 TO 2 INCHES OUT AHEAD OF UPPER LEVEL TROUGH/SURFACE FRONT...COMBINED WITH STRONG MOISTURE CONVERGENCE ALONG FRONT. HAVE CONTINUED PREVIOUS PRECIPITATION CHANCES IN THE LIKELY CATEGORY FRIDAY NIGHT. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY MAIN FORECAST CONCERNS ARE TEMPERATURES THROUGH THE PERIOD. THE 20.00Z ECMWF AND GFS ARE IN GOOD AGREEMENT IN BUILDING UPPER RIDGE INTO THE UPPER MIDWEST AND GREAT LAKES REGION BY 00Z MONDAY. MAIN DIFFERENCE BETWEEN THE MODELS IS GFS IS MORE PROGRESSIVE WITH OVERALL UPPER LEVEL PATTERN THAN ECMWF THROUGH PERIOD...AS ECMWF IS MORE AMPLIFIED WITH UPPER LEVEL RIDGE AND SLOWER IN MOVING UPPER LEVEL TROUGH INTO THE NORTHEAST U.S. EARLY IN THE PERIOD AND BREAKING DOWN UPPER LEVEL RIDGE LATE IN THE PERIOD. 20.00Z GFS IS SLIGHTLY FASTER IN MOVING UPPER LEVEL TROUGH EAST OF THE FORECAST AREA EARLY IN THE PERIOD AND BREAKING DOWN RIDGE LATE IN THE PERIOD. THE 20.00Z GFS ENSEMBLE MEAN INDICATE A SLOWER SOLUTION OF MOVING UPPER LEVEL TROUGH INTO THE NORTHEAST U.S. EARLY IN THE PERIOD AND BREAK DOWN OF UPPER LEVEL RIDGE OVER THE CENTRAL U.S. LATE IN THE PERIOD. BASED ON ECMWF AND GFS ENSEMBLE MEAN IN RELATIVE GOOD AGREEMENT WITH OVERALL UPPER LEVEL PATTERN THROUGH PERIOD...CONFIDENCE IN FORECAST IS MODERATE. WITH GOOD SUBSIDENCE UNDERNEATH UPPER LEVEL RIDGE AND BOTH THE 20.00Z GFS AND ECMWF INDICATING 850MB TEMPERATURES RANGING FROM PLUS 12 DEGREES TO PLUS 15 DEGREES CELSIUS ACROSS FORECAST AREA...THIS WILL ALLOW FOR DRY WEATHER CONDITIONS AND SLIGHTLY ABOVE NORMAL TEMPERATURES THROUGH THE PERIOD. && .AVIATION... WITH THE LOSS OF DIURNAL HEATING...THE OPEN CELLULAR CONVECTION WILL QUICKLY DISSIPATE BETWEEN 20.23Z AND 21.02Z. SOUTHERLY WINDS ON THE BACK SIDE OF A HIGH...LOCATED ACROSS THE EASTERN GREAT LAKES LATE THIS AFTERNOON...WILL BRING A RETURN OF GULF MOISTURE BACK TO THE AREA. SOME HIGH CLOUDS WILL MOVE NORTHWARD INTO THE AREA THIS EVENING AND THEN GRADUALLY BECOME THICKER AND LOWER LATE TONIGHT AND THURSDAY MORNING. THERE SHOULD BE SUFFICIENT MOISTURE... INSTABILITY...AND LIFT FOR A CHANCE OF SHOWERS AND THUNDERSTORMS ON THURSDAY AFTERNOON. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...DTJ AVIATION..........BOYNE wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 230 PM CDT TUE AUG 19 2008 .SHORT TERM...THROUGH FRIDAY NIGHT PRIMARY FORECAST CONCERNS WERE WITH CLOUD TRENDS TONIGHT...THEN RAIN CHANCES DURING THE LATTER PART OF THE WEEK. EARLY AFTERNOON SURFACE ANALYSIS HAD HIGH PRESSURE OVER NORTHERN GREAT LAKES...WHILE SUBTLE FRONT EXTENDED FROM NORTHERN IL INTO SOUTHEAST MN. SURFACE DEW POINTS WERE A GOOD INDICATOR OF RELATIVE HUMIDITY GRADIENT ACROSS THE FORECAST AREA...WITH VALUES RANGING FROM MID 50S IN PARTS OF CENTRAL WI TO UPPER 60S IN NORTHEAST IOWA AND SOUTHEAST MN. VISIBLE SATELLITE IMAGERY INDICATED STRATUS THAT AFFECTED PART OF FORECAST AREA THIS MORNING HAD DISSIPATED. HOWEVER...STRATUS STILL LINGERED ACROSS PARTS OF EASTERN WI. WATER VAPOR IMAGERY AND 19.12Z UPPER AIR DATA INDICATED RIDGE ALOFT OVER UPPER MISSISSIPPI VALLEY. MEANWHILE...CLOSED 500MB LOW WAS SITUATED NEAR TX/OK BORDER...WITH MID LEVEL TROUGH CARVING OUT ACROSS THE PACIFIC NORTHWEST. 19.12Z NCEP AND EUROPEAN DETERMINISTIC MODELS WERE IN OVERALL GOOD AGREEMENT WITH REGARD TO UPPER LEVEL AND SURFACE FEATURES THROUGH 23.00Z...FRIDAY EVENING. THEREFORE...CONFIDENCE HAS BEEN INCREASING THAT THE FORECAST AREA SHOULD RECEIVE RAIN DURING THE LATTER PART OF THE WEEK. THIS WAS ALSO CORROBORATED BY PROBABILITIES OF MEASURABLE QPF IN THE 19.09Z SREF DATA INCREASING TO 60-65 PERCENT BY FRIDAY. TONIGHT...LOW LEVEL SOUTHEASTERLY FLOW SUGGESTS STRATUS COULD DEVELOP AND EXPAND ACROSS PORTIONS OF THE FORECAST AREA. IN FACT...BOUNDARY LAYER RELATIVE HUMIDITY IN LATEST RUC...NAM AND ARXMESOWRF INDICATED STRATUS SHOULD EMANATE FROM EASTERN WI...WHERE LOW CLOUDS CURRENTLY RESIDE. PROBABILITIES FOR LOW CLOUDS APPEAR TO BE HIGHEST ESPECIALLY FOR LOCATIONS ALONG AND EAST OF THE MISSISSIPPI RIVER. PLEASE REFERENCE AVIATION DISCUSSION BELOW FOR ADDITIONAL DETAILS. THURSDAY AND THURSDAY NIGHT...NCEP DATA SUITE HAS TRENDED TOWARD A SOONER ARRIVAL OF RAIN CHANCES ON THURSDAY ASSOCIATED WITH EJECTION OF SOUTHERN PLAINS MID LEVEL WAVE...WHICH EUROPEAN MODELS HAD INDICATED PREVIOUSLY. AS A RESULT...CONFIDENCE WAS HIGH ENOUGH TO EXPAND RAIN CHANCE OVER A BIT MORE OF THE FORECAST AREA ON THURSDAY. AMPLE GULF MOISTURE EXPECTED TO BE BROUGHT NORTHWARD...AS EVIDENCED BY PRECIPITABLE WATER VALUES POTENTIALLY REACHING 1.5-2.0 INCHES. EVEN SO...FORCING APPEARS TO BE WEAK...WHICH WAS INDICATED BY WEAK UPWARD VERTICAL MOTION SIGNAL IN TIME/HEIGHT CROSS SECTIONS. THUS... RAIN CHANCES WERE MAINTAINED IN THE LOW-END CHANCE CATEGORY AT THIS POINT...WHICH SEEMS REASONABLE. FRIDAY AND FRIDAY NIGHT...RAIN PROBABILITIES INCREASE IN THIS TIME FRAME. IN FACT...SUFFICIENT FORCING ALONG APPROACHING COLD FRONT SUGGESTS RAIN CHANCES WILL PROBABLY WARRANT AN INCREASE FRIDAY NIGHT. AT THIS TIME...MAINTAINED RAIN CHANCES AS IN CURRENT DATA BASE... ALTHOUGH CONSISTENCY OF FORCING SIGNALS SHOULD LEND HIGHER CONFIDENCE FOR INCREASING RAIN CHANCES FRIDAY AND/OR FRIDAY NIGHT WITH SUBSEQUENT FORECASTS. .LONG TERM...SATURDAY THROUGH TUESDAY PRIMARY CONCERNS WERE WITH RAIN CHANCES LINGERING INTO SATURDAY ASSOCIATED WITH PASSAGE OF COLD FRONT...THEN DRY WEATHER POTENTIAL THROUGH REST OF THE WEEKEND AND INTO FIRST PART OF NEXT WEEK. 19.12Z DETERMINISTIC GFS AND ECMWF CONTINUED TO HAVE GOOD CONSENSUS CONCERNING OVERALL DETAILS OF UPPER LEVEL AND SURFACE WAVE ADVANCING ACROSS SOUTHERN CANADA ON SATURDAY. AS A RESULT...SURFACE COLD FRONT ATTENDANT TO THIS SYSTEM APPEARS TO ADVANCE THROUGH THE FORECAST AREA SATURDAY MORNING. DETERMINISTIC MODELS HAVE SUGGESTED FRONT SHOULD SCOUR CLOUDS AND RAIN OUT OF FORECAST AREA SATURDAY AFTERNOON. ON THE OTHER HAND... 19.00Z GEFS SUPPORTED HIGH PROBABILITIES OF QPF LINGERING THROUGH THE DAY. CONFIDENCE WAS NOT HIGH ENOUGH TO END RAIN CHANCES OVER ANY ONE PART OF THE FORECAST AREA THIS FAR AHEAD OF TIME. HOWEVER...OPTED TO TREND RAIN CHANCES DOWNWARD SATURDAY AFTERNOON. BASED ON CONSISTENCY IN DETERMINISTIC GFS AND ECMWF DATA SUITE...AS WELL AS 19.00Z GEFS...SIGNAL OF BUILDING RIDGE AT SURFACE AND ALOFT LENDS FAIRLY HIGH CONFIDENCE FOR A PERIOD OF DRY WEATHER SUNDAY INTO TUESDAY. CAVEAT TO THIS WOULD BE EVENTUAL TRACK OF REMAINS OF TROPICAL STORM FAY...WHICH AT THIS TIME...REMAINS HIGHLY UNCERTAIN. && .AVIATION...TONIGHT AND WEDNESDAY VISIBLE SATELLITE IMAGERY SHOWS THAT ANOTHER AREA OF LAKE STRATUS IS MOVING INTO SOUTHEAST WISCONSIN THIS AFTERNOON. BOTH THE 19.12Z RUC AND NAM/WRF HAVE A FAIRLY GOOD HANDLE ON THE CLOUDS CURRENTLY. THEY SHOW THAT IFR/MVFR CLOUDS WILL SPREAD INTO SOUTHWEST...CENTRAL...AND WEST CENTRAL WISCONSIN THIS EVENING...AND THEN THEY MOVE NORTH INTO NORTHWEST AND NORTH CENTRAL WISCONSIN DURING THE OVERNIGHT AS THE WINDS BECOME MORE SOUTHERLY ALOFT. KLSE LOOKS TO BE ON THE WESTERN EDGE...SO I WENT WITH A SCATTERED TO BROKEN 1500 FOOT DECK DURING THIS TIME PERIOD. THE REMAINDER OF THE AREA WILL SEE THE DIURNAL CLOUDS QUICKLY DISSIPATING BETWEEN 19/23Z AND 20.01Z. BOTH THE GFS AND NAM/WRF MOS SUGGEST THAT DENSE FOG WILL DEVELOP AT KLSE IN THE 10Z TO 13Z TIME FRAME ON WEDNESDAY. WITH THE MOS WINDS AROUND 5 TO 7 KNOTS AND TEMPERATURE/DEW POINT SPREADS AT 3F OR GREATER...I AM UNCLEAR WHETHER THIS WILL ACTUALLY OCCUR...SO I HAVE JUST KEPT 4SM BR IN THE KLSE BETWEEN 20.10Z AND 20.13Z. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...THOMPSON AVIATION..........BOYNE wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LITTLE ROCK AR 1246 AM CDT THU AUG 21 2008 .AVIATION... SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE ACROSS PARTS OF NORTHERN AND SOUTHWESTERN ARKANSAS. LOWERED CEILINGS AND VISIBILITY WILL CONTINUE THROUGH THE MID MORNING. RAINFALL WILL DIMINISH AND CONDITIONS WILL IMPROVE BY THE AFTERNOON HOURS. && .PREV DISCUSSION... /ISSUED 955 PM CDT WED AUG 20 2008/ UPDATE... BULK OF RAINFALL HAS SHIFTED INTO NRN AR ATTM. THE UPR LOW WAS NOTED OVR NERN OK EARLY THIS EVENING...WITH A SHRTWV VCNTY OF SWRN AR. SCTD SHRA/ISOLD TSRA HAS PERSISTED OVR PARTS OF SWRN AR AND EXPECT THIS ACTIVITY TO SLOLY LIFT NWD OVERNIGHT AS THE UPR SHRTWV LIFTS ACRS THE FA. BASED ON LATEST RUC/NAM DATA...FCST QPF AMOUNTS NOT AS HVY AS PREV INDCD...SO HAVE OPTED TO CANCEL THE FF WATCH. UPDATED HRLY TEMPS TO REFLECT CURRENT TRENDS. MIN TEMP FCST ON TRACK. NO OTHER CHGS TO GOING FCST. ALL UPDATES ARE OUT. /44/ PREV DISCUSSION... /ISSUED 641 PM CDT WED AUG 20 2008/ AVIATION... FIRST ROUND OF RAINFALL MOVING ACROSS THE NORTHEAST...WITH THE NEXT ROUND ACROSS THE SOUTHWEST. CONDITIONS WILL REMAIN MVFR TO IFR THROUGH THE NIGHT...WITH LIFR CONDITIONS TOWARDS SUNRISE. AS THE SYSTEM BEGINS TO MOVE NORTHEAST THURSDAY...CONDITIONS WILL GRADUALLY IMPROVE AFTER 15Z THURSDAY. && .PRELIMINARY POINT TEMPS/POPS... BATESVILLE AR 80 71 85 71 / 60 50 20 20 CAMDEN AR 84 73 88 73 / 60 30 20 20 HARRISON AR 78 68 83 70 / 70 40 20 20 HOT SPRINGS AR 81 72 87 73 / 60 30 20 20 LITTLE ROCK AR 82 72 86 73 / 60 40 20 20 MONTICELLO AR 85 73 89 72 / 60 40 20 20 MOUNT IDA AR 81 71 87 72 / 60 30 20 20 MOUNTAIN HOME AR 79 69 83 70 / 70 50 20 20 NEWPORT AR 81 71 86 71 / 60 50 20 20 PINE BLUFF AR 83 72 88 73 / 60 40 20 20 RUSSELLVILLE AR 79 70 85 71 / 60 40 20 20 SEARCY AR 81 71 86 72 / 60 50 20 20 STUTTGART AR 83 72 87 72 / 60 50 20 20 && .LZK WATCHES/WARNINGS/ADVISORIES...NONE. && $$ AVIATION...60 ar AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 538 AM EDT THU AUG 21 2008 .SYNOPSIS... TROPICAL CYCLONE FAY IS FORECAST TO MOVE WEST TO NORTHWEST OVER PARTS OF NORTH FLORIDA THROUGH SAT. THE REMNANTS OF FAY SHOULD MEANDER TO THE WEST OF OUR REGION THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... TROPICAL STORM FAY SHOULD BEGIN A WEST TO NORTHWEST DRIFT TODAY WITH GUSTY ONSHORE WINDS INCREASING OVER OUR IMMEDIATE COASTAL AREAS. OUR FLASH FLOOD WATCH HAS BEEN IN A HOLDING PATTERN AS FAY STALLED...BUT OUR MOST SIGNIFICANT IMPACTS WILL BEGIN TO BE FELT TODAY WITH INCREASING RAINS...HEAVY AT TIMES ALONG WITH WINDY COASTAL CONDITIONS. WIND GUSTS TO TROPICAL STORM FORCE ARE MOST LIKELY ALONG BEACHES AND BARRIER ISLANDS OF GEORGIA LATER TODAY. BREEZY CONDITIONS SHOULD DEVELOP ALONG THE ALTAMAHA REGION THIS AFTERNOON SUPPORTED BY 45-50 KT 950 MB FLOW FROM THE MODELS. WITH THE PRES GRAD SUPPORTED BY HIGH PRES TO THE N...DIURNAL SURGING WILL ENHANCE BREEZY TO WINDY CONDITIONS UP THROUGH CENTRAL COASTAL SOUTH CAROLINA AS WELL THIS AFTERNOON. SQUALLS IN THE VICINITY OF HEAVY TROPICAL SHOWERS WILL ENHANCE WINDS JUST ABOUT ANYWHERE AS THE DAY WEARS ON. LATEST MODELS INCLUDING THE RUC AND SREF INDICATE SHOWERS WILL BEGIN TO BLOSSOM BY MID MORNING IF NOT SOONER. WIDESPREAD SHOWERS IN A SIGNIFICANT LOW LEVEL CONVERGENCE PATTERN ALONG THE COAST WILL SPREAD INLAND TODAY WITH HEAVY RAINFALL AT TIMES...ESPECIALLY IN EXTREME SOUTHERN SOUTH CAROLINA AND OVER SOUTHEAST GEORGIA. 2.5 INCH PRECIPITABLE WATER VALUES WILL BE ACROSS THE SOUTHERN TWO THIRDS OF OUR FORECAST AREA TODAY. ANOTHER CONCERN WILL BE THE POTENTIAL FOR ISOLATED TORNADOES THIS AFTERNOON. WIND FIELDS WILL BE PEAKING IN CONJUNCTION WITH SOME BREAKS IN THE CLOUDS ON THE N SIDE OF THE MAIN CLOUD SHIELD. LARGE 0-3KM CAPES IN EXCESS OF 150 J/KG ARE INDICATED ON NAM FORECAST SOUNDINGS. FORECAST HODOGRAPHS SUPPORT LOW-TOPPED SUPERCELLS BUT NAM SUGGESTS 0-1KM EHI VALUES WILL REMAIN FAIRLY LOW. A POTENTIALLY INCREASING RISK FOR TROPICAL SPAWNED TORNADOES EXISTS LATER TODAY. LAKE WINDS...A TIGHTENING GRADIENT BETWEEN HIGH PRESSURE BUILDING IN FROM THE NORTH AND TROPICAL STORM FAY LINGERING TO THE SOUTH WILL ALLOW WINDS AT LAKE MOULTRIE TO STEADILY INCREASE THROUGH THE DAY. SUSTAINED EAST WINDS WILL REACH 20 TO 25 KT FROM LATE MORNING THROUGH THE EVENING HOURS...WITH WAVES ON THE LAKE BUILDING TO 1 TO 2 FT. WILL MAINTAIN THE CURRENT LAKE WIND ADVISORY FOR LAKE MOULTRIE FROM 10 AM THIS MORNING UNTIL 11 PM TONIGHT. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... TONIGHT AND FRI LOOK LIKE THE PERIODS WHERE OUR FLASH FLOOD WATCH MAY BE ALIGNED CORRECTLY WITH RECENT MODEL INDICATIONS/GUIDANCE. BANDS OF STRONG CONVERGENCE OFF THE NE AND E SIDE OF THE TROPICAL CYCLONE ARE FORECAST TO EDGE OVER COASTAL AREAS WITH TIME AND WITH RICH MOISTURE PROFILES...FORECAST SOUNDINGS ARE HIGHLY SUGGESTIVE FOR EXCESSIVE RAINFALL...ESPECIALLY FROM SAVANNAH SOUTH. DEPENDANT ON HOW THESE BANDS SET UP AND GIVEN TRAINING POTENTIAL...SOME AREAS OUTSIDE THE CURRENT WATCH LIKE THE CHARLESTON TRI-COUNTY REGION MAY ALSO SEE SOME FLOODING POTENTIAL THROUGH FRI. THIS IS ESPECIALLY TRUE IF HEAVY RAIN FALLS NEAR TIMES OF HIGH TIDE ANYWHERE ALONG OUR COAST. WITH SUBSTANTIAL CLOUD COVER WE LOWERED HIGH TEMPERATURES SEVERAL DEGREES MANY COASTAL AREAS ON FRI AND WE INDICATE CATEGORICAL POPS MOST ZONES S AND SW OF BEAUFORT COUNTY. ISOLATED TORNADOES MAY BE A RISK TONIGHT AND FRIDAY...ESPECIALLY SINCE LOW LEVEL INSTABILITY MAY BE PEAKING WITH THE MOST UNSTABLE LOW LEVEL ENVIRONMENT PROGGED COAST AND FAR SE GEORGIA. WIDESPREAD SHOWERS WILL BE ON A DECREASING TREND FRI NIGHT AS MORE DIRECT EFFECTS FROM FAY/S CIRCULATION. HIGHEST POPS WILL DURING THE FRI NIGHT PERIOD SHOULD IN SE GEORGIA GIVEN LATEST FORECAST TRACK TIMING AND MODEL OUTPUT. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... FAY WILL LIKELY STILL BE A FLORIDIAN SYSTEM ON SAT...BUT BY THIS TIME IT SHOULD BE SOMEWHERE IN THE PANHANDLE OR JUST S OR N IN THE NORTHERN GULF OR SOUTHERN ALABAMA. CORE RAINS SHOULD BE SW OF OUR AREA THIS WEEKEND WHILE DEEP MOISTURE IS EXPECTED TO DECREASE DESPITE A DEEP LAYERED ONSHORE FLOW. MOST OF THE LATEST GLOBAL MODELS INDICATE SOME DECENT DRYING WILL NUDGE INTO OUR FORECAST AREA BY SUNDAY. WE HAVE CONTINUED SIMILAR TRENDS TO PREVIOUS FORECAST PERSISTENCE AND MAINTAINED 20-30 MOSTLY DIURNAL POPS SOUTH CAROLINA ZONES...LOWEST SUNDAY AND CHANCE POPS OVER PARTS OF INLAND SE GEORGIA...HIGHEST SATURDAY. LESS CLOUDS OVERALL SHOULD ALLOW MAX TEMPERATURES TO WARM BACK CLOSE TO 90 WELL INLAND BY SUNDAY AFTERNOON. THE REMNANT LOW OF FAY WILL LIKELY LIFT SLOWLY N OR NE TOWARD THE TENNESSEE VALLEY OR MAYBE THE MOUNTAINS INTO MID WEEK. DEEP MOISTURE COULD MAKE ANOTHER PASS AT OUR REGION IN THE MID WEEK TIME FRAME POTENTIALLY INCREASING POPS AND CLOUD COVER ONCE AGAIN. NO SIGNIFICANT CHANGES TO LATTER PERIODS THIS MORNING. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... CONDITIONS WILL CONTINUE TO DETERIORATE AT BOTH TERMINALS THROUGH THE MORNING AND AFTERNOON...AS TROPICAL STORM FAY LINGERS TO THE SOUTH OF THE FORECAST AREA. LATEST RADAR TRENDS SHOW INCREASING SHOWER DEVELOPMENT ALONG THE SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA COASTS THIS HOUR. ALL MODEL GUIDANCE LEANS TOWARD PERIODS OF RAIN AND PERSISTENT MVFR CEILINGS THROUGH THE MAJORITY OF THE TAF PERIOD. HAVE THUS PRESENTED A MORE PESSIMISTIC SCENARIO AT BOTH KCHS AND KSAV TODAY. SHOWER ACTIVITY IS EXPECTED TO INCREASE IN COVERAGE AFTER 12Z AT BOTH TERMINALS. IFR CIGS AND VSBYS REMAIN POSSIBLE TODAY WITHIN HEAVIER SHOWERS...HOWEVER WILL NOT INCLUDE IN THE 06Z TAF ISSUANCE DUE TO LOW CONFIDENCE IN TIMING AND DURATION. BEST CHANCE FOR MORE PERSISTENT MVFR CEILINGS AND LONG DURATION SHOWER ACTIVITY WILL BE AT KSAV...WITH RAIN CHANCES HIGHEST DURING THE AFTERNOON HOURS. HAVE INDICATED MVFR CEILINGS FOR THE ENTIRE TAF PERIOD AT KSAV...WHILE MAINTAINING PREVAILING VFR CEILINGS AT KCHS WITH JUST TEMPORARY MVFR CONDITIONS. STRONG EAST WINDS WILL BE A MAJOR ISSUE AT BOTH KCHS AND KSAV THROUGHOUT THE DAY...DUE TO THE TROPICAL SYSTEM TO THE SOUTH AND A TIGHTENED PRESSURE GRADIENT TO THE NORTH. SHORTLY AFTER SUNRISE...WIND SPEEDS WILL INCREASE AT BOTH TERMINALS...WITH EAST WINDS BETWEEN 15 AND 25 KNOTS AT THE CHS TERMINAL AND 20 TO 30 KNOTS AT THE SAV TERMINAL. HAVE NOT IMPROVED CONDITIONS BY MUCH AFTER SUNSET...MAINTAINING MVFR CEILINGS AND GUSTY WINDS. EXTENDED AVIATION OUTLOOK...DEPENDING UPON THE EVOLUTION OF TS FAY...THE TERMINALS COULD EXPERIENCE MORE PROLONGED PERIODS OF MVFR TO IFR CONDITIONS THROUGH SATURDAY. CONDITIONS LOOK TO IMPROVE TO PREVAILING VFR LEVELS BY SUNDAY. && .MARINE... LATEST SURFACE ANALYSIS SHOWS AN INCREASINGLY TIGHT GRADIENT BETWEEN SURFACE HIGH PRESSURE BUILDING INTO THE MID ATLANTIC STATES AND TROPICAL STORM FAY ALONG THE CENTRAL FLORIDA COAST. GRADIENT WINDS HAVE SUBSEQUENTLY INTENSIFIED ACROSS THE COASTAL WATERS THIS MORNING...WITH BUOY OBSERVATIONS FROM NORTH TO SOUTH INDICATING SOLID 20 TO 25 KT EAST WINDS OVER THE PAST FEW HOURS. FOLLY BEACH AND DOWNTOWN CHARLESTON ARE ALSO REPORTING WINDS 15 TO 25 KT THIS HOUR. ONGOING WARNINGS AND ADVISORIES AGREE WELL WITH THE LATEST TROPICAL STORM FAY TRACK FROM THE NATIONAL HURRICANE CENTER. TROPICAL STORM WARNINGS FOR THE SOUTHEAST GEORGIA WATERS WILL ACCOUNT FOR SUSTAINED WINDS 25 TO 30 KT WITH FREQUENT GUSTS UP TO 45 KT. FURTHER NORTH IN THE SOUTH CAROLINA WATERS...HIGH END SMALL CRAFT ADVISORY CONDITIONS WILL PERSIST TODAY AND TONIGHT. CANNOT RULE OUT OCCASIONAL GUSTS TO 35 KT IN THE NORTHERN WATERS...ESPECIALLY WITHIN SQUALLS EMBEDDED IN THE OUTER RAIN BANDS. HOWEVER...DO NOT FEEL THAT THE FREQUENCY OF THE GUSTS WILL BE SUFFICIENT TO JUSTIFY GALE WARNINGS AT THIS TIME. AS A RESULT OF PERSISTENTLY STRONG ONSHORE FLOW...SEAS WILL CONTINUE TO BUILD THROUGH THE SHORT TERM PERIOD. LATEST BUOY REPORTS ARE INDICATING UP TO 10 FT SEAS IN THE OUTER WATERS THIS MORNING. HAVE INCREASED SEAS TO 11 TO 13 THIS AFTERNOON INTO THIS EVENING IN THE OFFSHORE GEORGIA WATERS...WITH 8 TO 10 FT SEAS POSSIBLE IN THE NEARSHORE WATERS. TROPICAL STORM FAY IS EXPECTED TO PUSH WEST BACK INTO THE FLORIDA PENINSULA TODAY. ALTHOUGH THE STORM WILL REMAIN SOUTH AND WEST OF THE COASTAL WATERS...THE PRESSURE GRADIENT WILL REMAIN TIGHT AND MAINTAIN ENHANCED ONSHORE FLOW THROUGH AT LEAST FRIDAY. SEAS WILL ALSO BE SLOW TO SUBSIDE INTO THE WEEKEND. SMALL CRAFT ADVISORIES COULD CONTINUE INTO SATURDAY DUE TO SEAS. IF THE TROPICAL STORM PROGRESSES ALONG THE FLORIDA PANHANDLE AS CURRENTLY FORECAST...HIGH PRESSURE WILL BE ABLE TO BUILD SOUTHWARD INTO THE COASTAL WATERS OVER THE WEEKEND. ONSHORE FLOW WILL THUS PERSIST...WITH IMPROVING CONDITIONS THROUGH THE EXTENDED PERIOD. && .TIDES/COASTAL FLOODING... STRONG ONSHORE FLOW WILL CONTINUE TO INCREASE TODAY AS THE PRESSURE GRADIENT TIGHTENS BETWEEN HIGH PRESSURE TO THE NORTH AND TROPICAL STORM FAY TO THE SOUTH. THIS INTENSIFYING ONSHORE FLOW...COMBINED WITH INCREASING RAIN COVERAGE FROM THE OUTER BANDS OF THE TROPICAL SYSTEM...WILL BE SUFFICIENT TO PRODUCE SHALLOW COASTAL FLOODING ALONG THE SOUTHEAST SOUTH CAROLINA COAST AROUND THE TIME OF HIGH TIDE. HIGH TIDE WILL OCCUR BETWEEN 1140 AM AND NOON AT CHARLESTON HARBOR AND FORT PULASKI. HAVE ISSUED A COASTAL FLOOD ADVISORY FROM 10 AM UNTIL 3 PM ACCORDINGLY. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...FLASH FLOOD WATCH THROUGH FRIDAY EVENING FOR GAZ099>101- 114>119-137>141. TROPICAL STORM WARNING FOR GAZ116>119-138>141. SC...FLASH FLOOD WATCH THROUGH FRIDAY EVENING FOR SCZ047>049-051. LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 11 PM EDT THIS EVENING FOR SCZ045. COASTAL FLOOD ADVISORY FROM 10 AM THIS MORNING TO 3 PM EDT THIS AFTERNOON FOR SCZ048>051. HIGH SURF ADVISORY UNTIL 6 PM EDT FRIDAY FOR SCZ048>051. MARINE...TROPICAL STORM WARNING FOR AMZ354-374. SMALL CRAFT ADVISORY UNTIL 4 PM EDT SATURDAY FOR AMZ350-352. SMALL CRAFT ADVISORY UNTIL 6 PM EDT FRIDAY FOR AMZ330. && $$ ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 344 AM CDT THU AUG 21 2008 .SHORT TERM...TODAY THROUGH FRIDAY NIGHT... SRN PLAINS UPPER LOW HAS OPENED UP AND IS ON THE MOVE THIS MORNING..WITH CIRCULATION CENTER LOCATED NEAR SPRINGFIELD MO AND MOVING FAIRLY RAPIDLY NNEWD. MID/UPPER LEVEL DEFORMATION AXIS IS CLEARLY VISIBLE IN WV SAT IMAGERY TO THE NE OF THE SYSTEM..WITH BROAD/WEAK ASCENT AND INCREASING DEEP LAYER MOISTURE ACROSS FAR ERN MN AND NW WI EARLY THIS MORNING. RATHER STRONG LLJ ALSO APPEARS TO BE AIDING SHALLOW LOW LEVEL ASCENT..AS BOTH KMPX/KDLH RADARS HAVE DETECTED NUMEROUS TRANSIENT SHALLOW CONVECTIVE ECHOES ACROSS WRN WI FOR THE PAST SEVERAL HOURS. ALTHOUGH MOST WIDESPREAD PRECIP WILL LIKELY HOLD OFF UNTIL THE 21-06Z TIME FRAME TONIGHT..WE HAVE STARTED OFF WITH LOW POPS THIS MORNING..AND WE HAVE ALSO DRASTICALLY INCREASED SKY COVER FOR ALL OF TODAY ACROSS ROUGHLY THE SE HALF OF OUR FORECAST AREA. ELSEWHERE..LACK OF CLOUD COVER OUT WEST TODAY SHUD RESULT IN LLJ MOMENTUM MIXING OUT..AND WITH ALREADY STRONG SFC PRESSURE GRADIENT..WINDS SHUD BE CRANKING PRETTY GOOD FROM THE SOUTH BY 10-11 AM ALONG AND WEST OF THE HIGHWAY 169 CORRIDOR. TEMPS SHUD HAVE LITTLE PROBLEM REACHING THE MID 80S IN MOST LOCALES IN THE WRN CWA TODAY. FORECAST FOR FRIDAY IS RATHER COMPLICATED AND DEPENDENT ON OVERNIGHT CONVECTIVE EVOLUTION..BOTH WITH REMNANTS OF UPPER LOW MOVING ACROSS NW WI/WRN LK SUPERIOR AND WITH POTENTIAL FOR MCS PROPAGATING EWD FROM ND FRIDAY MORNING. GIVEN THE LATEST GUIDANCE..WE EXPECT SHOWERS AND PERHAPS A FEW WEAK TSTORMS ASSOCIATED WITH THE SHEARING OUT UPPER LOW TO BE DIMINISHING IN COVERAGE FRIDAY MORNING ACROSS OUR ERN ZONES. THE REMNANTS OF SOME TYPE OF MCS MAY MAKE A RUN AT THE NW DLH CWA 12-18Z FRIDAY MORNING..BUT UPDRAFTS ARE EXPECTED TO WEAKEN. NARROW AXIS OF 1500-2500 CAPE AIDED BY 66-70 DEWPOINTS IS FORECASTED TO DEVELOP AHEAD OF THE FRONT BY MIDDAY FRIDAY..WITH TSTORM DEVELOPMENT ROUGHLY ALONG AN AXIS FROM KINL-KBRD EARLY TO MID AFTERNOON AS CAP IS ERODED BY SUSTAINED MESOSCALE LIFT/FGEN WITHIN THE FRONTAL ZONE. THE STRONGEST DEEP LAYER SHEAR AND FLOW ALOFT IS FORECASTED TO REMAIN WEST OF THE SFC MASS CONVERGENCE AXIS..BUT LATEST GUIDANCE IS IN LINE WITH PREVIOUS THINKING THAT AT LEAST SUFFICIENT DEEP LAYER SHEAR FROM 30-40 KTS WILL BE SUPERIMPOSED WITH THE INSTABILITY AXIS..AND SUPPORTIVE OF A FEW SVR TSTORMS. GIVEN THE TIME OF YEAR WITH SOMEWHAT WEAK MID LEVEL LAPSE RATES AND HIGH FREEZING LEVELS..PRIMARY SVR THREAT SHUD BE DAMAGING WIND WITH MULTICELL/LINE SEGMENT STRUCTURES..AND PERHAPS SOME LOW END SVR HAIL. WE HAVE CARRIED THE HIGHEST POPS FRI EVENING AS INCREASING LLJ 00-06Z SHUD RESULT IN GREATEST AREAL COVERAGE. PRECIP CHANCES SHUD END FAIRLY QUICKLY FROM WEST TO EAST OVERNIGHT FRIDAY NIGHT AS FRONT RAPIDLY SWEEPS EWD AND COOLER/DRIER AIR FILTERS IN BEHIND THE FRONT COINCIDENT WITH STRONG DEEP LAYER SUBSIDENCE. .LONG TERM...SATURDAY THROUGH WEDNESDAY... QUIET PATTERN ADVERTISED BY MDL CONSENSUS AS BOTH GFS/EC PUSH NRN BRANCH MID LVL TROF EAST OF CWA SATURDAY EVENING. DEEP LAYER DRYING SATURDAY ALONG WITH UNIDIRECTIONAL SFC/85H FLOW SHOULD ALLOW FOR BREEZY CONDITIONS.MID LVL RIDGE BUILDS EAST FROM NRN PLAINS SUN/MON WITH PWATS BELOW .75 INCHES. SHOULD SEE ABUNDANT SUNSHINE UNTIL TUESDAY WHEN RETURN FLOW ESTABLISHES AND SOME INCREASE IN DEEP LAYER RH OCCURS. && .AVIATION...LLWS WILL CONTINUE THROUGH EARLY THIS MORNING AS INCREASING GEOSTROPHIC FLOW CONTINUES JUST ABOVE DECOUPLED BDRY LAYER. LATEST KDLH VWP SHOWS 2KFT FLOW NOT AS STRONG OVER DLH AS RUC FCST. EARLIER TAMDAR SOUNDINGS FROM HIB/TVF/BRD VICINITY SHOWING RUC FCST 925 FCST VALUES CLOSER TO VERIFICATION. WILL EVALUATE ONCE AGAIN FOR NEXT ISSUANCE OF TAFS AROUND 1130Z. OTHERWISE NOCTURNAL JET SHOULD RESTRICT WIDESPREAD DEVELOPMENT OF FG THIS MORNING AS TURBULENT FLOW WILL FAVOR STRATUS DECK INSTEAD. HAVE OPTED FOR TEMPO VFR CEILING AND/OR MVFR VIS FROM 9Z-13Z AT HIB/DLH. EARLY MORNING CLOUDS WILL GRADUALLY DISSIPATE AS BDRY LYR HEATING AND RESULTING MECHANICAL MIXING KEEP VFR CONDITIONS ACROSS THE CWA DURING THE DAY. LARGE PLUME OF MSTR HEADING INTO NW WISC WILL FAVOR MORE EXTENSIVE CLOUD DECK WITH SCHC TRW BY AFTERNOON NEAR HYR. && POINT TEMPS/POPS... DLH 77 65 82 58 / 10 20 40 60 INL 87 66 83 55 / 10 20 40 20 BRD 86 67 86 57 / 10 20 50 40 HYR 82 64 83 63 / 30 40 30 50 ASX 73 64 81 63 / 20 40 30 60 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ MILLER/CANNON mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 316 AM CDT THU AUG 21 2008 .DISCUSSION... THE CHALLENGE WITH THE FORECAST IS THE CHANCES OF PRECIP THROUGH TODAY AND FRI...AND ANY STRONG TO SEVERE POTENTIAL OF THUNDERSTORMS ON FRI. VERY UNIQUE UPPER LEVEL PATTERN FOR THIS TIME OF YEAR...WITH MORNING GOES WV LOOP REVEALING A LONG-LIVED UPPER LEVEL LOW NOW LIFTING NNE FROM THE OZARKS. SATELLITE AND PROFILERS INDICATING STILL A WELL DEFINED MID-LEVEL CIRCULATION WITH THIS AND RUC/NAM ANALYSES INDICATES A CONTINUED PV ANOMALY. TRAJECTORY OF THE H7 LOW/WAVE WOULD TAKE IT NNE ACROSS CENTRAL FORECAST AREA TODAY INTO TONIGHT. HAVE GENERALLY CONFINED POPS FOR TODAY TO THE EAST OF THIS TRACK...WHERE MID-LEVEL DIFLUENCE EXISTS ABOVE SATURATING UPGLIDE. ADIABATIC OMEGA AND QG FORCING ARE BOTH FAIRLY WEAK IN MAGNITUDE IN ERN MN AND WRN WI. CONVECTIVE PARAMETERS ARE ALSO VERY WEAK...WITH ONLY MINIMAL UPRIGHT CONVECTIVE POTENTIAL. SO HAVE SCT SHWRS AND ISOLD THUNDER IN THE ERN FORECAST AREA...MAINLY DURING THE AFTN AND EVE. HAVE SLIGHT CHANCES FOR SHRA/SPRINKLES TO THE WEST OF THIS. WRN MN LOOKS TO REMAIN DRY TODAY AND THIS EVE...WITH BREEZY CONDITIONS. NOT TOO FAR FROM WIND ADVISORY CRITERIA IN A FEW PLACES THERE THIS AFTN...GIVEN MSLP GRADIENT AND ISALLOBARIC INFLUENCE. MIXING WILL ALSO ALLOW SOME GUSTS TO 35-40 MPH ESPECIALLY IN SOME OF THE HIGHER LOCALES. TEMPS TODAY IN SE MN AND WRN WI WILL BE HINDERED GREATLY DUE TO THE CLOUD COVER...WITH POSSIBLY ONLY MID 70S FOR HIGHS IN PLACES. GIVEN SATELLITE TRENDS EARLY THIS MORNING AND FORECAST MODEL TIME HEIGHTS...IT APPEARS THAT STRATUS WILL DEVELOP TONIGHT IN ERN MN AND WRN WI IN THE WAKE OF SHOWERS. HAVE BUMPED UP CLOUD COVER AND ADJUSTED MIN TEMPS FOR THIS. THIS AFOREMENTIONED SYSTEM IS BEING CONSUMED AND FORCED NNE BY A LARGER...PROGRESSIVE..AND SIMPLY STRONGER SYSTEM PUSHING QUICKLY EAST ACROSS THE NW U.S./BRITISH COLUMBIA BORDER EARLY THIS MORNING. CONVECTION LOOKS TO DEVELOP ASSOCIATED WITH THIS IN ND THIS EVE. PARAMETERS ARE FAVORABLE FOR AN MCS BUT PROPAGATION WOULD TAKE ONE ENE...WELL NORTH OF THE CWA EARLY FRI MORNING. JUST A SMALL CHANCE FOR ISOLD ELEVATED CONVECTION ON THE LLJ LATE TONIGHT IN WRN MN. AS JET ROUNDS THE BASE OF THIS TROUGH ON FRIDAY...DEEP CYCLOGENSIS WILL OCCUR IN SOUTH CENTRAL CANADA FORCING COOL AND DRY AIR ADVECTION EASTWARD FROM THE NRN ROCKIES. THIS COLD FRONT /AND POSSIBLY PRE-FRONTAL TROUGH/ WILL ENTER THE FORECAST AREA FRI AFTN. STRONG CAP FORECAST FOR FRI MORNING AND EARLY AFTN. BUT CAP IS FORECAST TO WEAKEN OVER THE POOLED INSTABILITY AXIS ALONG THE FRONT. DIAGNOSTIC MODELS FORECAST MUCAPES 1500-2000 J/KG BUT SREF INDICATING PROBABILITIES OF SUCH VALUES ONLY AROUND 30 PERCENT. MORNING STRATUS MAY FURTHER INHIBIT FULL HEATING TO THESE VALUES. LAPSE RATES ARE ALSO NOT VERY FAVORABLE FOR EXPLOSIVE CONVECTIVE POTENTIAL. ON THE SHEAR SIDE OF THINGS...DEEP LAYER SHEAR IS MARGINAL BUT INCREASING ESPECIALLY DURING THE EVE. LOW LEVEL SHEAR IS STRONG...THANKS TO THE PERSISTENT LLJ. A PROBLEM WITH SUSTAINED STRONG CONVECTION IS THAT FRONT IS BEING STRETCHED OUT...WITH LOW SO FAR NORTH AND ANOTHER WAVE FURTHER SOUTHWEST ON THE FRONT IN THE CTRL PLAINS. SO CONVERGENCE BECOMES SOMEWHAT MINIMIZED. SOME SCT CONVECTION SEEMS LIKELY BY LATE FRI AFTN AND MORE SO DURING THE EVE...BUT WIDESPREAD STRONG CONVECTION AT THIS TIME SEEMS UNLIKELY. SOME SEVERE POSSIBLE THOUGH ESPECIALLY IF CONVECTION CAN ORGANIZE. THIS IS BECAUSE LOWER AND MID TROP WIND FIELD BEHIND THE FRONT IS STRONG AND UNIDIRECTIONAL FROM THE WNW. POSSIBLY A FEW STRONG MULTI-CELLED CLUSTERS. BEYOND...THE FRONT DOES APPEAR TO WANT TO STALL GIVEN A BACKUP OF THINGS IN THE ERN AND SRN PART OF THE COUNTRY...INCLUDING T.S. FAY. BUT ALL GUIDANCE INDICATES THIS WILL OCCUR PAST OUR AREA...MEANING A FAIRLY NICE AND SLIGHTLY COOLER THAN NORMAL WEEKEND. HAVE MADE LITTLE ADJUSTMENTS DURING THAT TIME INTO MONDAY. && .AVIATION.../06Z TAF ISSUANCE/ GENERALLY VFR CONDITIONS FOR MOST OF THE FORECAST PERIOD...EXCEPT FOR THE PERIOD AFTER 00Z. SOME PATCHY MVFR VSBYS IN FOG OVER WEST CENTRAL WI IN THE EARLY MORNING HOURS. THROUGH ABOUT 15Z...GENERALLY SCT 040-050 SC ALONG WITH INCREASING HIGH CLOUDS FROM LOW PRESSURE SYSTEM LIFTING NNE FROM THE SOUTHERN PLAINS. PRECIPITABLE WATER WILL BE INCREASING OVER SOUTHEAST MN AND WEST CENTRAL BY FRIDAY MORNING ALLOWING FOR BKN CU AROUND 050 OVER EASTERN AREAS IN THE AFTERNOON THROUGH EVENING. INSTABILITY RATHER WEAK...BUT MID LEVEL LOW LIFTING TOWARD SOUTH CENTRAL MN WILL AID IN SOME SHRA DEVELOPMENT SOUTHEAST MN AND WEST CENTRAL WI AFTER ABOUT 22Z. THUNDER POSSIBLE BUT WILL NOT INCLUDE AT TAF SITES AT THIS TIME. DEEPER LOW LEVEL MOISTURE BY FRIDAY EVENING MAY CAUSE MVFR CIGS OVER PARTS OF THE AREA. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ MTF/JPR mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 240 AM CDT THU AUG 21 2008 .SYNOPSIS... UPR AIR PATTERN CONTINUES TO BE CHARACTERIZED BY A WEAK CLOSED MID LVL LOW OVER OKLAHOMA...WITH A BROAD AREA OF ANTICYCLONIC UPR LVL FLOW OVER CANADA...AND TROUGHS OVER THE NORTHWEST AND NORTHEASTERN COASTS. SEVERAL SMALLER SCALE UPR LVL WAVES ARE ROTATING EAST AWAY FROM THE NORTHWEST TROUGH...ONE OF WHICH WAS CROSSING THE HIGH PLAINS WEDNESDAY EVENING. SHOWERS AND THUNDERSTORMS FORMED WITH THE APPROACH OF THIS DISTURBANCE...FOCUSED ALONG A WEAK SFC TROUGH EXTENDING SOUTH FROM THE NORTHERN HIGH PLAINS. HOWEVER...LIMITED LOW LVL MOISTURE AND A CAPPING INVERSION HAVE PREVENTED THIS ACTIVITY FROM SPREADING EAST INTO THE CWA. SHORT TERM FCST PROBLEM IS FOG ADVANCING NORTH INTO THE CWA. AT THIS POINT...DO NOT EXPECT FOG TO DEVELOP NORTH OF HIGHWAY 2 AND WEST OF HIGHWAY 7/183 DUE TO STRONGER MIXING. && .DISCUSSION... A SFC LOW IS FCST TO CONSOLIDATE OVER THE NORTHERN HIGH PLAINS THURSDAY AFTERNOON AHEAD OF A STRONG UPR LVL TROUGH PROGRESSING EAST ACROSS THE NORTHERN ROCKIES. THIS WILL MAINTAIN A STRONG SFC PRESSURE GRADIENT...WHICH WILL FAVOR BREEZY CONDITIONS SIMILAR TO WEDNESDAY AFTERNOON. OVER THE WESTERN HALF OF THE CWA...BOUNDARY LAYER MIXING WILL BE STRONGER...WITH WINDS VEERING SLIGHTLY TO THE SOUTHWEST. THIS AREA WILL FAVOR DAYTIME HIGHS IN THE UPPER 80S TO MID 90S...WITH LOWER 80S FURTHER TO THE EAST. SOME STRATUS ARE POSSIBLE OVER THE EASTERN HALF OF THE CWA THURSDAY NIGHT...BUT LATEST FCST SOUNDINGS INDICATE THAT BOUNDARY LAYER MOISTURE DEPTH WILL BE RATHER SHALLOW...WHICH MAY OFFSET THAT POTENTIAL SOMEWHAT DUE TO STRONG MIXING FROM NOCTURNAL LLJ. THE UPPER TROUGH IS EXPECTED TO MOVE EAST ACROSS THE NORTHERN PLAINS ON FRIDAY...AND WILL BE ACCOMPANIED BY A SFC FRONTAL PASSAGE OVER NORTH CENTRAL/WESTERN NEBRASKA DURING THE MID DAY HOURS. FAIRLY COOL AIRMASS IS CURRENTLY POSITIONED BENEATH THE UPPER TROUGH OVER SOUTHWEST CANADA...AND LATEST OBJECTIVE GUIDANCE SUGGESTS THAT TEMPERATURES WILL NOT WARM SUBSTANTIALLY AFTER THE FROPA. THEREFORE HAVE CUT DAYTIME HIGHS ON FRIDAY BACK A FEW DEGREES. ON THE OTHER HAND...POST FRONTAL CLOUDINESS OVER THE SOUTHERN HALF OF THE CWA WILL LIKELY KEEP OVERNIGHT LOWS A BIT WARMER COMPARED TO NORTH CENTRAL NEBRASKA. AIRMASS BEHIND THE ADVANCING FRONTAL BOUNDARY IS FCST TO REMAIN STABLE DURING FRIDAY AFTERNOON...AND THIS CONTINUES TO SUGGEST THAT DAYTIME POPS SHOULD REMAIN LOW. AS THE MAIN UPR DISTURBANCE PASSES WELL TO THE NORTHEAST OF THE REGION...AND ZONAL FLOW DEVELOPS...FRONT WILL LIKELY STALL JUST SOUTH OF THE CWA FRIDAY NIGHT. THE NAM AND GFS CONTINUE TO INDICATE LOW LVL WAA AND ISENTROPIC LIFT DEVELOPING NORTH OF THE FRONT DURING FRIDAY NIGHT OVER SOUTHWEST NEB. THIS...COMBINED WITH MUCAPE OF 1000-1500 J/KG...SHOULD BE SUFFICIENT FOR ELEVATED THUNDERSTORMS BETWEEN 00-12Z SATURDAY. LOW LVL WAA/ISENTROPIC LIFT CONTINUE ACROSS THE EASTERN AND SOUTHERN PORTIONS OF THE CWA THROUGH SATURDAY AFTERNOON AND NIGHT...WITH SHOWERS/STORMS REMAINING IN THE FCST. MID LVL ANTICYCLONE THEN BECOMES ESTABLISHED OVER THE FOUR CORNERS REGION BY SUNDAY AFTERNOON...PLACING THE CWA WITHIN NORTHWEST FLOW ALOFT. FOCUS FOR THUNDERSTORMS AT THE SFC APPEARS TO BE LACKING IN LATEST MODEL FCSTS DURING THE AFTERNOON...THUS HAVE TRIMMED POPS DOWN A BIT...BUT REMAINING FOCUSED OVER SOUTHWEST NEB. LLJ THEN STRENGTHENS DURING THE NIGHT...WHICH MAY FAVOR NOCTURNAL CONVECTION OVER WESTERN/SOUTHWEST NEB. LEE TROUGH BECOMES POSITIONED OVER THE WESTERN PORTION OF THE CWA ON MONDAY. ATMOSPHERE REMAINS POTENTIALLY UNSTABLE WITH LOW 60S DEWPOINTS AND STEEP MID LVL LAPSE RATES IN PLACE. HOWEVER...SFC CONVG IS NOT PARTICULARLY STRONG...AND LARGE SCALE DESTABILIZATION PROCESSES ARE NOT IN PLACE...WHICH CONTINUES TO SUGGEST LEAVING THE FCST DRY FOR NOW. && .AVIATION... MAIN AVIATION FORECAST FOCUS THE EXTENT OF FOG AND STRATUS THIS MORNING. STRONG SURFACE GRADIENT ACROSS WESTERN NEBRASKA KEPT SURFACE WINDS STRONG AND WELL MIXED THROUGH THE OVERNIGHT. THIS MIXING HELD FOG AND STRATUS AT BAY THROUGH THE EARLY MORNING HOURS AND WILL NEED TO BE MONITORED. RUC MODEL CONTINUES TO SHOW STRONG GRADIENT AND SURFACE WINDS HOLDING ACROSS THE WEST THROUGH MORNING. BASED ON THIS REMOVED MENTION OF IFR CIGS AND VSBYS AT KVTN. CHOOSE TO KEEP MENTION OF IFR CONDITIONS IN AT KLBF BUT SHORTENED THE DURATION FOR NOW. IT WILL BE A CLOSE CALL AS BEST GRADIENT IS ACROSS THE NORTHWEST AND AS A RESULT LIGHTER WINDS AT KLXN HAVE ALREADY ALLOWED FOR LOWER VSBYS AND APPROACHING STRATUS SEEN ON SATELLITE FOR LAST FEW HOURS. IF IFR CONDITIONS DO NOT REACH KLBF THEY WILL BE NEAR AND CERTAINLY ACROSS PORTIONS OF CENTRAL AND EASTERN NEBRASKA...SEE THOSE TAFS AND AREA FORECAST DISCUSSIONS FOR ADDITIONAL INFORMATION. AFTER THIS MORNING/S CLOUDS CLEAR SCT SKIES EXPECTED AFTER 15Z AND THE PRIMARY CONCERN BECOMES STRONG AND GUSTY WINDS. && .LBF WATCHES/WARNINGS/ADVISORIES...NONE. && $$ AVIATION...HIRSCH SYNOPSIS/DISCUSSION...GARNER ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE FORT WORTH TX 321 AM CDT THU AUG 21 2008 .DISCUSSION... THE UPPER LEVEL LOW THAT HAS BROUGHT BENEFICIAL BUT FLOODING RAINS TO NORTH TEXAS THE PAST FEW DAYS IS NOW SLIDING INTO KANSAS /PER RUC ANALYSIS/. THE ASSOCIATED TROUGH EXTENDS SOUTH ACROSS TEXAS WITH THE AXIS CENTERED OVER THE WESTERN HALF OF THE CWA. SOME WEAK SHORTWAVES CONTINUE TO MOVE AROUND THE BASE OF THE TROUGH. ONE SHORTWAVE IS NOW EXITING NORTHEAST TEXAS AND IS AIDING IN SHOWER AND THUNDERSTORM DEVELOPMENT IN OUR EXTREME NE CWA. A STRONGER SHORTWAVE IS FORECASTED TO SKIRT THE RED RIVER THIS AFTERNOON. THE BEST CHANCE FOR RAIN TODAY WILL BE ACROSS THE EASTERN HALF OF THE CWA...AHEAD OF THE TROUGH AXIS AND APPROACHING SHORTWAVE...WHERE LIFT WILL BE STRONGEST. ANOTHER POTENTIAL PLAYER FOR TODAY COULD BE THE LEFT OVER BOUNDARY/SURFACE TROUGH RUNNING NORTHEAST TO SOUTHWEST ACROSS ALMOST THE MIDDLE OF THE CWA. WITH SOME HEATING LATER TODAY...SHOWERS AND THUNDERSTORMS MAY DEVELOP ALONG THAT BOUNDARY OR ANY OTHER RESIDUAL BOUNDARIES. HOWEVER...WILL HAVE THE HIGHEST POPS IN THE EAST. PWATS WILL REMAIN NEAR 2 INCHES IN THE EAST SO HEAVY RAINFALL IS STILL A THREAT TODAY IN THAT AREA. THE WEATHER PATTERN OVER THE NEXT SEVERAL DAYS WILL REMAIN SOMEWHAT UNSETTLED AS THE REMNANTS OF THE UPPER LEVEL LOW NEVER REALLY LEAVE THE REGION AND THE UPPER LEVEL RIDGE TO THE WEST NEVER REALLY BUILDS IN. THE UPPER LEVEL RIDGE ONLY MAKES IT AS FAR AS THE TEXAS PANHANDLE BEFORE BEING HALTED. ALL MODELS ARE IN GOOD AGREEMENT THAT ENERGY FROM THE TROUGH WILL REMAIN OVER NORTHEAST TEXAS AND THEN DRIFT BACK OVER NORTH TEXAS OVER THE NEXT SEVERAL DAYS. THUS WILL KEEP 20-30 POPS IN THE FORECAST THROUGH THE WEEKEND WITH BEST CHANCE FOR RAIN AGAIN IN THE EAST AND SOUTHEAST. SUNDAY LOOKS TO BE THE NEXT BEST CHANCE FOR RAIN ACROSS ALL OF NORTH TEXAS WITH THE HIGHEST POPS ALONG THE RED RIVER. BY MONDAY...THE UPPER LEVEL RIDGE GETS NUDGED BACK WEST AS FAY MOVES INTO THE CENTRAL GOM COAST AND NORTHERLY FLOW ALOFT SETS UP. MODELS SUGGEST THAT SEVERAL WEAK DISTURBANCES WILL RIDE THE NORTHERLY FLOW INTO TEXAS AND WILL CONTINUE 20 POPS FOR THE AFTERNOON/EVENING HOURS THROUGH THE REMAINDER OF THE FORECAST. HAVE STUCK CLOSE TO GUIDANCE FOR HIGH TEMPERATURES IN THE BEGINNING OF THE FORECAST AND THEN UNDERCUT GUIDANCE A DEGREE OR TWO FOR THE LAST FEW DAYS. HIGH TEMPERATURES WILL MOSTLY TOP OUT IN THE 90S WITH A FEW SCATTERED UPPER 80S THIS WEEKEND. REASON FOR UNDERCUTTING GUIDANCE ON DAYS 6 AND 7 WAS THOUGHT MOS TEMPS WERE TOO HIGH FOR NORTHERLY FLOW. OVERNIGHT LOWS WILL CONTINUE TO BE IN THE UPPER 60S TO MID 70S. 82/JLD && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 92 74 94 75 92 / 20 10 10 10 30 WACO, TX 92 72 93 74 92 / 20 20 20 10 30 PARIS, TX 87 70 91 71 90 / 50 20 30 10 30 DENTON, TX 91 72 93 72 92 / 20 10 10 10 30 MCKINNEY, TX 91 71 91 71 92 / 30 10 10 10 30 DALLAS, TX 92 72 92 73 92 / 20 10 10 10 30 TERRELL, TX 91 72 94 73 91 / 30 20 20 10 30 CORSICANA, TX 91 72 93 73 93 / 30 20 20 10 30 TEMPLE, TX 93 71 95 73 91 / 20 20 20 10 30 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 58/82 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DULUTH MN 1120 AM CDT THU AUG 21 2008 .UPDATE... ISSUED A SPS FOR WRN HALF OF FA TO ADDRESS THE BREEZY CONDITIONS THIS AFTERNOON AND EVENING. A 30 KT LLJ AT 925 MB AHEAD OF APPROACHING COLD FRONT ALREADY MIXING TO SFC IN ERN DAKOTAS AND WRN MN. WIDESPREAD AWOS/ASOS REPORTS OF SUSTAINED 20 KTS GUSTING AROUND 30 KT IN THIS REGION. DO NOT ANCPD NEEDING A WIND ADVISORY FOR ANY OF DLH ZONES DUE TO THE HEAVILY FORESTED AREAS IN NC AND NE MINNESOTA. ALTHOUGH...LOCATIONS IN OPEN FIELDS COULD SEE LOCALLY HIGHER WINDS NEAR ADVISORY CRITERIA. THE WINDS WILL SUBSIDE SLIGHTLY OVERNIGHT AS THERMAL GRADIENT WEAKENS. HOWEVER...STRONG PRESSURE GRADIENT REMAINS IN PLACE TO ALLOW FOR WINDS TO REMAIN GUSTY. SOUTH WINDS WILL INCREASE RAPIDLY AGAIN ON FRIDAY OVER THE FA AS THE COLD FRONT PUSHES EAST THROUGH WRN MN. && .PREV DISCUSSION... /ISSUED 344 AM CDT THU AUG 21 2008/ SHORT TERM...TODAY THROUGH FRIDAY NIGHT... SRN PLAINS UPPER LOW HAS OPENED UP AND IS ON THE MOVE THIS MORNING..WITH CIRCULATION CENTER LOCATED NEAR SPRINGFIELD MO AND MOVING FAIRLY RAPIDLY NNEWD. MID/UPPER LEVEL DEFORMATION AXIS IS CLEARLY VISIBLE IN WV SAT IMAGERY TO THE NE OF THE SYSTEM..WITH BROAD/WEAK ASCENT AND INCREASING DEEP LAYER MOISTURE ACROSS FAR ERN MN AND NW WI EARLY THIS MORNING. RATHER STRONG LLJ ALSO APPEARS TO BE AIDING SHALLOW LOW LEVEL ASCENT..AS BOTH KMPX/KDLH RADARS HAVE DETECTED NUMEROUS TRANSIENT SHALLOW CONVECTIVE ECHOES ACROSS WRN WI FOR THE PAST SEVERAL HOURS. ALTHOUGH MOST WIDESPREAD PRECIP WILL LIKELY HOLD OFF UNTIL THE 21-06Z TIME FRAME TONIGHT..WE HAVE STARTED OFF WITH LOW POPS THIS MORNING..AND WE HAVE ALSO DRASTICALLY INCREASED SKY COVER FOR ALL OF TODAY ACROSS ROUGHLY THE SE HALF OF OUR FORECAST AREA. ELSEWHERE..LACK OF CLOUD COVER OUT WEST TODAY SHUD RESULT IN LLJ MOMENTUM MIXING OUT..AND WITH ALREADY STRONG SFC PRESSURE GRADIENT..WINDS SHUD BE CRANKING PRETTY GOOD FROM THE SOUTH BY 10-11 AM ALONG AND WEST OF THE HIGHWAY 169 CORRIDOR. TEMPS SHUD HAVE LITTLE PROBLEM REACHING THE MID 80S IN MOST LOCALES IN THE WRN CWA TODAY. FORECAST FOR FRIDAY IS RATHER COMPLICATED AND DEPENDENT ON OVERNIGHT CONVECTIVE EVOLUTION..BOTH WITH REMNANTS OF UPPER LOW MOVING ACROSS NW WI/WRN LK SUPERIOR AND WITH POTENTIAL FOR MCS PROPAGATING EWD FROM ND FRIDAY MORNING. GIVEN THE LATEST GUIDANCE..WE EXPECT SHOWERS AND PERHAPS A FEW WEAK TSTORMS ASSOCIATED WITH THE SHEARING OUT UPPER LOW TO BE DIMINISHING IN COVERAGE FRIDAY MORNING ACROSS OUR ERN ZONES. THE REMNANTS OF SOME TYPE OF MCS MAY MAKE A RUN AT THE NW DLH CWA 12-18Z FRIDAY MORNING..BUT UPDRAFTS ARE EXPECTED TO WEAKEN. NARROW AXIS OF 1500-2500 CAPE AIDED BY 66-70 DEWPOINTS IS FORECASTED TO DEVELOP AHEAD OF THE FRONT BY MIDDAY FRIDAY..WITH TSTORM DEVELOPMENT ROUGHLY ALONG AN AXIS FROM KINL-KBRD EARLY TO MID AFTERNOON AS CAP IS ERODED BY SUSTAINED MESOSCALE LIFT/FGEN WITHIN THE FRONTAL ZONE. THE STRONGEST DEEP LAYER SHEAR AND FLOW ALOFT IS FORECASTED TO REMAIN WEST OF THE SFC MASS CONVERGENCE AXIS..BUT LATEST GUIDANCE IS IN LINE WITH PREVIOUS THINKING THAT AT LEAST SUFFICIENT DEEP LAYER SHEAR FROM 30-40 KTS WILL BE SUPERIMPOSED WITH THE INSTABILITY AXIS..AND SUPPORTIVE OF A FEW SVR TSTORMS. GIVEN THE TIME OF YEAR WITH SOMEWHAT WEAK MID LEVEL LAPSE RATES AND HIGH FREEZING LEVELS..PRIMARY SVR THREAT SHUD BE DAMAGING WIND WITH MULTICELL/LINE SEGMENT STRUCTURES..AND PERHAPS SOME LOW END SVR HAIL. WE HAVE CARRIED THE HIGHEST POPS FRI EVENING AS INCREASING LLJ 00-06Z SHUD RESULT IN GREATEST AREAL COVERAGE. PRECIP CHANCES SHUD END FAIRLY QUICKLY FROM WEST TO EAST OVERNIGHT FRIDAY NIGHT AS FRONT RAPIDLY SWEEPS EWD AND COOLER/DRIER AIR FILTERS IN BEHIND THE FRONT COINCIDENT WITH STRONG DEEP LAYER SUBSIDENCE. LONG TERM...SATURDAY THROUGH WEDNESDAY... QUIET PATTERN ADVERTISED BY MDL CONSENSUS AS BOTH GFS/EC PUSH NRN BRANCH MID LVL TROF EAST OF CWA SATURDAY EVENING. DEEP LAYER DRYING SATURDAY ALONG WITH UNIDIRECTIONAL SFC/85H FLOW SHOULD ALLOW FOR BREEZY CONDITIONS.MID LVL RIDGE BUILDS EAST FROM NRN PLAINS SUN/MON WITH PWATS BELOW .75 INCHES. SHOULD SEE ABUNDANT SUNSHINE UNTIL TUESDAY WHEN RETURN FLOW ESTABLISHES AND SOME INCREASE IN DEEP LAYER RH OCCURS. AVIATION...LLWS WILL CONTINUE THROUGH EARLY THIS MORNING AS INCREASING GEOSTROPHIC FLOW CONTINUES JUST ABOVE DECOUPLED BDRY LAYER. LATEST KDLH VWP SHOWS 2KFT FLOW NOT AS STRONG OVER DLH AS RUC FCST. EARLIER TAMDAR SOUNDINGS FROM HIB/TVF/BRD VICINITY SHOWING RUC FCST 925 FCST VALUES CLOSER TO VERIFICATION. WILL EVALUATE ONCE AGAIN FOR NEXT ISSUANCE OF TAFS AROUND 1130Z. OTHERWISE NOCTURNAL JET SHOULD RESTRICT WIDESPREAD DEVELOPMENT OF FG THIS MORNING AS TURBULENT FLOW WILL FAVOR STRATUS DECK INSTEAD. HAVE OPTED FOR TEMPO VFR CEILING AND/OR MVFR VIS FROM 9Z-13Z AT HIB/DLH. EARLY MORNING CLOUDS WILL GRADUALLY DISSIPATE AS BDRY LYR HEATING AND RESULTING MECHANICAL MIXING KEEP VFR CONDITIONS ACROSS THE CWA DURING THE DAY. LARGE PLUME OF MSTR HEADING INTO NW WISC WILL FAVOR MORE EXTENSIVE CLOUD DECK WITH SCHC TRW BY AFTERNOON NEAR HYR. && POINT TEMPS/POPS... DLH 80 65 82 58 / 10 20 40 60 INL 87 66 83 55 / 10 20 40 20 BRD 86 67 86 57 / 10 20 50 40 HYR 82 64 83 63 / 30 40 30 50 ASX 82 64 81 63 / 20 40 30 60 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ GRANING/04 mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 625 AM CDT THU AUG 21 2008 .AVIATION.../12Z TAF ISSUANCE/ DETERIORATING CONDITIONS WILL BE THE GENERAL THEME FOR AVIATION CONDITIONS OVER THE UPCOMING 24 HOURS. MID AND HIGH CLOUDS CURRENTLY STREAMING INTO THE SOUTHEAST PORTION OF THE AREA WILL CONTINUE TO THICKEN AS THE MORNING PROGRESSES... WITH PCPN IN THE DEFORMATION ZONE OF THE APPROACHING UPPER LOW TRYING TO MOVE NORTHWARD AS WELL. THE AREA OF OBSERVED PCPN MATCHES UP REASONABLY WELL WITH THE JUXTAPOSITION OF DEEP LAYER MOISTURE AND 850-500MB Q-VECTOR CONVERGENCE SHOWN BY THE NAM AND GFS. THIS WOULD BRING THE BEST CHANCE OF PCPN INTO THE EASTERN PORTION OF THE AREA... MAINLY OVER WEST CENTRAL WISCONSIN... LATER THIS AFTERNOON. IT APPEARS AS THOUGH KMSP WILL BE NEAR THE WESTERN EDGE OF THE PCPN SHIELD... AND WITH THE FORCING ACTUALLY ADVERTISED TO WEAKEN A BIT... AM NOT CONVINCED PCPN WILL GET INTO KMSP SO MAINTAINED JUST A VCSH FOR THAT AREA. HOWEVER... DID INCLUDE A TEMPO FOR SHRA OVER KEAU LATER TODAY SINCE IT LOOKS LIKE A BETTER CHANCE IN THAT AREA. CEILINGS ARE NOT EXPECTED TO LOWER TOO DRAMATICALLY WITH THIS ACTIVITY... AND SHOULD REMAIN VFR THROUGH THE DAY ACROSS THE ENTIRE AREA... WITH MINIMAL RESTRICTIONS EXPECTED OVER THE WEST. HOWEVER... TONIGHT APPEARS TO BE A DIFFERENT STORY ENTIRELY... WITH BOUNDARY LAYER THROUGH 850MB RH VALUES CLIMBING DRAMATICALLY... PARTICULARLY OVER THE EASTERN TWO THIRDS OF THE AREA. LOWERED CEILINGS ACROSS THE AREA THROUGH THE NIGHT... WITH THE LOWEST CEILINGS OVER THE EAST WHERE FORECAST SOUNDINGS SUGGEST LOW LOWEST STRATUS WILL BE PRESENT. LOOKING AT UPSTREAM CONDITIONS TO OUR SOUTH THIS MORNING... IT CERTAINLY APPEARS AS THOUGH WIDESPREAD IFR AND MVFR CONDITIONS WILL DEVELOP ACROSS MOST OF THE AREA... WITH PERHAPS THE FAR WEST ESCAPING THINGS. THE OTHER ISSUE OF CONCERN TODAY WILL BE GUSTY WINDS... WITH AN INCREASING PRESSURE GRADIENT THROUGH THE DAY AS THE FRONTAL BOUNDARY OVER THE HIGH PLAINS MOVES EAST. SOUTHERLY FLOW WILL BE STRONGEST OVER THE WEST... WHERE SOME GUSTS IN EXCESS OF 35KT LOOK LIKE A GOOD BET... BUT GUSTS OVER 25KT LOOK POSSIBLE LATER TODAY AS FAR EAST AS THE MN/WI STATE LINE. THINGS SHOULD DECOUPLE SUFFICIENTLY TONIGHT FOR THE GUSTINESS TO DIE OFF... ALTHOUGH IT WILL REMAIN SOMEWHAT BREEZY AND A POTENT LOW LEVEL JET CAN BE EXPECTED JUST OFF THE DECK. && .PREV DISCUSSION... /ISSUED 316 AM CDT THU AUG 21 2008/ THE CHALLENGE WITH THE FORECAST IS THE CHANCES OF PRECIP THROUGH TODAY AND FRI...AND ANY STRONG TO SEVERE POTENTIAL OF THUNDERSTORMS ON FRI. VERY UNIQUE UPPER LEVEL PATTERN FOR THIS TIME OF YEAR...WITH MORNING GOES WV LOOP REVEALING A LONG-LIVED UPPER LEVEL LOW NOW LIFTING NNE FROM THE OZARKS. SATELLITE AND PROFILERS INDICATING STILL A WELL DEFINED MID-LEVEL CIRCULATION WITH THIS AND RUC/NAM ANALYSES INDICATES A CONTINUED PV ANOMALY. TRAJECTORY OF THE H7 LOW/WAVE WOULD TAKE IT NNE ACROSS CENTRAL FORECAST AREA TODAY INTO TONIGHT. HAVE GENERALLY CONFINED POPS FOR TODAY TO THE EAST OF THIS TRACK...WHERE MID-LEVEL DIFLUENCE EXISTS ABOVE SATURATING UPGLIDE. ADIABATIC OMEGA AND QG FORCING ARE BOTH FAIRLY WEAK IN MAGNITUDE IN ERN MN AND WRN WI. CONVECTIVE PARAMETERS ARE ALSO VERY WEAK...WITH ONLY MINIMAL UPRIGHT CONVECTIVE POTENTIAL. SO HAVE SCT SHWRS AND ISOLD THUNDER IN THE ERN FORECAST AREA...MAINLY DURING THE AFTN AND EVE. HAVE SLIGHT CHANCES FOR SHRA/SPRINKLES TO THE WEST OF THIS. WRN MN LOOKS TO REMAIN DRY TODAY AND THIS EVE...WITH BREEZY CONDITIONS. NOT TOO FAR FROM WIND ADVISORY CRITERIA IN A FEW PLACES THERE THIS AFTN...GIVEN MSLP GRADIENT AND ISALLOBARIC INFLUENCE. MIXING WILL ALSO ALLOW SOME GUSTS TO 35-40 MPH ESPECIALLY IN SOME OF THE HIGHER LOCALES. TEMPS TODAY IN SE MN AND WRN WI WILL BE HINDERED GREATLY DUE TO THE CLOUD COVER...WITH POSSIBLY ONLY MID 70S FOR HIGHS IN PLACES. GIVEN SATELLITE TRENDS EARLY THIS MORNING AND FORECAST MODEL TIME HEIGHTS...IT APPEARS THAT STRATUS WILL DEVELOP TONIGHT IN ERN MN AND WRN WI IN THE WAKE OF SHOWERS. HAVE BUMPED UP CLOUD COVER AND ADJUSTED MIN TEMPS FOR THIS. THIS AFOREMENTIONED SYSTEM IS BEING CONSUMED AND FORCED NNE BY A LARGER...PROGRESSIVE..AND SIMPLY STRONGER SYSTEM PUSHING QUICKLY EAST ACROSS THE NW U.S./BRITISH COLUMBIA BORDER EARLY THIS MORNING. CONVECTION LOOKS TO DEVELOP ASSOCIATED WITH THIS IN ND THIS EVE. PARAMETERS ARE FAVORABLE FOR AN MCS BUT PROPAGATION WOULD TAKE ONE ENE...WELL NORTH OF THE CWA EARLY FRI MORNING. JUST A SMALL CHANCE FOR ISOLD ELEVATED CONVECTION ON THE LLJ LATE TONIGHT IN WRN MN. AS JET ROUNDS THE BASE OF THIS TROUGH ON FRIDAY...DEEP CYCLOGENSIS WILL OCCUR IN SOUTH CENTRAL CANADA FORCING COOL AND DRY AIR ADVECTION EASTWARD FROM THE NRN ROCKIES. THIS COLD FRONT /AND POSSIBLY PRE-FRONTAL TROUGH/ WILL ENTER THE FORECAST AREA FRI AFTN. STRONG CAP FORECAST FOR FRI MORNING AND EARLY AFTN. BUT CAP IS FORECAST TO WEAKEN OVER THE POOLED INSTABILITY AXIS ALONG THE FRONT. DIAGNOSTIC MODELS FORECAST MUCAPES 1500-2000 J/KG BUT SREF INDICATING PROBABILITIES OF SUCH VALUES ONLY AROUND 30 PERCENT. MORNING STRATUS MAY FURTHER INHIBIT FULL HEATING TO THESE VALUES. LAPSE RATES ARE ALSO NOT VERY FAVORABLE FOR EXPLOSIVE CONVECTIVE POTENTIAL. ON THE SHEAR SIDE OF THINGS...DEEP LAYER SHEAR IS MARGINAL BUT INCREASING ESPECIALLY DURING THE EVE. LOW LEVEL SHEAR IS STRONG...THANKS TO THE PERSISTENT LLJ. A PROBLEM WITH SUSTAINED STRONG CONVECTION IS THAT FRONT IS BEING STRETCHED OUT...WITH LOW SO FAR NORTH AND ANOTHER WAVE FURTHER SOUTHWEST ON THE FRONT IN THE CTRL PLAINS. SO CONVERGENCE BECOMES SOMEWHAT MINIMIZED. SOME SCT CONVECTION SEEMS LIKELY BY LATE FRI AFTN AND MORE SO DURING THE EVE...BUT WIDESPREAD STRONG CONVECTION AT THIS TIME SEEMS UNLIKELY. SOME SEVERE POSSIBLE THOUGH ESPECIALLY IF CONVECTION CAN ORGANIZE. THIS IS BECAUSE LOWER AND MID TROP WIND FIELD BEHIND THE FRONT IS STRONG AND UNIDIRECTIONAL FROM THE WNW. POSSIBLY A FEW STRONG MULTI-CELLED CLUSTERS. BEYOND...THE FRONT DOES APPEAR TO WANT TO STALL GIVEN A BACKUP OF THINGS IN THE ERN AND SRN PART OF THE COUNTRY...INCLUDING T.S. FAY. BUT ALL GUIDANCE INDICATES THIS WILL OCCUR PAST OUR AREA...MEANING A FAIRLY NICE AND SLIGHTLY COOLER THAN NORMAL WEEKEND. HAVE MADE LITTLE ADJUSTMENTS DURING THAT TIME INTO MONDAY. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ TRH/MTF mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 1046 AM EDT THU AUG 21 2008 .SYNOPSIS... SURFACE HIGH PRESSURE OVER THE EASTERN GREAT LAKES WILL PUSH SOUTHEAST INTO THE MID ATLANTIC REGION THROUGH THE END OF THE WEEK. A COLD FRONT WILL MOVE INTO THE REGION FROM THE NORTHWEST ON SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MADE ONLY MINOR ADJUSTMENTS TO THE GOING FORECAST WITH MOST OF THE REASONING UNCHANGED. MID CLOUDS PROVING A BIT PERSISTENT ACROSS THE WESTERN CWA...WHICH MAY KEEP THE IN/OH BORDER REGION JUST BELOW 90. OTHERWISE LOWER 90S ARE EXPECTED...AGAIN ABOVE GUIDANCE BY A COUPLE OF DEGREES. NAM AND RUC STILL SHOWING SOME INSTABILITY SHOWERS OVER THE WESTERN CWA LATE THIS AFTERNOON...BUT AS USUAL DEWPOINTS AND INSTABILITY SEEM OVERDONE. IT IS NOT OUT OF THE QUESTION...BUT FOR NOW THE FORECAST WILL REMAIN DRY. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... ABOVE AVG TEMPS WILL CONTINUE ACROSS THE REGION THROUGH SATURDAY AS THE OHIO VALLEY REMAINS IN SOUTHERLY FLOW AROUND THE BACK SIDE OF HIGH PRESSURE TO THE EAST. NEXT FRONTAL BOUNDARY IS STILL PROGGED TO COME IN FROM THE NORTHWEST ON SUNDAY. KEPT CHANCE TO SLIGHT CHANCE POPS GOING AHEAD OF THIS FEATURE ON SATURDAY GIVEN THE UNSTABLE AIRMASS WHICH IS FORECAST...BUT SLOWED THEM DOWN SLIGHTLY WITH UPPER FORCING STAYING NORTH OF THE REGION. IF SLOWER MODEL TRENDS CONTINUE...POPS MAY NEED TO BE CUT BACK EVEN MORE. INCREASED POPS ON SUNDAY WITH FRONTAL BOUNDARY SLIDING SOUTH TO NEAR THE OHIO RIVER BY SUNDAY NIGHT. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... IN THE EARLIER PART OF THIS EXTENDED...THE FORECAST TRENDS TOWARD THE 00Z ECMWF WHICH WAS SLOWER WITH THE APPROACH OF THE FRONT OVER THE WEEKEND THAN THE 00Z AND 12Z GFS. GFS ENSEMBLES WERE ALSO MORE IN AGREEMENT WITH THE 00Z ECMWF. USED A BLEND OF THE GFS ENSEMBLES AND 00Z ECMWF TOWARD DAYS 6 AND 7...TUE AND WED. THIS IS SIMILAR TO HPC`S SOLUTION. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT WHICH WILL REMAIN JUST TO THE SOUTH OF OUR FORECAST AREA ON MON. AS A RESULT OF THE PROXIMITY OF THE FRONT...KEPT A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS IN THE SOUTHERN PART OF THE FORECAST AREA MON. BY MID WEEK NEXT WEEK...THE OHIO VALLEY REGION MAY BEGIN TO SEE AN INCREASE IN MOISTURE AND CHANCES OF PRECIPITATION AS A RESULT OF THE REMNANTS OF FAY. THIS WILL DEPEND ON WHERE THE REMNANTS OF FAY TRACK AND THE TIMING OF THAT MOVEMENT. HOWEVER...AT THIS TIME THERE IS MUCH UNCERTAINTY AS TO HOW THE REMNANTS OF FAY WILL EVOLVE AND TRACK OVER TIME. HIGH TEMPERATURES WILL COOL INTO THE LOWER TO MID 80S BY MID WEEK NEXT WEEK. LOW TEMPERATURES WILL BE MAINLY IN THE 60S WITH SOME UPPER 50S IN THE NORTH. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... MID/UPPER LEVEL TROUGH OVER THE MISSISSIPPI VALLEY WILL CONTINUE TO WORK ITS WAY SLOWLY EAST AND WEAKEN THROUGH THE TAF PERIOD. AS IT DOES...HIGH AND THEN MID LEVEL CLOUDS SHOULD SLOWLY OVERSPREAD THE AREA FROM THE WEST TODAY. SOUTHERLY LOW LEVEL FLOW FORECAST TO INCREASE A BIT LATER TONIGHT AND AS IT DOES...LOW LEVELS BEGIN TO MOISTEN UP A BIT. THIS COULD LEAD TO SOME LOWER VFR CIGS ACROSS THE WEST OVERNIGHT. OUTLOOK...THUNDERSTORMS WILL BE POSSIBLE ON SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HAWBLITZEL LONG TERM...PARKER AVIATION...JGL oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE FORT WORTH TX 1104 AM CDT THU AUG 21 2008 .UPDATE... FORECAST LOOKS ON TRACK...JUST MINOR CHANGES TO ACCOUNT FOR LATEST TRENDS IN CLOUDS/DEWPOINTS/WINDS. REMOVED POPS WEST OF I-35 AS AREA WILL BE UNDER A REGION OF INCREASING HEIGHTS/SUBSIDENCE THROUGH THE AFTERNOON HOURS. LOW LEVEL MOISTURE (THUS INSTABILITY) WILL REMAIN ACROSS THE EASTERN CWA...AND COUPLED WITH DRYING ALOFT THERE IS A LOW POTENTIAL FOR WET MICROBURSTS THIS AFTERNOON. COVERAGE OF CONVECTION SHOULD REMAIN NEAR OR LESS THAN 30 PERCENT GIVEN LACK OF DYNAMIC FORCING THAT HAD BEEN PRESENT THE LAST SEVERAL DAYS. TR.92 && .AVIATION... PATCHY FOG IS MAKING THIS MORNINGS TAFS DIFFICULT. THE VISIBILITY WENT DOWN AS LOW AS 3/4SM WITH A VERTICAL VISIBILITY OF 100 FEET AT KAFW. AS OF 1153Z...THEY HAD CLIMBED UP TO 5SM BKN005. HAVE GENERALLY KEPT VSBYS 3-5SM AND SCT-BKN 003-006 THROUGH 14Z...WITH AN IMPROVEMENT TO MVFR 14-16Z...AND VFR THEREAFTER, WE SHOULD SEE SOME ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON...BUT AREAL COVERAGE WILL BE LESS THAN WE HAVE SEEN FOR THE LAST DAYS. LIGHT AND VARIABLE WINDS SHOULD BECOME SOUTHERLY 5 TO 8 KNOTS THIS AFTERNOON. 58 && .PREV DISCUSSION... /ISSUED 321 AM CDT THU AUG 21 2008/ THE UPPER LEVEL LOW THAT HAS BROUGHT BENEFICIAL BUT FLOODING RAINS TO NORTH TEXAS THE PAST FEW DAYS IS NOW SLIDING INTO KANSAS /PER RUC ANALYSIS/. THE ASSOCIATED TROUGH EXTENDS SOUTH ACROSS TEXAS WITH THE AXIS CENTERED OVER THE WESTERN HALF OF THE CWA. SOME WEAK SHORTWAVES CONTINUE TO MOVE AROUND THE BASE OF THE TROUGH. ONE SHORTWAVE IS NOW EXITING NORTHEAST TEXAS AND IS AIDING IN SHOWER AND THUNDERSTORM DEVELOPMENT IN OUR EXTREME NE CWA. A STRONGER SHORTWAVE IS FORECASTED TO SKIRT THE RED RIVER THIS AFTERNOON. THE BEST CHANCE FOR RAIN TODAY WILL BE ACROSS THE EASTERN HALF OF THE CWA...AHEAD OF THE TROUGH AXIS AND APPROACHING SHORTWAVE...WHERE LIFT WILL BE STRONGEST. ANOTHER POTENTIAL PLAYER FOR TODAY COULD BE THE LEFT OVER BOUNDARY/SURFACE TROUGH RUNNING NORTHEAST TO SOUTHWEST ACROSS ALMOST THE MIDDLE OF THE CWA. WITH SOME HEATING LATER TODAY...SHOWERS AND THUNDERSTORMS MAY DEVELOP ALONG THAT BOUNDARY OR ANY OTHER RESIDUAL BOUNDARIES. HOWEVER...WILL HAVE THE HIGHEST POPS IN THE EAST. PWATS WILL REMAIN NEAR 2 INCHES IN THE EAST SO HEAVY RAINFALL IS STILL A THREAT TODAY IN THAT AREA. THE WEATHER PATTERN OVER THE NEXT SEVERAL DAYS WILL REMAIN SOMEWHAT UNSETTLED AS THE REMNANTS OF THE UPPER LEVEL LOW NEVER REALLY LEAVE THE REGION AND THE UPPER LEVEL RIDGE TO THE WEST NEVER REALLY BUILDS IN. THE UPPER LEVEL RIDGE ONLY MAKES IT AS FAR AS THE TEXAS PANHANDLE BEFORE BEING HALTED. ALL MODELS ARE IN GOOD AGREEMENT THAT ENERGY FROM THE TROUGH WILL REMAIN OVER NORTHEAST TEXAS AND THEN DRIFT BACK OVER NORTH TEXAS OVER THE NEXT SEVERAL DAYS. THUS WILL KEEP 20-30 POPS IN THE FORECAST THROUGH THE WEEKEND WITH BEST CHANCE FOR RAIN AGAIN IN THE EAST AND SOUTHEAST. SUNDAY LOOKS TO BE THE NEXT BEST CHANCE FOR RAIN ACROSS ALL OF NORTH TEXAS WITH THE HIGHEST POPS ALONG THE RED RIVER. BY MONDAY...THE UPPER LEVEL RIDGE GETS NUDGED BACK WEST AS FAY MOVES INTO THE CENTRAL GOM COAST AND NORTHERLY FLOW ALOFT SETS UP. MODELS SUGGEST THAT SEVERAL WEAK DISTURBANCES WILL RIDE THE NORTHERLY FLOW INTO TEXAS AND WILL CONTINUE 20 POPS FOR THE AFTERNOON/EVENING HOURS THROUGH THE REMAINDER OF THE FORECAST. HAVE STUCK CLOSE TO GUIDANCE FOR HIGH TEMPERATURES IN THE BEGINNING OF THE FORECAST AND THEN UNDERCUT GUIDANCE A DEGREE OR TWO FOR THE LAST FEW DAYS. HIGH TEMPERATURES WILL MOSTLY TOP OUT IN THE 90S WITH A FEW SCATTERED UPPER 80S THIS WEEKEND. REASON FOR UNDERCUTTING GUIDANCE ON DAYS 6 AND 7 WAS THOUGHT MOS TEMPS WERE TOO HIGH FOR NORTHERLY FLOW. OVERNIGHT LOWS WILL CONTINUE TO BE IN THE UPPER 60S TO MID 70S. 82/JLD && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 91 74 94 75 92 / 20 10 10 10 30 WACO, TX 92 72 93 74 92 / 10 10 20 10 30 PARIS, TX 87 70 91 71 90 / 40 10 30 10 30 DENTON, TX 91 72 93 72 92 / 20 10 10 10 30 MCKINNEY, TX 91 71 91 71 92 / 20 10 10 10 30 DALLAS, TX 91 72 92 73 92 / 20 10 10 10 30 TERRELL, TX 91 72 94 73 91 / 20 10 20 10 30 CORSICANA, TX 91 72 93 73 93 / 20 10 20 10 30 TEMPLE, TX 92 71 95 73 91 / 10 10 20 10 30 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 25/92 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE FORT WORTH TX 714 AM CDT THU AUG 21 2008 .AVIATION... PATCHY FOG IS MAKING THIS MORNINGS TAFS DIFFICULT. THE VISIBILITY WENT DOWN AS LOW AS 3/4SM WITH A VERTICAL VISIBILITY OF 100 FEET AT KAFW. AS OF 1153Z...THEY HAD CLIMBED UP TO 5SM BKN005. HAVE GENERALLY KEPT VSBYS 3-5SM AND SCT-BKN 003-006 THROUGH 14Z...WITH AN IMPROVEMENT TO MVFR 14-16Z...AND VFR THEREAFTER, WE SHOULD SEE SOME ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON...BUT AREAL COVERAGE WILL BE LESS THAN WE HAVE SEEN FOR THE LAST DAYS. LIGHT AND VARIABLE WINDS SHOULD BECOME SOUTHERLY 5 TO 8 KNOTS THIS AFTERNOON. 58 && .PREV DISCUSSION... /ISSUED 321 AM CDT THU AUG 21 2008/ THE UPPER LEVEL LOW THAT HAS BROUGHT BENEFICIAL BUT FLOODING RAINS TO NORTH TEXAS THE PAST FEW DAYS IS NOW SLIDING INTO KANSAS /PER RUC ANALYSIS/. THE ASSOCIATED TROUGH EXTENDS SOUTH ACROSS TEXAS WITH THE AXIS CENTERED OVER THE WESTERN HALF OF THE CWA. SOME WEAK SHORTWAVES CONTINUE TO MOVE AROUND THE BASE OF THE TROUGH. ONE SHORTWAVE IS NOW EXITING NORTHEAST TEXAS AND IS AIDING IN SHOWER AND THUNDERSTORM DEVELOPMENT IN OUR EXTREME NE CWA. A STRONGER SHORTWAVE IS FORECASTED TO SKIRT THE RED RIVER THIS AFTERNOON. THE BEST CHANCE FOR RAIN TODAY WILL BE ACROSS THE EASTERN HALF OF THE CWA...AHEAD OF THE TROUGH AXIS AND APPROACHING SHORTWAVE...WHERE LIFT WILL BE STRONGEST. ANOTHER POTENTIAL PLAYER FOR TODAY COULD BE THE LEFT OVER BOUNDARY/SURFACE TROUGH RUNNING NORTHEAST TO SOUTHWEST ACROSS ALMOST THE MIDDLE OF THE CWA. WITH SOME HEATING LATER TODAY...SHOWERS AND THUNDERSTORMS MAY DEVELOP ALONG THAT BOUNDARY OR ANY OTHER RESIDUAL BOUNDARIES. HOWEVER...WILL HAVE THE HIGHEST POPS IN THE EAST. PWATS WILL REMAIN NEAR 2 INCHES IN THE EAST SO HEAVY RAINFALL IS STILL A THREAT TODAY IN THAT AREA. THE WEATHER PATTERN OVER THE NEXT SEVERAL DAYS WILL REMAIN SOMEWHAT UNSETTLED AS THE REMNANTS OF THE UPPER LEVEL LOW NEVER REALLY LEAVE THE REGION AND THE UPPER LEVEL RIDGE TO THE WEST NEVER REALLY BUILDS IN. THE UPPER LEVEL RIDGE ONLY MAKES IT AS FAR AS THE TEXAS PANHANDLE BEFORE BEING HALTED. ALL MODELS ARE IN GOOD AGREEMENT THAT ENERGY FROM THE TROUGH WILL REMAIN OVER NORTHEAST TEXAS AND THEN DRIFT BACK OVER NORTH TEXAS OVER THE NEXT SEVERAL DAYS. THUS WILL KEEP 20-30 POPS IN THE FORECAST THROUGH THE WEEKEND WITH BEST CHANCE FOR RAIN AGAIN IN THE EAST AND SOUTHEAST. SUNDAY LOOKS TO BE THE NEXT BEST CHANCE FOR RAIN ACROSS ALL OF NORTH TEXAS WITH THE HIGHEST POPS ALONG THE RED RIVER. BY MONDAY...THE UPPER LEVEL RIDGE GETS NUDGED BACK WEST AS FAY MOVES INTO THE CENTRAL GOM COAST AND NORTHERLY FLOW ALOFT SETS UP. MODELS SUGGEST THAT SEVERAL WEAK DISTURBANCES WILL RIDE THE NORTHERLY FLOW INTO TEXAS AND WILL CONTINUE 20 POPS FOR THE AFTERNOON/EVENING HOURS THROUGH THE REMAINDER OF THE FORECAST. HAVE STUCK CLOSE TO GUIDANCE FOR HIGH TEMPERATURES IN THE BEGINNING OF THE FORECAST AND THEN UNDERCUT GUIDANCE A DEGREE OR TWO FOR THE LAST FEW DAYS. HIGH TEMPERATURES WILL MOSTLY TOP OUT IN THE 90S WITH A FEW SCATTERED UPPER 80S THIS WEEKEND. REASON FOR UNDERCUTTING GUIDANCE ON DAYS 6 AND 7 WAS THOUGHT MOS TEMPS WERE TOO HIGH FOR NORTHERLY FLOW. OVERNIGHT LOWS WILL CONTINUE TO BE IN THE UPPER 60S TO MID 70S. 82/JLD && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 92 74 94 75 92 / 20 10 10 10 30 WACO, TX 92 72 93 74 92 / 20 20 20 10 30 PARIS, TX 87 70 91 71 90 / 50 20 30 10 30 DENTON, TX 91 72 93 72 92 / 20 10 10 10 30 MCKINNEY, TX 91 71 91 71 92 / 30 10 10 10 30 DALLAS, TX 92 72 92 73 92 / 20 10 10 10 30 TERRELL, TX 91 72 94 73 91 / 30 20 20 10 30 CORSICANA, TX 91 72 93 73 93 / 30 20 20 10 30 TEMPLE, TX 93 71 95 73 91 / 20 20 20 10 30 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 58/84 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 1113 AM CDT THU AUG 21 2008 .UPDATE...TODAY LATEST WATER VAPOR SATELLITE IMAGERY INDICATING UPPER LEVEL LOW LIFTING NORTH INTO THE UPPER GREAT LAKES REGION THIS MORNING. LATEST MOSAIC RADAR INDICATING SHIELD OF LIGHT PRECIPITATION EXTENDING FROM SOUTHWEST WISCONSIN INTO CENTRAL ILLINOIS. THIS IS IN RESPONSE TO WEAK MOISTURE/THETA E CONVERGENCE AT 850MB PER LATEST RUC. LATEST 15Z RUC INDICATE THIS FORCING TO CONTINUE TO LIFT NORTH ACROSS FORECAST AREA THIS AFTERNOON. LATEST LOCAL RUN RUCWRF MODEL DOING REAL WELL WITH CURRENT PRECIPITATION AND SHIFTS PRECIPITATION NORTH ACROSS FORECAST AREA THIS AFTERNOON. HAVE UPDATED FORECAST TO ADJUST PRECIPITATION TRENDS LATE THIS MORNING. HAVE ALSO ADJUSTED TEMPERATURES A COUPLE OF DEGREES DOWNWARD...BASED ON CLOUDS WILL HOLD DOWN TEMPERATURES DURING THE AFTERNOON HOURS ACROSS FORECAST AREA. && .PREV DISCUSSION... /ISSUED 341 AM CDT THU AUG 21 2008/ .SHORT TERM...TODAY THROUGH SATURDAY NIGHT MAIN FORECAST CONCERNS THIS PACKAGE...RAIN CHANCES TODAY INTO SAT... TEMPERATURES THROUGH THE PERIOD. 06Z DATA ANALYSIS HAD BROAD HIGH PRESSURE CENTERED OVER NY/PA WITH RIDGING WEST INTO THE UPPER MIDWEST. LOW PRESSURE WAS LOCATED OVER CENTRAL MAN WITH TROUGHING INTO EASTERN WY. ANOTHER WEAK WAVE OF LOW PRESSURE/TROUGH WAS LOCATED OVER EAST TX TO SOUTHWEST MO. SFC OBS/ FOG-PRODUCT IMAGERY DEPICTED THE BKN/OVC MID CLOUD DECK MOVING NORTH ACROSS IA/IL/SOUTHERN IL...AHEAD OF THE SHORTWAVE ENERGY/UPPER LOW LIFTING OUT OF THE SOUTHERN PLAINS. REGIONAL RADARS SHOWED RATHER WIDESPREAD -RA LIFTING NORTH THRU MO...BUT BATTLING SOME DRIER LOW LEVEL AIR AS IT MOVED INTO SOUTHERN IA. NO MAJOR ERRORS NOTED WITH 21.00Z NAM/GFS INITIALIZATIONS WITH SOLUTIONS QUITE SIMILAR FOR TODAY THRU SAT NIGHT. HOWEVER...PER WV IMAGERY BOTH LOOKED WEAK WITH THE SHORTWAVE LIFTING ACROSS AR. DPROG/DT OF 500MB HGTS AT 21.00Z SHOWED NAM/GFS RUNS OF 19.00Z AND 20.00Z VERIFIED WELL ACROSS NOAM/EASTERN PAC WITH THE BETTER RUN-TO- RUN CONSISTENCY AGAIN TO GFS. THRU 36HRS TREND IS TOWARD THE FASTER PREVIOUS GFS RUNS AS THE TROUGH MOVES INTO THE NORTHERN PLAINS... SUPPORTED BY ECMWF/UKMET. FAY REMAINS PROBLEMATIC...STUCK IN WEAK STEERING FLOW. MODEL CONSISTENCY REMAINS QUITE GOOD IN THE 36-84HR TIME-FRAME AS THE TROUGH/UPPER LOW LIFTS TO SOUTHERN HUDSONS BAY AND RIDGING BUILDS OVER THE NORTHERN ROCKIES/PLAINS AND CANADIAN PRAIRIES. CHECK OF OBS VS. MODEL DATA AT 06Z SHOWED NAM/GFS REASONABLE WITH THE SFC MASS FIELDS ACROSS CENTRAL NOAM. PER WV IMAGERY BOTH NAM/GFS CONTINUED TO APPEAR TOO WEAK WITH THE SHORTWAVE LIFTING NORTH ACROSS AR...WITH NAM BETTER THAN GFS AND ECMWF BETTER THAN NAM. A BLEND OF NAM/GFS LOOKED BEST WITH THE 00Z-06Z PRECIP ACROSS THE CENTRAL CONUS...WHILE GFS BETTER BUT STILL TOO LIGHT WITH FAY QPF ACROSS FL. DIFFICULT TO FAVOR EITHER MODEL THIS CYCLE WITH THE POOR DEPICTION OF THE AR SHORTWAVE ROTATING NORTH TOWARD THE AREA TODAY. THIS ISSUE LEADS TO CONFIDENCE IN THE AVERAGE RANGE THIS CYCLE. WITH NAM/ECMWF...BETTER WITH THE AR SHORTWAVE EARLY THIS MORNING...LEANED TOWARD THEIR SOLUTIONS TODAY/TONIGHT. THEN FAVORED MODEL BLEND/COMPROMISE FOR FRI THRU SAT NIGHT. IN THE SHORT TERM...DEEPER MOISTURE AND SHORTWAVE ENERGY WILL CONTINUE TO LIFT NORTH INTO/ACROSS THE AREA TODAY INTO THIS EVENING. SOME ISENTROPIC UPGLIDE IN THE 300-310K LAYER ALONG WITH THETA-E CONVERGENCE...BUT BULK OF LIFT LOOKS TO COME FROM PV ADVECTION AHEAD OF THE SHORTWAVE AND AGEOSTROPHIC FLOW/DIVERGENCE IN RIGHT ENTRANCE REGION OF A 40KT 300MB JET MAX. WITH SHORTWAVE OF INTEREST LOOKING STRONGER THAN DEPICTED IN ANY MODEL...PV ADVECTION/LIFT ACROSS THE AREA THIS AFTERNOON EVENING SHOULD BE STRONGER THAN PROGGED. RAISED RAIN CHANCE TO LIKELY FOR MUCH OF THE AREA THIS AFTERNOON AND TO HIGH-END CHANCE FOR THIS EVENING. BULK OF PRECIP TO BE -RA OR -SHRA AS LITTLE IN THE WAY OF CAPE EXPECTED ACROSS THE AREA THIS AFTERNOON/EVENING. NAM THE MOST ROBUST...INDICATING UP TO 500 J/KG OF MOST-UNSTABLE CAPE. GIVEN THE STRENGTH OF THE SHORTWAVE AND POTENTIAL FOR SOME WEAK CAPE...DID LEAVE ISOLD TSRA IN GRIDS FOR THE AFTERNOON/EVENING HOURS. MAIN WAVE/TROUGH LIFTS NORTH OF THE AREA FOR LATER TONIGHT AND TRENDED -RA/-SHRA CHANCES DOWN A BIT. LIMITED FORCING/LIFT ACROSS THE AREA FRI WITH NORTHERN STREAM TROUGH AND COLD FRONT WEST OF THE AREA. INSTABILITY INCREASES ACROSS THE AREA FOR THE AFTERNOON...MOST UNSTABLE CAPES OF 1K TO 1.5K J/KG...WITH SOME WEAK SFC-700MB WARM ADVECTION AHEAD OF THE FRONT. CONTINUED A SMALL -SHRA/TSRA CHANCE FRI...MAINLY DURING THE AFTERNOON. COLD FRONT STILL ON TRACK TO PUSH ACROSS THE AREA FRI NIGHT...INTO THE MOIST/UNSTABLE AIRMASS. CONVERGENCE/LIFT WITH THE FRONT TRENDING WEAKER WITH A MORE SHEARED LOOK/POSITIVE TILT TO THE 850-500MB TROUGH WITH THE FRONT. MAIN SHORTWAVE ENERGY AND TROUGH SHEARS/LIFTS NORTH OF THE AREA AS WELL. FRONT DOES GENERATE WEAK- MDT 850-700MB FN AND QG CONVERGENCE AS IT PUSHES ACROSS TONIGHT. PREVIOUS GRID SETS CARRIED HIGH-END CHANCE/LOW-END LIKELY -SHRA/TSRA CHANCES FOR LATER FRI NIGHT...WHICH LOOKS WELL TRENDED FOR NOW. LOW LEVEL COLD ADVECTION/SUBSIDENCE/DRYING SPREAD ACROSS THE AREA BEHIND THE FRONT ON SAT. WITH FRONT STILL IN/NEAR THE AREA EARLY SAT MORNING...LINGERING -SHRA/ISOLD TSRA CHANCE REASONABLE. SOME 850- 700MB MOISTURE TRANSPORT AND WEAK 700MB WARM ADVECTION ABOVE THE ADVANCING HIGH/COOL DOME MAY BE ENOUGH FOR A SMALL -SHRA/TSRA CHANCE ACROSS THE SOUTH END OF THE FORECAST AREA SAT AFTERNOON AND LEFT THE SMALL -SHRA/TSRA CHANCE THERE. HIGH TEMPS TRICKY TODAY AND DEPEND ON HOW QUICKLY THICKER CLOUDS/ ANY -RA MOVES IN. TRENDED HIGHS DOWN TOWARD A BLEND OF GUIDANCE VALUES. FAVORED A BLEND OF GUIDANCE LOWS/HIGHS FOR TONIGHT THRU FRI NIGHT. GUIDANCE HIGHS FOR SAT SIMILAR AND APPEAR REASONABLE. WITH THE COOLER...DRIER HIGH BUILDING IN AND MOSTLY CLEAR SKIES...TRENDED SAT NIGHT LOWS DOWN ABOUT A CATEGORY TOWARD 21.00Z GFS MEX-MOS VALUES. .LONG TERM...SUNDAY THROUGH WEDNESDAY MEDIUM RANGE MODEL RUNS OF 21.00Z IN GOOD AGREEMENT WITH EACH OTHER AND THEIR PREVIOUS RUNS FOR SUN/MON. THUS GOOD CONSENSUS/FORECAST CONFIDENCE FOR A DRY/QUIET PERIOD OF WEATHER FOR SUN/MON AS DRIER HIGH PRESSURE SETTLES INTO THE REGION AND RIDGING ALOFT BUILDS EAST INTO CENTRAL NOAM. DID LOWER LOWS SUN NIGHT TO REFLECT THE COOLER... DRIER HIGH TO BE CENTERED NEAR/OVER THE AREA. BY TUE...ECMWF/GFS HAVE TRENDED TOWARD A WEAK UPPER TROUGH DEVELOPING OVER THE NORTHERN PLAINS...THEN MOVE THIS TROUGH ACROSS THE AREA WED. GFS STRONGER WITH MORE OF A LOW/MID LEVEL REFLECTION OF IT. MAY YET NEED A SMALL RAIN CHANCE WED IF THIS TREND CONTINUES. HOWEVER GFS ENSEMBLES AND MODEL CONSENSUS SUPPORTS THE GOING DRY FORECAST FOR TUE/WED AND DID NOT MAKE ANY CHANGES BEYOND SUN NIGHT FOR NOW. && .AVIATION...TODAY AND TONIGHT REMAINS OF THE SOUTHWEST U.S. CUT OFF LOW WILL LIFT NORTHEAST ACROSS THE AREA TODAY AND TONIGHT. DEEP GULF OF MEXICO MOISTURE WILL GRADUALLY WORK NORTH INTO THE AREA CAUSING CEILINGS TO LOWER THROUGH THE DAY BUT SHOULD REMAIN IN VFR HEIGHTS THROUGH 22.00Z. AFTER THAT...THE RICH LOW LEVEL MOISTURE IS EXPECTED TO ALLOW MVFR CEILINGS TO DEVELOP DURING THE EVENING WITH IFR CONDITIONS POSSIBLE STARTING AROUND 22.06Z. SCATTERED SHOWERS ARE EXPECTED TO DEVELOP DURING THE AFTERNOON AND CONTINUE INTO THE EARLY EVENING BEFORE BECOMING MORE ISOLATED IN COVERAGE. COULD BE SOME PERIODS OF MVFR VISIBILITY IN THESE SHOWERS. VERY LITTLE CAPE EXPECTED TO DEVELOP THIS AFTERNOON SO ANY THUNDERSTORMS SHOULD BE ISOLATED AND NO PLANS TO EVEN CARRY A CB QUALIFIER AT EITHER TAF SITE. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...RRS AVIATION..........04 wi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1219 PM CDT THU AUG 21 2008 .UPDATE... UPDATED FOR 18Z AVIATION DISCUSSION BELOW. && .DISCUSSION... /ISSUED 316 AM CDT THU AUG 21 2008/ THE CHALLENGE WITH THE FORECAST IS THE CHANCES OF PRECIP THROUGH TODAY AND FRI...AND ANY STRONG TO SEVERE POTENTIAL OF THUNDERSTORMS ON FRI. VERY UNIQUE UPPER LEVEL PATTERN FOR THIS TIME OF YEAR...WITH MORNING GOES WV LOOP REVEALING A LONG-LIVED UPPER LEVEL LOW NOW LIFTING NNE FROM THE OZARKS. SATELLITE AND PROFILERS INDICATING STILL A WELL DEFINED MID-LEVEL CIRCULATION WITH THIS AND RUC/NAM ANALYSES INDICATES A CONTINUED PV ANOMALY. TRAJECTORY OF THE H7 LOW/WAVE WOULD TAKE IT NNE ACROSS CENTRAL FORECAST AREA TODAY INTO TONIGHT. HAVE GENERALLY CONFINED POPS FOR TODAY TO THE EAST OF THIS TRACK...WHERE MID-LEVEL DIFLUENCE EXISTS ABOVE SATURATING UPGLIDE. ADIABATIC OMEGA AND QG FORCING ARE BOTH FAIRLY WEAK IN MAGNITUDE IN ERN MN AND WRN WI. CONVECTIVE PARAMETERS ARE ALSO VERY WEAK...WITH ONLY MINIMAL UPRIGHT CONVECTIVE POTENTIAL. SO HAVE SCT SHWRS AND ISOLD THUNDER IN THE ERN FORECAST AREA...MAINLY DURING THE AFTN AND EVE. HAVE SLIGHT CHANCES FOR SHRA/SPRINKLES TO THE WEST OF THIS. WRN MN LOOKS TO REMAIN DRY TODAY AND THIS EVE...WITH BREEZY CONDITIONS. NOT TOO FAR FROM WIND ADVISORY CRITERIA IN A FEW PLACES THERE THIS AFTN...GIVEN MSLP GRADIENT AND ISALLOBARIC INFLUENCE. MIXING WILL ALSO ALLOW SOME GUSTS TO 35-40 MPH ESPECIALLY IN SOME OF THE HIGHER LOCALES. TEMPS TODAY IN SE MN AND WRN WI WILL BE HINDERED GREATLY DUE TO THE CLOUD COVER...WITH POSSIBLY ONLY MID 70S FOR HIGHS IN PLACES. GIVEN SATELLITE TRENDS EARLY THIS MORNING AND FORECAST MODEL TIME HEIGHTS...IT APPEARS THAT STRATUS WILL DEVELOP TONIGHT IN ERN MN AND WRN WI IN THE WAKE OF SHOWERS. HAVE BUMPED UP CLOUD COVER AND ADJUSTED MIN TEMPS FOR THIS. THIS AFOREMENTIONED SYSTEM IS BEING CONSUMED AND FORCED NNE BY A LARGER...PROGRESSIVE..AND SIMPLY STRONGER SYSTEM PUSHING QUICKLY EAST ACROSS THE NW U.S./BRITISH COLUMBIA BORDER EARLY THIS MORNING. CONVECTION LOOKS TO DEVELOP ASSOCIATED WITH THIS IN ND THIS EVE. PARAMETERS ARE FAVORABLE FOR AN MCS BUT PROPAGATION WOULD TAKE ONE ENE...WELL NORTH OF THE CWA EARLY FRI MORNING. JUST A SMALL CHANCE FOR ISOLD ELEVATED CONVECTION ON THE LLJ LATE TONIGHT IN WRN MN. AS JET ROUNDS THE BASE OF THIS TROUGH ON FRIDAY...DEEP CYCLOGENSIS WILL OCCUR IN SOUTH CENTRAL CANADA FORCING COOL AND DRY AIR ADVECTION EASTWARD FROM THE NRN ROCKIES. THIS COLD FRONT /AND POSSIBLY PRE-FRONTAL TROUGH/ WILL ENTER THE FORECAST AREA FRI AFTN. STRONG CAP FORECAST FOR FRI MORNING AND EARLY AFTN. BUT CAP IS FORECAST TO WEAKEN OVER THE POOLED INSTABILITY AXIS ALONG THE FRONT. DIAGNOSTIC MODELS FORECAST MUCAPES 1500-2000 J/KG BUT SREF INDICATING PROBABILITIES OF SUCH VALUES ONLY AROUND 30 PERCENT. MORNING STRATUS MAY FURTHER INHIBIT FULL HEATING TO THESE VALUES. LAPSE RATES ARE ALSO NOT VERY FAVORABLE FOR EXPLOSIVE CONVECTIVE POTENTIAL. ON THE SHEAR SIDE OF THINGS...DEEP LAYER SHEAR IS MARGINAL BUT INCREASING ESPECIALLY DURING THE EVE. LOW LEVEL SHEAR IS STRONG...THANKS TO THE PERSISTENT LLJ. A PROBLEM WITH SUSTAINED STRONG CONVECTION IS THAT FRONT IS BEING STRETCHED OUT...WITH LOW SO FAR NORTH AND ANOTHER WAVE FURTHER SOUTHWEST ON THE FRONT IN THE CTRL PLAINS. SO CONVERGENCE BECOMES SOMEWHAT MINIMIZED. SOME SCT CONVECTION SEEMS LIKELY BY LATE FRI AFTN AND MORE SO DURING THE EVE...BUT WIDESPREAD STRONG CONVECTION AT THIS TIME SEEMS UNLIKELY. SOME SEVERE POSSIBLE THOUGH ESPECIALLY IF CONVECTION CAN ORGANIZE. THIS IS BECAUSE LOWER AND MID TROP WIND FIELD BEHIND THE FRONT IS STRONG AND UNIDIRECTIONAL FROM THE WNW. POSSIBLY A FEW STRONG MULTI-CELLED CLUSTERS. BEYOND...THE FRONT DOES APPEAR TO WANT TO STALL GIVEN A BACKUP OF THINGS IN THE ERN AND SRN PART OF THE COUNTRY...INCLUDING T.S. FAY. BUT ALL GUIDANCE INDICATES THIS WILL OCCUR PAST OUR AREA...MEANING A FAIRLY NICE AND SLIGHTLY COOLER THAN NORMAL WEEKEND. HAVE MADE LITTLE ADJUSTMENTS DURING THAT TIME INTO MONDAY. && .AVIATION.../18Z TAF ISSUANCE/ TOUGH SET OF TAFS...WITH STRONG WINDS...PRECIP CHANCES...AND FOG/STRATUS LIKELY. PLUME OF MOISTURE FROM THE GULF POURING INTO THE AREA...AS AN UPR LOW MOVES NEWRD ACRS THE AREA. 88D MOSAIC SHOWS BULK OF SHRA IN SE MN AND INTO ERN IA/SWRN WI ATTM...AND 305K ISEN ANALYSES PROJECT THIS TO REALLY ONLY AFFECT EAU SUBSTANTIALLY THIS AFTN/EVE. UPSTREAM CONDS BROUGHT ON BY UPR LOW SHOWED WIDESPREAD IFR CIGS...WITH LARGELY MVFR/OCCASIONAL IFR VSBYS. THIS AIRMASS SHUD SPREAD ACRS THE REST OF THE AREA OVRNGT...LEADING TO WIDESPREAD IFR CIGS FROM LATE EVE THRU EARLY TO MID MRNG TMRW. INCR PRES GRAD WILL LEAD TO HIGHER WINDS TMRW...AS COLD FRONT APPROACHES. AFT 18Z TMRW...ATTENTION TURNS TO CONVECTIVE POTENTIAL AS FRONT PUSHES EWRD. LIKELIHOOD OF TSRA BEST FROM STC EWRD DURG THE MID/LATE AFTN AND INTO THE EVE. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ MTF/KAT mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE FORT WORTH TX 131 PM CDT THU AUG 21 2008 .UPDATE... WILL ISSUE A QUICK UPDATE TO INCREASE POPS IN THE SOUTHWEST BASED ON CURRENT RADAR TRENDS. INSTABILITY SHOULD BE SUFFICIENT TO SUSTAIN SCATTERED SHOWERS/STORMS THROUGH SUNSET. NO OTHER MAJOR CHANGES AT THIS TIME. .79... && .AVIATION... 1233 PM DRY AIR CONTINUES TO WORK INTO THE MID-LEVELS OF THE ATMOSPHERE AS SUBSIDENCE BEHIND THE UPPER TROUGH MOVES IN. THE PRIMARY AREAS FOR PRECIP WILL BE EAST AND SOUTH OF THE METROPLEX WHERE THE BEST MOISTURE REMAINS. COVERAGE IS TOO LOW TO MENTION ANY PRECIP FOR THE METROPLEX TAFS BUT WILL MONITOR THE SITUATION THROUGHOUT THE AFTERNOON AND AMEND TAFS IF NECESSARY. DONT THINK WE WILL SEE A COMPLETE REPEAT OF THIS MORNINGS IFR CIGS AND MVFR VISIBILITIES. MOISTURE LAYER JUST OFF THE SURFACE WILL NOT BE AS DEEP AND SURFACE WIND SPEEDS WILL ALSO BE AROUND 8 KNOTS KEEPING THE AIR RELATIVELY MIXED. BUT WITH SATURATED SOILS...CANT RULE OUT SCT LOW CLOUDS AND SLIGHT RESTRICTIONS IN VISIBILITY. 85/NH && .UPDATE... FORECAST LOOKS ON TRACK...JUST MINOR CHANGES TO ACCOUNT FOR LATEST TRENDS IN CLOUDS/DEWPOINTS/WINDS. REMOVED POPS WEST OF I-35 AS AREA WILL BE UNDER A REGION OF INCREASING HEIGHTS/SUBSIDENCE THROUGH THE AFTERNOON HOURS. LOW LEVEL MOISTURE (THUS INSTABILITY) WILL REMAIN ACROSS THE EASTERN CWA...AND COUPLED WITH DRYING ALOFT THERE IS A LOW POTENTIAL FOR WET MICROBURSTS THIS AFTERNOON. COVERAGE OF CONVECTION SHOULD REMAIN NEAR OR LESS THAN 30 PERCENT GIVEN LACK OF DYNAMIC FORCING THAT HAD BEEN PRESENT THE LAST SEVERAL DAYS. TR.92 && .PREV DISCUSSION... /ISSUED 321 AM CDT THU AUG 21 2008/ THE UPPER LEVEL LOW THAT HAS BROUGHT BENEFICIAL BUT FLOODING RAINS TO NORTH TEXAS THE PAST FEW DAYS IS NOW SLIDING INTO KANSAS /PER RUC ANALYSIS/. THE ASSOCIATED TROUGH EXTENDS SOUTH ACROSS TEXAS WITH THE AXIS CENTERED OVER THE WESTERN HALF OF THE CWA. SOME WEAK SHORTWAVES CONTINUE TO MOVE AROUND THE BASE OF THE TROUGH. ONE SHORTWAVE IS NOW EXITING NORTHEAST TEXAS AND IS AIDING IN SHOWER AND THUNDERSTORM DEVELOPMENT IN OUR EXTREME NE CWA. A STRONGER SHORTWAVE IS FORECASTED TO SKIRT THE RED RIVER THIS AFTERNOON. THE BEST CHANCE FOR RAIN TODAY WILL BE ACROSS THE EASTERN HALF OF THE CWA...AHEAD OF THE TROUGH AXIS AND APPROACHING SHORTWAVE...WHERE LIFT WILL BE STRONGEST. ANOTHER POTENTIAL PLAYER FOR TODAY COULD BE THE LEFT OVER BOUNDARY/SURFACE TROUGH RUNNING NORTHEAST TO SOUTHWEST ACROSS ALMOST THE MIDDLE OF THE CWA. WITH SOME HEATING LATER TODAY...SHOWERS AND THUNDERSTORMS MAY DEVELOP ALONG THAT BOUNDARY OR ANY OTHER RESIDUAL BOUNDARIES. HOWEVER...WILL HAVE THE HIGHEST POPS IN THE EAST. PWATS WILL REMAIN NEAR 2 INCHES IN THE EAST SO HEAVY RAINFALL IS STILL A THREAT TODAY IN THAT AREA. THE WEATHER PATTERN OVER THE NEXT SEVERAL DAYS WILL REMAIN SOMEWHAT UNSETTLED AS THE REMNANTS OF THE UPPER LEVEL LOW NEVER REALLY LEAVE THE REGION AND THE UPPER LEVEL RIDGE TO THE WEST NEVER REALLY BUILDS IN. THE UPPER LEVEL RIDGE ONLY MAKES IT AS FAR AS THE TEXAS PANHANDLE BEFORE BEING HALTED. ALL MODELS ARE IN GOOD AGREEMENT THAT ENERGY FROM THE TROUGH WILL REMAIN OVER NORTHEAST TEXAS AND THEN DRIFT BACK OVER NORTH TEXAS OVER THE NEXT SEVERAL DAYS. THUS WILL KEEP 20-30 POPS IN THE FORECAST THROUGH THE WEEKEND WITH BEST CHANCE FOR RAIN AGAIN IN THE EAST AND SOUTHEAST. SUNDAY LOOKS TO BE THE NEXT BEST CHANCE FOR RAIN ACROSS ALL OF NORTH TEXAS WITH THE HIGHEST POPS ALONG THE RED RIVER. BY MONDAY...THE UPPER LEVEL RIDGE GETS NUDGED BACK WEST AS FAY MOVES INTO THE CENTRAL GOM COAST AND NORTHERLY FLOW ALOFT SETS UP. MODELS SUGGEST THAT SEVERAL WEAK DISTURBANCES WILL RIDE THE NORTHERLY FLOW INTO TEXAS AND WILL CONTINUE 20 POPS FOR THE AFTERNOON/EVENING HOURS THROUGH THE REMAINDER OF THE FORECAST. HAVE STUCK CLOSE TO GUIDANCE FOR HIGH TEMPERATURES IN THE BEGINNING OF THE FORECAST AND THEN UNDERCUT GUIDANCE A DEGREE OR TWO FOR THE LAST FEW DAYS. HIGH TEMPERATURES WILL MOSTLY TOP OUT IN THE 90S WITH A FEW SCATTERED UPPER 80S THIS WEEKEND. REASON FOR UNDERCUTTING GUIDANCE ON DAYS 6 AND 7 WAS THOUGHT MOS TEMPS WERE TOO HIGH FOR NORTHERLY FLOW. OVERNIGHT LOWS WILL CONTINUE TO BE IN THE UPPER 60S TO MID 70S. 82/JLD && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 91 74 94 75 92 / 20 10 10 10 30 WACO, TX 92 72 93 74 92 / 10 10 20 10 30 PARIS, TX 87 70 91 71 90 / 40 10 30 10 30 DENTON, TX 91 72 93 72 92 / 20 10 10 10 30 MCKINNEY, TX 91 71 91 71 92 / 20 10 10 10 30 DALLAS, TX 91 72 92 73 92 / 20 10 10 10 30 TERRELL, TX 91 72 94 73 91 / 20 10 20 10 30 CORSICANA, TX 91 72 93 73 93 / 20 10 20 10 30 TEMPLE, TX 92 71 95 73 91 / 10 10 20 10 30 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 85/92/25 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE FORT WORTH TX 1233 PM CDT THU AUG 21 2008 .AVIATION... DRY AIR CONTINUES TO WORK INTO THE MID-LEVELS OF THE ATMOSPHERE AS SUBSIDENCE BEHIND THE UPPER TROUGH MOVES IN. THE PRIMARY AREAS FOR PRECIP WILL BE EAST AND SOUTH OF THE METROPLEX WHERE THE BEST MOISTURE REMAINS. COVERAGE IS TOO LOW TO MENTION ANY PRECIP FOR THE METROPLEX TAFS BUT WILL MONITOR THE SITUATION THROUGHOUT THE AFTERNOON AND AMEND TAFS IF NECESSARY. DONT THINK WE WILL SEE A COMPLETE REPEAT OF THIS MORNINGS IFR CIGS AND MVFR VISIBILITIES. MOISTURE LAYER JUST OFF THE SURFACE WILL NOT BE AS DEEP AND SURFACE WIND SPEEDS WILL ALSO BE AROUND 8 KNOTS KEEPING THE AIR RELATIVELY MIXED. BUT WITH SATURATED SOILS...CANT RULE OUT SCT LOW CLOUDS AND SLIGHT RESTRICTIONS IN VISIBILITY. 85/NH && .UPDATE... FORECAST LOOKS ON TRACK...JUST MINOR CHANGES TO ACCOUNT FOR LATEST TRENDS IN CLOUDS/DEWPOINTS/WINDS. REMOVED POPS WEST OF I-35 AS AREA WILL BE UNDER A REGION OF INCREASING HEIGHTS/SUBSIDENCE THROUGH THE AFTERNOON HOURS. LOW LEVEL MOISTURE (THUS INSTABILITY) WILL REMAIN ACROSS THE EASTERN CWA...AND COUPLED WITH DRYING ALOFT THERE IS A LOW POTENTIAL FOR WET MICROBURSTS THIS AFTERNOON. COVERAGE OF CONVECTION SHOULD REMAIN NEAR OR LESS THAN 30 PERCENT GIVEN LACK OF DYNAMIC FORCING THAT HAD BEEN PRESENT THE LAST SEVERAL DAYS. TR.92 && .PREV DISCUSSION... /ISSUED 321 AM CDT THU AUG 21 2008/ THE UPPER LEVEL LOW THAT HAS BROUGHT BENEFICIAL BUT FLOODING RAINS TO NORTH TEXAS THE PAST FEW DAYS IS NOW SLIDING INTO KANSAS /PER RUC ANALYSIS/. THE ASSOCIATED TROUGH EXTENDS SOUTH ACROSS TEXAS WITH THE AXIS CENTERED OVER THE WESTERN HALF OF THE CWA. SOME WEAK SHORTWAVES CONTINUE TO MOVE AROUND THE BASE OF THE TROUGH. ONE SHORTWAVE IS NOW EXITING NORTHEAST TEXAS AND IS AIDING IN SHOWER AND THUNDERSTORM DEVELOPMENT IN OUR EXTREME NE CWA. A STRONGER SHORTWAVE IS FORECASTED TO SKIRT THE RED RIVER THIS AFTERNOON. THE BEST CHANCE FOR RAIN TODAY WILL BE ACROSS THE EASTERN HALF OF THE CWA...AHEAD OF THE TROUGH AXIS AND APPROACHING SHORTWAVE...WHERE LIFT WILL BE STRONGEST. ANOTHER POTENTIAL PLAYER FOR TODAY COULD BE THE LEFT OVER BOUNDARY/SURFACE TROUGH RUNNING NORTHEAST TO SOUTHWEST ACROSS ALMOST THE MIDDLE OF THE CWA. WITH SOME HEATING LATER TODAY...SHOWERS AND THUNDERSTORMS MAY DEVELOP ALONG THAT BOUNDARY OR ANY OTHER RESIDUAL BOUNDARIES. HOWEVER...WILL HAVE THE HIGHEST POPS IN THE EAST. PWATS WILL REMAIN NEAR 2 INCHES IN THE EAST SO HEAVY RAINFALL IS STILL A THREAT TODAY IN THAT AREA. THE WEATHER PATTERN OVER THE NEXT SEVERAL DAYS WILL REMAIN SOMEWHAT UNSETTLED AS THE REMNANTS OF THE UPPER LEVEL LOW NEVER REALLY LEAVE THE REGION AND THE UPPER LEVEL RIDGE TO THE WEST NEVER REALLY BUILDS IN. THE UPPER LEVEL RIDGE ONLY MAKES IT AS FAR AS THE TEXAS PANHANDLE BEFORE BEING HALTED. ALL MODELS ARE IN GOOD AGREEMENT THAT ENERGY FROM THE TROUGH WILL REMAIN OVER NORTHEAST TEXAS AND THEN DRIFT BACK OVER NORTH TEXAS OVER THE NEXT SEVERAL DAYS. THUS WILL KEEP 20-30 POPS IN THE FORECAST THROUGH THE WEEKEND WITH BEST CHANCE FOR RAIN AGAIN IN THE EAST AND SOUTHEAST. SUNDAY LOOKS TO BE THE NEXT BEST CHANCE FOR RAIN ACROSS ALL OF NORTH TEXAS WITH THE HIGHEST POPS ALONG THE RED RIVER. BY MONDAY...THE UPPER LEVEL RIDGE GETS NUDGED BACK WEST AS FAY MOVES INTO THE CENTRAL GOM COAST AND NORTHERLY FLOW ALOFT SETS UP. MODELS SUGGEST THAT SEVERAL WEAK DISTURBANCES WILL RIDE THE NORTHERLY FLOW INTO TEXAS AND WILL CONTINUE 20 POPS FOR THE AFTERNOON/EVENING HOURS THROUGH THE REMAINDER OF THE FORECAST. HAVE STUCK CLOSE TO GUIDANCE FOR HIGH TEMPERATURES IN THE BEGINNING OF THE FORECAST AND THEN UNDERCUT GUIDANCE A DEGREE OR TWO FOR THE LAST FEW DAYS. HIGH TEMPERATURES WILL MOSTLY TOP OUT IN THE 90S WITH A FEW SCATTERED UPPER 80S THIS WEEKEND. REASON FOR UNDERCUTTING GUIDANCE ON DAYS 6 AND 7 WAS THOUGHT MOS TEMPS WERE TOO HIGH FOR NORTHERLY FLOW. OVERNIGHT LOWS WILL CONTINUE TO BE IN THE UPPER 60S TO MID 70S. 82/JLD && .PRELIMINARY POINT TEMPS/POPS... DALLAS-FT. WORTH, TX 91 74 94 75 92 / 20 10 10 10 30 WACO, TX 92 72 93 74 92 / 10 10 20 10 30 PARIS, TX 87 70 91 71 90 / 40 10 30 10 30 DENTON, TX 91 72 93 72 92 / 20 10 10 10 30 MCKINNEY, TX 91 71 91 71 92 / 20 10 10 10 30 DALLAS, TX 91 72 92 73 92 / 20 10 10 10 30 TERRELL, TX 91 72 94 73 91 / 20 10 20 10 30 CORSICANA, TX 91 72 93 73 93 / 20 10 20 10 30 TEMPLE, TX 92 71 95 73 91 / 10 10 20 10 30 && .FWD WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 85/92/25 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 338 PM CDT THU AUG 21 2008 .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT PRECIPITATION CHANCES FROM TONIGHT THROUGH SATURDAY ARE THE PRIMARY CONCERNS FOR THIS PART OF THE FORECAST. AT 3 PM...A 500 MB SHORT WAVE TROUGH WAS MOVING NORTH INTO SOUTHERN IOWA AND NORTHERN ILLINOIS. THIS SYSTEM WAS SPREADING LIGHT TO MODERATE RAIN NORTHWARD INTO THE FORECAST AREA. THE 21.12Z MODELS ARE IN FAIRLY GOOD AGREEMENT THAT THIS SYSTEM WILL MOVE NORTH INTO OUR AREA THIS EVENING...AND EXIT THE REGION TOWARD SUNRISE ON FRIDAY. AS THIS SYSTEM CONTINUES TO MOVE NORTHWARD... THIS GRADUALLY WEAKENS. AS A RESULT...I PLACED THE HIGHEST PRECIPITATION PROBABILITIES IN THE FORECAST FOR THIS EVENING...AND THEN WENT WITH JUST CHANCE PROBABILITIES AFTER MIDNIGHT. WITH THE BEST FORCING LOCATED ACROSS WISCONSIN...I WENT WITH MY HIGHER CHANCE PROBABILITIES ACROSS WESTERN WISCONSIN. ON FRIDAY...THE MODELS ARE SOMEWHAT CAUGHT BETWEEN SYSTEM. A MUCH WEAKER UPPER LEVEL SYSTEM WILL BE MOVING NORTHWARD THROUGH THE WESTERN GREAT LAKES...AND A MUCH STRONGER 500 MB SHORT WAVE MOVING INTO WESTERN ONTARIO AND WESTERN MINNESOTA. AS A RESULT...I HAVE JUST HAVE SLIGHT CHANCE TO CHANCE PRECIPITATION PROBABILITIES INTO THE FORECAST. ON FRIDAY NIGHT AND SATURDAY...THE MODELS ARE CONSISTENTLY SHOWING THAT A POSITIVELY TILTED 500 MB WAVE WILL MOVING THROUGH ONTARIO AND NORTHERN GREAT LAKES. MUCH OF THE SYNOPTIC FORCING LOOKS TO BE NORTH OF THE AREA. AS A RESULT...THE PRECIPITATION AMOUNTS AND CHANCES ARE STARTING TO LOOK LESS THAN WHAT THEY WERE A COUPLE OF DAYS AGO. I WAS REALLY TEMPTED TO LOWER THE PRECIPITATION PROBABILITIES INTO THE CHANCE RANGE. HOWEVER FOR CONSISTENCY SAKE AND THERE STILL BEING A CHANCE THAT THE MODELS MAY REVERT BACK TO THEIR ORIGINAL SOLUTION...I HELD OFF MAKING TOO MANY CHANGES TO THESE TIME PERIODS. .LONG TERM...SUNDAY THROUGH THURSDAY THE 21.12Z MEDIUM RANGE MODELS ARE IN FAIRLY GOOD AGREEMENT THAT A 500 MB RIDGE WILL BE IN CONTROL OF THE WEATHER THROUGH TUESDAY NIGHT... AND THEN THEY START TO CARVE OUT 500 MB TROUGH ACROSS THE PLAINS AND THE UPPER MISSISSIPPI RIVER VALLEY. THE ECMWF IS MUCH FASTER THAN ITS 21.00Z SOLUTION AND ALSO THE GFS AND GEM. THE GENERATION OF THIS TROUGH MAKES A LOT OF SENSE WHEN ONE LOOKS AT THE VARIOUS STRONG TROPICAL FORCING FEATURES ARE LOCATED AROUND THE GLOBE. THE MODELS TYPICALLY DO NOT HANDLE THESE SITUATIONS THAT WELL...SO THIS LEADS TO MUCH UNCERTAINTY IN THIS PART OF THE FORECAST. AT THIS TIME...IT LOOKS LIKE THE BEST PROBABILITY OF PRECIPITATION LOOKS TO BE FROM WEDNESDAY INTO THURSDAY. IN ADDITION THERE IS QUITE A BIT OF UNCERTAINTY WHERE THE REMNANTS OF TROPICAL STORM FAY WILL END UP NEXT WEEK. THE GEM SUGGEST THAT THIS MOISTURE MAY END UP IN OUR AREA ON THURSDAY. MEANWHILE MANY OF THE OTHER MEDIUM RANGE MODELS SUGGEST THE TENNESSEE AND OHIO VALLEYS WILL BE AFFECTED ANYWHERE FROM WEDNESDAY INTO THURSDAY. && .AVIATION...TONIGHT THROUGH FRIDAY MORNING AN UPPER LEVEL DISTURBANCE OVER THE CENTRAL PLAINS WILL CONTINUE TO MOVE NORTHWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION THIS AFTERNOON AND INTO TONIGHT. LATEST MOSAIC RADAR INDICATED A SHIELD OF PRECIPITATION EXTENDED FROM SOUTHEASTERN MINNESOTA TO NORTHERN MINNESOTA. VISIBILITIES UNDERNEATH PRECIPITATION WERE RANGING FROM 2SM TO 5SM AND CEILINGS VARIED FROM BELOW A 1000 FEET TO 5000 FEET. LIMITED INSTABILITY ASSOCIATED WITH THE UPPER LEVEL DISTURBANCE...HAVE NO MENTION OF THUNDER AT BOTH TAF SITES THIS AFTERNOON AND INTO TONIGHT. WITH THE ABUNDANT LOW LEVEL MOISTURE AND UPPER LEVEL DISTURBANCE TRACKING NORTH INTO BOTH TAF SITES. BEGAN LOWERING CEILINGS AND VISIBILITIES TO MVFR CONDITIONS BY 20Z THURSDAY. LATEST RUC AND NAM INDICATE INVERSION DEVELOPING OVER THE REGION LATE THIS EVENING. WITH DECENT AMOUNT OF LOW LEVEL MOISTURE...HAVE LOWERED CEILINGS TO IFR CONDITIONS AT BOTH LSE AND RST TAF SITES BY 04Z AND 05Z FRIDAY. A TIGHT PRESSURE GRADIENT DEVELOPS OVER THE AREA FRIDAY MORNING. HAVE INTRODUCED WIND GUSTS UP TO 23 KNOTS AT RST AFTER 15Z. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ AVIATION - DTJ SHORT AND LONG TERM - BOYNE wi