Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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268 FXUS61 KPHI 231756 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1256 PM 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/... Widespread rain has moved offshore, but a raw, chilly, and humid airmass remains in place with patchy fog and drizzle. The next batch of rain approaches northern zones later this afternoon. Most of the freezing rain has ended over the Poconos so will cancel the Winter Weather Advisory. There are a few spots where temps remain below freezing, so will cover spotty freezing rain with a Special Weather Statement. Afternoon high temps should be mostly in the 40s but may reach low 50s in southern DE. && .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 /18Z FRIDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...IFR conditions through this afternoon. Rain approaches northern terminals as well later this afternoon. SE winds 10 kt or less. Tonight...IFR/LIFR conditions in fog and stratus. 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. && .MARINE... East to southeast winds 15-20 kt. Seas on the ocean remain above 5 ft, so SCA remains in place. Sub-SCA conditions expected tonight, but VSBY restrictions in fog expected. 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. && .HYDROLOGY... Periods of rain through the weekend could result in minor and poor drainage flooding. The heaviest rain is expected Saturday night and Sunday, when up to additional inch of rain will fall. By the time the rain ends Monday morning, the region will have received between 1 and 2 inches of rain since Thursday, with the highest amounts falling over the northern third of the forecast area. By Sunday night and Monday, there will be rises on areas rivers and streams, with some possibly approaching bankful. && .CLIMATE... **Top 3 warmest February on record and top 10 wettest February on record.** February projected climate ranking as of Noon today based on our mid shift fcst through the 28th and mins this morning; and for rainfall, amounts through Noon today. RDG and TTN not included due to too much missing data. ABE #3 warmest 38.2 or 7.5F warmer than the 30.7 norm. 39.2-2017 38.6-1998 38.2-2018 36.8-1954 ACY #1 warmest 43.0 or 7.7F warmer than the 35.3 norm. Tied with last year. #2 40.6 in 1954 ILG #3 warmest 41.6 or 6.6F warmer than the 35.0 norm. 43.1-2017 42.3-1903 41.6-2018 41.2-1976 PHL #3 warmest 42.0 or 6.3F warmer than the 35.7 norm. 44.2-2017 42.2-1925 42.0-2018 41.8-1998 41.4-1890 Water equivalent monthly pcpn PHL ranked #10 with 5.28" (0.21 as of Noon daily) ILG ranked #8 with 5.49" (0.49 as of Noon daily) ABE ranked #16 with 4.29" (0.07 as of Noon daily) ACY ranked #2 with 6.12" (0.28" as of Noon daily) Wettest is 6.50-2010. Our expectation is that ACY will exceed the previous all time record rainfall for February, by the end of the weekend. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. 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 Hydrology... Climate...

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