Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 140420 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1120 PM EST Mon Nov 13 2017 .SYNOPSIS...
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Low pressure is well to our east overnight as high pressure builds across the Ohio Valley. The area of high pressure will then build into our region from the west for Tuesday and Wednesday. A cold front approaching from the northwest is forecast to arrive on Thursday, followed by high pressure for Friday. Another cold front is expected to pass through our region on Saturday night.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Models have not resolved the residual near-surface moisture well today (a fairly typical bias, particularly given the widespread rain this morning). Skies will continue to clear from north to south and winds have diminished more than anticipated. This has led to some patchy and locally dense fog to develop across eastern PA and northern parts of NJ. Temperatures are also below freezing in areas near and north of I-80 as well which may result in the formation of icy spots. Eventhough model data is not indicating fog, current expectations are for fog to form further south across NJ and northern Delmarva as well after it clears out tonight. Forecast lows are several degrees below average (again), with temperatures ranging from the upper 20s in the southern Poconos to the mid/upper 30s in the urban corridor and along the beaches. Forecast was based on a blend of the MAV/MET/ECS, with incorporation of high-resolution guidance during the evening (given expected variation in the nocturnal cooling trend based on variable cloud cover). Low temperatures with the evening update were lowered across the Lehigh Valley and Northern NJ by a couple of degrees where radiational cooling has been most prominent. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Another broad surface high moves into the Northeast tomorrow, with a reinforcing northwest-flow vort max moving through New England during the afternoon. The combination of these two features will allow for a small increase in northerly/northwesterly surface flow tomorrow. Lift is negligible and moisture even more so. Thus, no precipitation is expected with the passage of the shortwave trough. Temperatures should be a little warmer tomorrow, as cloud cover will be less prevalent than today (though a cloud deck may develop during max heating, especially north/west of Philly). Forecast highs are a combination of MAV/MET/ECS, which are in very good agreement. Probably the biggest forecast challenge will be the proximity of lower clouds near the coast. Some of the guidance is allowing lower clouds to sneak into coastal areas of central/northern New Jersey during the day, which may lead to cooler than forecast temperatures. With stiff northerly winds, this would be a raw day on the coast, for sure. Was fairly pessimistic with the forecast from Long Beach Island northward, and did allow for inland penetration of the lower clouds north-northwest into portions of northern New Jersey as well. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... The mid level flow is anticipated to become increasingly amplified during the period from Wednesday through Monday. A trough should develop over the east with ridging over the west. Surface high pressure is forecast to influence our weather on Tuesday night and Wednesday before moving off the coast on Wednesday night. Temperatures should be slightly below normal. A mid level short wave trough and an associated surface cold front are expected to push through our region on Thursday. Light rain showers are possible on Wednesday night in advance of the boundary. The front is forecast to pass through eastern Pennsylvania, northeastern Maryland, New Jersey and Delaware during the late morning hours. High pressure and dry weather are anticipated to follow the front for Thursday night and Friday. A strong cold front is forecast to approach from the west on Saturday and it should pass through our region on Saturday night. The boundary is expected to have more moisture associated with it than Thursday`s cold front. As a result, there is a likelihood of rain showers on Saturday. Another blast of cold air is expected to follow the front for Sunday and Monday. We have used the low end of guidance for temperatures. Cold advection stratocumulus is anticipated, especially on Sunday. Also, scattered snow showers and flurries are possible in our northern counties, especially in the elevated terrain. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...Clouds have cleared much of the area, as of 04z. Once the overcast cleared out, local fog formation is occurring. KRDG will likely continue to have variable visibilities throughout the overnight. Restrictions look to hold off a few more hours at other TAF sites say till around 08z. For now, most locations have a VFR restriction (08-13Z) which may need to be lowered with the 06Z TAFS based on trends that have occurred this evening. Winds under 10 knots from the north. Tuesday...A SCT-BKN cloud deck around 3000 feet may develop by late morning over much of the area but especially north of KPHL. Latest forecast trends suggest the sky cover may remain more scattered in nature, but should a BKN deck develop early enough in the day, a period of MVFR conditions may occur during the morning hours. Winds will be north or northwest 5 to 15 kts. OUTLOOK... Tuesday night and Wednesday...Mainly VFR. Wednesday night...Mainly VFR with a low or slight chance of showers. Thursday through Friday...Mainly VFR. Friday night...VFR lowering to MVFR in spots. A chance of showers. Saturday...Mainly MVFR and VFR with showers likely.
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&& .MARINE...
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Seas are 4-6 feet across the far southern waters (i.e. buoy 44009) with gusts up to 25 knots. The northerly flow will continue into Tuesday morning, which should keep the seas up across the southern waters. As a result, a Small Craft Advisory has been issued through 12z/7AM Tuesday for the two southern Atlantic coastal waters zones. Elsewhere, seas and winds are expected to be below SCA overnight and Tuesday. OUTLOOK... Tuesday night through Thursday morning...No marine headlines are anticipated. Thursday afternoon and Thursday night...A Small Craft Advisory may be needed for northwest wind gusts of 25 to 30 knots. Localized gale force gusts are possible. Friday and Friday night...No marine headlines are anticipated. Saturday...A Small Craft Advisory may be needed for southwest wind gusts of 25 to 30 knots. Gale force gusts are possible on Saturday afternoon.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 7 AM EST Tuesday for ANZ454-455.
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&& $$ Synopsis...Iovino Near Term...CMS/Gaines Short Term...CMS Long Term...Iovino Aviation...CMS/Gaines/Iovino Marine...CMS/Gaines/Gorse/Iovino

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