Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 021932 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 332 PM EDT TUE SEP 2 2014 .SYNOPSIS... A COLD FRONT WILL CROSS THE REGION TONIGHT. HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE WEST AND PERSIST THROUGH FRIDAY. ANOTHER COLD FRONT WILL CROSS THE REGION ON SATURDAY AND THEN STALL TO THE SOUTH OF OUR AREA. HIGH PRESSURE WILL BUILD ACROSS THE GREAT LAKES REGION AND THEN SLIDE ACROSS TO THE NORTH OF THE REGION EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... FRONT IS JUST NOW MOVING OFF THE GREAT LAKES INTO FAR WESTERN PA. DO NOT EXPECT IT TO MAKE ITS ARRIVAL MUCH BEFORE 06Z. HIGH RES MODELS LIKE THE HRRR HAVE BEEN CONSISTENT IN SHOWING A LINE OF CONVECTION MOVING IN AHEAD OF THE FRONT LATE THIS EVENING. HOWEVER, BY THAT TIME, INSTABILITY SHOULD BE WANING AND THERE COULD BE A SMALL BOUNDARY LAYER INVERSION. THUS, THE LINE SHOULD BE DISSIPATING AS IT MOVES THROUGH THE REGION. PWATS ARE STILL WELL ABOVE NORMAL, SO LOCALIZED HEAVY RAIN WILL BE POSSIBLE. WHILE THE HIGHEST SHEAR VALUES SHOULD REMAIN NW OF OUR REGION, COULD SEE A FEW STRONG WINDS GUSTS WHEN THE FRONT INITIALLY ARRIVES IN SOUTHEAST PA BUT THAT THREAT SHOULD BE SHORT LIVED AS WE TRANSITION FROM SURFACE BASED TO ELEVATED INSTABILITY. GIVEN THE VERY LATE ARRIVAL OF THE COLD FRONT, AND THE FACT THAT THE TEMPERATURE GRADIENT ACROSS THE FRONT IS RATHER SMALL, MINS TONIGHT SHOULD NOT BE TOO MUCH LOWER THAN THEY WERE THIS MORNING. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... AS MENTIONED PREVIOUSLY, THERE WON`T BE A LARGE DIFFERENCE IN THE TEMPERATURES POST FRONTAL (HIGHS WILL GENERALLY BE IN THE 80S ACROSS THE REGION). HOWEVER, WHAT THE FRONT WILL BE BRINGING IS CONSIDERABLE DRY AIR ADVECTION. DEW POINTS INTO THE UPPER 50S AND LOWER 60S ACROSS THE REGION BY TOMORROW AFTERNOON. THUS, WHILE HEAT INDEX VALUES HAVE BEEN ABOUT 5 DEGREES ABOVE AIR TEMPERATURE TODAY, BY TOMORROW, HEAT INDEX VALUES WILL BE RIGHT AT THE AIR TEMPERATURES. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... WEDNESDAY NIGHT THROUGH FRIDAY...HIGH PRESSURE DOMINATES OUR WEATHER THROUGH THE END OF THE WEEK AS IT SHIFTS JUST TO TOUR SOUTH AND EAST LATE WEDNESDAY THROUGH FRIDAY. THIS WILL KEEP US IN A MORE SOUTH TO SOUTHWESTERLY FLOW AND IN RETURN WE WILL CONTINUE TO SEE AN INCREASE IN MOISTURE ACROSS THE REGION. TEMPERATURES WILL CONTINUE TO MIMIC MORE OF MID SUMMER AS OPPOSED TO LATE SUMMER AND WE WILL SEE MAX TEMPS REACH INTO THE UPPER 80S TO AROUND 90 ON BOTH THURSDAY AND FRIDAY. SATURDAY...THE HIGH SHIFTS FURTHER OFFSHORE AND WE WILL BE AWAITING THE PASSAGE OF A COLD FRONT THROUGH THE DAY. THE FRONT APPEARS TO BE SLOW MOVING AND MAY TAKE ALL DAY TO CROSS FROM THE NORTHWESTERN PORTIONS OF THE AREA AND THEN THROUGH THE SOUTHERN MOST POINTS. WE WILL LIKELY SEE A PRE-FRONTAL TROUGH DEVELOP ACROSS THE AREA AND THIS WILL LIKELY HELP SERVE AS A FOCUS FOR ANY PRE-FRONTAL CONVECTION AND SHOWERS. SATURDAY WILL BE THE LAST DAY OF THIS HEAT WAVE AS COOLER AIR BEHIND THE FRONT WILL DROP TEMPS QUITE A BIT. SUNDAY...THE FRONT IS SLOW ENOUGH THAT WE MAY NOT SEE IT CLEAR THE DELMARVA AREA UNTIL SUNDAY MORNING. AS THE FRONT PUSHES SOUTH, THE QUESTION WILL BE, WHERE WILL THE FRONT STALL? CURRENT MODEL GUIDANCE INDICATES THAT THE FRONT WILL HAVE ENOUGH OF A PUSH TO GET SOUTH OF OUR AREA, WHICH SHOULD ALLOW FOR SOME COOLER AND DRIER AIR TO INFILTRATE OUR REGION. THE SLOW NATURE OF THE FRONT WILL ALLOW FOR SHOWERS TO CONTINUE, ESPECIALLY FURTHER SOUTH, INTO SUNDAY. AS THE FRONT PUSHES FURTHER SOUTH, ANY LINGERING SHOWERS SHOULD END FROM NORTH TO SOUTH. WITH HIGH PRESSURE BUILDING INTO THE GREAT LAKES AREA AND THE STALLED BOUNDARY TO OUR SOUTH, WE WILL BE IN A MORE EASTERLY FLOW REGIME WITH MOSTLY CLOUDY SKIES. THIS WILL ALLOW US TO BE COOLER ACROSS THE AREA. TEMPERATURES WILL ONLY MAKE IT INTO THE 70S THROUGH THE REGION AND IT WILL TRULY FEEL LIKE FALL OUT THERE. MONDAY THROUGH TUESDAY...THE BOUNDARY REMAINS STALLED TO OUR SOUTH BUT AS WE HEAD INTO MONDAY, A WAVE DEVELOPS ALONG IT AND IT STARTS TO MOVE A BIT. IT CURRENTLY LOOKS LIKE THE WAVE HELPS MOVE THE FRONT SLIGHTLY NORTH AND THEN TO THE EAST, KEEPING THE MAIN BOUNDARY TO OUR SOUTH. COOLER TEMPERATURES WILL CONTINUE ON MONDAY AND TUESDAY WITH HIGHS INTO THE MID TO UPPER 70S, WITH SOME LOWER 80S POSSIBLE AS SKIES CLEAR OUT AND WE START TO SEE MORE SUNSHINE. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. ISOLATED TSRA WILL BE POSSIBLE THROUGH 00Z THIS EVENING. HOWEVER, THINK THE BULK OF THE THUNDERSTORM ACTIVITY SHOULD REMAIN WEST OF THE REGION. THE COVERAGE THROUGH THIS TIME IS TOO LIMITED TO MENTION IN MOST OF THE TAFS FOR NOW. STARTING AROUND 00Z, WE SHOULD SEE A LINE OF SHRA AND TSRA MOVE INTO THE REGION FROM THE WEST. HIGH RESOLUTION MODELS HAVE BEEN CONSISTENT IN SHOWING THIS GENERAL PATTERN AND TIMING. HOWEVER, THERE IS SOME QUESTION OF THE SOUTHERN EXTENT OF THE LINE (WHICH MAY NOT GO SOUTH OF PHL), AND IF THE LINE WILL START TO SCT BEFORE IT REACHES THE DELAWARE RIVER VALLEY. THEREFORE HAVE INCLUDED A TEMPO FOR THE SE PA SITES (KRDG AND KABE) AND KTTN WHERE THERE IS HIGHER CONFIDENCE, BUT ONLY HAVE MENTION OF VCSH FOR MOST OF THE REST OF THE SITES. ONCE THE FRONT MOVES THROUGH AFTER 06Z, EXPECT NORTHWESTERLY WINDS AND GENERALLY VFR CONDITIONS. THERE IS A SMALL RISK OF BR DEVELOPMENT BUT WITH DRY AIR ADVECTION BEHIND THE FRONT, THINK THIS IS UNLIKELY. OUTLOOK... WEDNESDAY NIGHT THROUGH FRIDAY... MAINLY VFR CONDITIONS EXPECTED. SOME FOG IS POSSIBLE WHICH MAY CAUSE MVFR/IFR CONDITIONS ON THU AND FRI MORNINGS. SATURDAY THROUGH SUNDAY...MAINLY VFR CONDITIONS EXPECTED WITH MVFR/IFR CONDITIONS POSSIBLE IN SHOWERS AND THUNDERSTORMS. && .MARINE... SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH TOMORROW. GUSTY WINDS WILL BE POSSIBLE IN THE VICINITY OF ANY THUNDERSTORMS THIS AFTERNOON AND TONIGHT. AN ABRUPT WIND SHIFT TO NORTHWESTERLY WINDS IS EXPECTED WITH A COLD FRONT THAT WILL MOVE THROUGH LATE TONIGHT. HOWEVER, WIND GUSTS SHOULD REMAIN WELL BELOW 20KT EVEN WITH THE FRONT. OUTLOOK... WEDNESDAY NIGHT THROUGH SUNDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED. SOME STRONGER GUSTS AND HIGHER WAVES ARE POSSIBLE IN SHOWERS AND THUNDERSTORMS, MAINLY IN THE SATURDAY/SUNDAY TIMEFRAME. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...MEOLA NEAR TERM...JOHNSON SHORT TERM...JOHNSON LONG TERM...MEOLA AVIATION...JOHNSON/MEOLA MARINE...JOHNSON/MEOLA

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