Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 272120 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 520 PM EDT WED APR 27 2016 .SYNOPSIS... A FRONTAL BOUNDARY WILL REMAIN JUST TO OUR SOUTH INTO FRIDAY, BEFORE GETTING PUSHED INTO THE SOUTHEASTERN STATES DURING FRIDAY INTO SATURDAY. AN AREA OF LOW PRESSURE WILL TRACK ALONG THIS BOUNDARY THURSDAY BEFORE SHIFTING OUT TO SEA FRIDAY. HIGH PRESSURE CENTERED NEAR HUDSON BAY CANADA SATURDAY WILL EXTEND INTO OUR REGION THROUGH MUCH OF SUNDAY. LOW PRESSURE WILL THEN TRACK ACROSS OUR AREA MONDAY BEFORE MOVING OFFSHORE MONDAY NIGHT INTO TUESDAY. A COLD FRONT MAY THEN APPROACH FROM THE NORTHWEST WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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SENT OUT AN UPDATE TO ACCOUNT FOR SOME SPRINKLES AND LIGHT SHOWERS SOUTH OF A READING-TRENTON-MANTOLOKING LINE. THESE SPRINKLES WILL ADJOIN THE LIGHT SHOWERS THAT WERE ALREADY IN THE GRIDS FURTHER TO THE SOUTH. RUNNING WITH THE NAM THE NEXT SEVERAL HOURS AND SHUT OFF THE SPRINKLES THIS EVENING. PREVIOUS DISCUSSION... THE BIG QUESTION TONIGHT WILL BE HOW FAR SOUTH THE CLEARING LINE GETS. NORTH OF THIS CLEARING LINE, EXPECT GOOD RADIATIONAL COOLING CONDITIONS LEADING TO PATCHY FROST. WHERE THE CLOUDS LINGER, EXPECT LITTLE DROP OFF IN OVERNIGHT TEMPS, WITH LOWS GENERALLY IN THE MID TO UPPER 40S. AT THIS POINT, THINK THAT THE CLEARING LINE WILL NOT GET MUCH FURTHER SOUTH THAN WHERE IT IS AS OF 3 PM. HOWEVER, IF IT DOES, THE FROST ADVISORY MAY NEED TO BE EXPANDED. ACROSS DELMARVA, A FEW LIGHT SHOWERS MAY DEVELOP AS THE ONSHORE FLOW CONTINUES.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... THE NEXT SHORT WAVE TROUGH APPROACHES THE REGION TOMORROW. MODELS HAVE TRENDED SLIGHTLY LATER WITH HOW FAST THE TROUGH APPROACHES, AND THUS LATER WITH THE ONSET OF RAIN. THUS, I ADJUSTED POPS DOWN THROUGH THE MORNING HOURS (EXCEPT IN DELMARVA WHERE THE ONSHORE FLOW MAY CONTINUE TO LEAD TO LIGHT PRECIP). I ALSO TRENDED TEMPS DOWN SLIGHTLY GIVEN TRENDS TODAY. TOMORROW SHOULD BE SIMILAR EXCEPT THERE SHOULD BE LITTLE IN THE WAY OF CLEARING BEFORE SUNSET. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... THE SYNOPTIC PATTERN IS FORECAST TO BE COMPRISED OF A STRONG CLOSED LOW THAT SLOWLY EXITS THE CANADIAN MARITIMES AREA THROUGH FRIDAY. OUR REGION HOWEVER REMAINS WITHIN A CYCLONIC FLOW REGIME INTO THE WEEKEND. SOME SHORT WAVES TRAVERSING THE FLOW WILL DRIVE SOME MAINLY WEAK SURFACE LOWS NEAR OR ACROSS OUR REGION INTO EARLY NEXT WEEK. THIS INITIALLY OCCURS AS A FRONTAL ZONE IS STALLED JUST TO OUR SOUTH, BUT THEN GETS PUSHED WELL TO OUR SOUTH FRIDAY INTO SATURDAY. A MORE NOTABLE FEATURE LOOKS TO ARRIVE EARLY NEXT WEEK AS ENERGY EJECTS OUT OF THE PLAINS AND ACROSS THE UPPER OHIO VALLEY. THIS PATTERN WILL TEND TO KEEP OUR WEATHER UNSETTLED AT TIMES AND ON THE COOLER SIDE. WE USED A MODEL/CONTINUITY BLEND THROUGH SATURDAY, THEN BLENDED IN THE 12Z WPC GUIDANCE THEREAFTER. SOME ADJUSTMENTS WERE THEN MADE FOLLOWING ADDITIONAL COLLABORATION WITH OUR NEIGHBORING OFFICES. FOR THURSDAY NIGHT AND FRIDAY...A STRONG CLOSED LOW IN THE CANADIAN MARITIMES AREA WILL GRADUALLY SHIFT EASTWARD. THIS KEEPS CYCLONIC FLOW OVERALL ACROSS OUR REGION, AND THE CURRENT CLOSED LOW IN THE PLAINS IS FORECAST TO OPEN UP AND MOVE ACROSS OUR AREA FRIDAY. SOME GUIDANCE WANTS TO SHARPEN THIS SOME AS IT ARRIVES /AND SOME DIFFER ON THE TIMING/, HOWEVER OVERALL THE MOISTURE AVAILABILITY MAY BE ON THE LOWER SIDE. THERE SHOULD STILL BE ENOUGH FORCING TO PROMOTE SOME SHOWERS DURING THE FIRST HALF OF THURSDAY EVENING AS AN INITIAL WEAK SURFACE FEATURE EXITS, THEN DURING FRIDAY AS THE PLAINS TROUGH ARRIVES. AS A RESULT CHC POPS FOR THE AREA WITH THE IDEA FOR AT LEAST SCATTERED SHOWERS, HOWEVER IT APPEARS RAINFALL AMOUNTS WILL BE ON THE LIGHT SIDE. GIVEN A NORTHEASTERLY LOW-LEVEL FLOW AND THE PROSPECTS FOR A LOT OF CLOUD COVER, TEMPERATURES WILL BE ON THE COOL SIDE. FOR SATURDAY AND SUNDAY...AS ADDITIONAL ENERGY AMPLIFIES SOME FROM THE PLAINS TOWARD THE OHIO VALLEY INTO SUNDAY, HIGH PRESSURE AT THE SURFACE CENTERED NEAR HUDSON BAY WILL WEDGE DOWN INTO OUR AREA. THIS WILL RESULT IN A CONTINUATION OF AN ONSHORE FLOW IN THE LOWER LEVELS. THE AMOUNT OF CLOUD COVER AT LEAST FOR SATURDAY AND TO START SUNDAY WILL DEPEND ON HOW MUCH DRY AIR GETS PUSH SOUTHWARD ALONG WITH SUBSIDENCE. LOW PRESSURE THEN MIGRATING FROM THE CENTRAL PLAINS TO THE UPPER OHIO VALLEY SUNDAY WILL PUSH A WARM FRONT TOWARD OUR AREA SUNDAY NIGHT. SOME WAA AND ISENTROPIC LIFT SHOULD BE ENOUGH TO PRODUCE SOME SHOWERS STARTING MAINLY SUNDAY AFTERNOON AND ESPECIALLY AT NIGHT. THERE COULD END UP BEING ENOUGH OVERRUNNING TO RESULT IN A PERIOD OF STEADIER RAIN. FOR NOW, MAINTAINED AS SHOWERS. FOR MONDAY THROUGH WEDNESDAY...AN UPPER-LEVEL TROUGH IS FORECAST TO AMPLIFY INTO THE EAST MONDAY ALLOWING SURFACE LOW PRESSURE TO SHIFT OFFSHORE. WHILE SOME SHOWERS ARE POSSIBLE MONDAY, A DRYING TREND IS CURRENTLY FORECAST WITH A COLD FRONT OFFSHORE. ANOTHER COLD FRONT THOUGH MAY APPROACH THE AREA LATER WEDNESDAY IN ASSOCIATION WITH AN UPPER-LEVEL TROUGH, ALLOWING FOR AT LEAST SOME TEMPERATURE MODERATION AHEAD OF IT. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. ADDED SOME VCSH`S TO OUR SOUTHERN TERMINALS THROUGH THE EVENING HOURS. PREVIOUS DISCUSSION... EXPECT CEILINGS TO GENERALLY STAY BELOW 5000 FT AGL THROUGH THE OVERNIGHT HOURS. HOWEVER, AT THIS POINT, EXPECT THAT CEILINGS WILL BE MOSTLY VFR OVERNIGHT. THERE IS A CHANCE THAT LOCALIZED MVFR CEILINGS COULD DEVELOP, BUT I DON`T HAVE ENOUGH CONFIDENCE TO INCLUDE IN ANY TAF AT THIS TIME. CEILINGS AND VISIBILITIES WILL ONCE AGAIN LOWER AFTER 18Z TOMORROW AS THE NEXT ROUND OF SHOWERS MOVES INTO THE REGION. WINDS SHOULD BE MOSTLY LIGHT AND VARIABLE THROUGH AT LEAST 12Z. AFTER 12Z, EXPECT WINDS TO SETTLE OUT OF THE NORTHEAST OR EAST, BUT REMAIN NEAR 10 KT. OUTLOOK... THURSDAY NIGHT...MVFR TO POSSIBLY IFR ALONG WITH SOME SHOWERS AND LOCAL FOG. FRIDAY...MVFR CONDITIONS WITH SOME SHOWERS, WHICH SHOULD IMPROVE TO VFR AT NIGHT. SATURDAY AND SUNDAY...VFR CEILINGS WHICH MAY THIN OUT FOR A TIME FROM THE NORTH SATURDAY, THEN CLOUDS INCREASE AND LOWER DURING SUNDAY WITH SHOWERS LATER SUNDAY. MONDAY...SUB-VFR CONDITIONS POSSIBLE WITH SHOWERS OR A PERIOD OF RAIN.
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&& .MARINE...
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ADDED SOME SPRINKLES SOUTH OF MANASQUAN. THESE SPRINKLES WILL ADJOIN THE LIGHT SHOWERS THAT WERE ALREADY IN THE GRIDS FURTHER TO THE SOUTH. RUNNING WITH THE NAM THE NEXT SEVERAL HOURS AND SHUT OFF THE SPRINKLES THIS EVENING. PREVIOUS DISCUSSION... WINDS AND SEAS SHOULD REMAIN BELOW SCA CRITERIA TONIGHT AND TOMORROW. A FEW GUSTS NEAR OR ABOVE 20 KT WILL BE POSSIBLE TOMORROW MORNING AND SEAS WILL SUBSEQUENTLY INCREASE AS WELL. OUTLOOK... THURSDAY NIGHT THROUGH SATURDAY...NORTHEASTERLY WINDS INCREASE WITH GUSTS TO 25 KNOTS POSSIBLE, THEN DIMINISH SOME DURING SATURDAY. SEAS ARE ANTICIPATED TO BUILD INTO THE 3-6 FOOT RANGE /LOWEST IN DELAWARE BAY/ BEFORE SUBSIDING SOME DURING SATURDAY AND SATURDAY NIGHT. SUNDAY AND MONDAY...NORTHEASTERLY WINDS INCREASE AGAIN ESPECIALLY MONDAY WITH GUSTS POTENTIALLY NEARING 25 KNOTS. THIS WOULD ALLOW SEAS TO ALSO BUILD TO AROUND 5 FEET ON THE ATLANTIC COASTAL WATERS.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...FROST ADVISORY FROM 4 AM TO 8 AM EDT THURSDAY FOR PAZ062. NJ...FROST ADVISORY FROM 4 AM TO 8 AM EDT THURSDAY FOR NJZ001- 007>010. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE NEAR TERM...JOHNSON/KRUZDLO SHORT TERM...JOHNSON LONG TERM...GORSE AVIATION...GORSE/JOHNSON MARINE...GORSE/JOHNSON

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