Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 190126 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 926 PM EDT Tue Oct 18 2016 .SYNOPSIS... High pressure will remain over the Southeast coast before moving into the western Atlantic waters into the end of the week. Meanwhile, a weak cold front will approach the region on Wednesday, pass through on Wednesday night, and then will return to the north as a warm front on Thursday. Low pressure developing over the Ohio Valley will pass to the north on Friday, dragging a strong cold front through the region. High pressure then builds in from the south as low pressure deepens to the north over the weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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Initial bank of mid level clouds tried to move into the region, but have been dissipating as they move further east into our region. However, as the upper level short wave ridge shifts further off shore later tonight, expect mid level clouds to increase. The question is though, will we see the mid level clouds move in before dew point depressions drop to near zero. If not, we could have another night of patchy fog, possibly dense in a few locations. For now, given the uncertainty with the low clouds, mention general patchy fog across the region. Temperature wise, it will be another unseasonably warm night, with lows higher than the normal highs in many areas. The front will still stay far enough west that we should see dry weather through the overnight hours.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Another very warm day is in store, possibly the warmest yet. The aforementioned cold front will be making its way from w to e from morning through the afternoon. The only caveat on temps is if there are too many clouds to suppress temps. The frontal passage looks to be dry with any precip holding off until after the end of the period, despite lowering and thickening clouds. Temps should make it into the 80s in most areas. && .LONG TERM /THURSDAY THROUGH TUESDAY/... A prolonged period of unsettled weather on tap for the middle to the end of the week. Cold front works its way through the region Wednesday night. Not sure how far south that front will actually go, as it may get hung up across central NJ and southern PA before stalling out. That front then returns to the north as a warm front on Thursday. Meanwhile, a deepening upper level trough will dig into the central U.S. on Thursday, and primary low pressure will develop over the Ohio Valley during that time. That low will track to the north and east, passing through western NY/PA as it lifts into eastern Canada on Friday. As that trough approaches, it will become negatively tilted, and models indicating the potential for secondary low pressure development off the Mid-Atlantic coast. In addition, a weak tropical low currently east of the Caribbean Islands will track to the north, and that aforementioned secondary low may tap into and merge with the tropical low. Models keep this system over the western Atlantic waters As the primary low lifts into Canada, it will drag a strong cold front through the region Friday and Friday night. As a result, scattered showers will develop Wednesday night with the approach of the initial cold front, and then showers will increase and become more widespread on Thursday and Friday. Cannot rule out a rumble of thunder, especially on Friday, but it is too soon to include in the forecast at this time. Over the weekend, low pressure over eastern Canada will intensify as high pressure strengthens over the Southeast U.S. The pressure gradient will tighten between those 2 systems over the Northeast and Mid-Atlantic, and can expect gusty W-NW winds for the region. Upper trough remains over the area, and with several shortwaves diving into the base of the trough, some showers are possible, but no strong signal for showers yet. Trough continues to depart for the start of the new week as high pressure builds in from the west. Well above normal temps on tap to close out the work week, and then temps fall below normal for the weekend and new week. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions should continue through at least 06Z. After 06Z, there remains a chance for low clouds and fog. Exact timing and lowest conditions are uncertain as guidance has done poorly the last several nights with the fog, and we remain in the same air mass. A complication tonight is that a cold front will inch closer to the region last tonight (but still stay west of the region through at least 12Z). Even with it remaining just west of the region, leading mid level clouds associated with the trough could move into our region (ceilings around 5000 ft AGL). If this happens early enough, this could limit fog development especially from the Delaware Valley and west. Any low clouds and fog should dissipate no later than 15Z. Wind speeds through 18Z will be light, generally below 10kt. However, wind direction will be shifting from southerly to southwesterly, to westerly. Once the front arrives, expect winds to shift to northwesterly and be near 10kt. OUTLOOK... Wednesday night...Mainly VFR, but some showers possible, which could lower conditions to MVFR at least. Thursday through Friday night...Showers developing on Thursday, becoming more widespread into Friday, tapering off Friday night. MVFR conditions likely, with the chance for IFR and lower. Saturday through Sunday...Mainly VFR. NW winds with 25-35 KT gusts possible.
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&& .MARINE... Along the northern coastal waters, wind gusts at or above 25 kt will be possible through the overnight hours. In addition, waves have already started to increase and may go above 5 ft for several hours tonight. Thus, the small craft advisory remains in effect through 7 AM EDT. For the southern coastal waters and the Delaware Bay, a few gusts near 20 kt will be possible overnight, but winds and seas should remain below SCA criteria. Through the day time hours tomorrow, winds and seas should stay below SCA criteria. OUTLOOK... Wednesday through Friday afternoon...Forecast winds and seas below SCA criteria. Friday night through Sunday...A strong cold front passes across the waters Friday night. Tight pressure gradient develops over the weekend with winds gusting to at least 30 KT with the potential for gale force wind gusts. && .CLIMATE... The following sites tied or set record highs for Tuesday, 10/18 New RecordOld Record Allentown, PA8581 (1963) Reading, PA8585 (1908) *record tied Georgetown, DE8481 (1996) Wilmington, DE8381 (1938) Trenton, NJ8382 (1908) Here are the record high temperatures for Wednesday (10/19)...and across southern portions of the area on Thursday (10/20). WED OCT 19 THU OCT 20 Mount Pocono, PA 80 in 1963 75 in 1963 Reading, PA 84 in 1963 80 in 1947/1953/1969 Allentown, PA 82 in 1963 78 in 1936 Trenton, NJ 83 in 1963 80 in 1969 Philadelphia, PA 80 in 1947 80 in 1916/1938 Atlantic City, NJ 80 in 1991 85 in 1987 Wilmington, DE 81 in 1963 82 in 1969 Georgetown, DE 81 in 1953 83 in 1953 Thursday is dependent on sunshine. For now, no records but this could change in future forecasts. We`ve left the records in this section since it could be near record in a few locations, especially south of Philly. Monthly averages are projecting 3 degrees or so above normal, ranking a top 15 warmest October for PHL/ABE. This is stated with the usual mid month uncertainty. What we do know is that the warmth of this week will virtually lock in an above normal month, especially since the pattern for the last week of October does not indicate any lengthy period of below normal temperatures. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 7 AM EDT Wednesday for ANZ450>452. && $$ Synopsis...MPS Near Term...Johnson/Nierenberg Short Term...Nierenberg Long Term...MPS Aviation...Johnson/Nierenberg/MPS Marine...Johnson/Nierenberg/MPS Climate... is the U.S. government's official web portal to all federal, state and local government web resources and services.