Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 290100 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 900 PM EDT SAT MAR 28 2015 .SYNOPSIS... A HIGH PRESSURE SYSTEM OVER THE GREAT LAKES WILL SINK SOUTHEAST AND REACH THE SOUTHEAST COAST SUNDAY. A COLD FRONT WILL MOVE THROUGH THE REGION ON MONDAY. ON ITS HEALS WILL BE A FAST MOVING LOW PRESSURE SYSTEM WHICH SHOULD SWEEP THROUGH THE AREA TUESDAY. HIGH PRESSURE WILL BUILD INTO THE REGION FOR WEDNESDAY. ANOTHER COLD FRONT IS EXPECTED LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... SNOW SHOWERS AND FLURRIES ARE CONTINUING TO DISSIPATE ACROSS THE SOUTHERN PORTIONS OF THE AREA AS INSTABILITY BEGINS TO WANE AND THE VORTICITY IMPULSE TO THE WEST IS BEGINNING TO SLIDE INTO OUR SOUTHERN AREAS THIS EVENING. THERE COULD STILL BE A FEW ISOLATED SHOWERS/FLURRIES ACROSS SOUTHEASTERN PENNSYLVANIA, SOUTHERN NEW JERSEY, AND THE DELMARVA FOR A COUPLE OF MORE HOURS, SO WE`LL KEEP SLIGHT CHANCE POPS IN FOR A LITTLE WHILE LONGER. ALL SHOWERS SHOULD FULLY DISSIPATE AFTER MIDNIGHT AS THE VORTICITY IMPULSE SLIDES TO OUR EAST OVERNIGHT. THE GUSTY WINDS WILL BE AROUND MOST OF THE NIGHT AND WITH A SECONDARY SURGE OF COLDER AIR IN THE LOW-LEVELS WE COULD SEE GUSTS INCREASE SLIGHTLY STRONGER THAN THEY WERE DURING THE DAY. NONE-THE- LESS THE PRESSURE GRADIENT WILL BE TIGHT ENOUGH TO KEEP US WELL MIXED SO NOT EXPECTING MUCH IN THE WAY OF RADIATIONAL COOLING AS THE CLOUDS DISSIPATE. WENT WITH A STRAIGHT BLEND OF THE MET/MAVMOS TONIGHT. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... HIGH PRESSURE MOVES IN ALOFT AND AT THE SURFACE TO PROVIDE A RATHER TRANQUIL DAY WITH DRY CONDITIONS. SKIES WILL REMAIN MOSTLY SUNNY WITH THE MASSIVE AMOUNT OF SUBSIDENCE TAKING PLACE BUT THIS WILL ALSO LIMIT THE HEIGHTS TO WHICH WE CAN MIX. THE AIRMASS ALOFT STARTS TO MODERATE LATER IN THE DAY AND AS THE WINDS BACK TOWARDS THE WEST- SOUTHWEST WE SHOULD SEE TEMPERATURES SEVERAL DEGREES WARMER THAN ON SATURDAY. WE EDGED CLOSER TO THE WARMER MAVMOS FOR HIGHS TOMORROW THOUGH IT IS QUITE POSSIBLE THAT WITH ANY DOWNSLOPING ADDITION WE COULD TACK ON ANOTHER DEGREE...EXPECTING MID TO UPPER-40S. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... WITH A SPLIT FLOW PATTERN...VERY LIMITED MODEL AGREEMENT...AND A SERIES OF FRONTAL PASSAGES OVER THE NEXT WEEK, THIS DEFINITELY HAS ALL THE HALLMARKS OF A TRANSITION SEASON PATTERN. SUNDAY NIGHT MONDAY...THE FIRST LOW TO TALK ABOUT IN THE LONG TERM SHOULD PASS WELL TO OUR NORTH, CROSSING OVER THE GREAT LAKES AND INTO NORTHERN NEW ENGLAND. HOWEVER, THE ASSOCIATED COLD FRONT SHOULD SWEEP THROUGH OUR REGION DURING THE DAY ON MONDAY. ISENTROPIC LIFT LOOKS TO BE ENOUGH FOR LIGHT PRECIPITATION, PRIMARILY IN THE FORM OF RAIN GIVEN THE TIMING OF THE FRONT. HOWEVER, IF THE FRONT COMES THROUGH EARLY ENOUGH, SOME SNOW IS POSSIBLE IN THE HIGHER TERRAIN WEST OF THE FALL LINE. TUESDAY AND TUESDAY NIGHT...FAST MOVING CLIPPER SYSTEM IS EXPECTED THROUGH THIS TIME. ANY WINDOW OF OPPORTUNITY FOR PRECIPITATION WITH THIS SYSTEM WILL BE BRIEF. HOWEVER, MODEL DISAGREEMENT ON TRACK AND TIMING OF THIS LOW LEADS TO CONSIDERABLE UNCERTAINTY WITH PRECIPITATION TYPE. THE ECMWF AND CMC HAVE A TRACK MUCH FURTHER SOUTH THAN THE GFS, KEEPING MOST OF THE AREA IN THE COLD SECTOR THROUGH THIS ENTIRE PERIOD. HOWEVER, EVEN IN THE COLD SECTOR, PRECIPITATION SHOULD BE MOSTLY RAIN DURING THE DAY. THE BIG QUESTION WILL BE IF THE SYSTEM IS SLIGHTLY SLOWER, WITH THE FURTHER SOUTH TRACK, HOW MUCH SNOW WILL BE POSSIBLE. FOR NOW, HAVE KEPT MOSTLY RAIN MENTIONED IN THE FORECAST AS IT APPEARS TO BE A FAST MOVING SYSTEM. THE EXCEPTION TO THIS IS THE POCONOS AND NW NJ WHERE IF PRECIP CAN LINGER INTO THE LATE EVENING HOURS, SNOW WILL BE POSSIBLE. WEDNESDAY AND THURSDAY...HIGH SHOULD FIRST BUILD IN OVER THE REGION THEN TRACK EAST OFF THE COAST THROUGH THIS TIME, BRINGING WHAT APPEARS AT THIS POINT TO BE THE BEST CHANCES FOR BEAUTIFUL SPRING DAYS, WITH HIGHS GENERALLY IN THE 50S AND 60S. THURSDAY NIGHT THROUGH SATURDAY...HERE IS WHERE THE MODEL DIFFERENCES ARE REALLY NOTICEABLE. WE`LL BE WATCHING TWO SURFACE LOWS THROUGH THIS TIME. ONE WILL BE LIFTING INTO QUEBEC THURSDAY NIGHT INTO FRIDAY, WHILE THE OVER WILL BE DEVELOPING OVER THE SOUTHERN HIGH PLAINS DURING THAT SAME PERIOD BEFORE LIFTING NE TOWARD OUR REGION ON SATURDAY. IF YOU BELIEVE THE GFS, THE FIRST LOW WILL PULL A STRONG COLD FRONT ACROSS OUR REGION LATE THURSDAY. LIKE THE PREVIOUS SHIFT THOUGH, KEPT THE FORECAST CLOSER TO THE ECMWF AS THAT FAR NORTH OF A TRACK DOESN/T REALLY FAVOR A STRONG FRONTAL PASSAGE FOR US. THE SECOND LOW HOWEVER, TRACKING VERY CLOSE TO US, APPEARS TO BE OUR BEST CHANCE FOR PRECIPITATION (POSSIBLY EVEN THUNDERSTORMS - THOUGH INSTABILITY APPEARS TO BE VERY ELEVATED AT THIS TIME), AND ITS COLD FRONT SHOULD BRING TEMPERATURES BACK DOWN INTO THE 40S AND 50S TO START THE WEEKEND. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. THIS EVENING - TONIGHT...VFR. CIGS AROUND 5,000-8000 FEET WILL SCATTER OUT OVERNIGHT AS CLOUDS LIFT AND DISSIPATE. NORTHWEST WINDS AROUND 15 KNOTS WITH GUSTS INTO THE LOW-20 KTS RANGE. SUNDAY...VFR. BY MID- SUNDAY MORNING THE GUSTS BEGIN TO WANE AND WINDS SLACKEN UNDER CLEAR SKIES. WINDS BACK TOWARDS THE WEST- SOUTHWEST. OUTLOOK... SUNDAY NIGHT INTO MONDAY...MVFR CEILINGS AND VISIBILITIES POSSIBLE IN SHRA AND SHSN PRIMARILY SUNDAY NIGHT INTO MONDAY MORNING, OTHERWISE VFR EXPECTED. COLD FRONT ON MONDAY WILL BRING AN ABRUPT SHIFT OF GUSTY NORTHWESTERLY WINDS. TUESDAY...MVFR CEILINGS AND VISIBILITIES WITH -RA POSSIBLE THROUGH THE DAY AND OVERNIGHT. WEDNESDAY AND THURSDAY...MOSTLY VFR CONDITIONS...SHRA MOVING IN LATE THURSDAY. && .MARINE... TONIGHT...WE CONTINUE WITH THE SCA THROUGH MID-SUNDAY AS WINDS AND SEAS ARE EXPECTED TO REMAIN ELEVATED. GUSTS UPWARDS OF 25 KNOTS ARE STILL EXPECTED ACROSS THE WATERS, AND WITH A SECONDARY SURGE OF COLDER AIR TONIGHT, WE COULD GUSTS CLIMB UPWARDS OF 30 KNOTS TONIGHT. SUNDAY...SUB-SCA EXPECTED BY SUNDAY AFTERNOON AS HIGH PRESSURE SETTLES IN OVERHEAD. WE LOSE THE GUSTS RATHER QUICKLY AND WITH THE OFFSHORE WINDS THE SEAS SHOULD QUICKLY DROP AS WELL. WINDS BEGIN TO VEER TOWARDS THE WEST-SOUTHWEST BY SUNDAY AFTERNOON. OUTLOOK... SUNDAY NIGHT...ANOTHER ROUND OF SCA CONDITIONS, AND POSSIBLY GALE CONDITIONS, IS POSSIBLE IN THE INCREASING SW FLOW PRECEDING THE NEXT COLD FRONT. MONDAY AND MONDAY NIGHT...THE COLD FRONT SHOULD SWEEP THROUGH MONDAY, BRINGING AN ABRUPT SHIFT OF WESTERLY AND NORTHWESTERLY WINDS. GUSTS NEAR OR ABOVE 25 KT WILL BE POSSIBLE THROUGH THE EVENING HOURS. SEAS WILL BE SLOW TO SUBSIDE. TUESDAY THROUGH WEDNESDAY...WINDS ARE EXPECTED TO STAY BELOW SCA CRITERIA THROUGH THIS PERIOD. HOWEVER, IF THE PASSING LOW PRESSURE SYSTEM IS STRONGER THAN FORECAST, WINDS ABOVE 25 KT ARE POSSIBLE PRIMARILY TUESDAY NIGHT. SEAS NEAR OR ABOVE 5 FT ARE POSSIBLE ON THE COASTAL WATERS THROUGH THIS TIME, BUT THERE IS STILL CONSIDERABLE UNCERTAINTY. THURSDAY...INCREASING SOUTHERLY AND SOUTHWESTERLY FLOW WILL RESULT IN ANOTHER ROUND OF SCA CONDITIONS ON THURSDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT SUNDAY FOR ANZ430-431- 450>455. && $$ SYNOPSIS...JOHNSON NEAR TERM...HEAVENER/ROBERTSON SHORT TERM...HEAVENER LONG TERM...JOHNSON AVIATION...HEAVENER/JOHNSON/ROBERTSON MARINE...HEAVENER/JOHNSON

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