Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 270305 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1005 PM EST MON JAN 26 2015 .SYNOPSIS... A RAPIDLY INTENSIFYING LOW PRESSURE SYSTEM EAST OF THE VIRGINIA CAPES WILL MOVE NORTHEAST AND PASS NEAR CAPE COD MASSACHUSETTS DURING THE MIDDLE OF THE DAY ON TUESDAY BEFORE WEAKENING AS IT MOVES TOWARD THE CANADIAN MARITIMES ON WEDNESDAY. A HIGH PRESSURE SYSTEM FROM THE WEST IS EXPECTED TO ARRIVE OVER THE REGION ON WEDNESDAY NIGHT. A CLIPPER TYPE LOW PRESSURE SYSTEM IS EXPECTED TO FOLLOW WITH ITS COLD FRONT MOVING THROUGH EARLY FRIDAY. ANOTHER HIGH PRESSURE SYSTEM IS THEN ANTICIPATED FOR SATURDAY. ANOTHER LOW PRESSURE SYSTEM SHOULD MOVE THROUGH THE EASTERN UNITED STATES LATE SUNDAY OR EARLY MONDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... MAJOR WINTER STORM CONTINUES TO STRENGTHEN THIS EVENING OFF THE EAST COAST. THE TROUGH ALOFT HAS BECOME FULLY NEGATIVELY TILTED TO OUR SOUTH AND WEST THIS EVENING. A SHORT WAVE/VORTICITY MAX HAS ROUNDED THE BASE AND WILL LIFT TO THE NORTHEAST OVERNIGHT. AS THIS HAPPENS, THE SURFACE LOW OFF THE DELMARVA COAST THIS EVENING WILL RAPIDLY INTENSIFY AS IT LIFTS TO THE NORTHEAST AND SOUTH OF LONG ISLAND OVERNIGHT. HEAVY SNOW IS NOW BEGINNING TO FILL IN FROM EASTERN MASSACHUSETTS, SOUTHWARD ACROSS LONG ISLAND, AND OFF THE NEW JERSEY COAST, AND IS CONTINUING TO SHOW SIGNS OF PIVOTING AND MOVING TOWARD OUR AREA OVER THE NEXT FEW HOURS. ADDITIONALLY, SNOW HAS ALSO BEEN DEVELOPING AND MOVING ACROSS MUCH OF OUR AREA OVER THE LAST SEVERAL HOURS AS WELL. MODEL GUIDANCE CONTINUES TO SHOW SNOWFALL SPREADING ACROSS THE AREA FROM NORTHEAST TO SOUTHWEST THROUGH THE NIGHT AS STRONG OMEGAS WITHIN THE DENDRITIC GROWTH ZONE ARE EXPECTED TO BEGIN DEVELOPING ACROSS THE EASTERN HALF OF THE AREA BETWEEN NOW AND MIDNIGHT, AND CONTINUE INTO THE MORNING HOURS TUESDAY. WE HAVE NOT MADE ANY CHANGES TO THE WARNINGS AND ADVISORIES FROM EARLIER TODAY AS WE HAVE NOT GOTTEN INTO THE HEAVIEST SNOW PERIOD YET. HOWEVER, THE LATEST NAM HAS CUT BACK ON ITS SNOW TOTALS AND IS MORE IN LINE WITH OTHER GUIDANCE. SO WE HAVE CUT BACK TOTALS SOME ACROSS THE AREA, BUT WE WILL WAIT TO MAKE BIG CHANGES UNTIL WE GET MORE INTO THE HEART OF THE STORM AND HAVE ALL THE 00Z GUIDANCE IN TO GET A BETTER HANDLE ON THE POTENTIAL SNOW AMOUNTS. THE HIGHEST AMOUNTS CONTINUE TO BE EXPECTED ACROSS NORTHEAST AND EASTERN NEW JERSEY AND DECREASING SOUTH AND WEST FROM THERE. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... IT LOOKS LIKE THE SFC LOW WILL REACH ITS DEEPEST POINT SOMETIME AROUND 12Z TO 15Z TUESDAY MORNING SOMEWHERE SOUTH OF CAPE COD OR EASTERN LONG ISLAND. SOME WRAP-AROUND BANDS OF HEAVY SNOW WILL LIKELY BE CONTINUING OVER NRN NJ FOR A WHILE IN THE MORNING BUT WILL START TO WEAKEN AND/OR MOVE NEWD BY MID-DAY. A FEW MORE INCHES OF ACCUMULATION ARE EXPECTED IN THE MORNING BUT NOT MUCH ELSE IN THE AFTERNOON. POPS ON TUES GO FROM CATEGORICAL IN THE MORNING TO NONE OR SLGT CHC IN THE LATE AFTN...DECREASING FROM SW TO NE AS THE STORM PULLS AWAY. GUSTY WINDS MAY CAUSE BLOWING SNOW TO CONTINUE EVEN THOUGH PRECIP HAS ENDED. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... THE GFS INITIALIZATION LOOKED SLIGHTLY BETTER THAN THE WRF-NMMB. THE TROF ITSELF LOOKED SLIGHTLY BROADER, NOT AS SHARP, BUT ALREADY WAS TAKING A SLIGHTLY NEGATIVE TILT. THERMALLY 850MB AND 925MB IT WAS A MIXTURE OF GFS AND WRF-NMMB. OVERALL THERE HAS NOT BEEN THAT MUCH OF A CHANGE IN THE LONG TERM WITH A CLIPPER TYPE SYSTEM FOR THURSDAY NIGHT AND POSSIBLY A STRONGER SYSTEM LATE SUNDAY INTO MONDAY. IT WILL BE UNSEASONABLY COLD AND MOST IF NOT ALL OF THE PCPN WILL BE IN THE FORM OF SNOW. FOR TUESDAY NIGHT EVEN LOOKING AT THE SLOWEST MODELING SOLUTIONS, THEY BARELY HAVE ANY MEASURABLE IN OUR CWA. THE FASTER CAN GGEM/UKMET/GFS SNOW IS LONG GONE. WE REMOVED POPS EXCEPT FOR FAR NERN CWA AND POSSIBLY SOME LAKE EFFECT SNOW SHOWERS MAKING IT INTO THE POCONOS. WINDS WILL BE DECREASING, BUT WIND CHILL FACTORS WILL STILL FALL INTO THE SINGLE NUMBERS AND BELOW ZERO NORTHWESTERN CWA. BECAUSE OF THE FRESH SNOW COVER, WE SIDED WITH THE COLDER DATASETS, CLOSER TO NAM MOS. A QUIETER DAY ON WEDNESDAY WITH HIGH PRESSURE NOSING CLOSER TO OUR AREA. THE PREDICTED LOW LEVEL MOISTURE DOES NOT LOOK THAT IMPRESSIVE AND SKIES SHOULD BE MOSTLY SUNNY. EVEN SO, WE LIKELY WILL NOT REACH THE FREEZING MARK IN THE BULK OF OUR CWA. WEDNESDAY NIGHT WILL BE A VERY COLD NIGHT. HOW COLD WILL DEPEND UPON HOW QUICKLY CLOUDINESS STARTS MOVING ACROSS FROM THE NEXT CLIPPER LIKE SYSTEM. WINDS WILL BE LIGHT REGARDLESS. WE ARE COLDER THAN ALL OF THE GUIDANCE DATASETS WITH MIN TEMPS AND IN REALITY MAY NOT BE COLD ENOUGH. DECREASING SUNSHINE AS THURSDAY PROGRESSES. THERE IS GOOD MODELING CONSENSUS OF MID LEVEL OMEGA AND QVEC CONVERGENCE WITH THIS SYSTEM ARRIVING BY 00Z. GIVEN THAT THE WAA PHASE LIKES TO SNEAK IN EARLY, WE KEPT PCPN CHANCES IN FOR LATE IN THE DAY. PTYPE SHOULD BE PRIMARILY SNOW. SOME MIXING BASED ON FCST 925MB TEMPS ABOVE ZERO MIGHT OCCUR FAR SE. THE BULK OF THE CLIPPER PCPN IS EXPECTED TO OCCUR AT NIGHT. ASSUMING IT DOES NOT ARRIVE IN TIME FOR THE EVENING COMMUTE, ITS APPEARING TO BE A BORDERLINE ADVISORY CRITERIA TYPE EVENT SNOW. PCPN SHOULD END BY FRIDAY MORNING WITH A WINDIER DAY IN WAKE OF THE SYSTEM`S COLD FRONT. COLDER WEATHER FOR FRIDAY NIGHT AND SATURDAY AS THE NEXT ARCTIC/CANADIAN AIR MASS MOVES EASTWARD. WE THEN REPEAT THE PROCESS LATER IN THE WEEKEND AS THE HIGH PRESSURE SYSTEM MOVES OFFSHORE AND ANOTHER FRONT APPROACHES THE REGION. ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO FORM ON THE FRONT. THIS ONE COULD TAP GULFMEX MOISTURE AND THUS BE A SNOWIER SYSTEM. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. **HIGH IMPACT EVENT, ESPECIALLY TONIGHT AND TUESDAY MORNING** TONIGHT-EARLY TUESDAY...CONDITIONS VARY FROM SITE TO SITE THIS EVENING AS SCATTERED AREAS OF LIGHT SNOW CONTINUE TO DEVELOP. AS THE SNOW SPREADS ACROSS THE AREA OVERNIGHT, CONDITIONS WILL CONTINUE TO DETERIORATE THROUGH THE NIGHT AND IFR CONDITIONS WILL BECOME THE NORM AT ALL SITES. A PERIOD OF MODERATE TO AT TIMES HEAVY SNOW IS EXPECTED TO CONTINUE TO DEVELOP AND SPREAD ACROSS THE AREA THROUGH THE NIGHT, AND PRODUCE SNOWFALL RATES OF ONE TO TWO INCHES PER HOUR AT TIMES, ESPECIALLY THROUGH NJ AND THE DELAWARE VALLEY. IFR TO LIFR CIGS AND VSBYS ARE EXPECTED AS THE SNOW DEVELOPS AND MOVES ACROSS THE AREA. GUSTY NORTH- NORTHEAST WINDS WILL CONTINUE, WITH GUSTS TO AROUND 25-30 KNOTS AT TIMES. AREAS OF BLOWING SNOW ARE EXPECTED. REST OF TUESDAY...AROUND MIDDAY AND INTO THE AFTERNOON, IMPROVEMENT TO MVFR CONDITIONS ARE EXPECTED WITH SOME CONTINUED LIGHT SNOW REMAINING ACROSS THE REGION. BLOWING AND DRIFTING SNOW WILL BE AN ISSUE, THOUGH, AS WINDS BACK MORE TOWARD THE NORTHWEST WITH CONTINUED GUSTS INTO THE 25 TO 30 KNOT RANGE. SOME LATE-DAY IMPROVEMENT TO VFR IS EXPECTED, BUT TIMING IS A LITTLE UNCERTAIN. OUTLOOK... TUESDAY NIGHT...VFR. GUSTY NORTHWEST WINDS. WEDNESDAY AND WEDNESDAY NIGHT...PRIMARILY VFR. THURSDAY INTO FRIDAY MORNING...VFR TO START THURSDAY THEN LIKELY BECOMING MVFR OR IFR IN SNOW WITH HIGHEST CONFIDENCE NORTHERN AIRPORTS AND TERMINALS. FRIDAY AFTERNOON AND EVENING...VFR WITH GUSTY NORTHWEST WINDS. FRIDAY OVERNIGHT INTO SATURDAY...PRIMARILY VFR. && .MARINE... STORM AND GALE WARNINGS HAVE BEEN LEFT AS IS. WINDS ARE FCST TO INCREASE TONIGHT INTO TUESDAY AS LOW PRESSURE OFF THE MID-ATLANTIC COAST DEEPENS TO AROUND 975 MB BY 1200Z TOMORROW MORNING. WINDS ARE EXPECTED TO GUST TO NEAR 50 KT NORTH OF CAPE MAY AND 40 TO 45 KT SOUTH. SEAS WILL BUILD TO 10 TO 12 FT OR HIGHER TONIGHT WITH THE NE FETCH. WINDS AND SEAS WILL GRADUALLY SUBSIDE ON TUESDAY BUT CONDS WILL REMAIN QUITE ROUGH. ALSO...VSBY WILL BE VERY POOR AT TIME TONIGHT AND TUESDAY MORNING IN BANDS OF HEAVY SNOW. OUTLOOK... TUESDAY NIGHT...WE WILL BE TRANSCENDING FROM GALES INTO SMALL CRAFT ADVISORY CONDITIONS. FREEZING SPRAY. WEDNESDAY...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED WITH FREEZING SPRAY. WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...NO MARINE HEADLINES ARE ANTICIPATED. SOME FREEZING SPRAY POSSIBLE WEDNESDAY NIGHT. FRIDAY AND SATURDAY...A SCA SHOULD EVENTUALLY BE NEEDED FRIDAY AS A NORTHWEST FLOW OF COLD AIR ADVECTION DEVELOPS BEHIND THE DEPARTING CLIPPER LOW. WE MIGHT COME CLOSE TO GALE FORCE GUSTS FRIDAY NIGHT. WINDS SHOULD START DECREASING BELOW SMALL CRAFT ADVISORY LEVELS ON SATURDAY. && .TIDES/COASTAL FLOODING... NO CHANGE FOR THE COASTAL FLOODING HIGHLIGHTS WITH THIS FORECAST. STILL RELATIVELY HIGH CONFIDENCE OF THE UPPER END OF MINOR TO THE LOWER END OF MODERATE TIDAL FLOODING ALONG THE ATLANTIC COAST WITH TONIGHT/S HIGH TIDE CYCLE, SO KEPT THE COASTAL FLOOD WARNING AS IS. THERE IS LESS CONFIDENCE ON THE UPPER DELAWARE BAY AND THE TIDAL DELAWARE. BY THE TIME OF THE HIGH TIDE ON THE UPPER BAY, WINDS SHOULD HAVE SHIFTED TO NORTHWESTERLY, LIMITING TIDAL DEPARTURES. MINOR FLOODING IS POSSIBLE, BUT AT THIS TIME CONFIDENCE IS TOO LOW TO ISSUE ANY COASTAL FLOOD ADVISORIES FOR THESE LOCATIONS. && .CLIMATE... RECORD (VULNERABLE) DAILY SNOW FALL FOR OUR LONG TERM CLIMATE SITES. TUESDAY 1/27. ACY 4.0 1946 PHL 4.1 1941 ILG 2.9 2004 ABE 8.0 1897 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER STORM WARNING UNTIL 6 PM EST TUESDAY FOR PAZ070-071- 103>106. WINTER WEATHER ADVISORY UNTIL 3 PM EST TUESDAY FOR PAZ060-101- 102. WINTER STORM WARNING UNTIL 3 PM EST TUESDAY FOR PAZ054-055-061- 062. NJ...WINTER STORM WARNING UNTIL 6 PM EST TUESDAY FOR NJZ001-007>010- 015>019-021>025-027. COASTAL FLOOD WARNING UNTIL 7 AM EST TUESDAY FOR NJZ012>014- 020>027. BLIZZARD WARNING UNTIL 6 PM EST TUESDAY FOR NJZ012>014-020-026. DE...COASTAL FLOOD WARNING UNTIL 7 AM EST TUESDAY FOR DEZ002>004. WINTER WEATHER ADVISORY UNTIL 3 PM EST TUESDAY FOR DEZ001>004. MD...WINTER WEATHER ADVISORY UNTIL 3 PM EST TUESDAY FOR MDZ008-012- 015-019-020. MARINE...STORM WARNING UNTIL 6 PM EST TUESDAY FOR ANZ450>453. GALE WARNING UNTIL 6 PM EST TUESDAY FOR ANZ430-431-454-455. && $$ SYNOPSIS...DRAG/GIGI NEAR TERM...AMC/ROBERTSON SHORT TERM...AMC LONG TERM...GIGI AVIATION...DRAG/GIGI/KLINE/ROBERTSON MARINE...AMC/DRAG/GIGI TIDES/COASTAL FLOODING...JOHNSON CLIMATE...DRAG

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