Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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643 FXUS61 KPHI 042040 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 340 PM EST THU FEB 4 2016 .SYNOPSIS...
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AN AREA OF LOW PRESSURE WILL TRACK ALONG AN OFFSHORE FRONT TONIGHT AND FRIDAY MORNING BEFORE MOVING NORTHEAST OF OUR AREA. HIGH PRESSURE GRADUALLY BUILDS INTO OUR REGION LATE FRIDAY AND SATURDAY, THEN A WEAK COLD FRONT MOVES THROUGH EARLY SUNDAY. A STRONG OCEAN STORM SHOULD TRACK WELL OFFSHORE LATER SUNDAY INTO MONDAY, THEN ANOTHER STORM LOOKS TO REDEVELOP OFF OF THE MID ATLANTIC COAST LATER MONDAY AND TUESDAY BEFORE MOVING OUT TO SEA WEDNESDAY INTO THURSDAY.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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A WINTER WEATHER ADVISORY IS IN EFFECT FOR MUCH OF OUR FORECAST AREA FOR LATE TONIGHT THROUGH FRIDAY MORNING. A COLD FRONTAL BOUNDARY SITS JUST TO THE EAST OF OUR AREA THIS AFTERNOON AND HAS STALLED. A LOW PRESSURE SYSTEM HAS DEVELOPED ALONG THE FRONTAL BOUNDARY NEAR THE NORTH CAROLINA/VIRGINIA BORDER. AS THIS LOW TRACKS ALONG THE STALLED BOUNDARY, IT WILL DEEPEN AND STRENGTHEN. WITH THE CENTER OF THE LOW EXPECTED TO TRACK TO THE EAST OF THE AREA, WE SHOULD MISS OUT ON SOME OF THE STRONGEST WINDS BUT WE WILL STILL SEE SOME IMPACTS, ESPECIALLY OVERNIGHT, FROM THIS SYSTEM. TIMING...SOME RAIN IS ALREADY MOVING IN ALONG OUR COASTAL AND SOUTHERN ZONES AND WILL GRADUALLY SPREAD NORTHWARD THROUGH THE REGION. BASED ON MODEL GUIDANCE, THE TIMING LOOKS TO BE GENERALLY AGREED UP WITH AREAS FROM THE LEHIGH VALLEY, NORTH-CENTRAL NEW JERSEY AND POINTS SOUTH AND EAST HAVING PRECIPITATION OCCURRING BY MIDNIGHT. THE TIMING OF THE SNOW LOOKS LIKE IT WILL IMPACT PART, IF NOT ALL, OF THE MORNING COMMUTE AND THAT IS WHY WE HAVE INCLUDED AREAS TO THE WEST OF PHILADELPHIA. IT CERTAINLY LOOKS LIKE IT COULD BE A SLOPPY AND SLIPPERY MORNING COMMUTE ACROSS MUCH OF THE AREA. SNOW/RAIN...SNOW SEEMS LIKELY ACROSS THE REGION ALTHOUGH WITH TEMPERATURES STILL HANGING OUT IN THE 40S/50S THIS AFTERNOON, IT WILL LIKELY START AS RAIN, ESPECIALLY NEAR THE COAST, AND THEN TRANSITION OVER TO SNOW OVERNIGHT. AS THE PRECIPITATION FALLS, IT WILL START TO COOL THE COLUMN. THE BIG QUESTION WILL BE JUST HOW FAST THAT COLUMN COOLS. PRECIPITATION INTENSITY WILL DEFINITELY PLAY A ROLE AND AS WE SEE SOME HEAVIER PRECIPITATION FALL, THE COLUMN WILL COOL FASTER AND WE SHOULD SEE A QUICK CHANGEOVER FROM RAIN TO SNOW. THE BEST VERTICAL MOTION APPEARS TO OCCUR DURING THE OVERNIGHT/EARLY MORNING PERIOD AND THIS WOULD LEND TO HIGHER CONFIDENCE OF AN ACCUMULATING SNOW. WHILE THE GROUND TEMPS MAY BE FAIRLY WARM RIGHT NOW, INCREASED PRECIPITATION INTENSITY WILL ALLOW FOR ALL SURFACES TO ACCUMULATE, EVEN PAVED ROADS. AMOUNTS WILL VARY WITH LESSER AMOUNTS AS YOU MOVE FURTHER INLAND AND HIGHEST AMOUNTS MORE TOWARDS THE COAST. THERE STILL REMAINS SOME UNCERTAINTY WITH RESPECT TO SNOWFALL AMOUNTS AS SOME OF THE GUIDANCE HINTS AT HIGHER TOTALS (THAN CURRENTLY FORECAST) IN EASTERN NEW JERSEY. CONFIDENCE IS NOT HIGH ENOUGH AT THIS TIME TO ISSUE A WARNING BUT WILL NEED TO MONITOR AS THE SYSTEM DEVELOPS FURTHER.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
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SNOW WILL GRADUALLY BE ENDING THROUGH FRIDAY MORNING FROM WEST TO EAST AS THE LOW PRESSURE PULLS FURTHER AWAY FROM OUR AREA. MOST AREAS SHOULD SEE SNOW ENDING BY 10AM WITH SOME OF THE COASTAL LOCATIONS POSSIBLY SEEING SOME FLAKES THROUGH AROUND NOON. HIGH PRESSURE WILL BUILD TOWARDS OUR AREA FROM THE SOUTHEAST AND WE EXPECT THE AREA TO DRY OUT AND REMAIN THAT WAY AS WE HEAD INTO THE WEEKEND.
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&& .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
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SUMMARY...AN ACTIVE PATTERN WITH AN OCEAN STORM LATE SUNDAY INTO MONDAY WHICH SHOULD SLIDE WELL OFFSHORE, THEN QUICKLY ON ITS HEELS IS THE POTENTIAL FOR LOW PRESSURE TO REDEVELOP OFF THE MID ATLANTIC COAST MONDAY NIGHT INTO WEDNESDAY AS COLDER AIR ARRIVES. THE OVERALL SYNOPTIC SETUP INVOLVES A TROUGH FRIDAY NIGHT THAT CONTINUES TO SHIFT TO OUR EAST. A MORE COMPLEX PATTERN THEN EVOLVES WITH A CLOSED LOW IN CANADA WITH ANOTHER PIECE OF ENERGY IN THE SOUTHERN STATES SATURDAY. THE LATTER SHOULD ALLOW A STORM TO DEVELOP OVER THE WEEKEND OFF THE SOUTHEAST COAST WHICH THEN DEEPENS RAPIDLY, HOWEVER THE ORIENTATION OF THE TROUGH LOOKS TO BE SUCH TO KEEP IT OFFSHORE AS IT TURNS NORTHEASTWARD. AN IMPRESSIVE TROUGH THEN IN THE PLAINS MOVES EASTWARD EARLY NEXT WEEK AND THIS SHOULD ALLOW FOR SOME SORT OF REDEVELOPMENT OF LOW PRESSURE OFF THE MID ATLANTIC COAST LATE MONDAY AND TUESDAY. THIS SYSTEM MAY BE ONE TO WATCH GIVEN SUCH A DEEP INCOMING TROUGH THAT COULD CLOSE OFF INTO THE MID ATLANTIC REGION. HOWEVER, THE INTERACTION WITH THE INITIAL OCEAN STORM COULD VERY WELL INFLUENCE THE DEVELOPMENT OF THIS SECOND STORM. WE USED A MODEL BLEND WITH CONTINUITY FOR FRIDAY NIGHT INTO SUNDAY, THEN BLENDED IN MOSTLY THE 12Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR FRIDAY NIGHT...THE UPPER-LEVEL FLOW BACKS MORE TO THE SOUTHWEST AHEAD OF THE NEXT UPPER-LEVEL TROUGH THAT BEGINS TO SLIDE NEAR THE GREAT LAKES. THIS ALLOWS HIGH PRESSURE TO BUILD INTO OUR AREA, WHICH WILL RELAX THE PRESSURE GRADIENT. THERE SHOULD BE DECENT RADIATIONAL COOLING COMBINED WITH LOW DEW POINTS, THEREFORE A COLD NIGHT IS ANTICIPATED. FOR SATURDAY AND SUNDAY...SURFACE HIGH PRESSURE BUILDS IN BRIEFLY SATURDAY BEFORE WEAKENING INTO SUNDAY. OUR REGION LOOKS TO END UP BETWEEN SYSTEMS DURING THE WEEKEND AS A MAIN TROUGH SWINGS ACROSS NEW ENGLAND AND ANOTHER ONE CLOSES OFF ACROSS THE SOUTHEAST STATES. THE LATTER SHOULD DRIVE SURFACE LOW DEVELOPMENT OFF OF THE SOUTHEAST COAST DURING SUNDAY WHICH THEN SHOULD GO OUT TO SEA AS IT RAPIDLY INTENSIFIES, ALTHOUGH IT MAY TOSS AT LEAST SOME CLOUDINESS OUR WAY. THE NORTHERN SYSTEM SHOULD SEND A COLD FRONT INTO OUR AREA LATER SUNDAY, HOWEVER THIS FEATURE LOOKS WEAK AND MOISTURE STARVED. AS A RESULT, WE KEPT THE FORECAST DRY ATTM. FOR MONDAY AND TUESDAY...THE PATTERN IS FORECAST TO UNDERGO SIGNIFICANT AMPLIFICATION AS A ROBUST TROUGH MOVES ACROSS THE PLAINS AND INTO THE EAST DURING THIS TIME FRAME. THIS LOOKS TO RESULT IN LOW PRESSURE INTO THE GREAT LAKES, HOWEVER THEN HANDING OFF ENERGY EASTWARD THAT REDEVELOPS LOW PRESSURE OFF OF THE MID ATLANTIC COAST LATE MONDAY AND TUESDAY. THE REDEVELOPMENT/TRACK OF THIS STORM MAY DEPEND ON THE ACTUAL TRACK AND INTENSITY OF THE PREVIOUS ONE WHICH IS MORE OFFSHORE. IN ADDITION, THERE COULD BE A SURFACE TROUGH THAT EXTENDS ACROSS PORTIONS OF OUR AREA TUESDAY WHERE LIFT IS ENHANCED, HOWEVER THIS WILL DEPEND ON THE LOCATION OF THE SURFACE LOW REDEVELOPMENT. THIS HAS THE POTENTIAL TO BECOME A DECENT COASTAL STORM WITH COLD AIR COMING INTO PLAY. WHILE THERE IS A SIGNAL IN THE GUIDANCE REGARDING A STORM, THE TRACK AND INTENSITY IS LESS CERTAIN AND THAT WILL DETERMINE THE ACTUAL DETAILS /IF ANY/ FOR OUR AREA WHICH INCLUDES RAIN, SNOW, WIND AND COASTAL IMPACTS. GIVEN THE VARIABILITY IN THE MODEL GUIDANCE, NO MAJOR CHANGES WERE MADE TO THIS TIME FRAME. FOR WEDNESDAY AND THURSDAY...A STRONG UPPER-LEVEL TROUGH IS FORECAST TO BE IN THE EAST, BASICALLY MOVING OVER OUR AREA. THIS WOULD TAKE ANY COASTAL STORM OFF TO OUR NORTHEAST WEDNESDAY ALLOWING FOR GENERALLY IMPROVING CONDITIONS. AN ARCTIC FRONT OF SORTS MAY SLIDE ACROSS OUR AREA DURING WEDNESDAY, HOWEVER CYCLONIC FLOW WILL RESULT IN SOME CLOUDS AND COLDER AIR WITH POSSIBLY EVEN SOME SNOW SHOWERS. HIGH PRESSURE BEGINS TO ARRIVE DURING THURSDAY FROM THE WEST.
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&& .AVIATION /21Z THURSDAY THROUGH TUESDAY/...
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&& .MARINE...
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A GALE WARNING HAS BEEN ISSUED FOR THE COASTAL WATERS AND A SCA HAS BEEN ISSUED FOR THE DELAWARE BAY. GALE GUSTS ARE LIKELY OVER THE OCEAN WATERS FROM THE PRE DAWN HOURS THROUGH EARLY AFTERNOON. GUSTS ABOVE 25 KT ARE EXPECTED ACROSS THE DELAWARE BAY. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE AT THE MOUTH OF THE BAY. WINDS ARE EXPECTED TO SLOWLY SUBSIDE THROUGH LATE AFTERNOON, THOUGH SCA CONDITIONS ON THE COASTAL WATERS ARE LIKELY THROUGH MUCH OF THE DAY TIME HOURS. OUTLOOK... FRIDAY NIGHT...THE CONDITIONS ARE ANTICIPATED TO LOWER BELOW SMALL CRAFT ADVISORY CRITERIA DURING THE EVENING AS HIGH PRESSURE BEGINS TO BUILD IN. SATURDAY AND SUNDAY...THE CONDITIONS SHOULD BE BELOW SMALL CRAFT ADVISORY CONDITIONS FOR MUCH OF THIS TIME AS HIGH PRESSURE WEAKENS IN PLACE. HOWEVER, A POTENTIALLY STRONG OCEAN STORM TO OUR SOUTHEAST LATER SUNDAY COULD BE CLOSE ENOUGH TO ALLOW SEAS TO BUILD AND WINDS TO INCREASE TO ADVISORY LEVELS SUNDAY NIGHT. MONDAY AND TUESDAY...AN OFFSHORE STORM TRACKS WELL EAST OF OUR WATERS INTO MONDAY, WHICH COULD ENHANCE SEAS AND WIND GUSTS. ANOTHER COASTAL STORM MONDAY NIGHT THROUGH TUESDAY COULD RESULT IN GALE FORCE WINDS GUSTS, HOWEVER THIS WILL DEPEND ON THE TRACK AND INTENSITY OF THE STORM WHICH CURRENTLY HAS LOWER CONFIDENCE.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST FRIDAY FOR PAZ070-071-101>106. NJ...WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST FRIDAY FOR NJZ008>010-012-015>019. WINTER WEATHER ADVISORY FROM 1 AM TO NOON EST FRIDAY FOR NJZ013-014-020>027. DE...WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST FRIDAY FOR DEZ001. WINTER WEATHER ADVISORY FROM 1 AM TO NOON EST FRIDAY FOR DEZ002>004. MD...WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST FRIDAY FOR MDZ008-012. WINTER WEATHER ADVISORY FROM 1 AM TO NOON EST FRIDAY FOR MDZ015-019-020. MARINE...GALE WARNING FROM 4 AM TO 1 PM EST FRIDAY FOR ANZ450>455. SMALL CRAFT ADVISORY FROM 1 AM TO 4 PM EST FRIDAY FOR ANZ430- 431.
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&& $$ SYNOPSIS...GORSE NEAR TERM...MEOLA SHORT TERM...MEOLA LONG TERM...GORSE AVIATION...GORSE/MEOLA MARINE...GORSE/JOHNSON

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