Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 241020 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 620 AM EDT Sat Jun 24 2017 .SYNOPSIS... Tropical low pressure just west of the Appalachians will lift to the northeast through the Mid-Atlantic and Northeast this morning, and then a cold front will move across the region this afternoon. Surface high pressure builds into the Midwest as an upper trough digs into the eastern Great Lakes and Northeast tonight through Sunday. A weak cold front is expected to move through the region Monday night through Tuesday. High pressure returns to the area for the middle of next week before moving off the coast late in the week as low pressure passes north of the region. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The front with a band of heavy rains and sct tstms is crossing the Delaware Valley attm. Gusts in the 35 knot range have occrd at KILG recently and can be expected elsewhere with the line. The heavy showers should last 1-2 hours and produce some localized poor drainage flooding in a few areas. Previous... Much of the weather action will begin shortly after AFD release with a decent batch of showers and scattered thunder associated with a front and the remnant moisture from TS Cindy moving across the area. The warm and tropical airmass in place will create decent rainfall rates this morning with some 1-2 inch totals expected thru mid- morning. Once the front crosses the area, winds will shift to NW and rapid improvement from NW to SE will progress thru the area. Sunny skies will be across the region by this afternoon. It will remain very warm, but the airmass will become drier as the day progresses. Highs will reach the mid-upper 80s in most areas today. Winds will gust to 20-25 mph for much of the day.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... High pressure well to the west will begin to ridge across the area tonight. Fair weather with mostly clear skies are expected. Low temperatures will remain in the mid 60s to around 70 in most areas. The airmass will be much more comfortable tonight than in recent nights. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Surface high pressure builds into the Midwest and western Great Lakes Sunday morning. Dry conditions with low humidity on tap for most of the region, and downsloping westerly flow will push temperatures into the mid and upper 80s across the Delmarva, southeast PA, and much of NJ, and in the low to mid 80s for the Lehigh Valley, Poconos, and northwest NJ. Surface dewpoints will generally be in the 50s. With an upper trough digging through the eastern Great Lakes and Northeast, some shortwave energy will pass through the base of the trough, and could touch off some isolated showers and thunderstorms in the afternoon, mainly over the Poconos. Conditions dry out Sunday night. Cool and dry with lows in the 50s to low 60s. Surface high pressure continues to build into the OH/TN Valleys on Monday as H5 low moves into Great Lakes and upper trough becomes entrenched over the Great Lakes, Northeast, and into the Mid- Atlantic. With shortwave energy rotating around the base of the trough, some isolated to scattered showers and thunderstorms are possible, and then coverage becomes slightly more widespread on Tuesday as the base of the trough and a surface cold front passes through the region and moves offshore. Surface high pressure continues to slowly build east through Wednesday, and then the center of the high moves off the Mid- Atlantic coast by Wednesday night. For Monday through Wednesday, temperatures will be on the cool and dry side, with highs generally in the upper 70s to low 80s to start the week, and then in the low to mid 70s for the mid- week period. Dewpoints will be in the 50s. Overnight lows will be in the 50s to low 60s. With high pressure now off the Mid-Atlantic coast, return flow sets up, and temperatures return back into the mid 80s, and surface dewpoints creep back up into the low to mid 60s. By Friday, low pressure moves into the Great Lakes, and some mid-level shortwave energy spins off ahead of the low, and may touch off some scattered showers and thunderstorms. Temperatures once again rise into the upper 80s to around 90, along with dewpoints in the mid to upper 60s. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. A period of poor flying weather thru the mid-morning before a return back to VFR across the region. Prior to the mid-morning, showers and isolated thunder with lower CIGS and VSBYS expected across most areas with the remnants of Cindy and a front affecting the weather. S to SW winds ahead of the system will swing abruptly to NW around dawn and gust around 20-25 kts at times. Later today, clearing and NW winds backing to W late. Tonight...VFR, clear skies and light winds expected. OUTLOOK... Sunday...VFR. West winds 8-12 KT. Gusts to 19 KT possible in the afternoon. Sunday night...VFR. Light NW winds. Monday...VFR. West to southwest winds 5-10 KT. Isolated SHRA/TSRA possible in the afternoon, mainly north/west of the I-95 corridor terminals. Monday night...VFR. Light west winds. Tuesday...Mainly VFR. Sub-VFR conditions possible in scattered SHRA/TSRA in the afternoon. Tuesday night through Wednesday...VFR. && .MARINE...
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We will add the SCA flag for Delaware Bay with frequent gusts to 25 knt attm which will likely continue until after the low/front cross the area this morning. The SCA for the ocean will remain for the day with seas expected to remain above 5 ft thru the period. Rains and psbl thunder this morning, then rapid improvement by early afternoon. Fair weather expected tonight. OUTLOOK... Sunday through Wednesday...Winds and seas are expected to remain below SCA criteria. Scattered thunderstorms possible on Tuesday. RIP CURRENTS... Today, winds will be shifting off shore, but a 5 to 6 ft swell may lead to a moderate risk for the formation of dangerous rip currents. The rip current risk will probably decrease later today, possibly back to low risk.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ450>455. Small Craft Advisory until noon EDT today for ANZ430-431. && $$ Synopsis...MPS Near Term...O`Hara Short Term...O`Hara Long Term...MPS Aviation...MPS/O`Hara Marine...MPS/O`Hara

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