Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 281837 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 237 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 ASSOCIATED WITH A LOW PRESSURE SYSTEM WILL MOVE THROUGH THE REGION ON MONDAY. THIS WILL BE FOLLOWED QUICKLY BY AN ALBERTA CLIPPER TYPE LOW PRESSURE SYSTEM PASSING NEAR OR THROUGH THE AREA LATE ON TUESDAY. A HIGH PRESSURE SYSTEM SHOULD THEN BUILD INTO THE REGION FOR WEDNESDAY. A COLD FRONT IS PREDICTED TO REACH THE WESTERN GREAT LAKES ON THURSDAY MORNING AND APPROACH OUR AREA ON FRIDAY. && .NEAR TERM /THROUGH TONIGHT/...
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REGIONAL RADAR IS NOT SHOWING MUCH IN THE WAY OF SNOW SHOWERS ACROSS THIS AFTERNOON. THE MORNING SHOWERS ACROSS THE DELMARVA HAVE ALL BUT WEAKENED AND WITH SURFACE TEMPERATURES CLIMBING CLOSE TO 40F, ITS DOUBTFUL ANYTHING IS ACTUALLY STICKING ANYMORE. THAT BEING SAID, THE UPPER LEVEL ENERGY STILL IS PIVOTING THROUGH THE REGION AS WE SPEAK. A BIT MORE LOW-LEVEL INSTABILITY IS PRESENT COINCIDING WITH THE COLD POOL ALOFT DRIFTING THROUGH SO WE COULD STILL SEE WIDELY SCATTERED SNOW SHOWERS ACROSS THE AREA. HI-RES GUIDANCE HAS BEEN SHOWING THE BETTER AREAS ARE ONCE AGAIN THE DELMARVA AND PARTS OF THE PHILLY METRO AREA. IT IS POSSIBLE, CLOSER TO THE NJ COAST, THAT A WEAK TROUGH-LIKE FEATURE TRIES TO SPARK A FEW BETTER ORGANIZED SHOWERS. THE RGEM IS THE MORE ROBUST WITH THIS FEATURE BUT SOME OF THE SREF CORE MEMBERS SHOW THIS AS WELL. NOT ENTIRELY SURE, IF IT FORMS, IT WOULD HAVE MUCH LAND BASED IMPACTS, SO WE CONTINUE TO ADVERTISE THE CHANCE POPS THROUGH THE EVENING HOURS FROM PHILLY SOUTHWARD. 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.
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&& .SHORT TERM /SUNDAY/...
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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.
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&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... AN ACTIVE LONG TERM WITH A COUPLE OF PCPN SHOTS POSSIBLE. THE WRF-NMMB INITIALIZATION AT 500MB LOOKED BETTER THAN THE GFS, BOTH MODELS WERE ABOUT THE SAME AT 850MB AND 925MB WITH ANY ERRORS ON THE COLD SIDE BY ABOUT 1C. THE DP/DT WITH THE MODELS OVER THE PAST 24 HOURS WAS SHOWING A DEEPER EAST COAST TROF. BASED ON THIS MOVING FORWARD WE WERE SLOWER WITH THE EVOLUTION OF EVENTS. AN AIR MASS MODIFICATION WITH DECREASING WINDS IS PREDICTED FOR SUNDAY. GIVEN THE COLD START, CHANCES ARE THAT THE MAX TEMPS WILL OCCUR LATER IN THE AFTERNOON THAN USUAL. GIVEN FULL SUN AND A DOWNSLOPING WIND, WE WENT FULL ADIABATIC WITH MAX TEMPS CLOSE TO END OF THE AFTERNOON SOUNDING SUGGESTED MAX TEMPS. THE WEAKER OF THE NEXT TWO SYSTEMS WILL APPROACH OUR AREA ON MONDAY NIGHT. THERE WILL BE DECENT MID LEVEL QVEC CONVERGENCE, BUT THE PREDICTED ISENTROPIC LIFT AND FGEN FORCING ARE MORE MUTED. THE JET IS NOT IN A BAD POSITION. GIVEN THE OVERALL DRYNESS OF THE INITIAL AIR MASS, MODELS ARE NOT PREDICTING MUCH PCPN. BECAUSE OF THE DPVA AND THE MID LEVEL QVEC CONVERGENCE, PCPN SHOULD BE FALLING FROM A MID CLOUD DECK. NOT SURE IF IT WILL MAKE IT TO THE GROUND, BUT FOR NOW WE WENT HIGHER THAN STAT GUIDANCE BECAUSE OF THE FORCING. WHILE A LLJ WILL BE WARMING THE SUB CLOUD LAYER AND MIGHT BE ABLE TO OFFSET EVAPORATIONAL COOLING EFFECTS, SNOW AS A PTYPE IS A POSSIBILITY IN THE NORTHERN PART OF OUR CWA. BECAUSE QPF AMOUNTS ARE LOW, ANY ACCUMS ARE EXPECTED TO BE LESS THAN AN INCH. MIN TEMPS WILL LIKELY OCCUR EARLIER IN THE NIGHT AND RISE TOWARD MORNING. USUALLY THE CASE WITH THESE WEAK SYSTEMS, ANY PCPN OCCURS IN THE WAA PHASE WITH LITTLE IF ANY WITH THE CFP ITSELF. MODELS ARE PRETTY CLOSE ON THAT DURING THE DAY ON MONDAY. WITH THE LAGGING STRONGER CAA, THE DOWNSLOPING WINDS SHOULD MORE THAN COMPENSATE FOR COOLING ALOFT. A STAT GUIDANCE COMBO LOOKS DECENT FOR MAX TEMPERATURES. IT WILL BECOME WINDIER WIND PEAK GUSTS LIKELY REACHING AT LEAST 20 TO 30 MPH. THE RIDGING FROM THE NEXT HIGH PRESSURE SYSTEM PASSES OVER OUR FORECAST AREA ON MONDAY NIGHT. BUT WE MAY REMAIN IN A BIT OF A GRADIENT AND DID NOT BOTTOM MIN TEMPERATURES. AT LEAST ON PAPER TODAY, THE NEXT ALBERTA TYPE LOW PRESSURE SYSTEM LOOKS MORE ROBUST. A MUCH BETTER PREDICTED COUPLET OF MID LEVEL FGEN AND QVEC FORCING IN OUR AREA. THIS CAN BE SEEN WITH IN THE QPF FIELD BY ITSELF. THERE ARE TRACK DIFFERENCES WITH DIFFERENCES IN OPINION AS TO THE GREATER IMPACT. FOR NOW WE HAVE COMPROMISED BETWEEN THE DATASETS, THUS ONSET OF UPPED PCPN CHANCES IS TUESDAY AFTERNOON AND CONTINUING INTO TUESDAY NIGHT. WHILE THE BOUNDARY LAYER WILL GET WARMED ON TUESDAY, IT IS STILL COLD ALOFT AND A CHANGE TO SNOW, ESPECIALLY OVER THE HIGHER TERRAIN NORTH WOULD BE THE LOGICAL OUTCOME FOR SUCH A SCENARIO. THIS ONE COULD BE SNOWIER. BECAUSE OF DIFFERENCES WITH THE TRACK AND THE INHERENT UNCERTAINTY OF TIMING, THERE EXISTS THE POTENTIAL FOR SOME BIG ERRORS WITH MAX TEMPS ON TUE. WE ARE TOWARD THE HIGHER END OF THE GUIDANCE SPECTRUM. WEAKER HIGH PRESSURE SYSTEM TO FOLLOW ON WEDNESDAY WHICH MEANS LITTLE IF ANY DROP IN MAXIMUM TEMPERATURES. THE REST OF THE LONG TERM WE SHIED AWAY FROM THE FASTER GFS CFP TIMING. THUS OUR MAX TEMPS THURSDAY ARE HIGHER THAN ITS STAT GUIDANCE. WE ALSO PUSHED BACK THE ONSET OF SHOWER CHANCES CLOSER TO THE ECMWF`S TIMING AND PERSISTED IT THROUGH FRIDAY. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. THIS EVENING - TONIGHT...VFR. BROKEN DECK AROUND 5KFT. WIDELY SCATTERED SNOW SHOWERS THIS AFTERNOON AND EVENING MAY OCCUR. NOT CONFIDENT ON DIRECT TERMINAL IMPACTS SO WE WILL NOT CARRY A TEMPO AT THIS TIME. BEST CHANCES MAY BE SOUTH AND WEST OF ILG. NORTHWEST WINDS AROUND 15 KNOTS WITH GUSTS INTO THE LOW-20 KTS RANGE. SUNDAY...VFR. CEILINGS LIFT A BIT AND SKIES BEGIN TO SCATTER/CLEAR OUT LATE TONIGHT. ANOTHER, BETTER, SURGE OF COLD AIR SHOULD ALLOW FOR SLIGHTLY STRONGER GUSTS THEN SATURDAY AFTERNOON PRODUCED. BY MID- SUNDAY MORNING THE GUSTS BEGIN TO WANE AND WINDS SLACKEN UNDER CLEAR SKIES. WINDS BACK TOWARDS THE WEST-SOUTHWEST. OUTLOOK... SUNDAY NIGHT AND MONDAY...SOME LOWER MVFR CIGS AND VSBYS IN SCATTERED RAIN, HIGHER TERRAIN SNOW, SHOWERS. THERE IS A CHANCE FOR LLWS AT SOUTHERN AIRPORTS. NORTHWEST WINDS ON MONDAY SHOULD GUST TO AROUND 25 KNOTS. MONDAY NIGHT...VFR. TUESDAY AND TUESDAY NIGHT...POTENTIAL MVFR OR IFR RESTRICTIONS IN RAIN AND POSSIBLY SNOW AT HIGHER TERRAIN AIRPORTS. WEDNESDAY...VFR OR BECOMING VFR AS THE DAY PROGRESSES.
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&& .MARINE...
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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-SOUTWHEST BY SUNDAY AFTERNOON. OUTLOOK... SUNDAY NIGHT AND MONDAY...ANOTHER ROUND OF SCA CONDITIONS IS POSSIBLE IN THE INCREASING SW FLOW PRECEDING THE NEXT CFP. WHILE AIR TEMPERATURES WILL BE WARMING MONDAY, MIXING NEAR COASTAL AREAS COULD KEEP SCA CONDITIONS PERSISTING EVEN AFTER THE CFP. MONDAY NIGHT...SUB SCA CONDITIONS OUTLOOKED TO RETURN AS THE PRESSURE GRADIENT WEAKENS AGAIN. TUESDAY THROUGH WEDNESDAY...PRIMARILY SUB SMALL CRAFT ADVISORY CONDITIONS ARE OUTLOOKED. THE ONE CAVEAT IS THAT WITH A CLIPPER LOW PRESSURE SYSTEM PASSING THROUGH OR NEAR OUR COASTAL WATERS, WE WILL HAVE TO MONITOR A STRONGER OVERALL LOW THAT MIGHT INCREASE BOTH WINDS AND SEAS INTO SMALL CRAFT ADVISORY CRITERIA.
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&& .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...GAINES/GIGI NEAR TERM...HEAVENER SHORT TERM...HEAVENER LONG TERM...GIGI AVIATION...GAINES/GIGI/HEAVENER MARINE...GAINES/GIGI/HEAVENER

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