Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 242054 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 354 PM EST Tue Jan 24 2017 .SYNOPSIS... The coastal low will move east of Cape Cod this evening. High pressure builds over our region on Wednesday. A cold front passes southeastward off the mid Atlantic coast Thursday followed by a second cold front moving through our region late in the weekend. Another frontal system approaches early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Low pressure south of Long Island, New York will continue to drift northeast and make its way into the Gulf of Maine overnight tonight. A steady northwest flow will continue across the area through the overnight hours. Winds will gust 20-25 mph at times through this evening, but winds could increase to 25-30 mph at times overnight. For some places, wind gusts may drop off from time to time. The mid level low remains offshore this evening and is helping to enhance lift across the eastern half of the area. Light to at times moderate rainfall will continue through late this afternoon and early evening for portions of northern and east central New Jersey where the greatest moisture/lift combination is located. As the surface low continues to drift eastward, the rainfall will taper off into this evening. We have kept the Winter Weather Advisory in place for Carbon/Monroe, Pennsylvania and Sussex, New Jersey. There continues to be a few places, mainly in the higher elevations, where temperatures are around freezing, or could fall below freezing through sunset. With the light rain or drizzle moving across the area, some light freezing rain or drizzle is possible until the precipitation tapers off this evening. There may also be some sleet or snow mixes in for the higher elevations, although it is expected to be little to no accumulation.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... On Wednesday, our area will be on the far northern fringe of high pressure centered across the Bahamas, while low pressure moves into the Canadian maritimes. Northwest flow will continue across the area through the day, with the strongest winds expected for the first half of the day. Winds could continue to gust 20-25 mph early in the day, before gusts diminish later in the afternoon. Some cloud cover can be expected early in the day, especially for the western half of the area, before the clouds begin to break and clearing skies develop for the second half of the day. Temperatures should warm quite nicely with everyone expected to be above normal. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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500 MB: Weak ridging Wednesday night will be followed by several short waves that develop the mean of a positive trough in the eastern USA that may strengthen to 3 sd below normal in the central Appalachians late Sunday. Temperatures: calendar day averages about 13-14 degrees above normal Thursday, 7 to 8 degrees above normal Friday, maybe around 2 degrees above daily, this Saturday through Tuesday. Forecast basis: Unless otherwise noted, a 50 50 blend of the 12z/24 GFS/NAM MOS guidance Wednesday night-Thursday night, thereafter the 12z/24 GFS MEXMOS Friday, and then the 15z/24 WPC guidance Friday night - Tuesday, at times blended with the 12z/24 GFS MEXMOS guidance or the long term temps were adjusted because of the 12z/24 ECMWF 18z 2m temperatures. The dailies... Wednesday night...waa showers likely for at least portions of the area late at night and pops have been raised for sct event. The dry EC held me back ydy but now the UK and Canadian are onto it. Pending further review no ice hazard needed, though we are keeping in mind the new 1-3" sleet snow acc north of I-80 that will be very slow to melt. Early radiational cooling might allow some spotty freezing rain north of I-80. For now, not forecast. Confidence: average Thursday...leftover morning showers, mainly southeast of I95. Then caa and breezy during the afternoon with partial clearing. Confidence: above average We have a little snow grid for Thu night. (Poconos sct snow showers). Friday-Sunday...partly cloudy. northwest flow pattern. maybe some caa flurries in the Poconos at times, especially late Thu night or Friday. Breezy during the afternoons. Increasingly cold. Confidence: above average Monday...Still uncertainty regarding the development of some snow (12z/24 operational EC doesn`t have the same pattern as the GEFS) since a pretty strong trough may be forming in the lower Ohio valley late Sunday. Dont yet count out a light snow event for parts of the area (especially Delmarva) but the fcst for now is dry. Confidence: below average. Tuesday... Another frontal system may be approaching late in the day and followed WPC guidance.
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&& .AVIATION /21Z TUESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Conditions will vary between MVFR and VFR late this afternoon and into the early evening hours as moisture continues to wrap around a coastal low. As the low pulls away through the evening, all TAF sites are expected to return to VFR and continue for much of the night. However, we expect MVFR CIGS to return late in the night and toward daybreak Wednesday as moisture is expected develop around 2,000-3,000 feet. These lower CIGS are expected to continue through the morning, before lifting by midday Wednesday. Any light rain or drizzle will taper off through the afternoon and into the evening hours and the rest of the night is expected to be precipitation free. Northwest winds will gust 20-25 knots this afternoon and early evening, before winds could increase to 25-30 knots later this evening and overnight, although wind gusts may drop off from time to time overnight. Wind gusts around 20 knots will continue into Wednesday, before finally diminishing late in the day. OUTLOOK... Wednesday night and Thursday morning...VFR though a period of showers may very briefly lower conditions to MVFR after 06z/26. Confidence: average. Thursday afternoon...VFR with gusty westerly winds behind a cold front to 25 or 30 kt. Confidence: above average Friday, Saturday and Sunday...Mostly VFR conditions expected. Westerly winds gust each afternoon 20-30 kt. Confidence: above average. && .MARINE... The Gale Warning for the Atlantic Coastal waters and lower Delaware Bay has been extended until 6 am Wednesday. While winds are currently below gale force this afternoon, winds are expected to increase this evening and overnight to 35-40 knots. For upper Delaware Bay, winds are expected to remain 25-30 knots. Winds will diminish to Small Craft Advisory levels Wednesday morning, then fall below advisory levels later in the day. OUTLOOK... Wednesday night...no headlines. sw wind. Confidence: average Thursday through Friday...West wind gusts 25-30 KT and seas build above 5 feet with sca conditions likely, especially Atlantic waters. Confidence: above average Saturday and Sunday...West wind gusts near 25 knots possible. Confidence: above average && .CLIMATE...
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Philadelphia continues to project a January average of at least 38 degrees, 5 or more degrees above normal. This should be at least the 17th warmest January in the period of record back to 1874.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 6 PM EST this evening for PAZ054- 055. NJ...Winter Weather Advisory until 6 PM EST this evening for NJZ001. DE...None. MD...None. MARINE...Gale Warning until 6 AM EST Wednesday for ANZ431-450>455. Small Craft Advisory until 6 AM EST Wednesday for ANZ430. && $$ Synopsis...Drag Near Term...Robertson Short Term...Robertson Long Term...Drag 354 Aviation...Drag/Robertson Marine...Drag/Robertson Climate...

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