Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 222057 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 357 PM EST Thu Feb 22 2018 .SYNOPSIS... High pressure will slide across to the north of the region tonight as a nearly stationary boundary remains across just to our south. Meanwhile, a low pressure system will develop across the Great Lakes region and track eastward, dragging a cold front into our area on Saturday and stalling out across our southern zones. The boundary will start to lift northward as a warm front late Saturday into Sunday. Another low pressure system will cross to the north of our area with its attendant cold front moving through Sunday night. High pressure will build into the region through midweek. Another system will approach the region late Wednesday into Thursday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Rain continues across much of the northern half of the forecast area as low pressure along a stationary boundary across the Mid- Atlantic passes south of the region. A 1042 mb high builds into New England as a 1033 mb high sits off the Southeast U.S. coast. With CAA funneling into northern zones, expecting a period of freezing rain this evening for the Poconos and northwest NJ as surface temps drop to freezing. Rain moves offshore this evening, and conditions dry out for most of tonight. Patchy fog will develop tonight with abundant low level moisture in place. Another area of low pressure over the Tennessee Valley will develop tonight and lift north towards the region late tonight. Precip will develop out ahead of that low and lift into the region in the pre- dawn hours of Friday. Expecting Freezing Rain for the Poconos and northwest NJ once again. As a result, will keep the Winter Weather Advisory in effect, but will also extend it through Friday. Lows tonight will range from the mid and upper 20s in far northern zones to otherwise in the mid 30s for most of southeast PA and NJ. extreme southern NJ and the Delmarva will be in the upper 30s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... Freezing rain continues for far northern zones for much of Friday morning, eventually changing to plain rain by Friday afternoon. Aforementioned Winter Weather Advisory will be in effect until 1 pm Friday. For the rest of the region, plain rain, though a cold rain, as highs will generally be in the 40s. With the low taking more of a northerly path as opposed to the low today, looks as if the bulk of the precip will fall across PA and much of NJ, with lesser amounts of rain and lower PoPs for the Delmarva. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Unsettled weather will continue through the weekend before a quiet period begins for the early through mid week period. Friday night through Sunday night...An unsettled period for the region as several systems impact our areas weather. A low pressure system will develop across the Great Lakes region and track eastward towards our area, dragging a cold front into our area on Saturday and stalling out across our southern zones. The boundary will start to lift northward as a warm front late Saturday into Sunday. Another low pressure system will cross to the north of our area with its attendant cold front moving through Sunday night. With all of these systems will come periods of rain, including some heavier rain over the weekend. With some pretty wet antecedent conditions and frozen (or at least partially frozen) ground, we may see some localized flooding occur, especially in the more prone locations. Guidance is showing between 1-3 inches through this period with the bulk of the precip falling north and west of the I- 95 corridor. We will continue to monitor the flooding threat but right now it looks like the mainstem rivers will be mostly fine, at least through Sunday. Some residual draining may cause some rises into Monday and we will monitor that through the weekend. Monday through Wednesday...High pressure will build across the region allowing for the area to dry out and warm up a bit. Temperatures should rebound from where we are over the weekend and highs are expected to rise back into the upper 40s to mid 50s across the area. Wednesday night through Thursday...The high breaks down and slides to the southeast of the area. Meanwhile, an area of low pressure will develop across the midwest and track to the east. This system will push a warm front into Delmarva on Thursday. Low pressure may develop along this boundary and then track towards the coast Thursday night. Lots of uncertainty, especially with front locations and timing, but another round of rain is likely across parts of the area. With temps a bit colder across the northern zones, a few flakes may fall early Thursday if enough moisture remains across the region. && .AVIATION /21Z THURSDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Widespread MVFR conditions with local IFR conditions in pockets of moderate rain. Rain tapers off by 04Z, and MVFR/IFR conditions expected in fog and stratus. Another round of rain moves into the terminals prior to 12Z Friday. NE winds 10-15 kt. Friday...IFR conditions in rain and fog. NE winds 10-15 kt, becoming SE less than 10 in the afternoon. Outlook... Friday night...IFR conditions expected in rain and fog with patchy drizzle and fog developing overnight. West to southwest winds. Moderate confidence. Saturday through Saturday night...Mainly IFR conditions expected. A brief period of MVFR/VFR may occur around midday but conditions are expected to fall back down to IFR by the afternoon/evening as rain overspreads the area. Light north to northwest winds early will become more easterly through the day. Moderate confidence. Sunday...IFR conditions expected with limited improvement through the day. Confidence is low that we will return to VFR during the day. East to southeast winds will become southwest by the afternoon. Moderate confidence. Sunday night through Tuesday...VFR conditions expected. West to northwest winds becoming gusty to around 20 knots on Monday. High confidence. && .MARINE... A tight northeast pressure gradient will lie across the waters. For the ocean...northeast winds 15-20 kt with 25-30 kt gusts expected through Friday. Winds ease in the afternoon. Seas gradually subside. Tonight...SCA conditions on the ocean, with NE winds 15-20 kt with gusts up to 30 kt and 5-7 ft seas. On DE Bay, sub-SCA conditions. Friday...Winds gradually turn SE and diminish to around 10 kt. Seas gradually subside to 2 to 4 ft late in the day. Outlook... Friday night through Saturday night...Sub-advisory conditions are expected on the area waters. Sunday and Sunday night...Seas are expected to build and exceed 5 feet on the ocean on Sunday. Winds will also start to pick up, mainly on the southern waters, with wind gusts around 25 knots through Sunday evening. A Small Craft Advisory will likely be needed. Monday and Tuesday...Sub-advisory conditions are expected on the area waters. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 1 PM EST Friday for PAZ054-055. NJ...Winter Weather Advisory until 1 PM EST Friday for NJZ001. DE...None. MD...None. MARINE...Small Craft Advisory until 4 PM EST Friday for ANZ450>455. && $$ Synopsis...Meola Near Term...MPS Short Term...MPS Long Term...Meola Aviation...Meola/MPS Marine...Meola/MPS is the U.S. government's official web portal to all federal, state and local government web resources and services.