Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 230136 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 936 PM EDT SUN MAR 22 2015 .SYNOPSIS... STRONG COLD HIGH PRESSURE CENTERED NEAR THE UPPER GREAT LAKES WILL GRADUALLY BUILD SOUTHEASTWARD AND OVER OUR AREA THROUGH TUESDAY. A WARM FRONT ARRIVES ON WEDNESDAY, FOLLOWED BY A COLD FRONT THURSDAY NIGHT. NORTHEASTWARD MOVING LOW PRESSURE MAY FORM ON THAT FRONT ALONG THE SOUTH ATLANTIC COAST FRIDAY WITH A COLDER NORTHERLY FLOW TO FOLLOW NEXT WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH OVER EASTERN CANADA AND THE NORTHEASTERN U.S. THIS FEATURE WILL CONTINUE TO DOMINATE THE FLOW ACROSS OUR AREA THROUGH TONIGHT. MEANWHILE, HIGH PRESSURE AT THE SURFACE CENTERED NEAR THE UPPER GREAT LAKES WILL BUILD SOUTHEASTWARD. WINDS HAVE RELAXED ACROSS THE REGION AS THE HIGH STARTS TO PUSH CLOSER TO OUR AREA. WITH THE RELATIVELY CLEAR SKIES AND WEAKENING WINDS, WE SHOULD CONTINUE TO RADIATE FAIRLY WELL AND TEMPERATURES WILL DEFINITELY BE ON THE COLD SIDE. AS FOR THE LOW TEMPERATURES, WE USED A NAM/GFS MOS BLEND THEN ADJUSTED THESE DOWN SOME MAINLY FOR THE USUALLY COLDER LOCALES.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... THE CYCLONIC FLOW ALOFT IS MAINTAINED DURING MONDAY, ALLOWING FOR A CHILLY DAY. AT THE SURFACE, HIGH PRESSURE IS FORECAST TO BE SETTLING INTO OUR AREA ALTHOUGH ITS CENTER SLIDES ACROSS THE LOWER GREAT LAKES REGION. THIS WILL ALLOW FOR LESS OF A PRESSURE GRADIENT AND THEREFORE LESS WIND. A THERMAL GRADIENT ALOFT THOUGH ACROSS OUR AREA WILL PROBABLY RESULT IN SOME HIGH LEVEL CLOUDS AT TIMES, ESPECIALLY WITH SOME SHEARING ENERGY TO OUR SOUTH. SOME BOUTS OF WAA INTO THE OHIO VALLEY MAY ALSO AIDE IN SOME MID TO HIGH LEVEL CLOUD DEVELOPMENT. THE FORECAST SOUNDINGS OVERALL INDICATE THE CONVECTIVE TEMPERATURES BEING REACHED, HOWEVER THE LOW-LEVEL AIRMASS IS RATHER DRY. THERE MAY STILL BE ENOUGH THOUGH FOR LIMITED FLAT STRATOCUMULUS DEVELOPMENT. AS FOR THE HIGH TEMPERATURES, WE STARTED WITH A BLEND OF THE NAM/GFS MOS HOWEVER THE NAM MOS ESPECIALLY LOOKS TO CONTINUE WITH A COLD BIAS. THEREFORE WE BUMPED THEM UP SOME AND ARE CLOSER TO THE GFS MOS. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... 500 MB: A TROUGH IN THE NE USA MONDAY NIGHT AND TUESDAY GIVES WAY TO RIDGING WEDNESDAY INTO THURSDAY. THEREAFTER A HIGH AMPLITUDE TROUGH EVOLVES ALONG THE EAST COAST BY NEXT WEEKEND. TEMPERATURES: 10 TO 15 DEGREES BELOW NORMAL TUESDAY, 5 TO 10 DEGREES BELOW NORMAL WEDNESDAY, 5 TO 10 DEGREES ABOVE NORMAL THURSDAY, NEAR NORMAL FRIDAY AND 5 TO 10 DEGREES BELOW NORMAL NEXT WEEKEND. FORECAST BASIS: UNLESS OTHERWISE NOTED, A 50 50 BLEND 12Z/22 GFS/NAM MOS GUIDANCE MONDAY NIGHT-TUESDAY NIGHT, 12Z/22 MEX MOS WEDNESDAY AND WEDNESDAY NIGHT, THEN THE 16Z/22 WPC GRIDDED ELEMENTS OF MAX/MIN TEMP, 12 HOUR POP, 6 HOUR DEWPOINT-SKY-WIND FROM THURSDAY THROUGH NEXT SUNDAY. THE DAILIES... MONDAY NIGHT AND TUESDAY...POLAR HIGH CONTINUES TO BUILD OVER THE REGION RESULTING IN TUESDAY`S HIGH TEMPS ALMOST 15 DEGREES BELOW NORMAL. WITH THE HIGH NEARER THE REGION, AND A MINIMAL PRESSURE GRADIENT ACROSS THE REGION, WINDS WILL BE RATHER LIGHT - GUSTS AT OR BELOW (AOB) 15 MPH. THROUGH THIS PERIOD. CIGS AOA 5000 FT WILL BECOME PREDOMINANT ACROSS AT LEAST SE PA AND S NJ SOUTHWARD LATER MONDAY NIGHT THROUGH MIDDAY TUESDAY AS A WARM AIR ADVECTION PATTERN INTO THE DELMARVA ATTEMPTS TO SEND A PERIOD OF LIGHT SNOW OUR WAY. THIS IN ASSOCIATION WITH FAIRLY STRONG SHORT WAVE PASSING SEWD THROUGH THE MID ATLANTIC STATES. CONFIDENCE: ABOVE AVERAGE EXCEPT NOT ABSOLUTELY SURE THERE WONT BE A FEW FLURRIES OR PERIOD OF LIGHT SNOW OVER MD`S EASTERN SHORE TUESDAY MORNING (DRYING OUT FURTHER EAST). TUESDAY NIGHT...LOOKS LIKE A GOOD RADIATING NIGHT. LIGHT WIND AND CLEAR SKIES FOR THE MOST PART. CONFIDENCE: ABOVE AVERAGE. WEDNESDAY INTO THURSDAY...WARM FRONT-COLD FRONT SCENARIO. IT COULD BE RATHER COOL DURING THE DAY WEDNESDAY, ESPECIALLY I78 NORTH AND ALONG THE COASTS (SSTS UPPER 30S TO NEAR 40) WHERE WINDS WILL BE OFF THE WATER. THE 330 PM FCST TEMPS FOR WEDNESDAY ON THE IMMEDIATE NJ COAST MAY BE SEVERAL DEGREES TOO WARM. A PERIOD OF LIGHT RAIN OR DRIZZLE APPEARS PROBABLE FOR PORTIONS OF THE AREA, ESPECIALLY I-78 NORTH LATER WED OR WED NIGHT. FOG SHOULD DEVELOP LATE WED NIGHT, AGAIN ESPECIALLY NORTH AND HIGHER TERRAIN. FOR NOW BLANKETED THE FCST WITH PATCHY FOG LATE WED NIGHT/EARLY THU. THEN THE 12Z/22 ECMWF HAS CAUGHT UP WITH THE GFS AND IT LOOKS LIKE WE SHOULD TRANSITION TO A WINDY WARM THURSDAY AFTN (60S MUCH OF THE COASTAL PLAIN) WITH A CHANCE OF SHOWERS AND EVEN A STRONG GUSTY TSTM AHEAD OF THE APPROACHING COLD FRONT. PLENTY OF 0-6KM BULK SHEAR AND APPEARS TO BE SOME INSTABILITY THOUGH A BIT LIMITED WITH MLCAPE LESS THAN 400J. SCENARIO CONFIDENCE: ABOVE AVERAGE. THURSDAY NIGHT-SATURDAY...UNCERTAINTY EXISTS REGARDING THE EVOLUTION OF THE AMPLIFYING TROUGH ALOFT. ENSEMBLES ARE TOTALLY SPAGHETTI THOUGH THE 12Z OP RUNS ARE ALL STARTING TO INDICATE IT BEING WORTHY TO KEEP AN EYE ON THE SOUTHERN STREAM AND A POTENTIAL WET WEATHER MAKER FOR FRIDAY OR SATURDAY. IF THIS TRANSPIRES, WINTRY WEATHER WOULD BE POSSIBLE. THE 12Z/22 GGEM BEING THE INSIDE RUNNER WARMEST MODEL. SO WHILE THE DETAILS ARE TO BE DETERMINED OUR FCST HAS INDICATIONS OF THIS EVENT AND FROM MY OWN PERSPECTIVE IT IS CONSERVATIVE ON POPS (REFERENCE THE NAEFS). LATER IN THE WEEKEND...A RATHER COLD FOR THE SEASON NORTHERLY FLOW SHOULD FOLLOW WHATEVER DEPARTS FROM THE MID ATLANTIC COAST. PARTLY CLOUDY. CONFIDENCE: ABOVE AVERAGE && .AVIATION /02Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. TONIGHT...VFR. WINDS WILL REMAIN BELOW 10 KNOTS...BECOMING LIGHT AND VARIABLE OVERNIGHT. MONDAY...VFR. NORTH TO NORTHWEST WINDS AROUND 10 KNOTS... DIMINISHING TOWARDS MONDAY EVENING. OUTLOOK... MONDAY NIGHT AND TUESDAY...VFR CIGS AOA 5000 FT. IT SHOULD CLEAR TUESDAY AFTERNOON. MOSTLY NW WIND...GUSTS UNDER 15 KT. CONFIDENCE: ABOVE AVERAGE. TUESDAY NIGHT...VFR CLEAR. LIGHT WIND. CONFIDENCE: ABOVE AVERAGE. WEDNESDAY AND THURSDAY...VFR CIGS DEVELOP WEDNESDAY LOWERING TO IFR RAIN/DRIZZLE/FOG WEDNESDAY NIGHT AND IMPROVING TO VFR CIGS THU AFTN WITH A CHANCE OF MVFR CONDS IN AFTERNOON/EVENING SHOWERS/ISO TSTMS. SMALL CHANCE LLWS THURSDAY MORNING. PRESSURE GRADIENT DRIVEN SW WIND GUSTS OF 25-30 KT THU AFTN. CONFIDENCE: ABOVE AVERAGE ON THE SCENARIO BUT BELOW AVERAGE ON THE TIMING. FRIDAY...VFR CIGS. KEEPING AN EYE ON POSSIBLE LOW PRESSURE DEVELOPMENT JUST TO OUR SOUTH. CONFIDENCE: BELOW AVERAGE ON WHAT WILL OCCUR.
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&& .MARINE...
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HIGH PRESSURE AT THE SURFACE WILL GRADUALLY BUILD INTO THE AREA THROUGH MONDAY. THIS WILL RESULT IN LESS WIND AS THE PRESSURE GRADIENT RELAXES. OTHERWISE, NO HEADLINES ANTICIPATED THROUGH MONDAY AS THE FLOW TURNS MORE NORTHERLY. OUTLOOK... MONDAY NIGHT THROUGH WEDNESDAY...WINDS AND SEAS SHOULD REMAIN BELOW SCA CRITERIA. CONFIDENCE: ABOVE AVERAGE. WEDNESDAY NIGHT INTO THURSDAY...WINDS AND SEAS WILL INCREASE ABOVE SCA THRESHOLDS WEDNESDAY NIGHT. GUSTS ABOVE 30 KT WILL BE POSSIBLE ON THURSDAY AHEAD OF A COLD FRONTAL PASSAGE. CONFIDENCE: AVERAGE. FRIDAY...LINGERING SCA HAZARDOUS 5 FOOT SEAS POSSIBLE ON THE ATLANTIC WATERS, MAINLY DURING THE MORNING. OTHERWISE NO MARINE HAZARDS YET, THOUGH CONFIDENCE IS BELOW AVERAGE FOR THIS DAY SINCE A SECOND LOW PRESSURE SYSTEM MAY DEVELOP NEARBY ON FRIDAY.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...DRAG/GORSE NEAR TERM...GORSE/MEOLA SHORT TERM...GORSE LONG TERM...DRAG AVIATION...DRAG/MEOLA MARINE...DRAG/GORSE

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