Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 071442 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 942 AM EST Thu Dec 7 2017 .SYNOPSIS... High pressure over the area moves offshore tonight. Low pressure develops along a stationary boundary over the Southeast and passes south and east of the Mid-Atlantic region Friday night through Saturday. A cold front moves across the region on Sunday. Another area of low pressure will impact the area towards the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Beautiful December day in store for the region today. Cirrus to our south is lowly creeping northward but should not prevent us from getting plenty of sunshine. Some mid level clouds are moving through Pennsylvania this morning, with some broken sky conditions being reported. Because of the additional sunshine, temps are expected to be milder than ydy by several degrees...probably within 2f of normal. This forecast may be a degree or so on the high side but for now...am staying with 48 at PHL. A light westerly wind this morning will become gusty to around 20 mph during midday. This forecast was a 50 50 blend of the 00z/7 GFS/NAM MOS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... A trough at mid levels passing by across NYS should drag a band of sc near 6000 feet ewd across our area, mainly across the central and southern part of our forecast area overnight. Otherwise its thickening cirrus during the night in the rrq of the 160 kt 250 mb speed max which moves to the Gulf of Maine by morning . Light west wind. Flurries associated with instability crossing PA prior to sunset may drift into east central PA this evening before drying out. This forecast was a 50 50 blend of the 00z/7 GFS/NAM MOS except raised the guidance a bit in the south, especially SNJ and the Delmarva where skycover ahead of the se USA low will probably limit radiational cooling. The WRF was blended with the GFS/NAM MOS to assist in the upward temperature adjustment. The forecast temps are within 3 degrees of normal...a bit below from Philly north and a bit above over s DE. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Low pressure develops over a stationary cold front over the Southeast U.S., and this low lifts to the north and east along that boundary as a deep trough with strong shortwaves dig through the Great Lakes and Ohio Valley. This low looks to remain offshore as it passes south and east of the Mid-Atlantic Friday night and Saturday. Models have shifted the axis of precip to the south and east of the area, and there is not much QPF at all for the local area, with the bulk of the precip confined to southern DE and into southern NJ. Not expecting much more than a quarter to a half inch of snow for those southern areas, and this is down a bit from the previous forecast. One thing of concern is what has occurred in the past, where QPF amounts flip flop between the 00Z and 12Z model suites. So it is possible that with the models on 12Z Friday, we see QPF amounts and snow amounts go back up. As such, this remains a low confidence forecast from 00Z Saturday through 00Z Sunday. Temps look to be below normal Friday and Saturday with highs in the upper 30s to around 40 on Friday, and then a few degrees cooler on Saturday. Lows Friday night will range from the 20s to around 30. Meanwhile, low pressure passing through the Great Lakes will drag a cold front and the upper trough towards the region Saturday night, and this front will pass through the region on Sunday. Though there is limited low level moisture over the region, there may be some rain and or snow showers with its passage. Could be a quarter to a half inch of snow Saturday night in the Poconos. Below normal temps in place through the new week. High pressure passes through the region Monday, and then another area of low pressure ahead of a strong cold front will impact the region Tuesday. The coldest airmass of the season may then build into the region for the middle of the week, as current model guidance indicating highs in the 20s to low 30s on Wednesday. && .AVIATION /15Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through today...VFR with cirrus returning north this afternoon. Sct/bkn SC deck near 6000 ft develops vcnty KRDG/KABE. Light west southwest wind this morning perks up during late morning with midday/afternoon gusts around 20 kt. Tonight...A VFR bkn-ovc CIG near 6000 feet from sw PA and WVA this evening should quickly advance ewd across our area overnight, lasting at any location 2 -5 hours. Otherwise VFR lowering and thickening cirrus. Mainly light west wind. Outlook... Friday...VFR conditions expected. Friday night through Saturday...VFR north and west. MVFR/IFR conditions possible to the south and east, especially KMIV/KACY with rain and/or snow. Sunday...MVFR in snow showers early, then VFR. Monday...VFR.
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&& .MARINE...
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Added the southern NJ and DE coastal waters, including the lower DE bay, in to the the small craft advisory. Winds continue to gust above 25 knots this morning and will continue through the early afternoon. The advisory runs through 4pm but should winds show a marked decrease through this morning and into the afternoon, it may be able to be dropped early. The SCA for the NNJ waters (adjacent Monmouth-Ocean counties) continues through 6AM Friday. Wind gusts are modeled to increase 5 to 10 kt this afternoon and evening and conceivably we may see a short period of westerly gale force gusts this evening before a general wind diminishment toward dawn Friday. High confidence. S NJ waters SCA is not quite as robust. Average confidence on this part of the advisory. Outlook... Friday thru Saturday...Sub-SCA conditions. A chance for rain and possible snow late Friday through Saturday. Sunday...SCA conditions. Brief gale force winds possible as well Sunday afternoon. Scattered snow showers possible. Monday...Conditions gradually subside to sub-SCA criteria.
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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 6 PM EST this evening for ANZ452- 453. Small Craft Advisory until 6 AM EST Friday for ANZ450-451. Small Craft Advisory until 4 PM EST this afternoon for ANZ431- 454-455.
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&& $$ Synopsis...MPS Near Term...Drag/Meola Short Term...Drag Long Term...MPS Aviation...Drag/MPS Marine...Drag/Meola/MPS

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