Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 022030 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 330 PM EST Fri Dec 2 2016 .SYNOPSIS... Low pressure continues to slowly move through the Canadian Maritimes tonight through Saturday. Meanwhile, high pressure builds into the Midwest, and then passes overhead Sunday before moving offshore by Sunday night. A series of low pressure systems will pass through the region next week, with a strong cold front moving across the East Coast late in the week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... With the west-northwest flow, cloud cover has spread farther south to encompass the northern half of the area with partly to mostly cloudy skies. There remains some showers to our north associated with enhanced low level instability, as evident from steep lapse rates, and low level moisture combination. The best moisture/instability combination is expected to remain to our north this evening and overnight as a couple of short wave/vorticity impulses slide across the area. But we will keep a slight chance of showers across the Carbon/Monroe, Pennsylvanian and Sussex county, New Jersey as there could be some isolated showers this evening or overnight. The rest of the area is expected to remain precipitation free. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... There could still be some isolated showers across the far north at Saturday morning as a short wave/vorticity impulse passes by the area, but any precipitation is expected to dissipate and move out of the area by late morning. Northwest flow will continue across the area on Saturday and will likely be a little gustier than Friday. Wind gusts could reach 25 to 30 mph, with a few higher peak gusts. Cloud cover is expected to be more expansive Saturday than on Friday and will likely spread to cover the entire area. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... An active pattern will be in place for most of the new week. High pressure builds across the region this weekend, moving offshore by Sunday night. On Monday, H5 trough/shortwave combo will pass north of the region. Some rain is possible across the region Sunday night across the southern two-thirds of the CWA, while a rain/snow mix, changing to all snow, is possible for the Lehigh Valley, Poconos, and northern NJ. Light accumulations may be possible by Monday morning. Overall, QPF amounts will be light, generally less than 1/10 inch. Meanwhile, southern stream H5 trough/shortwave will move into southern TX, and low pressure will develop over the Gulf Coast. As a deepening upper low digs into the West Coast, it will carve out a ridge over the eastern half of the U.S. The southern stream low over the Gulf Coast will lift northeast into the TN/OH Valley Monday night and Tuesday. Secondary low develops out ahead of it, and then both systems slowly work their way east, moving offshore Wednesday night. A rain/snow mix is possible at the onset Monday night, with snow developing across northern zones. By Tuesday morning, warm front associated with this system lifts north through the region, allowing temps to warm up and changing precip to all rain. PWATs will also increase to around 1", which is +2SD above normal for this time of the year. Rain may be heavy at times. As this is ongoing, deep low pressure over the West Coast will deepen and broaden as it tracks east towards the Great Lakes. Strong cold front presses east, and an airmass with 850 MB temps of -20C to -25C will spread into the northern third of the nation. This front will works its way through the region sometime Thursday through Friday. Latest GFS has the front through by Thursday night, and temps fall off from highs in the 40s/50s Thursday to highs in the 30s/40s on Friday. A shot of rain and/or snow is possible with its passage. Several upper level disturbances passing through the region may keep some light precip in the forecast through Friday. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions will continue through the TAF period for all sites. Broken skies around 4,000-6,000 feet are expected to continue into this evening, before clouds retreat some back to the northwest and become more scattered overnight. The broken skies will be expected to fill back in around daybreak and continue through the day Saturday for all sites. Bases are expected to lower back to 3,500- 5,000 feet. It is possible that some CIGS may approach 3,000 feet around daybreak, but we`ll keep it at 3,500 feet for now and adjust if condition slower. Winds will continue to be gusty through this afternoon and evening, although the gusts will lighten some toward sunset. The gusts will likely drop off for a period overnight into Saturday morning, but the gusts will increase again by mid-morning Saturday and gusts 25-30 knots during the day. OUTLOOK... Saturday night and Sunday...VFR. NW winds 5-10 KT. Sunday night and Monday...Sub-VFR possible, mainly Sunday night and Monday morning. Light snow possible at KABE/KRDG, with light rain possible elsewhere. Conditions improve Monday afternoon. W-NW winds. Monday night through Wednesday...Periods of MVFR/IFR conditions. Generally rain, but some snow is possible at onset Monday night, and then again Tuesday morning for KABE/KRDG. && .MARINE... We`ve upgraded the Gale Watch to a Gale Warning for the late night through Saturday period. Small Craft Advisory level winds will continue this evening before winds increase Saturday morning and continue through the day. The Upper Delaware Bay continues with a Small Craft Advisory for now. OUTLOOK... Saturday night...SCA may be needed Saturday night for 25 KT wind gusts on the ocean waters once gales end. Sunday through Monday night. Generally tranquil conditions. Tuesday through Wednesday...Low pressure passes across the waters. Seas built to 5-7 feet on the ocean. Wind gusts to 25 KT possible. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning from 4 AM to 6 PM EST Saturday for ANZ431-450>455. Small Craft Advisory until 6 PM EST Saturday for ANZ430. && $$ Synopsis...MPS Near Term...Robertson Short Term...Robertson Long Term...MPS Aviation...Robertson/MPS Marine...Robertson/MPS is the U.S. government's official web portal to all federal, state and local government web resources and services.