Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 032048 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 348 PM EST TUE MAR 3 2015 .SYNOPSIS... A WARM FRONT WILL LIFT THROUGH THE AREA OVERNIGHT...FOLLOWED BY A ARCTIC COLD FRONT DURING THE DAY WEDNESDAY. THE FRONT WILL PUSH TO OUR SOUTH INTO THURSDAY WHILE LOW PRESSURE DEVELOPS AND MOVES ALONG THE BOUNDARY. HIGH PRESSURE WILL RETURN TO THE MID ATLANTIC REGION FOR FRIDAY AND FRIDAY NIGHT. A FRONTAL PASSAGE IS EXPECTED SATURDAY INTO SATURDAY NIGHT...FOLLOWED BY HIGH PRESSURE AGAIN SUNDAY INTO SUNDAY NIGHT. ANOTHER FRONTAL PASSAGE IS EXPECTED MONDAY INTO MONDAY NIGHT. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... THE CENTER OF HIGH PRESSURE HAS SHIFTED OFFSHORE THIS AFTERNOON. MEANWHILE, A TROUGH OF LOW PRESSURE WAS LIFTING NORTHEASTWARD ACROSS THE UPPER MIDWEST. SOUTHERLY FLOW IN BETWEEN THESE TWO SYSTEMS WILL CONTINUE TO STRENGTHEN OVER THE EASTERN SEABOARD. WARM AND MOIST AIR TRANSPORTED BY THESE WINDS WILL OVERRUN THE RETREATING COLD AIR THAT WAS PREVIOUSLY OVER OUR AREA. THE LEADING EDGE OF ISENTROPIC LIFT AND LOW-LEVEL CONVERGENCE MATCHED UP WELL WITH THE BAND OF PRECIPITATION THAT IS CURRENTLY MOVING INTO THE DELMARVA AND EASTERN PA. THE LEADING PRECIP WILL CONTINUE TO MOVE NORTHEASTWARD INTO THE REST OF THE CWA JUST IN TIME FOR THE START OF THE AFTERNOON COMMUTE. SNOW HAD ALREADY CHANGED OVER TO SLEET AT RDG-PTW-ILG AND LIQUID (RAIN/FREEZING RAIN) OVER SOUTH-CENTRAL PA AND ALONG THE CHESAPEAKE BAY AS OF 230 PM. THE TREND WAS TO SPEED UP THE TRANSITION TO SLEET AND RAIN/FREEZING RAIN BY A COUPLE OF HOURS FROM EARLIER FORECASTS BASED ON THE LATEST OBS AND MESOSCALE MODEL GUIDANCE. DEWPOINTS ARE LOW ENOUGH THAT AT LOCATIONS WHERE TEMPS ARE JUST ABOVE FREEZING PRIOR TO THE ONSET WILL WET-BULB DOWN TO AT OR JUST BELOW FREEZING ONCE PRECIP STARTS. EXPANDED THE WINTER WEATHER ADVISORY SOUTHWARD INTO CENTRAL DELMARVA AND FAR SOUTHERN NJ. A BRIEF PERIOD OF FREEZING RAIN WILL QUICKLY DEVELOP OVER THESE AREAS SINCE THE FASTER CHANGEOVER OCCURRED BEFORE THE SURFACE TEMPS WERE ABLE TO RESPOND TO THE WARMING SOUTHERLY WINDS. THE TIMING OF THE CHANGEOVER TO FREEZING RAIN LOOKS TO COINCIDE WITH THE START OF THE EVENING COMMUTE FOR THE I-95 CORRIDOR. EVEN WITH MINIMAL ICING, TRAVEL WILL BE ADVERSELY IMPACTED AS UNTREATED ROADS AND SIDEWALKS BECOME SLIPPERY, ESPECIALLY CONSIDERING THE TIMING. UNLIKE THE EVENT LAST SUNDAY WHERE THERE WAS NOT MUCH WIND AND WAA IN THE BOUNDARY LAYER, THE STRONG SOUTHERLY WINDS ALOFT WILL BE ABLE TO HAVE MORE OF AN INFLUENCE IN THE BOUNDARY LAYER, WHICH WILL BE MUCH MORE EFFECTIVE AT SCOURING OUT THE COLD AIR; SO THE WINDOW OF FREEZING RAIN WILL BE BRIEF. THE ONE EXCEPTION MAY BE THE I-78 CORRIDOR NORTHWARD WHERE THE TERRAIN COULD TRAP THE COLD AIR IN THE TYPICAL SHELTERED VALLEYS. WE ARE EXPECTING THE FREEZING RAIN TO PERSIST INTO THE OVERNIGHT IN THESE NORTHERN AREAS AND LOCALLY HIGHER AMOUNTS OF ICING BETWEEN ONE AND TWO TENTHS OF AN INCH ARE POSSIBLE. MUCH OF THE COASTAL PLAIN IS FORECAST TO RISE INTO THE 40S TONIGHT WITH A SOUTHEAST TO SOUTHWEST WIND. READINGS ARE EXPECTED TO BE MAINLY IN THE 30S IN AREAS TO THE NORTHWEST OF THE INTERSTATE 95 CORRIDOR. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... WINTER WEATHER ADVISORY CONTINUES INTO THE FIRST PART OF WEDNESDAY MORNING FOR THE POCONOS AND FAR NORTHWEST NJ, WHERE POCKETS OF SUB-FREEZING TEMPS AND FREEZING RAIN WILL PERSIST. OTHERWISE, WEDNESDAY WILL BE A RELATIVELY QUIET PERIOD IN BETWEEN TWO WINTER EVENTS. A COLD FRONT WILL APPROACH FROM THE NORTHWEST IN THE MORNING AND SLOWLY SAG SOUTHEASTWARD THROUGHOUT THE DAY. EXPECT PERIOD OF RAIN THROUGHOUT THE DAY FOR MUCH OF THE AREA. THE COVERAGE OF RAIN WILL BE HIGHEST NEAR THIS FRONTAL BOUNDARY. QPF AMOUNTS WILL BE LIGHT- LESS THAN A HALF INCH. LEANED TOWARD THE COOLER MET GUIDANCE FOR TEMPS GIVEN THE PERSISTENT CLOUDS AND PRECIP OVER THE AREA, AS WELL AS THE END TO THE WAA REGIME WITH WINDS VEERING OUT OF THE SOUTH AND SOUTHWEST. HIGHS WEDNESDAY RANGE FROM THE MID 30S IN THE POCONOS TO THE UPPER 40S IN SOUTHERN DE. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... WINTER STORM WATCH ISSUED FOR THE ENTIRE CWA FOR WEDNESDAY NIGHT INTO THURSDAY WITH THE POTENTIAL FOR SIGNIFICANT SNOWFALL ACCUMULATIONS. MORE DETAILS WILL FOLLOW SHORTLY IN AN UPDATED LONG TERM DISCUSSION. THE START OF THE LONG TERM FORECAST BEGINS WITH A MESSY FORECAST, BUT IMPROVING WEATHER DOES RETURN BY THE END OF THE WEEK AND WEEKEND. THE NEXT SHORT WAVE ALOFT IS EXPECTED WEDNESDAY EVENING AND OVERNIGHT, WHILE AN AREA OF LOW PRESSURE DEVELOPS ALONG THE FRONTAL BOUNDARY TO THE SOUTH. THIS SHOULD PUSH ANOTHER AREA OF PRECIPITATION ACROSS THE AREA DURING THE EVENING AND INTO THE OVERNIGHT. WITH THE FRONT TO OUR SOUTH, TEMPERATURES ARE EXPECTED TO COOL THROUGH THE NIGHT. WHILE PRECIPITATION MAY BEGIN AS RAIN, IT IS EXPECTED TO TRANSITION TO A WINTRY MIX, BEFORE CHANGING OVER TO ALL SNOW. THE GFS AND ECMWF ARE CLOSER TO ONE ANOTHER WITH THEIR THERMAL PROFILE AND SHOW THIS TRANSITION BETTER THAN THE NAM. THE NAM HAS A LARGE WARM NOSE WELL ABOVE THE SURFACE AND WOULD LEAD TO MORE SLEET. WHILE WE THINK THERE WILL BE A COUPLE OF HOURS OF SLEET WHEN THE TRANSITION BEGINS, THE FORECAST IS MORE IN LINE WITH THE GFS/ECMWF. THE LOW PRESSURE MOVING ALONG THE FRONT WILL PUSH OFFSHORE TO OUR SOUTH EARLY ON THURSDAY AND MOVE TO OUR EAST THROUGH THE DAY. MEANWHILE, THE MAIN TROUGH ALOFT WILL BE APPROACHING DURING THE DAY AND HELP KICK THE WHOLE SYSTEM AWAY FROM THE AREA BY THE END OF THE DAY. HOWEVER, BEFORE THIS ALL MOVES OUT, THE SNOW WILL HAVE TO PROGRESS THROUGH THE REMAINDER OF THE AREA. ALL IN ALL, IT LOOKS LIKE OUR ENTIRE AREA WILL SEE AN ACCUMULATING SNOWFALL, WITH THE I-95/I-295 CORRIDOR POSSIBLY SEEING THE MOST SNOW WITH AS MUCH AS 6-8 INCHES POSSIBLE, WITH LESS ON EITHER SIDE. THIS WOULD HAVE A LARGE IMPACT ON THE MORNING RUSH THURSDAY. ALL PRECIPITATION SHOULD BE ENDING BY THE EVENING THURSDAY. CLEARING CONDITIONS WILL RETURN TO THE AREA, ALONG WITH ANOTHER SHOT OF COLD AIR. OVERNIGHT LOWS ARE EXPECTED TO ONCE AGAIN RETURN TO SINGLE DIGITS FOR MUCH OF THE AREA OVERNIGHT THURSDAY INTO FRIDAY MORNING. HIGH PRESSURE BRIEFLY RETURNS TO THE AREA FRIDAY INTO FRIDAY NIGHT. THIS WILL CONTINUE THE COLD WEATHER. TEMPERATURES WILL REMAIN WELL BELOW NORMAL, ALTHOUGH FRIDAY NIGHT IS NOT EXPECTED TO BE AS COLD AS THURSDAY NIGHT. A FRONTAL BOUNDARY IS EXPECTED SATURDAY INTO SATURDAY NIGHT, ALTHOUGH THERE IS NOT MUCH MOISTURE ASSOCIATED WITH IT AT THIS TIME. SO FOR NOW THE FORECAST WILL REMAIN DRY. HIGH PRESSURE ONCE AGAIN BRIEFLY RETURNS TO THE AREA SUNDAY INTO SUNDAY NIGHT, BEFORE ANOTHER FRONTAL BOUNDARY APPROACHES MONDAY INTO MONDAY NIGHT. AGAIN NOT MUCH MOISTURE IS EXPECTED WITH THIS FRONTAL BOUNDARY EITHER, SO FOR NOW WE WILL KEEP THE WEATHER DRY THROUGH MONDAY. && .AVIATION /21Z TUESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS WILL DETERIORATE TO MVFR AS PRECIPITATION STARTS TO OVERSPREAD THE REGION. THERMAL PROFILES SHOW A WARM LAYER DEEPENING ABOVE THE SURFACE WHICH WILL CAUSE SLEET TO FALL, MIXING WITH SNOW EARLY, WITH AND THAN A QUICK TRANSITION TO FREEZING RAIN AT THE TERMINALS LATE THIS AFTERNOON. ALL TERMINALS ARE EXPECTED TO CHANGE OVER TO PLAIN RAIN BY AROUND 03-05Z EXCEPT MAYBE ABE FOR A FEW HOURS INTO THE OVERNIGHT. CONDITIONS WILL REMAIN MVFR/IFR THROUGH WEDNESDAY. WINDS OUT OF THE SOUTH THIS AFTERNOON WILL CONTINUE TO GRADUALLY VEER TOWARDS THE SOUTHWEST TONIGHT. IN ADDITION, WINDS AROUND 2000FT ABOVE THE SURFACE ARE AROUND 50 KT WHILE WINDS AT THE SURFACE ARE LESS THAN 10 KNOTS. LOW LEVEL WIND SHEER WILL BE AN ISSUE FROM THIS EVENING THROUGH LATE. WIND SHEER WILL LESSEN BY EARLY WEDNESDAY AND WINDS WILL VEER TO THE WEST AND GRADUALLY BECOMING NORTHWEST WEDNESDAY MORNING. OUTLOOK... WEDNESDAY NIGHT-THURSDAY...RAIN EARLY, CHANGING TO A WINTRY MIX THEN SNOW OVERNIGHT AND CONTINUING INTO THURSDAY. ACCUMULATING SNOWFALL IS EXPECTED FOR THE TAF SITES OVERNIGHT WEDNESDAY INTO THURSDAY. THURSDAY NIGHT...IMPROVING TO VFR DURING THE EVENING. FRIDAY-SATURDAY...MOSTLY VFR. && .MARINE... SOUTHERLY WINDS WILL INCREASE THIS EVENING. ALTHOUGH STORM-FORCE WINDS WILL BE LOCATED ONLY 1,000 FT AGL AND GALE-FORCE WINDS 200 FT AGL, A STRONG INVERSION WILL NOT BE FAVORABLE FOR THESE WINDS TO MIX DOWN TO THE SURFACE. HOWEVER, THE PRESSURE GRADIENT TIGHTENS ENOUGH FOR SUSTAINED WINDS TO APPROACH SCA CRITERIA TONIGHT. SEAS ARE ALSO FORECAST TO BUILD TO 4-5 FT OVERNIGHT. THEREFORE, A SCA WAS ISSUED FOR THE COASTAL WATERS. THE WINDS TURN MORE WESTERLY ON WEDNESDAY AND DECREASE JUST AHEAD OF A COLD FRONT. DO NOT EXPECT SCA GUSTS. HOWEVER, ELEVATED SEAS NEAR 5 FT MAY LINGER INTO THE MORNING. CONFIDENCE WASN`T HIGH ENOUGH TO EXTEND THE ADVISORY AT THIS POINT. OUTLOOK... WEDNESDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED, ALTHOUGH WINDS MAY GUST NEAR 20 KNOTS. A FRONTAL BOUNDARY IS EXPECTED LATE WEDNESDAY NIGHT. THURSDAY-THURSDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS EXPECTED TO DEVELOP BEHIND THE COLD FRONT AND CONTINUE INTO THURSDAY NIGHT. FRIDAY-SATURDAY...SUB-SMALL CRAFT ADVISORY CONDITIONS RETURN. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR PAZ060>062-105. WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR PAZ054-055-060>062-101>106. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR PAZ070-071. WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR PAZ070- 071-101>104-106. WINTER WEATHER ADVISORY UNTIL 9 AM EST WEDNESDAY FOR PAZ054- 055. NJ...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR NJZ007>010. WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR NJZ001-007>010-012-015. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR NJZ021>025. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR NJZ021>025. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR NJZ013-014-016>020-026-027. WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR NJZ012>020-027. WINTER WEATHER ADVISORY UNTIL 9 AM EST WEDNESDAY FOR NJZ001. DE...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR DEZ002. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR DEZ002>004. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR DEZ001. WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR DEZ001. MD...WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR MDZ015-019-020. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR MDZ015-019-020. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR MDZ008-012. WINTER WEATHER ADVISORY UNTIL 1 AM EST WEDNESDAY FOR MDZ008- 012. MARINE...SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 6 AM EST WEDNESDAY FOR ANZ450>455. && $$ SYNOPSIS...FRANCK NEAR TERM...KLEIN SHORT TERM...KLEIN LONG TERM...ROBERTSON/KLEIN AVIATION...MEOLA/ROBERTSON MARINE...KLEIN/ROBERTSON

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