Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 210747 AFDPHI Area Forecast Discussion...CORRECTED National Weather Service Mount Holly NJ 347 AM EDT Tue Mar 21 2017 .SYNOPSIS... Weak low pressure passes through the Mid-Atlantic this morning. A cold front approaches tonight and passes through the region by Wednesday morning. High pressure then builds in from the west and moves offshore by the end of the week. As it does, a warm front lifts north through the region on Friday. Low pressure then approaches late in the upcoming weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A weak surface low will pass to our south this morning, while a weak surface trough will move into the area from the west later this morning as well. Meanwhile, a mid-level short wave/voticity impulse is approaching the area this morning and has sparked off an area of showers to our west. These showers will move across the area through the morning hours, and will generally be light in nature. As the short wave passes east of the area later this morning, any showers will dissipate as they move offshore. Cloud cover across the area this morning will begin to break up and thin out as the short wave moves eastward as well. The rest of the day will shape up quite nicely with most places a few degrees above normal. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... A cold front will move across the area overnight tonight, however no precipitation is expected as it is fairly moisture starved. If there would be any precipitation it would across the far south where the best chance for enhance low-mid level moisture is forecast. Behind the front, cool air and gusty winds will develop by daybreak. Winds behind the front could start gusting 20-25 mph during the pre-dawn hours Wednesday. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Cold front will be south of the Mid-Atlantic region by Wednesday morning, and then strong CAA will be underway with well below normal temperatures for the mid-week period. Low pressure near the Canadian Maritimes will intensify, and although there should not be many direct impacts from this low, a tight NW pressure gradient will form between that and high pressure building into the Great Lakes. This will tap into cold Canadian air, resulting in highs in the 20s in the Poconos, 30s for most of PA/NJ, and in the low 40s for MD/DE. With NW winds 15-20 MPH with gusts up to 30 MPH, wind chills will range from the single digits up north to the 20s for most of the CWA. Lows Wednesday night will be quite cold for this time of the year, ranging from the single digits in the Poconos to the teens for much of NJ/PA, and around 20 for the Delmarva. Temperatures moderate a bit on Thursday as heights rise as the low over the Canadian Maritimes moves offshore, and high pressure over the Great Lakes builds east. Although still below normal, highs will be in the 30s and 40s. By Friday, high pressure moves off the Mid-Atlantic coast, and return flow sets up as a warm front lifts towards the region. Some overrunning precip will develop ahead of that warm front, and a brief period of freezing rain is possible for the Lehigh Valley/Pocono Mountains early Friday morning. Rain then develops for most of the area by Friday afternoon as that warm front continues to lift north through the region. Temperatures return back closer to normal, topping off in the 40s and 50s. On Saturday, high pressure off the Mid-Atlantic coast drifts out to sea. Meanwhile, low pressure organizes over the Southern Plains and Midwest. This will put the Northeast and Mid-Atlantic in the warm sector, and temperatures will soar well into the 60s, and possibly the low 70s across MD/DE. Although some sites may come close, high temperature records look to be safe. Thereafter, low pressure over the Midwest tracks east through the Ohio Valley and then towards the Appalachians Sunday and Monday. Based on the latest forecast, there may be enough cold air at the surface initially for a period of freezing rain Sunday night/Monday morning. Otherwise, temperatures currently look to be warm enough to support all rain, and can expect precip for the start of the new week. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions will continue across the TAF sites. An area of light showers will move across the area during the morning hours, but will dissipate and move offshore by mid-late morning. A brief period of MVFR VSBYs will temporarily occur with some showers. Winds will generally be out of the west- northwest around 5 knots or less during the pre- dawn hours, then increase to 5-10 knots during the day and into the evening hours. A cold front will cross the area overnight tonight. The front is expected to be dry, with mainly mid-high level cloudiness. Winds will become gusty behind the front with northwest gusts 20-25 knots possible. Outlook... Wednesday through Thursday night...VFR. NW winds 15-20 KT with 25-30 KT gusts on Wednesday. Friday...Sub-VFR conditions in -RA. A brief period of -FZRA possible at KRDG/KABE Friday morning. Saturday...VFR initially. MVFR or lower late in the afternoon and at night in -RA.
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&& .MARINE... Conditions will remain below Small Craft Advisory levels through today. However, winds will increase overnight behind a cold frontal passage to Small Craft Advisory levels, then Gale force by daybreak Wednesday. Outlook... Wednesday...Strong NW flow, with Gales on the NJ ocean waters and SCA conditions on DE ocean waters and DE Bay. Brief period of Gales possible on DE ocean waters late Wednesday morning. Wednesday night...Conditions subside to sub-SCA criteria. Thursday...Sub-SCA conditions. Friday...SCA conditions possible on the NJ ocean waters. Saturday...Sub-SCA conditions. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning from 6 AM to 11 PM EDT Wednesday for ANZ450>453. Small Craft Advisory from 6 AM Wednesday to 6 AM EDT Thursday for ANZ454-455. Small Craft Advisory from 6 AM Wednesday to 2 AM EDT Thursday for ANZ430-431. && $$ Synopsis...MPS Near Term...Robertson Short Term...Robertson Long Term...MPS Aviation...Robertson/MPS Marine...Robertson/MPS

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