Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 162325 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 625 PM EST Thu Nov 16 2017 .SYNOPSIS... Low pressure will continue to move into the Canadian Maritimes through Friday, while high pressure briefly builds across the east coast during Friday. An area of low pressure will move across the eastern Great Lakes Saturday, then into New England Saturday night into Sunday. A warm front will lift across the area Saturday, followed by a strong cold front overnight Saturday into early Sunday morning. High pressure will build to our south Monday into Tuesday, before a dry cold front moves across the area Tuesday night. High pressure then builds in later Wednesday into Thursday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Cold front has moved off shore. A few sites continue to report light precip, primarily in the higher terrain (likely orographically influenced). Any of this lingering precipitation will be very light (either flurries or sprinkles). Still expected the mid level cloud deck from the I95 corridor to the west will dissipate through the late evening as strong subsidence moves in. A deepening surface low to our NE and high pressure building in from the west will maintain a rather tight pressure gradient across the area. This along with low cold advection should keep gusty NW winds going through much of the night. Overnight min temps look to be about 10 deg F colder than this morning.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... For Friday, the upper level trof moves offshore to be replace by ridging aloft. The ridge of surface high pressure will approach from the west but with weakening trend. The airmass remains rather dry with possibly just a few high clouds spilling over the upper ridge. Winds will continue NW and somewhat gusty in the morning, with some downward mixing of momentum, but less so in the afternoon. Temps will be a few degrees cooler than today, but with plenty of sunshine. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... The main focus in the extended will be the storm system expected Saturday through Sunday. Otherwise, fairly quiet weather through much of the rest of the extended period. Friday night is expected to be rather tranquil as high pressure weakens across the area, then retreats southward. No precipitation is expected through Friday night. However, as we move into Saturday, strong south to southwest flow begins to develop during the day between the departing high pressure to our south, and an area of low pressure moving through the Ohio Valley and into the eastern Great Lakes. Meanwhile, a warm front is forecast to lift across the area during the day Saturday as well as a short wave/vorticity impulse slides north across the area as well. This is expected to lead to a period of showers during the afternoon, especially along and north of the I-95 corridor. South to southwest winds are expected to increase through the day as well, with gusts reaching 25-35 mph. As we move into Saturday night, a strong cold front is expected to move across the area. Ahead of this front, gusty southwest winds will continue through the night with gusts of 25-35 mph possible. As the front moves through during the overnight, shower chances will be increasing across the area, and move from west to east fairly quickly. There is not much instability forecast, so we do not have thunder in the forecast at this time. However, PW values increase to 1.00-1.25 inches, so there could be some moderate, to occasionally heavy rainfall at times. The cold front is expected to have moved through the area, and either be offshore, or just along the coastal areas of New Jersey and Delaware by around daybreak Sunday. Showers will come to an end behind the cold front, with the exception of possible continued showers in the Poconos as some lake effect streamers may develop. As the strong cold front moves across the area, winds will continue to be gusty, but become west to northwest as it shifts eastward. Wind gusts could reach 35-40 mph at times as the front crosses the area early Sunday, before slowly diminishing during the day. As we go into Sunday night, winds could remain gusty around 20-30 mph and all precipitation is expected to have ceased. The only exception is the possibility for some flurries in the Poconos Sunday evening. High pressure builds to our south Monday into Tuesday. Dry weather is expected Monday through Tuesday, but winds will likely remain gusty around 20-25 mph. A cold front is forecast to move across the area Tuesday night into early Wednesday morning, but it is currently expected to be a dry frontal passage. High pressure is expected to then build across the area later Wednesday into Thursday. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR conditions expected. Ceilings around 5000 ft AGL will be possible through 06Z from the I95 corridor and further west (including KPHL, KILG, KABE, KRDG, KPNE, KTTN). However, clouds are expected to dissipate late tonight. Winds should continue to gust NW around 20 kt this evening but may die down for a while overnight. Confidence in VFR is high; in wind gusts overnight is below average. Friday...VFR conditions. Some NW wind gusts to around 20 kt through midday, decreasing in the afternoon. Confidence is high. OUTLOOK... Friday night...VFR conditions expected. High confidence. Saturday...VFR early, with deteriorating conditions through the day with scattered showers during the afternoon associated with a warm front. Gusty south-southwest winds 20-25 knots. Moderate confidence. Saturday night...IFR conditions likely, with periods of showers associated with a cold front. Gusty southwest winds 30-35 knots possible. Moderate confidence. Sunday...Improving to MVFR, then VFR behind the cold frontal passage. Gusty west-northwest winds 30-35 knots. Moderate confidence. Sunday night...Generally VFR. Gusty northwest winds 25-30 knots. Moderate confidence. Monday...Generally VFR. Gusty west-northwest winds 20-25 knots. Moderate confidence. Monday night-Tuesday...VFR. Winds may gust 15-20 knots during the afternoon Tuesday. Moderate confidence.
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&& .MARINE... The Gale warning remains in place, starting at 21z and continuing to 11z Friday morning. NW winds will be increasing late this afternoon and evening with frequent gale force gusts expected during the night. Seas will build to 4-6 feet well offshore and 3-5 ft over the lower Delaware Bay. Winds and seas will gradually subside on Friday, but a SCA will likely be needed during much of the day. Otherwise clear skies are expected. OUTLOOK... Friday night...Conditions fall below advisory levels. Saturday-Sunday night...An extended period of gale force wind gusts are expected starting Saturday afternoon, then continuing Saturday night through early Sunday night. Conditions likely to lower to Small Craft Advisory levels overnight. Monday-Tuesday...Small Craft Advisory conditions expected to continue into Monday and Tuesday. A brief lull may be possible late Monday into Monday evening. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 AM EST Friday for ANZ430-431-450>455. && $$ Synopsis...Robertson Near Term...AMC/Johnson Short Term...AMC Long Term...Robertson Aviation...AMC/Johnson/Robertson Marine...AMC/Robertson

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