Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 161317 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 917 AM EDT Wed Aug 16 2017 .SYNOPSIS... High pressure will build across the region today before moving offshore on Thursday. A warm front will lift northward towards the area late Thursday and then moves through the area on Friday. A cold front will approach from the west on Friday, pushing through the region Friday night through Saturday. High pressure returns for Sunday through Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure builds in from the west today. Morning sunshine will give way to diurnally driven afternoon scattered to broken clouds. Light northwest wind trends west during the afternoon with sea breezes along the coast. With a weak wind shift (drier dewpoints) developing across our area very late this afternoon near or north of I78...its not impossible to see a sprinkle in parts of e central or se PA and central or S NJ toward sunset. HRRRX and NSSL WRF have it. Blended POPS and review of KI suggest not forecasting a sprinkle in NJ or DE but instead leave it for the southern part of DE. Forecast basis was a 50 50 blend of the 00z/16 GFS/NAM MOS guidance. Max temps a couple of degrees above normal. High Risk for dangerous rc formation continues per the 13 second 4-5 ft se swell from Gert, washing ashore. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... Again, its not impossible to see isolated sprinkles vcnty Philly to ACY at 00z down into s DE but not lasting long. Otherwise becoming mostly clear. The wind shift progresses southward to near PHL by 12z Thursday. Light north-northeast wind to its north and and light south to southwest to its south. Cooler and much more comfortable I78 northward, though short lived. Patchy fog probably forms toward dawn Thursday, but not nearly to the extent we see it this morning and not expecting a dense fog advy situation. Forecast basis was a 50 50 blend of the 00z/16 GFS/NAM MOS guidance. && .LONG TERM /THURSDAY THROUGH TUESDAY/... High pressure will start to slide offshore on Thursday with a warm front developing across Virginia. The warm front will push northward on Thursday and will start to move into our area late Thursday, pushing through the region on Friday. Showers and thunderstorms will start to develop just north of and along the warm front on Thursday afternoon and evening and then will overspread the region Thursday night and Friday as a warmer and moister airmass moves into the Mid- Atlantic. A cold front will approach the region from the west on Friday, crossing the region late Friday through Saturday. Another round of showers and thunderstorms are expected as the front moves through our area. Good shear and forcing across the area means some storms may be strong, possibly severe, and with PWATs running high again, heavy rain will also be a threat. SPC has a marginal risk for severe storms just to our west at this time. Some cooler air should arrive behind the front but it isn`t all that cool or dry so little relief is expected. A shortwave will cross through the region on Saturday keeping the chance for showers and thunderstorms throughout Saturday evening. As the wave pushes to the east, the showers/thunderstorms will decrease in coverage and drier air will start to move in. High pressure will build in for Sunday and a period of relatively nice weather should continue for the start of the week with the high shifting offshore on Monday. Another frontal system will approach the region for Tuesday/Wednesday with another chance for showers and thunderstorms. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Remaining IFR/MVFR stratus/fog dissipates by 14z. Then VFR sct- bkn clouds aoa 4000 ft develop midday with a west-northwest wind trending west to southwest late in the afternoon except sea breezes developing vcnty KACY. Isolated light showers possible se PA to s NJ after 21z. I think the NAM tsec is best for fcstg low lvl rh changes. NARRE has completely missed the dense fog in our area, yet unexpectedly to me has a stratus deck lingering to around 15z. Tonight...After any isolated light showers vcnty KILG/KPHL/KACY southward end by 01z, a VFR night with a wind shift progressing southward to near KPHL by 12z Thu. Winds turn light north-northeast north of the boundary and are light south to southwest to its south. Patchy IFR fog/stratus may form in the NJ and Delmarva countryside between 07z-10z/17, but not nearly to the extent of what we see/saw this morning. OUTLOOK: Thursday...Mainly VFR conditions expected. Sub-VFR conditions in afternoon/evening showers and thunderstorms. Fog possible early Thursday morning and again late Thursday night. Friday...Fog possible early morning. Sub-VFR conditions in showers and thunderstorms. Saturday...MVFR conditions expected Scattered showers and thunderstorms possible. Improving conditions late. Sunday...Mainly VFR conditions expected. && .MARINE... Seas are around 5 feet at the buoys off the NJ/DE coast as Hurricane Gert heads enewd well offshore toward the north central ATLC. Longer period swell from Gert is reaching the buoys (generally 12-13 seconds) and will continue this morning then easing slowly this afternoon and evening. Small craft advisory for seas continues. Light northwest flow this morning becomes southeast to south sea breezes during this afternoon. A wind shift back to northerly should develop for the NJ coastal waters late Wednesday night. Some fog may develop near the coast and near Delaware Bay early today, with visibility restrictions possible. However, this fog should dissipate rapidly after sunrise with a nice day expected, save for the aforementioned higher seas. OUTLOOK... Thursday thru Sunday...Sub-Small Craft Advisory conditions expected on the area waters through Sunday. Some gusts around 20-25 knots are possible Friday afternoon and evening. Showers and thunderstorms possible late Thursday through Saturday, with locally higher seas and winds. RIP CURRENTS... A high risk for the development of dangerous rip currents is in effect today. Long period swells from Hurricane Gert will continue to impact the coasts of Delaware and New Jersey. Swim only in the presence of lifeguards where safety prevails and if beaches are closed...respect the decisions of the local officials. Do we need a reminder? There have been numerous drowning fatalities this year along the NJ coast, and most of those at unguarded beaches. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...High Rip Current Risk until 9 PM EDT this evening for NJZ014- 024>026. DE...High Rip Current Risk until 9 PM EDT this evening for DEZ004. MD...None. MARINE...Small Craft Advisory for hazardous seas until 2 PM EDT this afternoon for ANZ450>455. && $$ Synopsis...Meola Near Term...Drag/MPS Short Term...Drag Long Term...Meola Aviation...Drag/Meola Marine...Drag/Meola

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