Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 221435 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 935 AM EST Thu Feb 22 2018 .SYNOPSIS... High pressure builds to our north today into tonight as a frontal boundary becomes stationary to our south. The high will build offshore of New England Friday as an area of low pressure moves out of the Great Lakes region Friday, and across southeast Canada Friday night. This will pull a cold front across the area, which may get hung up across our southern areas Saturday. This front may begin lifting back northward slightly Saturday night into Sunday as an area of low pressure lifts through the Great Lakes region Sunday. This will pull a cold front across the area by late Sunday into Sunday night. High pressure begins to build into the region Monday and Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Rain has moved into much of the forecast are this morning, and will pretty much continue, on and off, through the day. For the Poconos and far northwest NJ, temperatures have dropped into the mid 30s, and should continue to fall to just below freezing, resulting in a potential period of freezing rain. Winter Weather Advisory remains in effect. Otherwise, temperatures will fall into the 30s and 40s throughout, and into the low 50s in the Delmarva. This remains a low-confidence advisory as there are mixed signals from the model guidance as to precip type (rain, freezing rain or sleet) and whether precip will end before temps fall below freezing late this afternoon or evening. The advisory might need to be extended or re-issued for late tonight or early Friday morning, as another batch of precip is forecast to move in around that time. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Rain is forecast to taper off this evening but we are maintain chance PoPs through the night. Temps will continue to fall into the evening and sub-freezing temps will be more widespread over NW NJ and adjacent PA. There may be some lingering freezing rain over these areas so the winter weather advisory extends through the evening hours. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... The first half of the long term period is forecast to be a bit unsettled with several rounds of precipitations late this week into this weekend. Then dry weather returns again for the early to middle of next week. On Friday, high pressure will build offshore of New England, while the frontal boundary to our south may begin to lift slightly northward. Meanwhile, a cold front will be moving toward the area from the west as an area of low pressure lifts out of the Great Lakes region and across southeast Canada through Friday night. North of this warm front, and in advance of the approaching cold front, there will be several short wave/vorticity impulses move across the area. This will lead to enhanced lift across the area, which will combine with enhanced moisture aloft to create a period of precipitation from Friday morning through Friday evening. The rainfall will likely begin to taper off Friday evening, although some patchy drizzle may linger into the overnight hours. Temperatures will likely be below freezing for portions of northeastern Pennsylvania and northwestern New Jersey Friday morning into early afternoon Friday. This will likely lead to a period of freezing rain. Since there will be likely be a break in freezing precipitation this evening and overnight, we will not extend the advisory through Friday morning at this time. The frontal boundary is then expected to become nearly stationary across our southern areas, or just to our south for Saturday into Saturday night. A couple of 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, a cold front is forecast to move across the area, which will bring another period of rainfall to the area. We expect three separate periods of enhanced rainfall from Friday through Sunday, with a chance of light rain or drizzle possible in between each. Each period of rainfall could bring up to a half inch to three quarters of an inch at a time, especially Sunday. Right now it looks like much of northeast Pennsylvania and northern New Jersey could see the bulk of the rainfall Friday through Saturday night, with everyone seeing enhance rainfall Sunday. Even with a break between each period of rainfall, some rivers and creek could see some rises through the weekend. After this extended period of rainfall, dry weather is forecast to return to the area for the early to middle of 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 Wednesday. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Current conditions are either MVFR or VFR with CIGs 3500-4500 feet. Those VFR CIGs will lower to MVFR between now and 16Z, and then MVFR conditions expected throughout, eventually lowering to IFR later this afternoon. Winds should be fairly steady from the northeast at around 10 kt. Tonight...Rain should taper off during the evening and visibility should improve. However cigs are forecast to remain in the IFR range. This is due in part to continued low-level flow off the ocean, with surface winds continuing from the NE at 5 to 10 kt. OUTLOOK... Friday-Friday night...IFR conditions expected with period of rain during the day. Patchy drizzle may develop later in the day into the evening. East to southeast wind during the day, become southwest then west during the evening and overnight. Moderate confidence. 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...VFR. Gusty west to northwest winds 15-20 knots. High confidence. && .MARINE... The cold front has passed north to south across the forecast waters and winds have shifted to the north behind the front. Winds should veer some to the NE today and increase to around 20 kt, with gusts 25 to 30 kt. Seas will also build in response to the increasing NE winds. A small craft advisory is in effect starting midday. Wind should begin to diminish tonight but seas will remain elevated. OUTLOOK... Friday...Small Craft Advisory extended into Friday as seas likely to remain elevated, although winds drop off below advisory levels. Friday night-Saturday night...Conditions expected to remain below advisory levels. Sunday-Sunday night...Small Craft Advisory level seas may return to the waters Sunday, before lowering overnight Sunday night. Monday...Conditions expected to remain below advisory levels. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory from 4 PM this afternoon to 11 PM EST this evening for PAZ054-055. NJ...Winter Weather Advisory from 4 PM this afternoon to 11 PM EST this evening for NJZ001. DE...None. MD...None. MARINE...Small Craft Advisory until 1 PM EST Friday for ANZ450>455. && $$ Synopsis...Robertson Near Term...AMC/MPS Short Term...AMC Long Term...Robertson Aviation...AMC/Robertson/MPS Marine...AMC/Robertson/MPS is the U.S. government's official web portal to all federal, state and local government web resources and services.