Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 212101 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 401 PM EST Wed Feb 21 2018 .SYNOPSIS...
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A cold front will move across the Middle Atlantic region tonight and then stall to the south. Several waves of low pressure will move northeast along this roughly stationary frontal zone, resulting in periods of rain from Thursday through Sunday. Another cold front will cross the area late on Sunday. This will be followed by high pressure which should be across the area through the middle of next week.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Cold front approaching from the west along with showers out ahead of it. The showers will overspread the region this evening from northwest to southeast. Precipitation amounts will generally be less than a half an inch overnight. There will be an axis of greater instability traversing southern portions of the area this evening, where we have inserted isolated thunder. Record temperatures this afternoon (see the climate section at the end of this product) will only cool into the 40s to near 50s tonight, with the exception of the highest elevations of the southern Poconos, e.g., Monroe County, where it may approach freezing by day break. There is a low potential of some light freezing rain over a couple hours centered around daybreak, mainly in Monroe County. Given borderline temperatures, confidence is low. We have mentioned in the HWO for now. Winds will veer form southwest to north-northeast overnight as the cold frontal passage occurs, with the potential for gusts up to around 20 mph at times.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
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As the deep layer flow becomes parallel to the front, it will stall nearby, with disturbances riding along it. This will lead to a more steady light rain during the day across the region. The highest amounts are forecast for the Lehigh Valley, where up to a half an inch of rain is possible. Some sleet could mix in during the afternoon across the Southern Poconos - Carbon, Monroe, and Sussex (NJ) Counties. Temperatures are expected to be warm enough to preclude freezing rain. Otherwise, skies will be overcast, and it will be much cooler. High temperatures will be in the 40s, with mid- 30s across the Southern Poconos. A rather raw East-Northeast wind will gust 20-25 mph at times, making it feel cooler.
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&& .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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A wet pattern is expected for the beginning of the long term with a stalled front in the vicinity and several waves traveling along it. The periods with the greatest chances for precip will be Thursday night into Friday...mostly N and W areas and Saturday afternoon through Sunday...all areas. Most areas will have rain during these periods, but there is the possibility for freezing rain and perhaps some sleet Thursday night and Friday morning for the higher elevations of the N/W areas. We may to consider some WSW flags for those periods in upcoming fcsts. We will be sending out a blast notification to some of the partners this afternoon. Temperatures will be near normal from Thu night through Friday night, but above normal Sat and Sunday. Overall, total precip through this period will range from 1.5 to 2.5 inches across the area. Some of the rivers and streams may show some effects later this weekend. Monday thru Wednesday look to be mostly dry attm with strong high pressure building down across the Ohio Valley then towards the East Coast. Temperatures should average a little above normal with highs across most areas in the low 50s. Up across the north, readings will be in the mid/upper 40s.
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&& .AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
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This evening...VFR conditions all TAF sites. Southwest winds gusting up to around 20 kts at times. Confidence: High. Tonight...Most TAF sites will come down to at least MVFR in showers, with the exception of PHL and ILG, where we are forecasting VFR. Southwest winds will veer to the North-Northeast, with gusts up to around 15 kts. Confidence: Moderate. Thursday...With additional rain moving in during the soring, widespread MVFR is expected. East-Northeast winds will gust up to around 20 kts at times. Confidence: Medium. OUTLOOK... Thu night thru Sunday...Widespread low CIGS and occasional low VSBYS in rains and fog. A little frozen precip confined to the far N/W areas near KMPO Thu night and Friday. Mostly E/NE winds thru the period, but some NW/W winds Sat. Speeds mostly around 10 knots. Sun night and Monday...Improving conditions Sunday night with VFR expected for Monday.
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&& .MARINE...
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SCA in effect for frequent wind gusts up to around 25 kts over all of DE Bay through 23Z this evening. A cold front moves across the waters tonight, with winds veering from Southwest to East-Northeast. Winds and seas will build again Thursday afternoon across the Atlantic Waters of DE and NJ. We have issued a SCA for this area beginning at 17Z Thu and continuing through Thu night. Still some uncertainty on reaching SCA wind criteria on DE Bay, so that will be revisited in a later forecast for a possible SCA. OUTLOOK... Thu night into Friday...SCA flag expected. Rain and fog. Fri night thru Sunday...Low end SCA winds and seas possible. Rain and fog much of the time.
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&& .CLIMATE...
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Numerous records already established today. We will have both daily and all-time February temperature records at some sites. We won`t have some of the final numbers until shortly after 4:30 p.m. The CLI products and RER`s will be issued around then.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from noon Thursday to 7 AM EST Friday for ANZ450>455. Small Craft Advisory until 6 PM EST this evening for ANZ430- 431.
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&& $$ Synopsis...O`Hara Near Term...Franck Short Term...Franck Long Term...O`Hara Aviation...Franck/O`Hara Marine...Franck/O`Hara

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