Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 031527 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1027 AM EST TUE MAR 3 2015 .SYNOPSIS... HIGH PRESSURE WILL MOVE FARTHER OUT TO SEA THROUGH TODAY. AS LOW PRESSURE MOVES THROUGH SOUTHEAST CANADA TONIGHT, A WARM FRONT WILL LIFT THROUGH THE AREA OVERNIGHT, FOLLOWED BY A 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 PM THIS EVENING/...
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AT 9 AM, 1032 MB SURFACE HIGH PRESSURE WAS CENTER OVER THE DELMARVA. THE LATEST WV AND IR SATELLITE IMAGERY SHOWS A PLUME OF MOISTURE ORIGINATING FROM THE TROPICAL PACIFIC THAT IS BEING TRANSPORTED BY A STRONG UPPER JET STREAK AROUND THE UPPER RIDGE TOWARD OUR REGION. MOST LOCATIONS ARE CLOUDY THIS MORNING WITH THICKER MID AND HIGH CLOUDS STREAMING INTO OUR AREA. THE HIGH WILL MOVE OFFSHORE THIS AFTERNOON WHILE AN AREA OF LOW PRESSURE OVER THE CENTRAL PLAINS TO UPPER MIDWEST. SOUTHERLY FLOW BETWEEN THESE TWO SYSTEMS WILL STRENGTHEN AS IT REACHES OUR AREA DURING THE AFTERNOON. WARM AND MOIST AIR TRANSPORTED BY THESE WINDS WILL OVERRUN THE RETREATING COLD AIR THAT IS ALREADY IN PLACE OVER OUR AREA. THIS WILL RESULT IN THE PRECIPITATION DEVELOPING OVER OUR AREA FROM WEST TO EAST BETWEEN 1 PM AND 4 PM. THE 12Z RAOB SOUNDINGS AT IAD/APG/OKX SHOW VERY DRY AIR IN THE LOW LEVELS SO IT MAY TAKE AN HOUR OR TWO LATER FOR THE PRECIP TO ACTUALLY REACH THE GROUND. EXPECT A BRIEF (1-3 HR; MAYBE EVEN SHORTER IN THE DELMARVA) PERIOD OF SNOW AT THE ONSET AND THEN SLEET BEFORE IT CHANGES TO RAIN AND FREEZING RAIN THIS EVENING. WE DID UPDATE THE POP AND WX GRIDS WITH THE MORNING ESTF TO TRY TO TIME ONSET OF PRECIP AND THE PTYPE TRANSITION BUT EDITS WERE OVERALL MINOR.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
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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. EVEN WITH MINIMAL ICING FARTHER SOUTH TOWARD THE I-95 CORRIDOR, TRAVEL WILL BE ADVERSELY IMPACTED AS UNTREATED ROADS AND SIDEWALKS BECOME SLIPPERY, ESPECIALLY CONSIDERING THE SNOW/SLEET STARTING AROUND RUSH HOUR THAT COULD TRANSITION TO A BRIEF PERIOD OF FREEZING RAIN TOWARD THE END OF THE EVENING COMMUTE. DO NOT SEE A NEED TO EXPAND THE CURRENT WINTER WEATHER ADVISORIES AND FARTHER SOUTH AND EAST AS THESE AREAS SHOULD CHANGEOVER FROM SNOW/SLEET TO RAIN. THE CURRENT FORECAST FOR SNOW/SLEET AND ICE ACCUMULATIONS APPEAR TO BE IN GOOD SHAPE. NOTE: THE CURRENT FORECAST STORM TOTAL SNOWFALL MAP ON OUR WEBPAGE IS FOR THE NEXT EVENT WEDNESDAY NIGHT AND THURSDAY SINCE SNOW/SLEET ACCUMULATIONS WITH TODAY`S EVENT WILL BE MINOR (1-2 INCHES W/ ISOLATED 3 INCHES IN NORTHEAST PA AND NORTHWEST NJ). 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. THE GUIDANCE HAS BEEN TRENDING DOWNWARD WITH RAINFALL AMOUNTS. WE ARE EXPECTING ANYWHERE FROM A QUARTER TO THREE QUARTERS OF AN INCH WHICH SHOULD NOT CAUSE MUCH OF A PROBLEM EVEN WITH SOME SNOW MELT.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/... 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. A COLD FRONT WILL BE MAKING ITS WAY ACROSS THE AREA DURING THE DAY WEDNESDAY AS PRECIPITATION SHOULD BE ON GOING. TEMPERATURES WILL BE RISING AS A WARM FRONT WILL HAVE LIFTED NORTH OF THE AREA, AND EVERYONE IS EXPECTED TO CHANGE OVER TO RAIN. THERE COULD BE SOME LINGERING FREEZING RAIN ACROSS FAR NORTHEAST PENNSYLVANIA AND NORTHWEST NEW JERSEY, SO WE EXTENDED THE ADVISORY A COUPLE OF HOURS. AS THE FRONT CONTINUES THROUGH THE AREA AND SAGS JUST TO OUR SOUTH, WE MAY GET A BREAK IN PRECIPITATION LATE IN THE DAY AS THE LEAD SHORT WAVE MOVES PAST OUR AREA. HOWEVER, THIS WILL ONLY BE TEMPORARY. THE NEXT SHORT WAVE ALOFT IS EXPECTED DURING THE 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 /15Z TUESDAY THROUGH SATURDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS ARE EXPECTED THROUGH AROUND 1900Z TO 2000Z, THEN CONDITIONS WILL DETERIORATE RAPIDLY AS SNOW AND SLEET BUILD INTO OUR REGION FROM THE WEST. WE ARE ANTICIPATING MAINLY IFR CONDITIONS FOR THIS EVENING AND TONIGHT. THE SNOW AND SLEET SHOULD TRANSITION THROUGH FREEZING RAIN THEN TO RAIN FOR TONIGHT. A LIGHT AND VARIABLE WIND THIS MORNING IS EXPECTED TO SETTLE INTO THE SOUTHEAST AND SOUTH FOR THIS AFTERNOON AND EVENING AROUND 5 TO 10 KNOTS. THE WIND MAY SHIFT TOWARD THE SOUTHWEST LATE TONIGHT. A LOW LEVEL SOUTHWESTERLY JET IS EXPECTED TO DEVELOP OVER OUR REGION TONIGHT. AS A RESULT, WE HAVE INCLUDED LOW LEVEL WIND SHEAR. OUTLOOK... WEDNESDAY...MVFR/IFR CONDITIONS WITH PERIODS OF RAIN EXPECTED. 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...
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM EST WEDNESDAY FOR PAZ060>062-105. WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM EST WEDNESDAY FOR PAZ054-055. WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 1 AM EST WEDNESDAY FOR PAZ070-071-101>104-106. NJ...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM EST WEDNESDAY FOR NJZ007>010. WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM EST WEDNESDAY FOR NJZ001. WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 1 AM EST WEDNESDAY FOR NJZ012>020-027. DE...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 1 AM EST WEDNESDAY FOR DEZ001. MD...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 1 AM EST WEDNESDAY FOR MDZ008-012. MARINE...SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 6 AM EST WEDNESDAY FOR ANZ450>455.
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&& $$ SYNOPSIS...ROBERTSON NEAR TERM...KLEIN SHORT TERM...IOVINO/KLEIN LONG TERM...ROBERTSON AVIATION...IOVINO/ROBERTSON MARINE...KLEIN/ROBERTSON

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