Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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599 FXUS61 KPHI 191536 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1036 AM EST Fri Jan 19 2018 .SYNOPSIS... High pressure across the central Gulf coast will build eastward today, then offshore over the weekend. An area of low pressure will move across eastern Canada over the weekend as a back door cold front approaches from the north. Another area of low pressure will move through the Great Lakes Monday night into Tuesday, pulling a cold front across the area. High pressure will build toward the area late Wednesday into Thursday of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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No major changes with the morning update. Surface high pressure builds in from the west, allowing for rising heights and thicknesses. Highs will be some 8-10 degrees warmer today than Thursday, topping off in the mid to upper 30s north and west of the Fall Line, and in the low to mid 40s across southern NJ and southeast PA, and in the mid to upper 40s in the Delmarva.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... High pressure continues to build in from the west and heights continue to rise. This results in overnight lows warmer tonight than this morning, but there will still be some radiational cooling that allows temperatures to drop into the teens and lower 20s. Otherwise, lows will be generally in the mid 20s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Quiet weather continues into the weekend, with a return of unsettled weather for early next week, followed by quiet weather again for the middle of next week. Dry conditions will continue for Saturday and Saturday night as high pressure builds to our south across the southeastern states then offshore Saturday. We will remain on the northern periphery of the high which will keep a dry, west to southwest flow across the area. Winds on Saturday are expected to gust 20-25 mph at times during the afternoon. On Sunday, a back door cold front will sag toward our area from the north as an area of low pressure slides eastward across eastern Canada, and cold high pressure builds across eastern Canada through Sunday night. Sunday is expected to remain dry, but cloud cover will be on the increase through the day. As we move into Sunday night and Monday, the back door frontal boundary is forecast to make its way across a portion of the area. As it does so, there will be some enhanced moisture and lift moving overtop of the front. This may lead to some light rain/drizzle developing across the area Sunday night into Monday. Temperatures are expected to drop below freezing for portions of northern New Jersey and northeastern Pennsylvania as some cold air gets dammed up. If any precipitation does occur, this could lead to some light freezing rain or drizzle overnight Sunday into Monday morning. Then Monday night into Tuesday morning, a cold front is expected to sweep across the area as an area of low pressure moves through the Great Lakes region. This will lead to a period of rainfall overnight Monday into Tuesday. It is possible that the rain could change over to snow across northern New Jersey and northeastern Pennsylvania before the precipitation ends Tuesday morning behind the cold frontal passage. For Tuesday night into Wednesday, the low pressure system moves across eastern Canada, while a secondary cold front moves toward the area from the west, which may cross the area during the day. Most of the area will remain dry, as any precipitation is forecast to remain to our north. If there is any precipitation, it would most likely occur across portions of northern New Jersey and northeastern Pennsylvania. High pressure returns for Thursday, leading to dry conditions. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR. SKC/FEW250. W-SW winds less than 10 KT. High confidence. Tonight...VFR. SKC/FEW250. Light and variable winds. High confidence. OUTLOOK... Saturday through Saturday night...VFR. West to southwest winds; winds may gust 15-20 knots at time. High confidence. Sunday...Conditions may lower to MVFR later during the day. West winds may gust 15-20 knots. Moderate confidence. Sunday night-Monday...MVFR conditions overnight Sunday into Monday. May become IFR, especially northern areas, with a chance of showers. Moderate confidence. Monday night-Tuesday..Conditions lower to IFR everywhere with periods of rain associated with a frontal passage. Southeast winds become westerly behind the front and begin gusting 25-30 knots. Moderate confidence. && .MARINE... Sub-SCA conditions today and tonight. Southwest winds on the ocean will generally range from 10-15 KT with gusts up to 20 KT. On Delaware Bay, SW winds will be 10 KT or less with 1-2 ft seas today and tonight. OUTLOOK... Saturday...Small Craft Advisory in effect for the northern half of the New Jersey coastal waters as winds expected to gust 25-30 knots. The southern New Jersey and Delaware coastal waters are only expected to gust around 20-25 knots, so we have not issued an advisory there. Saturday night...Winds are expected to drop below advisory levels by Saturday evening, but periodically gust around 20 knots. Sunday-Monday...Conditions expected to remain below advisory levels, but winds may periodically gust around 20 knots. Monday night...Conditions expected to return to Small Craft Advisory levels. Tuesday...Small Craft Advisory level wind continue, but may reach gale force. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 6 AM to 6 PM EST Saturday for ANZ450>452. && $$ Synopsis...Robertson Near Term...Johnson/MPS Short Term...MPS Long Term...Robertson 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.