Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 180846 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 346 AM EST Tue Feb 18 2020 .SYNOPSIS... High pressure departs to the north and east today as a trough of low pressure will bring a frontal system through the Mid Atlantic region. High pressure builds in behind the front and quiet weather ensues. Quiet weather then continues through the rest of the week with below normal temperatures. The next chance for significant precipitation will arrive as a low pressure system early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Low pressure currently over Lake Michigan will move northeast today into SE Ontario and then Quebec. At the mid-lvls the primary piece of shortwave energy associated this feature will also pivot well north of the area today. Warm advection (initially aloft) is beginning to overspread the area this morning as southerly flow increases ahead of the aforementioned low. Given the northward displacement of the upper-lvl dynamics and initially dry profiles expect the WAA driven precipitation this morning and early afternoon to be fairly light and spotty. The best potential for measurable precipitation (maybe up to a couple tenths of water) will be in the upslope favored areas of eastern PA and NW NJ (aided by some modest FGEN/convergence along the terrain). Could see some snow in the higher elevations of the Poconos this morning at precipitation onset, but think the heavier precipitation should not get going until profiles have warmed, holding accumulations to under an inch. Although there will be considerable cloud cover today given the overunning setup, the lack of a well-defined secondary low should allow most of the area to get into the warm sector by this afternoon. Consequently expect most areas along and east of the fall line to reach the 50s (probably upper 50s to near 60s in southern NJ and Delmarva) while temperatures will generally be in the 40s elsewhere (Sussex index looks to be about 20 degrees today). && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... The surface trough axis and cold front will pass over the area this evening, with additional rainfall possible in the vicinity of the front. Guidance has trended towards generating some weak waves along the southern end of the front which may slow the frontal progression somewhat. Consequently could see precipitation linger past midnight (potentially even into the pre-dawn hours Wednesday morning) in Delmarva and southern NJ and could even see a modest uptick in precipitation in these located due to convergence along the aforementioned wave and some-localized 925-850 FGEN. Clouds will likely not begin to push out (from NW-SE) until Wednesday morning, and these clouds combined with elevated post frontal winds should keep low temperatures 5-10 degrees above climo. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Expect generally quiet weather over the rest of this week heading into the weekend. Behind the front that crosses through the region on Tuesday night/Wednesday morning expect strong zonal flow to setup across the eastern CONUS with deep high pressure building across the Mid-Atlantic. With high pressure aloft and deep subsidence at the surface anticipate relatively light flow and strong radiational cooling each night. The latter portion of this week will feature temps below normal with lows in the teens and highs in the 30s. The zonal flow breaks down as an upper level trough tracks through on Friday however, the high pressure system still remains over the area so the only real noticeable weather change will be the warm air advection pushing into the region. The dry weather continues through the weekend with the next potential system arriving early next week. Deterministic guidance leaves a bit to be desired with regards to consistency in timing however the general idea is that we will see a low pressure system bring light rain to the region. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Expect MVFR CIGS to spread in around/after 12Z. After the this initial push of lower CIGS flight conditions could fluctuate considerably through the afternoon, potentially dipping to IFR at times while also having the ability to come up to VFR. Scattered rain showers will also be possible. Initial easterly-southeasterly winds 5-10 kts will shift more southerly by this afternoon. High confidence in a period of MVFR conditions this morning and winds, lower confidence in flight category evolution through the day. Tonight... A period of rain and lowered flight categories are likely this evening as a cold front moves through. Behind the front flight categories should improve back to VFR with all sites VFR by 09Z. Westerly winds 5-10kts will shift to the Northwest around 10-15 kts after about midnight. High confidence in winds and lowered flight categories in the evening, lower confidence in exact timing of recovery. .Outlook... Wednesday...Rapidly improving flight conditions from MVFR ceilings to VFR by mid morning. Lingering showers should clear early in the morning. Northwest winds from 5 to 10 knots with gusts from 15 to 20 knots. High confidence. Thursday through Saturday...VFR with northwesterly winds from 5 to 10 knots. High confidence. && .MARINE... Today...Marginal SCA conditions expected for the coastal waters off New Jersey as southeasterly winds gust 20-25 knots with seas 4-5 feet. Tuesday night...Winds/seas likely diminishing for a time in the evening before increasing late at night in the wake of a cold front as winds shift to NW with gusts up to 20-25 knots once again likely. Outlook... Wednesday through Thursday...Northwest winds continue behind the frontal system for Wednesday and Thursday. Speeds will generally be around 10 to 15 knots with gusts around 20 knots. Seas generally 2 to 4 feet. Thursday night through Friday...Northwesterly winds become northerly 10 to 20 knots with gusts up to 25 knots possible Friday afternoon. Seas around 1 to 3 feet. Saturday...Northerly winds shift back to westerly through the day. Wind speeds around 10 to 15 knots with gusts around 20 knots. Seas around 2 to 3 feet. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 9 AM this morning to 9 PM EST this evening for ANZ452-453. Small Craft Advisory until 9 PM EST this evening for ANZ450- 451. && $$ Synopsis...Deal Near Term...Carr Short Term...Deal Long Term...Deal Aviation...Carr/Deal Marine...Carr/Deal

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