Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 250534 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1234 AM EST TUE NOV 25 2014 .SYNOPSIS... A COLD FRONT WILL MOVE THROUGH THE REGION OVERNIGHT AND STALL JUST OFFSHORE THROUGH TUESDAY...ALLOWING HIGH PRESSURE TO BRIEFLY MOVE IN FROM THE SOUTHWEST. LOW PRESSURE WILL DEVELOP ALONG THIS STALLED FRONT AND AFFECT THE REGION AS A STRONG NOR EASTER ON WEDNESDAY. HIGH PRESSURE WILL MOVE IN ON THANKSGIVING AND DOMINATE UNTIL A COLD FRONTAL PASSAGE IN THE SUNDAY AND MONDAY TIME FRAME. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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COLD FRONT SLIDING THROUGH THE REGION NOW. CONSIDERABLE HIGH CLOUDS CONTINUE TO STREAM OVER THE REGION AHEAD OF AND JUST BEHIND THE FRONT, BUT WITH THE EXCEPTION OF ONE SITE IN BUCKS COUNTY, NO LOW CLOUDS HAVE DEVELOPED. NEAR THE SHORE, WE HAVE HAD REPORTS OF FOG. OBS SHOW THAT AT THE SHORE, WINDS HAVE A LIGHT ONSHORE COMPONENT. EXPECT THIS TO CHANGE IN A FEW HOURS ONCE THE FRONT MOVES THROUGH, BUT HAVE INCLUDED MENTION IN THE GRIDS AS WELL AS A NOW CAST FOR FOG REDUCING VISIBILITIES TO LESS THAN A MILE AT TIMES.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TODAY/... ONE LAST FAIR WEATHER DAY EXPECTED ON TUESDAY BEFORE THE UPCOMING STORM IN THE LONG TERM. OVERALL DRY WEATHER WITH MID AND HIGH LEVEL CLOUDS EXPECTED FOR MOST OF THE DAY. TEMPERATURES WILL BE 10-15 DEGREES COOLER WITH NORTHWEST FLOW ACROSS THE AREA AND LOWERING THICKNESSES AND 925 MB TEMPERATURES. HIGHS WERE A BLEND OF MIXED 925 MB TEMPS, MAV/MET MOS, AND MOSGUIDE WHICH KEEPS EVERYONE ABOVE NORMAL, BUT CLOSER THAN MONDAY. && .LONG TERM /TONIGHT THROUGH MONDAY/... **WINTER STORM/EVENT OF WET SNOW AT HAND E PA AND NW NJ** 500 MB: THE LEAD SHORT WAVE THAT PRODUCES OUR WINTER STORM WILL BE MOVING EASTWARD ALONG THE GULF COAST TUESDAY EVENING THEN UP THE EAST COAST LATE WEDNESDAY TO NEW ENGLAND BY THURSDAY MORNING. IT PASSES THROUGH NJ AS AN INTENSIFYING 200M 12 HR 500MB HFC NEAR 06Z THURSDAY. TEMPERATURES: MIN TEMPS WED MORNING WILL BE ABOUT 5 DEGREES ABOVE NORMAL BUT THE PROBLEM IS THE HIGH TEMPERATURES AFTER DAYBREAK WEDNESDAY WILL BE 8 TO 12 DEGREES BELOW NORMAL AS WET BULBING OCCURS IN THE INCREASING NORTHERLY SFC FLOW. LOWS WEDNESDAY NIGHT WILL BE NEAR OR SLIGHTLY BELOW NORMAL BUT NOT A HARD FREEZE SUBSEQUENT TO THIS SNOW. POPS: TUESDAY NIGHT AND WEDNESDAY NIGHT ARE BLENDED 12Z/24 NCEP MOS THEN THAT BLENDED WITH THE 09Z/24 SREF AND 00Z-12Z ECMWF 6 HR QPF INDICATIONS OF .10 OR GREATER. THE STORM... OUR RECOMMENDATION: TO REACH YOUR HOLIDAY DESTINATION ON TIME WITH PROBABLY A MINIMUM OF WEATHER RELATED TRAVEL DELAYS...AND ESPECIALLY TRAVELING WEST OF I-95 INTO NORTHWEST NJ...EASTERN PA...TRAVEL SHOULD BE COMPLETED AT THE LATEST...BY 10 AM WEDNESDAY. NORMALLY THIS STORM WOULDN`T HAVE GARNERED SO MUCH LEAD TIME ATTENTION BUT WE RESPONDED TO THE THE HEIGHTENED PUBLIC INTEREST ON WHAT IS USUALLY THE BUSIEST TRAVEL DAYS OF THE YEAR. THE WATCH WAS EXPANDED TO JUST NW OF I-95 IN THE 330 PM FORECAST. ITS POSSIBLE THAT THE SNOW AMOUNTS NEAR AND EAST OF I95 ARE A BIT TOO LOW AND THAT THE WATCH MIGHT HAVE NEEDED A SLIGHT SEWD EXTENSION INTO NE MD AND N DE. DEPENDS HOW FAST RAIN CHANGES TO SNOW THERE. TUESDAY NIGHT...LEFTOVER WARMTH AND IT APPEARS THE LEADING EDGE OF THE PCPN SHIELD WILL BEGIN AS RAIN MOST OF THE AREA EXCEPT WELL TO THE NORTHWEST OF I-95 (HIGHER TERRAIN). NO ACCUMULATION ANTICIPATED BEFORE 7 AM. LIGHT WEST WIND BECOMING N-NE TOWARD MORNING. WEDNESDAY THROUGH MIDNIGHT WEDNESDAY EVENING... THE WEDNESDAY AFTERNOON EVENING COMMUTE SHOULD BE PROBLEMATIC...ESPECIALLY HILLS AND OVER THE KITTATINNY RIDGE IN NW NJ-POCONOS OF NE PA. WEST OF I-95...MAINLY WHERE SOME BANDING AND ASSOCIATED SNOWFALL RATE ENHANCEMENT IS EXPECTED ALONG THE SE EDGE OF THE COMMA HEAD (THERMAL AXIS OF PIVA AND FGEN). ACCUMULATION HERE MAY BE MORE ON THE ORDER OF 12 TO 1? BANDING COULD RESULT IN ISOLATED GREATER THAN 10 INCH AMOUNTS IN THE POCONOS AND NORTHERN SUSSEX COUNTY NJ. I-95 CORRIDOR RAIN MIXING WITH OR CHANGING TO WET SNOW DURING MIDDAY OR EARLY AFTERNOON THEN REMAINING AS SNOW BEFORE ENDING DURING WEDNESDAY EVENING. WHILE QPF IS GREATER HERE...SNOWFALL SHOULD BE NOT BE GREATER THAN 10 TO 1 RATIO. SLOPPY WET SNOW THAT COULD CLING TO TREES AND WIRES AND OBSCURE ROAD SIGNS DURING THE AFTERNOON-EVENING IN A 32-33F SURFACE TEMPERATURE ENVIRONMENT. IF 4 TO 6 INCHES OF WET SNOW WERE TO ACCUMULATE ON BRANCHES/WIRES...THE RISK OF BROKEN TREE LIMBS SHOULD INCREASE CONSIDERABLY. TOTALS UNKNOWN BUT SUSPECT MAINLY 1 TO 5 INCH AMOUNTS. ADDED A WATCH TO PHILADELPHIA AT THE LAST MINUTE JUST BEFORE 330 PM DUE TO AUTOMATED PHRASING FROM OUR FORECAST GRIDS. COAST: RAIN POSSIBLY ENDING AS SNOW WEDNESDAY EVENING. TOTALS NIL TO 2 INCHES? NO ACCUMULATIONS DURING THE DAY AS PER THE WATER TEMPERATURE STILL IN THE MID 50S, THE ONSHORE FLOW AND PROXIMITY OF THE WARMING ALOFT NEAR THE SURFACE LOW AND EAST OF THE VORT PATH SHOULD KEEP THEM WELL ABOVE FREEZING THROUGHOUT THE DAY. THE CAVEAT TO ALL OF THIS IS THAT THE LOCATION OF THE RAIN/SNOW TRANSITION AND EVEN SNOW RATIOS IS VERY MUCH DEPENDENT ON THE TEMPERATURE PROFILE. THERE IS STILL MODEL DISAGREEMENT, SO SNOW AMOUNTS REMAIN UNCERTAIN FROM I95 EASTWARD REMAIN FAR FROM CERTAIN. THE COAST SHOULD CHANGE TO SNOW OR FLURRIES WEDNESDAY EVENING BEFORE ENDING WHEN A SLIGHT ACCUMULATION COULD OCCUR. PRECIPITATION EVERYWHERE MODERATE TO HEAVY FOR A TIME DURING THE DAY WITH TAIL END SNOW IN EASTERN PA AND NW NJ POSSIBLY STILL MODERATE DURING THE EVENING. NORTH TO NORTHEAST WIND GUST 15-25 MPH I95 EASTWARD. RECORD DAILY SNOWFALL IS FORECAST FOR KABE (VULNERABLE RECORD OF 1.7 INCHES) AND DITTO AT KILG WHERE THE VULNERABLE DAILY RECORD IS 0.1 INCHES. AFTER MIDNIGHT WEDNESDAY NIGHT...JUST A SMATTERING OF FLURRIES AND VARIABLE CLOUDINESS WITH LIGHT WIND AND TEMPERATURES NEAR FREEZING. THURSDAY THROUGH SUNDAY... * THANKSGIVING DAY WILL BE DRY WITH BELOW NORMAL TEMPERATURES. * FRIDAY AND SATURDAY WILL FEATURE DRY WEATHER W/UNSEASONABLY COOL TEMPERATURES. * A COLD FRONTAL PASSAGE EXPECTED IN THE SUNDAY-MONDAY PERIOD W/TEMPERATURES EXPECTED TO MODERATE TO SEASONABLE LEVELS. THE MAIN CHALLENGE THURSDAY AND BEYOND WILL BE HOW THE MODELS RESOLVE A MID-LEVEL SPLIT FLOW REGIME OVER THE EASTERN PACIFIC AND THE TRANSITION FROM A MERIDIONAL FLOW ACROSS THE CONUS TO A ZONAL FLOW...AS THE NAO BECOMES POSITIVE AND THE PNA BECOMES NEGATIVE. WITH THE FLOW BECOMING ZONAL...THE MAIN UNCERTAINTY WILL BE W/SHORTWAVE ENERGY RIDING ALONG THE US/CANADIAN BORDER OVER THE WEEKEND...WHERE PREDICTABILITY IS LOW. THERE ARE DIFFERENCES IN THE AMPLITUDE AND TIMING OF THIS FEATURE...WHICH TRANSLATES INTO UNCERTAINTY W/THE TIMING OF A COLD FRONT AND TEMPERATURES...ESP LATE IN THE WEEKEND INTO EARLY NEXT WEEK. THURSDAY... FLOW REMAINS CYCLONIC ALOFT WITH X-SECS INDICATING ABUNDANT MOISTURE IN THE LOW AND MID-LEVELS...SO EXPECTING CONSIDERABLE CLOUDINESS. LOW-LEVEL FLOW WILL BE OUT OF THE NORTHWEST WITH A TRAJECTORY OFF THE GREAT LAKES. THE BEST LIFT AND JET DYNAMICS WILL BE TO THE SOUTHEAST AND THE DOWNSLOPING FLOW SHOULD KEEP ANY -SHSN CONFINED TO THE HIGHER TERRAIN OF THE FAR NW CWA... NOT EXPECTING ANY ACCUMULATION. IT WILL BE BRISK WITH MIXING TO 900 HPA SUPPORTING WIND GUSTS TO AROUND 20 KNOTS. FRIDAY... STRONG MID-LEVEL HEIGHT RISES SIGNAL THE RETURN TO A MORE ZONAL FLOW W/SURFACE HIGH-PRESSURE INVOF THE APPALACHIANS. THE COLUMN WILL DRY OUT ALONG WITH STRONG SUBSIDENCE AND A SURFACE FLOW OUT OF THE NORTHWEST...SO EXPECTING A DRY DAY. SATURDAY... SURFACE RIDGE MOVES OFFSHORE LEADING TO A SOUTHWEST FLOW ACROSS THE REGION. THE MODELS INDICATE AN OVERRUNNING REGIME IN ADVANCE OF A WEAK SHORTWAVE OVER THE GREAT LAKES. ATTM... THE DEEPEST MOISTURE AND BEST DYNAMICS ARE NORTHWEST OF THE CWA...THEREFORE ANTICIPATING ANOTHER DRY DAY. LATE WEEKEND INTO EARLY NEXT WEEK... THE MODELS INDICATE A SLOW COLD FRONTAL PASSAGE DURING THIS TIME AS THE SURFACE FRONT BECOMES PARALLEL TO THE MID-LEVEL FLOW. THIS PRESENTS THE BEST CHANCE OF QPF IN THE LONG TERM BUT IT SHOULD BE FAIRLY LIGHT AS THERE IS NO GMEX CONNECTION. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. MOSTLY VFR CONDITIONS SHOULD CONTINUE THROUGH 12Z. A COLD FRONT IS MAKING ITS WAY THROUGH THE REGION NOW, AND SHOULD BE OFF SHORE BY 09Z. AT ACY, THE WINDS MAY DECOUPLE ENOUGH FOR BRIEF BR TO DEVELOP AHEAD OF THE FRONT. HOWEVER, ONCE THE FRONT MOVES THROUGH ALL SITES SHOULD BE VFR. WINDS WILL SHIFT MORE WESTERLY BEHIND THE FRONT, AND COULD GUST UP TO 20 KT AT TIMES THROUGH THIS AFTERNOON. OUTLOOK.... TUESDAY NIGHT...VFR CIGS LOWER TO MVFR CONDITION RAIN SOUTH OF PHL AFTER 06Z/26. LIGHT WNW WIND BECOMING NNE BY DAWN WEDNESDAY AT 5 TO 15 KT. WEDNESDAY AND WEDNESDAY EVENING...A COASTAL STORM WILL BRING WIDESPREAD MVFR VARIABLE IFR CEILINGS. REDUCTIONS IN VISIBILITY DUE TO RAIN ALONG THE COAST (KACY/KMIV), RAIN SNOW MIX EVENTUALLY CHANGING TO ALL SNOW IN THE DELAWARE RIVER VALLEY (KTTN KPNE KPHL AND KILG) AND MOSTLY SNOW KABE AND KRDG. IN ADDITION, EXPECT PERSISTENT NORTHERLY OR NORTHEASTERLY WINDS DURING THE DAY WITH GUSTS 12-25 KT FROM WEST TO EAST. PRECIPITATION SHOULD END AS SNOW MOST TAF SITES DURING THE EVENING AND BY MIDNIGHT BE DIMINISHED TO A FEW FLURRIES EXCEPT POSSIBLY NO SNOW AT KMIV/KACY. A PLOWABLE...POSSIBLY SLUSHY SNOW ACCUMULATION IS EXPECTED ON ANY UNTREATED RUNWAYS-PAVEMENTS AT KRDG AND KABE WEDNESDAY. THANKSGIVING...CONDITIONS SLOWLY RETURN TO VFR AND WINDS SHIFT TO WESTERLY OR NORTHWEST. THERE COULD BE BRIEF MVFR CONDITIONS IN SCATTERED SNOW SHOWERS LATER THURSDAY MAINLY JUST N OF KRDG AND KABE. WINDS MAY GUST TO 25 KT. FRIDAY...VFR CONDITIONS EXPECTED. SATURDAY...VFR CONDITIONS EXPECTED.
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&& .MARINE... A SMALL CRAFT ADVISORY WILL CONTINUE TONIGHT. THE BAY FLAG WILL END TUESDAY MORNING, AND THE OCEAN FRONT EXTENDED THROUGH THE DAY TUESDAY DUE TO ELEVATED SEAS. OUTLOOK... TUESDAY NIGHT...DIMINISHING NW TO N WIND WITH WINDS AND SEAS BELOW SCA CRITERIA. WINDS TURN NE BY DAWN. WEDNESDAY...GALE CONDITIONS POSSIBLE WITH STRONG NORTHERLY OR NORTHEASTERLY WINDS. A GALE WATCH HAS BEEN ISSUED FOR MOST OF THE WATERS....STRONGEST WINDS IN THE ATLANTIC WATERS EAST OF DELAWARE. WEDNESDAY NIGHT...WINDS WILL SLOWLY DIMINISH TO SCA CRITERIA. THURSDAY...WINDS ARE EXPECTED TO EVENTUALLY FALL BELOW SCA CRITERIA BUT ATLANTIC SEAS MAY NOT DROP BELOW 5 FT TIL AT NIGHT. FRIDAY...POSSIBLE SCA COLD AIR ADVECTION WEST TO NORTHWEST FLOW. SATURDAY...WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SCA THRESHOLDS. && .CLIMATE... FOR OUR EIGHT CLIMATE SITES, HERE ARE THE RECORD HIGH TEMPERATURES FOR NOVEMBER 24TH AND THE MOST RECENT YEAR OF OCCURRENCE. RECORDS HAVE OCCURRED. DETAILS IN THE RER`S. RECORD HIGHS 11/24: ACY: 72 SET IN 1999 PHL: 71 SET IN 1979 ILG: 73 SET IN 1979 ABE: 69 SET IN 1931 TTN: 71 SET IN 1979 GED: 75 SET IN 1992 RDG: 69 SET IN 1979 MPO: 64 SET IN 1931 RECORD HIGHEST TEMP SO LATE IN THE SEASON (NOV 24)...JUST IN CASE WE REACH THIS VALUE. ACY: 77 12/7/1997 PHL: 73 12/7/1998 AND LAST OF SEVERAL ILG: 75 12/4/1998 ABE: 72 12/29/1984 AND LAST OF SEVERAL TTN: 76 12/7/1998 (LATTER OF TWO) GED: 77 12/1/1991 (SHORTER POR) RDG: 77 12/29/1984 MPO: 67 11/29/1990 REGARDING THE MIDWEEK COASTAL STORM BRINGING SNOW TO A LARGE PORTION OF OUR REGION, WE HAVE INCLUDED DAILY SNOWFALL RECORDS BELOW FOR OUR FOUR PRIMARY CLIMATE SITES THAT HAVE A LONG-STANDING UNBROKEN PERIOD OF RECORD (POR) WITH RESPECT TO HISTORICAL SNOWFALL DATA. DAILY SNOWFALL RECORDS: NOVEMBER 26TH: NOVEMBER 27TH: PERIOD OF RECORD: ACY: TRACE 1977,1957,1955 1.2 INCHES 1978 1874 PHL: 6.0 INCHES 1898 6.9 INCHES 1949,1938 1872 ILG: 0.1 INCHES 1950 4.5 INCHES 1978 1894 ABE: 1.7 INCHES 1925 7.0 INCHES 1938 1922 OTHER COOPERATIVE SITE SHORTER HISTORICAL RECORD CAN BE FOUND AT THE NWS MOUNT HOLLY WEBSITE UNDER NOW DATA. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR PAZ054-055. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR PAZ060>062-101-103-105. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR PAZ070-071-102-104-106. NJ...WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR NJZ001-007-008. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR NJZ009. WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY NIGHT FOR NJZ010-015. DE...NONE. MD...NONE. MARINE...GALE WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY EVENING FOR ANZ431-450>455. SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ450>455. SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ430-431.
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&& $$ SYNOPSIS...FRANCK NEAR TERM...JOHNSON SHORT TERM...ROBERTSON LONG TERM...DRAG/FRANCK AVIATION...DRAG/FRANCK/JOHNSON/ROBERTSON MARINE...DRAG/FRANCK/ROBERTSON CLIMATE...

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