Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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459 FXUS61 KPHI 241023 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 623 AM EDT Fri Mar 24 2017 .SYNOPSIS... A warm front will lift to our northwest today, then a backdoor cold front pushes through the area Saturday. This front is forecast to stall near the southern portions of the area through Sunday, then return northward as a warm front Sunday night into Monday as low pressure moves through the Great Lakes. Another low pressure if forecast to move out of the midwest and offshore of the northeast Tuesday into Tuesday night, pulling a cold front across the east coast. High pressure will try to build down from the north Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Area of rain over western and central NY/PA is tracking to the east and is on pace to enter western portions of the forecast area after 8 am. Will not make significant changes to the forecast, as this is on track with the previous forecast. Will adjust hourly grids based on latest surface obs. Models fairly slow with the timing of the precip, with the precip holding off until after 8 am, with the 09Z HRRR not bringing precip into the Poconos/Lehigh Valley until closer to 10 am. 06Z NAM has most of the precip drying up before it really gets here, and does not really get into the region until closer to 11 am (15Z). The onset of precip will be key, as the longer it takes for the precip to enter the region, the better the chance for temperatures to rise above freezing for most of the area. Also, much of the area remains dry, with dewpoint depressions anywhere from 5 to 15 degrees. So it will take time for precip to develop this morning. Across the Poconos, where the Winter Weather Advisory is in effect, temps look to remain below freezing until close to noon. As a result, wintry precip expected for Carbon and Monroe counties, with several hundredths of an inch of ice possible this morning. Will not make any changes to the Advisory, as no significant changes are planned. For central NJ and into SE PA, a quick shot of FZRA and/or sleet is possible, but the bulk of the precip should be plain rain. This is a low QPF event for most of the region, as areas south of I-78 may only end up with a few hundredths of an inch of QPF, and between 0.10"-0.20" QPF possible north of I-78. Most of the Delmarva may end up staying dry. Precip tapers off across the region, generally between noon- 2pm. WAA will be underway behind the warm front, and increasing SW flow will push temperatures back up to near and slightly above normal levels. Highs this afternoon will top off near 60 across MD/DE, and in the low to mid 50s across southern NJ and SE PA. The Poconos and northern NJ will top off in the mid to upper 40s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... Zonal flow sets up tonight as high pressure remains anchored over the Southeast U.S. Conditions remain dry, but some mid- level moisture will spread into the region, keeping cloudy skies in place tonight. Lows will drop into the low to mid 40s north of I-76, mid to upper 40s across southern NJ and SE PA, and in the low 50s across MD/DE. && .LONG TERM /SATURDAY THROUGH THURSDAY/...
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A backdoor cold front will sink through the area during the day Saturday as high pressure moves across northern New England and eastern Canada. The front is then expected to stall just to our south through Sunday. As the front moves across the area, then stalls to our south, several short wave/vorticity impulses will slide across the area as well. This will lead to a chance of showers across the area, though it will not rain the entire time. Temperatures will be several degrees above normal Saturday before the front moves through, then return closer to normal Sunday on the northern side of the boundary. We will have to keep an eye on the temperatures across the far north Saturday night into Sunday. The NAM is hinting at the possibility for temperatures to drop close to freezing, which could lead to a period of freezing rain. For now, the forecast keeps all areas above freezing. The frontal boundary is then forecast to lift back northward as a warm front overnight Sunday into Monday as an area of low pressure moves through the Great Lakes region. Another couple of short wave/vorticity impulses are forecast to move across the area as the warm front lifts northward, and will enhance precipitation potential across the area. Sunday night into early Monday morning has the greatest chance of seeing more widespread precipitation potential. Another low pressure is then forecast to move out of the midwest then offshore of the northeast Tuesday into Tuesday night, pulling a cold front across the east coast. This will keep unsettled weather across the area through Tuesday night as several short waves/vorticity impulses slide across the area. Behind the cold front, drier weather is then expected to return for Wednesday into Thursday. Temperatures are currently forecast to be a few degrees above normal for the majority of next week.
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&& .AVIATION /10Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Warm front lifts north through the region this morning into this afternoon. Quick shot of FZRA possible from 13Z-15Z at KABE, otherwise, any rain that does fall will fall as plain rain. Brief MVFR conditions likely, otherwise, VFR. Conditions dry out after 18Z. Light S winds this morning will become SW 8-12 KT this afternoon, and then winds decrease to 5-10 KT tonight. OUTLOOK... Saturday-Tuesday...MVFR or IFR conditions with a chance of rain possible through the period.
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&& .MARINE...
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SW winds increase to 15-20 KT with gusts up to 25 KT across northern NJ waters this afternoon and into this evening. SCA remains in effect. Will hoist a SCA for DE Bay and DE ocean waters as confidence in a period of 25 KT gusts for this afternoon and early evening is increasing. Conditions gradually subside to sub-SCA conditions tonight. OUTLOOK... Saturday-Saturday night...Conditions expected to fall below advisory levels. Sunday-Sunday night...Small Craft Advisory levels possible. Monday-Tuesday...Winds may be below advisory levels, but seas could remain elevated leading to Small Craft Advisory levels.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...Winter Weather Advisory until 1 PM EDT this afternoon for PAZ054-055. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 10 AM this morning to 11 PM EDT this evening for ANZ450>453. Small Craft Advisory from 2 PM this afternoon to 8 PM EDT this evening for ANZ454-455. Small Craft Advisory from 2 PM this afternoon to 6 PM EDT this evening for ANZ430-431.
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&& $$ Synopsis...Robertson Near Term...MPS Short Term...MPS Long Term...Robertson Aviation...Robertson/MPS Marine...Robertson/MPS

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