Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 121626 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1226 PM EDT Sat Aug 12 2017 .SYNOPSIS... A cold front will move across the east coast tonight. High pressure will briefly build across the area Sunday night into early next week. The front will stall to the south Monday into Tuesday as an area of low pressure develops along the boundary and moves eastward along the front. Another frontal boundary may affect the area Wednesday, before high pressure briefly builds across the area Wednesday night, then offshore Thursday. A frontal system could then affect the area late next week or early next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Showers and isolated thunderstorms will continue to pass across parts of northeastern Maryland, Delaware and southern New Jersey early this afternoon. There will continue to be locally heavy rain. The showers and thunderstorms are expected to sink gradually to the south. Meanwhile low clouds will remain over eastern Pennsylvania, New Jersey and the upper Delmarva during the early afternoon. They are forecast to lift slowly. A cold front extended across the eastern Great Lakes and the Ohio River Valley around midday. The boundary will move eastward and it is expected to reach central Pennsylvania and western Virginia toward evening. A line of showers and thunderstorms is was developing in advance of the front and it should arrive in Berks County, the Poconos and the Lehigh Valley late this afternoon. The thunderstorms there may bring strong wind gusts and hail along with frequent cloud to ground lightning and heavy rainfall. Depending upon how much clearing takes place this afternoon, conditions may be slow to destabilize over parts of southeastern Pennsylvania and New Jersey. As a result, the showers and thunderstorms may lose some of their strength as they move farther to the east late in the day. High temperatures are expected to favor the upper 70s and lower 80s. Once the marine layer erodes, the wind should settle into the south and southwest around 8 to 12 MPH.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... The low pressure system will be crossing thru New england tonight. A weak cold front attached to the low will cross our area from NW to Se overnight. Scattered showers and a few tstms will be ahead of the front this evening into early tonight, before pops decrease towards dawn. Low will drop into the upper 50s to low 60s across the nrn areas, and remain closer to 70 over Delmarva and metro Philadelphia. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The cold front is forecast to push south of the area by Sunday morning, before a secondary front or surface trough may cross the area later on Sunday into Sunday night. Moisture and lift will weaken during the day, so it now looks like Sunday will be a dry day. The initial cold front is forecast to stall to our south through Monday and Tuesday. Weak high pressure is forecast to affect the area Sunday night into early next week. An area of low pressure is expected to develop along the front to the south and moves 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. Just like the last couple of days, the GFS remains farther south and east than the ECMWF with the low. There still remains the possibility some showers could move across portions of the area Monday through Tuesday, so we`ll keep chance POPS in the forecast for now. Also on Tuesday, a weak surface trough may move across the area which may help create a few showers or thunderstorms as well. Another frontal boundary may move across the area Wednesday, Wednesday, before high pressure briefly builds across the area Wednesday night, then offshore Thursday. This frontal boundary and subsequent high pressure are forecast to contain dry weather. However, we move into the end of the week into the early part of the weekend, a warm front may lift across the area as high pressure builds offshore, followed by a cold front. The timing is uncertain as the GFS is slower than the ECMWF, but they both do indicate this system. So we`ll have a chance of showers and thunderstorms from Thursday night through Friday night for now. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. A period of lower CIGS/VSBYS was across the terminals around midday. Conditions will improve somewhat during the afternoon hours. More showers and tstms are expected this afternoon and into the evening as a cold front crosses the area. More MVFR/IFR will be possible at those times. Light variable winds early today will become SW at 5 to 10 kts this afternoon. VFR conditions expected later tonight behind the cold front. OUTLOOK... Sunday-Wednesday...Generally VFR conditions. Scattered showers and thunderstorms possible Monday-Tuesday which may temporarily reduce conditions.
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&& .MARINE... Winds and seas will increase a bit this afternoon ahead of the low pressure system and front approaching from the Great Lakes. it doesn`t appear that SCA conditions will be reached, so we will hold on the flag for now. A few gusts in the low 20s kts are possible and seas could reach 3-4 ft on the ocean, so near SCA conditions. Sct showers and tstms will bring some locally higher winds and seas this afternoon and in to the evening. Fair weather expected later tonight behind the cold front. OUTLOOK... Sunday-Wednesday...Sub Small Craft Advisory conditions expected through the entire period. RIP CURRENTS... The risk for the development of dangerous rip currents remains low for today. However, it may approach moderate along the New Jersey Shore late in the day as wind speeds increase from the south. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...Iovino Short Term...O`Hara Long Term...Robertson Aviation...Robertson/O`Hara Marine...Robertson/O`Hara is the U.S. government's official web portal to all federal, state and local government web resources and services.