Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 280911 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 411 AM EST WED JAN 28 2015 .SYNOPSIS... DEEP LOW PRESSURE ACROSS THE CANADIAN MARITIME PROVINCES WILL CONTINUE TO WEAKEN TODAY. HIGH PRESSURE WILL BUILD ACROSS THE AREA THIS AFTERNOON THROUGH THURSDAY BEFORE MOVING EAST. LOW PRESSURE WILL MOVE ACROSS THE GREAT LAKES AND NEW ENGLAND THURSDAY NIGHT THROUGH FRIDAY AND CAUSE AN ARCTIC FRONT TO CROSS OUR REGION. MORE HIGH PRESSURE WILL RETURN FOR MUCH OF THE WEEKEND. A STORM WILL APPROACH THE AREA SUNDAY AFTERNOON AND AFFECT THE AREA INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE STRONG COASTAL STORM THAT BROUGHT BLIZZARD CONDITIONS TO NEW ENGLAND IS LOCATED OVER THE GULF OF MAINE EARLY THIS MORNING. MEANWHILE, HIGH PRESSURE WAS CENTERED OVER THE MIDWEST. THE PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS IS PRODUCING A SUSTAINED NORTHWEST OF 10-20 MPH WITH SLIGHTLY HIGHER GUSTS OVER THE MID ATLANTIC. TODAY WILL START OUT WITH WIND CHILL VALUES IN THE SINGLE DIGITS ACROSS MOST OF THE AREA. THE LOWEST REPORTED WIND CHILL EARLY THIS MORNING WAS -11F AT MPO. THE PRESSURE GRADIENT AND RESULTANT WIND FIELD WILL GRADUALLY RELAX THROUGHOUT THE DAY ACROSS OUR REGION AS THE COASTAL LOW WEAKENS TO OUR NORTHEAST AND HIGH PRESSURE BUILDS IN FROM THE WEST. FULL SUNSHINE AND ADIABATIC WARMING ASSOCIATED WITH THE STRENGTHENING SUBSIDENCE INVERSION AND DOWNSLOPING WINDS OFF THE HIGHER TERRAIN SHOULD ALL HELP MODERATE THE AIRMASS A BIT. NONETHELESS, WE ARE IN STORE FOR ANOTHER COLDER THAN NORMAL DAY. FOR THE MAX TEMP FORECAST, TRENDED TOWARD THE WARMER MAV GUIDANCE AND EVEN ABOVE GUIDANCE IN SOME PLACES AFTER FACTORING A 2-3F DEGREE MODEL COLD BIAS YESTERDAY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... HEIGHT RISES WILL OCCUR ALONG THE EASTERN SEABOARD TONIGHT AS AN UPPER RIDGE PROGRESSES EASTWARD. AT THE SURFACE, HIGH PRESSURE OVER THE APPALACHIANS THIS EVENING WILL BUILD DIRECTLY OVERHEAD DURING THE OVERNIGHT. MIN TEMPS WILL DEPEND ON HOW QUICKLY THE BOUNDARY LAYER CAN DECOUPLE. ONCE DECOUPLING HAPPENS, AIRMASS WILL RADIATE QUITE EFFECTIVELY UNDER LIGHT WINDS AND CLEAR SKIES. THE OFFICIAL MIN TEMP FORECAST IS ON THE COLD ENVELOPE OF MODEL GUIDANCE GIVEN THE FAVORABLE RADIATIONAL COOLING SETUP AND WITH A FRESH SNOWPACK. MIN TEMPS ARE IN THE SINGLE DIGITS NORTH AND EAST OF I-95 AND LOW TO MID TEENS IN THE CITIES AND ALONG THE COAST/DELMARVA WHERE THE PRESSURE GRADIENT WILL TAKE THE LONGEST TO WEAKEN. && .LONG TERM /THURSDAY THROUGH TUESDAY/... THU THRU FRIDAY...A FAST MOVING LOW PRESSURE AREA OVER THE WESTERN GREAT LAKES THU MORNING WILL PASS JUST NORTH OF THE AREA THU NIGHT AND THEN DEEPEN OFF THE NEW ENGLAND COAST FRIDAY. AN ARCTIC COLD FRONT WILL CROSS THE AREA FRIDAY. THIS SYSTEM WILL PRODUCE A WIDESPREAD SNOW ACROSS MOSTLY THE NRN HALF OF THE FORECAST AREA. POPS WERE RAISED A BIT WITH BOTH THE EC AND GFS MODELS IN GENERAL AGREEMENT. THE GFS 00Z IS SLIGHTLY FASTER WITH THE SYSTEM. TEMPERATURES IN THE (MOSTLY LIKELY) PRECIPITATION AREAS SUPPORT SNOW WITH AMTS PROBABLY IN THE 1 INCH RANGE IN MOST AREAS. A COUPLE 2 INCH AMTS POSSIBLE FAR NORTH OVER NRN NJ OR THE SRN POCONOS. WE HAVE GONE ALONG WITH THE TOTALS WHICH ARE SUPPORTED BY THE LATEST WWD. WINDS AND BECOMING VERY COLD LATER FRIDAY WITH WIND CHILLS DROPPING INTO THE SINGLE DIGITS NORTH AND TEENS OVER PHL AND DELMARVA BY EVENING. FRIDAY NIGHT THRU SUNDAY...HIGH PRESSURE BUILDS IN AND REMAINS FOR THE WEEKEND. BITTER COLD SAT WITH TEMPS SOME 15 TO 20 DEGREES BELOW NORMAL. SOME MODERATION IN TEMPS SUN...BUT STILL MOSTLY 5 TO 10 DEGREES BELOW NORMAL. FLAGS FOR WIND CHILL POSSIBLE FRI NIGHT AND SAT ACROSS THE FAR NORTH. SUN AFTERNOON THRU MON NIGHT...MORE WEATHER ACTION AS THE NEXT SYSTEM EMERGES FROM THE ROCKIES SAT NIGHT THEN TRACKS UP THE OHIO VALLEY AND ACROSS OUR AREA SUN NIGHT/MONDAY. THE SYSTEM IS SHOWN SCOOPING UP PLENTY OF MOISTURE BEFORE IT ARRIVES. THE GFS SHOWS A TRACK JUST NORTH OF THE AREA...THE EC JUST SOUTH. TEMPS AND POPS MOSTLY WPC LIKE WITH A FEW ADJUSTMENTS FOR BETTER ISC COORDINATION. CHC SNOW SUN AFTERNOON...THEN LIKELY SNOW SUN NIGHT. SNOW CHANGES TO RAIN S/E I-95 MONDAY. THERE WILL BE PLENTY OF REFINEMENTS...SO THIS IS THE BEST FCST FOR NOW. PAY ATTENTION TO THIS SYSTEM OVER THE NEXT FEW DAYS. TUE...ANOTHER DRY HIGH PRESSURE SYSTEM WITH ANOTHER PLUNGE OF ARCTIC AIR FOR TUE AND PROBABLY INTO WED. TEMPS POSSIBLY 10 TO 20 DEGREES BELOW NORMAL. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR TODAY AND TONIGHT. NW WINDS 10-15 KT WILL GUST UP TO 25 KT THIS MORNING AND 20 KT THIS AFTERNOON. LIGHT WINDS TONIGHT. OUTLOOK... THU...MOSTLY VFR. LOWER CONDITIONS WITH SNOW POSSIBLE WEST LATE. THU NIGHT THRU FRI...LOWER CONDITIONS WITH PCPN THU NIGHT. LINGERING SHOWERS EARLY FRI WITH GUSTY WINDS. FRI NIGHT THRU SUN...MOSTLY VFR. SMALL CHC FOR SNOW SUN AFTERNOON. && .MARINE... SCA REMAINS IN EFFECT FOR THE WATERS TODAY. ONLY CHANGE WAS TO EXTEND THE ENDING TIME OF THE SCA FOR THE DE BAY TO 6 PM (MATCHING THE ENDING TIME OF THE COASTAL WATERS) AS THE NW DIRECTION WILL CHANNEL DOWN THE BAY, ENHANCING WIND SPEEDS TO NEAR 25 KT. WAVEWATCH GUIDANCE VERIFIED 1-2 FT TOO LOW WITH WAVE HEIGHTS IN THE COASTAL ZONES, SO INCREASED SEAS A BIT TO 5-8 FT FOR THIS MORNING. NW WINDS AND SEAS WILL SUBSIDE TONIGHT. NO MARINE HAZARDS ARE EXPECTED OTHER THAN LIGHT FREEZING SPRAY. OUTLOOK... THU...SUB SCA CONDITIONS. THU NIGHT...BUILDING WINDS/SEAS SCA CONDITIONS. FRI/FRI NIGHT...GALE CONDITIONS POSSIBLE. SAT...GALE CONDITIONS DIMINISHING BACK TO SCA CONDITIONS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ430- 431-450>455. && $$ SYNOPSIS...O`HARA NEAR TERM...KLEIN SHORT TERM...KLEIN LONG TERM...O`HARA AVIATION...KLEIN/O`HARA MARINE...KLEIN/O`HARA

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