Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 260429 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1229 AM EDT Mon Sep 26 2016 .SYNOPSIS... High pressure centered over western Quebec will move into New England tonight before moving offshore on Monday. A cold front moves across the region Monday night into Tuesday morning, and then stalls off the coast Tuesday afternoon. Several waves of low pressure will develop over the Mid-Atlantic and will pass either through or south of the area into next weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Few changes needed for the evening and overnight updates. Temperatures were lowered in a few areas and a couple dew points were adjusted also. Hit the Pine Barrens pretty aggressively with this update on locally lower temperatures with some mesonet sites already down into the mid 40`s. Lows may fall below 40 in a couple of spots in the Pine Barrens so added a few areas into the mention of very patchy frost in rural Ocean county. Sky cover will remain mostly clr with only some thin ci/cs overhead tonight. High pressure across the northeast will keep mostly clear, calm conditions across the area. Temperatures will cool quite efficiently tonight with the clear skies and light winds. Some areas across the far north could drop low enough for some patchy frost to develop, but we do not think it will be widespread enough for a Frost Advisory. There could also be some patchy light fog in some areas, but we have left this out of the forecast as well as we do not expect it to be very thick or widespread. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... High pressure moves off the east coast during the day Monday, well ahead of an approaching frontal system. Monday will continue to be dry, although cloud cover will be on the increase through the day. With the high building offshore, winds will increase during the day as well as the pressure gradient increases. Winds could begin to gust around 15-20 mph by the afternoon. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A prolonged period of unsettled weather shaping up for most of the upcoming week, possibly into next weekend. Warm front will lift north through the region Monday evening ahead of a cold front west of the Appalachians. Not expecting much in the way of WAA, but temps should mainly hold somewhat steady for most areas. Surge of humid air expected between the warm front and the approaching cold front, allowing dewpoints to climb into the low 60s and max PWATs to increase to 1.75-2". Closed upper low digs into the Great Lakes behind the cold front, and several strong H5 shortwaves will rotate around the low and into the local CWA as the cold front passes through the region Monday night. Despite a 40 KT LLJ passing through the region Monday night, there is not much instability with this system, so not anticipating much in the way of convection. Cannot rule out a few rumbles of thunder, so will carry slight chance for thunder with categorical PoPs. With high low level moisture, can expect periods of moderate to locally heavy rain. Latest QPF forecast has about 1/2 to 3/4 inch rainfall, but if there is convection, then some areas could get around an inch. Not anticipating any flooding issues, given how dry it has been, and while this will not be a drought-buster, any rainfall is welcome. Cold front pushes through the region Tuesday morning, and becomes nearly stationary offshore and extending into the Mid-Atlantic area. Showers taper off over western zones in the morning, but showers will persist into Tuesday afternoon for southern and coastal areas. By Wednesday, closed low digs into the Great Lakes and Ohio Valley and will meander there through the end of the week. With shortwaves rotating around the low, and with the aforementioned stalled frontal boundary hanging over the Mid-Atlantic, several waves of low pressure will develop south of the local area, and will lift to the north and east into the end of the week. What remains to be seen is when this upper low will depart. Latest ECMWF keeps the low west of the area into Sunday, while the latest GFS has the low departing on Saturday, and has high pressure building east on Sunday. The trend among the models has been a cooler and wetter solution. Will therefore carry slight chance to chance PoPs for most of the region from Wednesday through Saturday, and then slight chance PoPs on Sunday. Given the rainfall deficit, any rainfall will be welcome. Temps will be near to slightly below normal for the long term period. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are expected to prevail through the TAF period as high pressure controls the weather tonight, then builds offshore Monday. Mostly clear skies are expected tonight into Monday morning, before clouds increase and lower through the afternoon. Winds become light and variable/calm overnight. The winds will increase out of the southeast during the day Monday as high pressure builds offshore, and could gust in the upper teens by the afternoon. Ceilings will build and lower starting late this afternoon (Monday) with MVFR conditions for the overnight hours Monday night. Rain showers will also lower vsbys some as well. Timing looks to be around 03z for KRDG on the 27th and more toward 08z at KACY. Ceilings should lift in the mid to late morning hours on Tuesday from KPHL and points to the NW. OUTLOOK... Monday night...Showers and isolated thunderstorms spread into the region from west to east. Conditions lowering to MVFR, but IFR and lower conditions possible in heavier showers. 40 KT LLJ will move overhead, but not anticipating LLWS in the TAFs. Tuesday...MVFR/IFR conditions early, and then improvement at western terminals (ABE/RDG) in the morning. Eastern terminals (MIV/ACY) may not improve to VFR until late afternoon. Winds shift from SW to W Tuesday morning. Tuesday night...Mainly VFR. Wednesday through Friday...Sub-VFR conditions in showers possible. Best chances are Thursday and Friday. Low confidence in forecast for the late week period. && .MARINE... The Small Craft Advisory has been cancelled for the Atlantic Ocean waters as seas have dropped below 5 feet. Winds and seas will remain below Advisory levels for the remainder of tonight into Monday. However, as high pressure builds offshore Monday, winds are expected to increase through the day and could begin gusting around 20 knots later in the day. OUTLOOK... Monday night and Tuesday morning...SCA now in effect from 22z Monday through 15Z Tuesday for both the ocean and the bay. Southerly winds ahead of a cold front increase to around 25 kt with seas around five feet on our ocean waters. Tuesday afternoon through Wednesday...Winds and seas below SCA threshold. Thursday through Friday...Seas may build to SCA levels. Low confidence in forecast for late week period. RIP CURRENTS... A moderate risk of rip currents will continue for the remainder of today. The risk for rip currents on Monday may likely remain moderate due to long period swells reaching the shore. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 6 PM this evening to 11 AM EDT Tuesday for ANZ430-431-450>455.
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