Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 211455 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 955 AM EST Wed Feb 21 2018 .SYNOPSIS... Unseasonable Bermuda High pressure off the East Coast will provide one more day of record-breaking warmth over the mid- Atlantic region. A cold front will push south across the area tonight and then stall to our south. Several waves of low pressure will move northeast along this roughly stationary frontal zone, resulting in periods of rain from Thursday through Sunday. Another cold front will cross the area late on Sunday followed by high pressure building in for the first part of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Deep layer southwest flow continues to transport an anomalously warm and increasingly moist air mass into the region. Both low clouds and fog were dissipating as of 9 AM, particularly over portions of eastern PA and Delmarva, as the diurnal boundary layer becomes established. Mixing up to around 950 hPa and increasing sunshine will yield high temperatures into the 70s outside the southern Poconos, generally 20-25 degrees above seasonal norms! A list of records is available in the climate section at the end of this product. With Dew Points rising into the 60s along the coastal plain, the humidity will be palpable. Based on the latest guidance and trends, showers associated with a cold front time into the southern Poconos and Lehigh Valley in the 3-5PM time frame, so we have maintained chance PoPs here. While we cannot rule out a rumble of thunder, the greatest chance is just west of our area, in agreement with SPC. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... The cold front will make its way into and across our area this evening and into the overnight hours. As it does so, a line of showers will be making their way across our area as some enhanced moisture and lift associated with the front move across the area. The front will continue to sink south of the area through the overnight, and the showers associated with the front itself will slide southward as well. However, there will continue to be a chance of rain later in the night as an approaching short wave brings additional enhanced moisture and lift to the area. One concern will be how cold the temperatures for the northern areas across the Poconos and northwest New Jersey can get. If they drop below freezing overnight, some freezing rain may develop. Everywhere else, temperatures will be well above freezing. && .LONG TERM /THURSDAY THROUGH TUESDAY/... A somewhat unsettled weather pattern will remain in place for the first few days of the extended period, Thursday through Saturday. Southwest flow aloft will carry moisture over the area as several weak disturbances move quickly along the residual frontal zone. It is difficult to say if any period will be rain free, but a general rain looks more likely during the days on Thursday and Friday and again Saturday night. Colder air will continue to filter in behind the cold front on Thursday, with high temps 25 to 30 deg colder than today. With rain overspreading the area, temps may be cold enough for freezing rain in far northwest NJ and adjacent PA Poconos, especially late in the day and into the night. There is forecast to be a persistent layer of above freezing air aloft so no snow is expected. Surface flow is forecast to become more southerly on Friday with rising temps and precip should become all rain by about midday. Saturday and Sunday should feature somewhat above normal temps but continued periods of rain with a frontal boundary still in the mid-Atlantic area. A pronounced upper trof and associated deepening surface low are forest to lift northeast from the southern Rockies to the Great Lakes during this period. The attendant cold front should move through our area Sunday afternoon, preceded by widespread rain or showers. For Monday and Tuesday, high pressure is then forecast to build eastward from the Ohio Valley into the mid-Atlantic, resulting in fair weather. The airmass behind Sunday`s front does not look especially cold and temperatures look to be near or slightly above normal. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... Today...IFR conditions will persist through the mid morning hours, then the low clouds and fog will lift and burn off; similarly to Tuesday morning. Once the low clouds and fog burn off, VFR conditions will remain for the remainder of the day. There is a small chance for showers late this afternoon, but more likely this evening as a cold front moves across the area tonight. Winds will be mostly south to southwest today, and could gust 15-25 knots by the late morning into the afternoon hours after the sun comes out and stronger mixing occurs. Tonight...VFR conditions are expected this evening and overnight across the area. There is a chance for showers this evening and overnight as a cold front moves across the area. Winds will start out southwest ahead of the front, then once the front moves through, winds will switch to the north to northwest and could gust 15-20 knots. OUTLOOK... Thursday...Sub-VFR conditions possible in rain. NE winds 10-15 kt. Confidence: Average. Thursday night...Sub-VFR conditions possible in scattered showers. Mixed frozen precip in rain and sleet possible at KRDG and KABE late. Confidence: Below average. Friday through Sunday...Sub-VFR conditions in periods of rain. Confidence: Average. && .MARINE... Based on trends as of mid-morning and guidance, issued a Small Craft Advisory for all of Delaware Bay through this evening for southwest wind gusts up to around 25 knots. Elsewhere across the Atlantic waters of NJ and DE, conditions are expected to remain below advisory levels through today and tonight, with southwest winds gusting to around 20 knots and seas 3-4 feet. Winds will veer to the north to northwest tonight as a cold front moves across the waters. The Dense Fog Advisory for all the waters will be allowed to expire at 15Z, as visibilities are expected to be predominantly over 1 NM by that time. Further localized restrictions are possible, especially across the Atlantic Waters of Southern NJ and Delaware. A Marine Weather Statement will be issued for the Atlantic waters of NJ and DE to highlight patchy fog, with 1-3 NM visibilities though this evening, as well as cold sea-surface temperatures given anomalously warm air temperatures and boating interests. OUTLOOK... Wednesday night...Sub-SCA conditions expected. SW winds turning NW overnight. Thursday through Friday...SCA conditions possible on the ocean waters. Saturday...Sub-SCA conditions anticipated. Sunday...SCA conditions possible. && .CLIMATE... More high temperature records are likely today. Here are the records for Wednesday, February 21: Atlantic City...74 in 1930 Philadelphia....72 in 1930 Wilmington......70 in 1953 Allentown.......67 in 1953 Trenton.........70 in 1930 Georgetown......71 in 2014 Mount Pocono....60 in 1930 Reading.........71 in 1930 The following are the record warm minimum temperatures for Wednesday, all which should be exceeded. ABE 46-1981 ACY 49-1954 PHL 49-2002 ILG 47-2002 RDG 48-1930 TTN 48-2002 The all time February max temps may be approached on Wednesday at ILG, TTN, GED RDG MPO. All the all time monthly max`s are listed below: ACY 77 2/25/30 PHL 79 2/25/30 ILG 78 2/24/85 ABE 77 2/24/17 TTN 76 2/25/30 GED 77 2/25/17 RDG 77 2/24/17 MPO 70 2/25/30 Our expectation is that ACY will exceed the previous all time record rainfall for February, by the end of the weekend. The record is 6.50 inches in 2010. #2 is 1958 with 5.98 inches. And...adding only half an inch to PHL and ILG will put both locations in the top 9 ranking for Feb rainfall. Have rechecked the monthly projection at PHL and the avg temp continues at 41.0 or 5.3F above avg which is 8th warmest on record, if it holds. Add or subtract a degree to the average/departure and the ranking changes from 3rd to 11th. The forecast 5.3F departure is ~2f warmer than the current departure. I`d expect similar for the rest of our area...a bit less in the north which will have better chances for colder air, and a bit more warming in the south where the positive departure as of yesterday was already 5F above normal, heading for 7+. So all in all it appears we`re heading for a top 10 warmest February. Last year was the warmest on record, a whopping 3+F degrees warmer than our current projection. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Dense Fog Advisory until 10 AM EST this morning for ANZ430-431- 450>455. Small Craft Advisory until 6 PM EST this evening for ANZ430- 431. && $$ Synopsis...AMC/Franck Near Term...Franck/Robertson Short Term...Robertson Long Term...AMC Aviation...AMC/Franck/Robertson Marine...AMC/Franck/Robertson Climate...

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