Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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665 FXUS61 KPHI 271932 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 332 PM EDT Tue Sep 27 2016 .SYNOPSIS... A cold front will stall offshore through Wednesday. Low pressure systems over the Great Lakes and Southeast U.S. are expected to drift toward the region for the later half of the week before finally lifting into New England for the weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Cold front has pushed offshore, but the tail end of the cold front extends back across the Delmarva and into the Southeast U.S. Weak low pressure will ride along that front this evening, and this may keep some light rain showers in the forecast for extreme southern portions of the CWA, mainly across S DE and across NJ, mainly south of ACY. Rainfall will be light, with generally a few hundredths of an inch of QPF, and rain should taper off by midnight. Otherwise, mid-level dry air surges into the region ahead of a closed upper low digging into the Great Lakes and Ohio Valley. Skies will partially clear out from west to east, and expecting a light pressure gradient over the region with winds becoming calm to light and variable. The combination of clearing skies, light winds, and abundant low level moisture may result in the development of patchy fog across parts of the forecast area late tonight into Wednesday morning. Not anticipating dense fog, but there may be a few spots where fog reduces visibilities to less than a mile. Lows tonight will generally range from the upper 40s to the north to the upper 50s across southern zones. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... The closed upper low will become entrenched over the southern Great Lakes on Wednesday. As it does, surface low pressure will develop along that stalled frontal boundary over the TN/OH Valleys during the day Wednesday, and will begin to slide along the boundary to the north and east. Both the GFS and the NAM are in decent agreement in holding off precip for the area until late in the day. Most of the day Wednesday should be mainly dry for most areas, but with a developing onshore flow, and increasing low level moisture, can expect low stratus to develop starting in the late morning. Cannot rule out some patchy drizzle during the day, but areas most impacted by any rain will be southern areas, and then rain slowly works its way up to the north late in the day. Will cap PoPs at slight chance for northern zones through most of the day, and will increase to chance late. For southern zones, will carry low chance for most of the day, raising to likely later on in the afternoon. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... An unsettled period is in store for the first part of the extendd pd. High pres will remain over ern Canada and New Eng, with a large upr low spinning around to our sw. One area of low pres, moves by to the w Wed night into erly Thu. THis feature has the potential to bring the heaviest, steadiest rain to the area durg this pd. However, guid continues to suggest that the highest qpf will be to our w. As is often the case with upr lows, there will be an abundance of clouds and periods of rain, but determining when and where it will rain is difficult and the mdls are disagreeing. Durg the day Thu, there cud be a break, especially over nrn areas. Mdls diverge considerably Thu night into erly Fri with the GFS remaining drier and the ECMWF and NAM wetter. Later Fri into Fri night could see another lull. Over the weekend, the upr low begins to fill and lift out and precip chcs will gradually decrease. However, there will at least be some chc on Sat, especially n and psbly into Sun before all rain chcs come to an end erly next week. Temps look to be around nrml. QPF values could reach 2 to psbly 3 inches on the lwr Delmarva and less elsewhere. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions expected through this evening. Winds are generally SW 5-10 KT, and will become LGT/VRB into this evening. E winds increase to 5-10 KT late Wednesday morning. Patchy fog may develop overnight at the fog-prone terminals, resulting in MVFR or locally IFR VSBY early Wednesday morning. Otherwise, VFR forecast through Wednesday afternoon. MVFR CIGs possible at KMIV/KACY by late Wednesday morning. OUTLOOK... Wed night thru Thu...MVFR/IFR conds likely with SHRA, some psbly hvy. Mdt confidence. ENE wind around 20 to 25 kts on Thu for KACY and psbly KMIV. Thu night thru Fri...Some improvement is psbl, but MVFR is likely with lower conds in any SHRA. ENE wind 20 to 25 kts for KACY. Low to mdt confidence. Sat thru Sun...Mainly VFR, but some lower conds psbl in sct shwrs. Mdt Confidence. && .MARINE... Occasional rain showers will pass through the waters through this evening. Most rainfall will be light, but a few moderate showers are possible. Light winds this evening, becoming NE 5-10 KT after midnight. Seas will remain 3 FT or less. On Wednesday, winds and seas will begin to ramp up as low pressure approaches from the south and west. Small Craft Advisory conditions with winds gusting to 25 KT and seas building to 5 FT will develop over northern ocean waters Wednesday afternoon, so a SCA has been issued for those waters for Wednesday afternoon. Rip Currents... Conditions have improved on the waters, so lowered the rip current risk from moderate to low for the rest of the afternoon and into this evening. With increasing easterly flow, there may be a moderate risk for the formation of dangerous rip currents on Wednesday. OUTLOOK... A gale watch for the waters and SCA elsewhere has been issued for Wed night thru Thu for increasing ENE wind and seas. Confidence was not high enough to extend gale watch further s. A prolonged sca will likely be needed into at least Saturday. Seas will build into Fri and could reach 9 to 10 feet before decreasing. && .TIDES/COASTAL FLOODING... Spotty minor tidal flooding on the oceanfront is possibile with the Thursday and Friday high tidal cycles. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Nierenberg Near Term...MPS Short Term...MPS Long Term...Nierenberg Aviation...Nierenberg/MPS Marine...Nierenberg/MPS Tides/Coastal Flooding...

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