Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 220921 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 421 AM EST Thu Feb 22 2018 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Cold front has pushed south of our forecast area as evidenced by winds shifting to the north through DE. Temps have fallen into the 40s north but still 60s south. Skies are cloudy everywhere but for the moment only light spotty showers are moving across northern NJ with no precip elsewhere. For today...with cloudy skies and continued low-level cold advection behind the front, temperatures will just hold steady or perhaps fall a few degrees during the day. Afternoon temps will range in the 30s and 40s over NJ and east PA, and in the 50s over northern Delmarva. The regional radar loop shows an area of rain from west PA southwest through the OH valley, which is forecast to overspread the region today. By late afternoon, temps may fall to around freezing in the Poconos and far northwest NJ, so there is the threat for some freezing rain. Hence a winter weather advisory has been issued for Carbon and Monroe Cos in PA and Sussex Co in NJ.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
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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.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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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.
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&& .AVIATION /09Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Current conditions are VFR except at ACY and MIV with cigs around OVC025. Rain will be moving into the area from west to east later the morning and conditions will deteriorate to MVFR and eventually IFR 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.
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&& .MARINE...
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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.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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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 from noon today to 1 PM EST Friday for ANZ450>455.
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&& $$ Synopsis...Robertson Near Term...AMC Short Term...AMC Long Term...Robertson Aviation...AMC/Robertson Marine...AMC/Robertson

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