Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231404 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 904 AM EST Fri Feb 23 2018 .SYNOPSIS... High pressure builds offshore of New England today as an area of low pressure moves out of the Great Lakes region and across southeast Canada tonight. A warm front to our south is forecast to lift across the area tonight, followed by a cold front early Saturday morning. The cold front will likely get hung up across our southern areas Saturday, or just to our south, before lifting back northward slightly Saturday night into Sunday as an occluded frontal boundary moves across the area during the day Sunday. High pressure begins to build into the region Monday night and Tuesday, before moving offshore Tuesday night. A backdoor cold front may approach the area from the north Wednesday, before a warm front and occluding low pressure system is forecast to approach the area from the south Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Made adjustment to PoP/weather grids based on latest radar. One area of rain currently moving through Lehigh Valley and northern New Jersey. The heavier precip is south of the Poconos and far northwest New Jersey, but there is still some light freezing rain and even some freezing fog. Winter Weather Advisory remains in effect until 1 pm. Otherwise, plain rain, albeit a cold rain as temperatures are in the mid and upper 30s. For southeast Pennsylvania, the Delmarva, and southern new Jersey, another area of rain will pass through the region through around 11 am. Temperatures here are a bit warmer, but not much. Another area of rain will approach the region this afternoon. Temperatures in the Poconos and northwest New Jersey should be above freezing by then, but will see how trends go. Later today the high pressure is forecast to weaken and move offshore, with winds veering more to the southeast as the front begins to return north as a warm front. Afternoon high temps should be mostly in the 40s but may reach low 50s in southern DE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... For tonight, rain should taper off by early evening but some drizzle and fog may persist overnight. Winds will become light SW and temps will hold steady or even climb a few degrees, especially south of PHL. A weak cold front is forecast to approach from the NW overnight, but this should have no effect other than a possible wind shift towards morning. && .LONG TERM /SATURDAY THROUGH THURSDAY/... An unsettled weekend is expected coming up, then dry weather returns again for the early to middle of next week, then more rainfall possible later in the week. By Saturday morning, a frontal boundary is expected to be moving into the area from the west and slowly move across the area during the day. The front is eventually expected to become nearly stationary across our southern areas, or just to our south later on Saturday into Saturday night. Several short wave/vorticity impulses are forecast to move across the area Saturday into Saturday night, which will lead to enhanced lift across the area and a couple of rounds of precipitation. Then on Sunday, the front to our south will begin lifting northward, but likely not make it very far across the area as an occluded frontal boundary and possible triple point low move across the area. As a stronger short wave/vorticity impulses moves across the area, there will be enhanced lift and moisture moving across the area, especially across potions of eastern Pennsylvania and northern New Jersey. This will lead to a period of potentially moderate to heavy rainfall Sunday morning. The rainfall will taper off through the day Sunday once the occluded front passes to our east, then conditions dry out Sunday night. Precipitation amounts across portions of eastern Pennsylvania and northern New Jersey could top 1-2 inches over the weekend, with areas farther south 0.5-1 inch. Local rivers and creeks will see some rises through the weekend into early next week, and there could be the potential for poor drainage and low lying flooding Sunday with the heavier rainfall. After this period of rainfall over the weekend, dry weather is forecast to return to the area for early next week. High pressure is forecast to begin approaching the area from the west on Monday, then fully build across the east coast Tuesday, before moving offshore Tuesday night. This will bring dry conditions Monday through Tuesday, expect possibly some light rain across the southern areas Monday if the front to the south remains close enough to push some moisture across the area. On Wednesday, a back door cold front may move into the area from the north. We expect this front to be dry, although the GFS is trying to show some possible showers across the area. There is a better chance of precipitation Wednesday night into Thursday as a warm front approaches the area from the south Wednesday night, before the occluding low pressure system moves into the area Thursday. This will likely bring another period of enhanced rainfall chances to the area. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Generally IFR to low-end MVFR conditions at the TAF sites this morning in rain/fog/low clouds. Several areas of rain will pass through the terminals, and conditions will range from IFR to MVFR throughout the day depending on where the rain is. Winds should diminish and veer to the SE later today as high pressure weakens and moves offshore. Tonight...Rain should move out with improving visibility in the evening, but cigs will remain IFR or low MVFR. Winds will become SW but generally less than 10 kt. OUTLOOK... Saturday-Saturday night...Conditions may improve to VFR briefly by midday, before diminishing again to IFR by the afternoon and evening as rainfall moves back into the area. Winds shift back to the northeast then east during the day and continue into the night. Moderate confidence. Sunday...IFR conditions for the first half of the day as a cold front moves across the area with a period of rainfall. East to southeast winds become southwest and west behind the front. Moderate confidence. Sunday night...VFR conditions return. High confidence. Monday-Tuesday...VFR. Gusty west to northwest winds 15-20 knots during the daytime. High confidence.
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&& .MARINE...
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Northeast winds have been decreasing overnight but seas remain elevated and will be slower to subside. The SCA remains in effect until mid/late afternoon when seas should fall below 5 ft. As high pressure moves offshore and weakens today, wind will veer to the S by late this afternoon. Winds become SW tonight and increase a bit, but should remain well below SCA level. OUTLOOK... Saturday-Saturday night...Conditions expected to remain below advisory levels. Sunday-Sunday night...Small Craft Advisory conditions likely return to the waters by Sunday morning and continue through the day, before lowering overnight Sunday night. Monday-Tuesday...Conditions expected to remain below advisory levels.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 1 PM EST this afternoon for PAZ054-055. NJ...Winter Weather Advisory until 1 PM EST this afternoon for NJZ001. DE...None. MD...None. MARINE...Small Craft Advisory until 4 PM EST this afternoon for ANZ450>455. && $$ Synopsis...Robertson Near Term...AMC/MPS Short Term...AMC Long Term...Robertson Aviation...AMC/Robertson/MPS Marine...AMC/Robertson/MPS

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