Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 020315 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1115 PM EDT MON SEP 1 2014 .SYNOPSIS... SOUTHERLY RETURN FLOW AROUND HIGH PRESSURE WILL RESULT IN WARM AND MUGGY CONDITIONS THROUGH TUESDAY. A COLD FRONT IS THEN EXPECTED TO MOVE ACROSS OUR AREA LATE TUESDAY AND EARLY WEDNESDAY. HIGH PRESSURE WILL BUILD IN BEHIND THIS FRONT BEGINNING WEDNESDAY AFTERNOON. ANOTHER COLD FRONT COULD APPROACH FROM THE WEST EARLY SATURDAY, BEFORE STALLING NEAR OR JUST SOUTH OF OUR REGION BY SUNDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A WARM AND MUGGY NIGHT FOR THE ENTIRE REGION. DESPITE A LACK OF ANY ORGANIZED FORCING, SOME SHOWERS HAVE DEVELOPED AND ARE MOVING TOWARD OUR WESTERN ZONES. THESE ARE ISOLATED, AND APPEAR TO BE TIED TO A SUBTLE WAA PUSH IN COMBINATION WITH LINGERING INSTABILITY. THE AIRMASS IS BUOYANT OWING TO THE MUGGY AND WARM BOUNDARY LAYER AND THEREFORE IT WILL NOT TAKE MUCH TO POP A FEW SHOWERS. OUR CONFIDENCE LOWERS WITH AN EASTWARD EXTENT, THEREFORE DID NOT BRING THE SLIGHT CHC POPS TO FAR EAST ATTM. WE WILL MONITOR RADAR TRENDS IN THE EVENT AN EXPANSION TO THE LOW POPS IS NEEDED. OVERALL, ANY SHOWERS ARE ANTICIPATED TO BE RATHER ISOLATED AND BRIEF. OTHERWISE, SOME CLOUDS AND PATCHY FOG THROUGH THE OVERNIGHT. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... FOR TUESDAY...OVERALL CONDS WILL BE SIMILAR TO LABOR DAY...BUT THE AIRMASS WILL BE SLIGHTLY WARMER WITH 850MB TEMPS A DEGREES OR TWO HIGHER. THUS AFTN MAX TEMPS ARE FCST TO REACH 90 OR LOW 90S IN MANY LOCS...ESP FROM PHL S AND E. SFC DEWPTS ARE FCST TO BE SLIGHTLY LOWER THAN TODAY...BUT APPARENT TEMPS WILL STILL BE UP IN THE LOWER TO MID 90S. A WELL-DEFINED UPPER-LEVEL SHORTWV TROF WILL BE APPROACHING FROM THE WEST ON TUESDAY...AND THE ASSOCD SFC COLD FRONT SHOULD BE PUSHING INTO NW PA BY AFTN. MOS GUIDANCE PLUS MODEL UVV/QPF SUGGESTS THAT THE BULK OF THE FRONTAL PRECIP/CNVTN WILL NOT REACH ERN PA UNTIL AFTER 00Z WED. HWVR...CANNOT RULE OUT SOME PRE-FRONTAL TROF CONVTN SO HAVE INCLUDED SLGT-CHC TO CHC POPS INCREASING FROM W TO E FOR TMRW AFTN. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... TUESDAY NIGHT...THE GFS SHOWED A SLIGHTLY SLOWER SOLUTION WITH THE LATEST RUN, NOW WITH THE COLD FRONT ARRIVING IN SE PA BY LATE EVENING, THE COASTAL WATERS BY WEDNESDAY MORNING. GIVEN THE RATHER LATE ARRIVAL OF THE FRONT, INSTABILITY SHOULD BE BE MINIMAL. ALSO, THE UPPER LEVEL SHORT WAVE TROUGH SHOULD STAY WELL TO THE NORTH OF THE REGION RESULTING IN LIMITED SYNOPTIC SCALE LIFT. THUS...DESPITE THE SLIGHT RISK FOR SEVERE STORMS TO OUR WEST, THINK THE SEVERE THREAT WITHIN OUR REGION WILL BE MINIMAL. WEDNESDAY AND THURSDAY...THOUGH THERE WON`T BE SIGNIFICANT COLD AIR ADVECTION BEHIND THE FRONT, THERE WILL BE CONSIDERABLE DRY AIR ADVECTION, ALBEIT SHORT LIVED. THUS, WHILE HIGHS WILL STILL BE ABOVE NORMAL, IT WILL FEEL A BIT MORE PLEASANT WITH HEAT INDEX VALUES NEAR AIR TEMPERATURES. FRIDAY INTO SUNDAY...AS THE SURFACE HIGH SLIDES OFF SHORE FRIDAY, THE REGION WILL ONCE AGAIN SEE LOW LEVEL MOIST FLOW AHEAD OF THE NEXT COLD FRONT. THE COLD FRONT IS SET TO ARRIVE SATURDAY...THOUGH THERE HAS BEEN POOR RUN TO RUN CONSISTENCY ON THE TIMING OF THE FRONT. AN ADDED COMPLICATION IS THAT BOTH THE GFS AND ECMWF CONTINUE TO SHOW THE FRONT STALLING, EITHER OVER OUR REGION OR JUST SOUTH OF THE REGION. DEPENDING ON HOW FAR NORTH IT STALLS, THE REGION COULD BE UNDER MOIST ON SHORE/UPSLOPE FLOW THROUGH EARLY NEXT WEEK. FOR NOW, HAVE STAYED CLOSE TO THE PREVIOUS FORECAST CONSIDERING THE UNCERTAINTY. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR IN GENERAL. LIGHT SOUTHWESTERLY WINDS, BECOMING CALM AT SEVERAL TERMINALS. PATCHY FOG SHOULD DEVELOP ESPECIALLY TOWARD DAYBREAK, HOWEVER THIS COULD BE DISRUPTED AT TIMES WITH SOME CLOUDS MOVING THROUGH. WITH SUCH A MUGGY AIRMASS IN PLACE, TEMPORARY IFR POSSIBLE TOWARD DAYBREAK TUESDAY MORNING AT THE FOG-PRONE TERMINALS SUCH AS KRDG/KMIV/KABE IF BREAKS IN THE CLOUD COVER PERSISTS LONG ENOUGH. AN ISOLATED SHOWER AROUND MAINLY WEST OF KPHL. TUESDAY, S-SW WINDS INCREASE DURING THE DAY AS THE PRESSURE GRADIENT INCREASES AHEAD OF A COLD FRONT THAT IS APPROACHING FROM THE WEST. CHANCES FOR SHRA/TSRA DELAYED UNTIL LATE IN THE DAY TUE WITH ARRIVAL OF FRONT NOT EXPECTED UNTIL TUE NGT. THIS FAR OUT, INCLUDED A PROB30 GROUP FOR SHRA IN THE 00Z TAFS STARTING AFTER 20Z FOR ONLY THE WESTERN TERMINALS /KRDG AND KABE/. OUTLOOK... TUESDAY NIGHT...THUNDERSTORMS AND AN ABRUPT WIND SHIFT POSSIBLE WITH A COLD FRONT THAT WILL MOVE THROUGH OVERNIGHT. MVFR CEILINGS AND VISIBILITIES AS LOW AS IFR WILL BE POSSIBLE WITH ANY THUNDERSTORMS. OTHERWISE VFR CONDITIONS EXPECTED. WEDNESDAY THROUGH FRIDAY...VFR CONDITIONS EXPECTED. FRIDAY NIGHT INTO SATURDAY...AS A COLD FRONT MOVES IN FROM THE WEST...IFR CONDITIONS AND THUNDERSTORMS POSSIBLE. && .MARINE... SUB SCA CONDS ARE EXPECTED THROUGH TUESDAY. SW WINDS WILL CONTINUE AROUND THE SUMMERTIME BERMUDA WITH AT 10 TO 15 KT OR SO. SEAS WILL BE IN THE 2 TO 4 FT RANGE OVER THE COASTAL WATERS. CHANCES FOR SHOWERS AND TSTMS LATE IN THE AFTN TUE AS A COLD FRONT APPROACHES FROM THE WEST. OUTLOOK... TUESDAY NIGHT...THOUGH SEAS SHOULD REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA, GUSTY WINDS WILL BE POSSIBLE IN THE VICINITY OF ANY STORMS THAT DEVELOP WITH THE COLD FRONT. WEDNESDAY THROUGH FRIDAY...WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA. FRIDAY NIGHT INTO SATURDAY...SEAS SHOULD REMAIN JUST BELOW SCA CRITERIA. GUSTY WINDS WILL BE POSSIBLE IN THE VICINITY OF ANY STORMS THAT DEVELOP. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...JOHNSON/KLEIN NEAR TERM...GORSE SHORT TERM...AMC LONG TERM...JOHNSON AVIATION...AMC/JOHNSON/KLEIN MARINE...AMC/JOHNSON/KLEIN

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