Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 131353 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 953 AM EDT Sun Aug 13 2017 .SYNOPSIS... A cold front will continue to move farther offshore and south of the area today, but begin to stall into the early part of the week. High pressure will build across the area tonight into Monday. An area of low pressure is forecast to develop along the boundary to our south and move eastward along the front Monday night into Tuesday, but pass to our south. Another frontal boundary is forecast to approach the area from the north Wednesday, before stalling near the area through the end of the week. An area of low pressure may move along this boundary and affect the area late in the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Overall, a beautiful weekend day to spend outdoors, which has been somewhat of a rare occurrence this summer. Minor adjustments were made to the temp, wind and sky grids for today`s forecast with the 930 AM ESTF update. Mid morning surface analysis shows an area of low pressure over eastern Ontario with a cold front extending southward from the low across eastern New England and off the northern Mid-Atlantic coast. Meanwhile, high pressure was centered over the Upper Midwest. A NW flow in wake of the cold front has drawn drier air into the area already but do not expect dewpoints to decrease much more from current readings (generally in the 60s). Winds will be strongest this morning with speeds peaking in the 10-15 mph range. Winds will slacken a bit this afternoon as the pressure gradient weakens in conjunction with the development of a weak surface trough over the coastal plain. Mid and high clouds were noted along and south of I-95 mid morning but will continue to thin out across the southern portion of the region. Farther north, CAA stratocu has started to move into NE PA and NW NJ. These clouds should thin out as they move farther downstream later this morning owing to downsloping flow. Stratocu should eventually dissipate this afternoon as subsidence builds overhead and drier air mixes down, leading to a sunny afternoon. Forecast high temperatures are in the 70s in the Poconos and low to mid 80s elsewhere.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... The high will slip by to the north tonight and fair weather should continue. Mostly clear skies are expected in most areas, but some extra cloudiness will arrive over Delmarva and srn NJ overnight. Low temperatures will drop into the mid/upper 60s south and mid 50s to low 60s north/west. && .LONG TERM /MONDAY THROUGH SATURDAY/...
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The cold front that moved through the area Saturday night/ Sunday morning is forecast to stall to our south through Monday and Tuesday. Weak high pressure is forecast to weaken across the area on Monday. Meanwhile, an area of low pressure is expected to develop along the front to the south and move to our east Monday night through Tuesday. Also, a possible tropical low may lift northward over the Atlantic and combine with this low and move eastward along the front. There still remains the possibility some showers could move across portions of the Delmarva and southern New Jersey Monday into Monday night, so we`ll keep slight chance/chance POPS in the forecast for now. On Tuesday, a weak surface trough may move across the area which may help create a few showers or thunderstorms. The best chance for any showers/thunderstorms looks to be across northeast Pennsylvania and northern New Jersey. By Wednesday, a back door frontal boundary is forecast to drop toward the area from the north. It is possible that this front could remain dry as it moves into the area. As we move into Thursday, this front may stall near the area, while a warm front approaches from the south as an area of low pressure moves into the Great Lakes. This low is forecast to begin to track eastward toward our area along the frontal boundary late in the week. There is considerable disagreement between the GFS/GEFS and the ECMWF with this system as the ECMWF has sped up even more compared to it`s 12z run and other model guidance. Nevertheless, the end of the week looks like it could be unsettled with a couple of periods of precipitation possible.
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&& .AVIATION /14Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. May briefly see MVFR CIGs at RDG/ABE between 14Z and 16Z this morning with developing stratocu with bases between 2500 and 3000 ft AGL. Otherwise, VFR today and tonight. NW winds 6-12 kt today, becoming light and variable late this afternoon in spots and tonight area wide. OUTLOOK... Monday-Monday night...Generally VFR. Scattered showers possible across the far south which may temporarily reduce conditions. Tuesday-Tuesday night...Generally VFR conditions. Isolated showers and thunderstorms possible across northern areas during the day which may temporarily reduce conditions. Wednesday-Wednesday night...Generally VFR conditions. Thursday...VFR conditions early, possibly lowering later in the day as showers move into the area.
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&& .MARINE...
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Fair weather is expected on the waters today and tonight. A cold front just to the east will move away as a ridge of high pressure builds in. Winds and seas will remain below SCA conditions. Winds will be west to northwest today and then variable tonight. OUTLOOK... Sunday-Thursday...Sub Small Craft Advisory conditions expected through the entire period. RIP CURRENTS... There is a low risk for the development of dangerous rip currents at the NJ and DE beaches today in part due to the offshore winds.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...Klein/ Short Term...O`Hara Long Term...Robertson Aviation...Klein/Robertson Marine...Klein/Robertson/O`Hara

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