Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 150730 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 230 AM EST Thu Feb 15 2018 .SYNOPSIS... A weak trough will traverse the area tonight through Thursday. A slow moving frontal boundary will move across the region Thursday night into Friday. High pressure builds into the area Friday night, then moves offshore Saturday. An area of low pressure is forecast to approach the region from the south late Saturday into Saturday night. High pressure briefly builds across the area again Sunday, then moves offshore Sunday night. A warm front is expected to lift across the region Monday into Monday night. && .NEAR TERM /THROUGH TODAY/...
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Instability burst waa showers driven by a 45 kt 850 wly jet core at 06z should end by 10z with the exception of maybe a sprinkle here and there. Then today...Considerable cloudiness, mostly high south of I78 but low cigs developing near I80 may not dissipate and so am concerned that temps will not reach my trimmed max`s up north. Otherwise in the south, stayed close to the prior fcst with also some concern there that max`s may not be reached. Nevertheless, we may be near record at ACY where todays record max is 65 in 1989. Lack of mixing a concern for not realizing MOS potential. Next pulse of waa instability burst may arrive near sundown in parts of e PA. Fcst max temp (18 to 24F above normal) was a blend of continuity and the new warmer MOS guidance s of I78 but used a cooler blend of NAM and prev fcst I80 north. POPS, mostly continuity except a 50 50 blend of the NAM/GFS mos after 21z.
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&& .SHORT TERM /TONIGHT/...
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850 speed max 50-60kt near the Mason Dixon line at 06z is part of driver for rain and some of that rain will be briefly mdt or heavy with qpf values double or triple what occurred overnight. used a blend of models and WPC QPF. The HRRRX favors mostly n of PHL early tonight and then slips south late at night. Temps were a 50 50 blend of the 00z/15 GFS/NAM MOS. MIN temps early this Friday morning (calendar will be 2359EST this Friday night) 27 to 33 F above normal.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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Several periods of unsettled weather, with a couple periods quiet weather mixed, are expected for the long term. All rain will end later in the morning and by the afternoon Friday as the cold front and associated short waves pass east of the area. High pressure builds across the area Friday night, before moving offshore Saturday. This will bring a period of dry conditions overnight Friday into early Saturday. However, the dry period is not expected to last long. As the high pressure retreats to our northeast, an area of low pressure will develop across the deep south, before moving offshore and strengthening as it moves up the coast. The low itself will remain just to our south, but there is plenty of moisture and lift forecast to move across our area, north of the low. The GFS, ECMWF, and Canadian are all in pretty agreement with the morning`s model runs. They all have the low passing just to our south, then east, and wrapping precipitation across our area, as early as the late afternoon, and continuing through the evening and overnight hours. The question becomes what the P-Types will be and how much snow will occur. Based on thicknesses and sounding, it looks like the precipitation would stay all snow for our Pennsylvania counties, most of New Jersey, and northern Delaware and Maryland. For southern portions of New Jersey and central/southern Delaware and Maryland, there could be some sleet and rain mixing in, possibly changing over to all rain for a period during the overnight hours. Depending on where this transition takes place, along with how warm we get during the day Saturday will limit snow accumulations for some area. We do not have an snowfall forecast map yet, that will come tonight, but we do expect some accumulating snowfall for a good portion of the area Saturday evening and Saturday night. The precipitation associated with the low is not expected to be very long duration as the low is forecast to move pretty quickly. Once it moves to our northeast, the precipitation will come to an end. High pressure is then expected for Sunday, before building offshore Sunday night. This will bring another period of dry weather to the area Sunday through Sunday night. On Monday, the high pushes farther out to sea, while a warm front is forecast to lift across the area. As this happens, a short wave/vorticity impulse is expected to move across the area as well, which could help produce some light precipitation. The forecast becomes a little uncertain again for Tuesday into Wednesday of net week. A cold front is forecast to move into the Ohio Valley and eastern Great Lakes region which may stall to our west. If this front does indeed stall to our west, the main focus for the precipitation would stay west of the area, although there is a chance of showers each day as a couple of short wave/vorticity impulses move across the area.
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&& .AVIATION /07Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Early this morning...Mostly VFR cigs aoa 5000 ft with vsby briefly near 5 mi in showers ending by 12z. Vcnty KABE/KRDG MVFR conds in showers may deteriorate to IFR conds in st/fog toward 12z. Wind mostly light south. Today...VFR cigs, generally aoa 12000 ft. Exception may be vcnty KRDG/KABE where MVFR or IFR conds in st/fog may only slowly improve to VFR midday. Southwest wind may gust 15 or 20 kt this afternoon. Tonight...VFR CIGS, probably lowering to MVFR/IFR conditions overnight, especially KABE/KRDG in periods of rain. LLWS possible vcnty KPHL/KILG/KMIV/KACY in the 04z-10z time frame. South to southwest wind. Please see TAFS for details. OUTLOOK... Friday...MVFR/IFR early with fog/drizzle possible, improving to VFR during the day. Moderate confidence. Gusty northwest winds 25-30 knots during the day Friday night...VFR. Gusty northwest winds 20-30 knots, diminishing overnight. High confidence. Saturday-Saturday night...VFR through much of the day. Increasing clouds late. Rain or snow possible across the south late, with conditions possibly lowering during the afternoon. Low to moderate confidence. Saturday night...Lowering to MVFR/IFR with rain or snow possible. Moderate confidence. Sunday-Sunday night...VFR. Moderate to high confidence. Monday...VFR early, lowering to MVFR or IFR during the day. Winds may gust around 15 to 20 knots. Chance of the rain during the afternoon and evening.
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&& .MARINE...
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SCA issued for a portion of the ATLC waters later this Thursday night as southwest winds gust 20-25 kt and seas build to 5 or 6 ft on the Atlc waters. Warm air (50s) over ssts` around 40 acts to suppress potential gustiness. Elsewhere, a south to southwest wind through tonight...strongest tonight. Fog may develop later today, or more likely tonight on the Atlantic waters, especially NJ. OUTLOOK... Friday...Small Craft Advisory conditions possible with gusty winds and building seas. Friday night...Small Craft Advisory conditions with gusty winds overnight. Saturday-Saturday night...Conditions lower below advisory levels, although winds may gust around 20 knots at times. Sunday-Monday...Sub Small Craft Advisory conditions expected.
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&& .CLIMATE... Highs may approach record values at Atlantic City Thursday and Friday. The current forecast high is in the low to mid 60s both days. All other climate sites are forecasted to be at least five degrees cooler than the record highs Thursday and Friday. Thursday February 15th- 65 back in 1989 Friday February 16th- 68 back in 1976 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Franck/Robertson 230 Near Term...Drag/Iovino 230 Short Term...Drag/Iovino 230 Long Term...Robertson Aviation...Drag/Robertson 230 Marine...Drag/Robertson 230 Climate...

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