Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 141808 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 208 PM EDT Thu Sep 14 2017 .SYNOPSIS... The remnants of Irma will drift across the Mid Atlantic and through New England today through Friday. High pressure will briefly build to our northwest Saturday, before weakening on Sunday and retreating northward through Monday. A weakening frontal boundary will approach the area Tuesday, before dissipating to our west. Tropical cyclone Jose will be monitored for its northward progress off the East Coast later in the weekend into early next week. && .NEAR TERM /THROUGH TONIGHT/...
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Our forecast grids were updated at 1230 PM through Friday with updated rain chances, reduction in areal coverage of thunder. Included T with heavy rain e PA and NNJ this aftn. Also added patchy fog late tonight using the UPS crossover tool. This per skies expected to at least partially clear after whatever coverage of showers persists into the evening hours. PWAT is a tad less today (~1.5") than ydy but still allows for brief heavy rain showers. Its a somewhat tropical looking sky here today. the southwest winds gusty 15-20 kt mid and late afternoon will diminish tonight and become nearly calm in a weak wind shift late tonight. At 330PM, our forecast will have the latest mesoscale output into the evening...attempting to better define coverage of showers. This forecast update this afternoon is a 50 50 blend of the 12z/14 GFS/NAM MOS.
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&& .SHORT TERM /FRIDAY/...
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Lingering mid level trough may spark afternoon showers....we`re not sure where but favored hilly terrain of ne PA and nw NJ but cant rule out a brief shower anywhere. Nice and warm. This part of the forecast is a 50 50 blend of the 12z/14 GFS/NAM MOS.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The main remnants of Irma finally move to our northeast by Friday, however, it`s associated mid level trough will be slow to pull out of the area. In fact, this weak trough aloft and associated vorticity could linger across the east coast Friday through the weekend. Also, a weak surface trough may linger as well. This will lead to enhanced lift across the area each day, mainly in the afternoon Friday, Saturday, and Sunday, which could lead to a chance for scattered showers each day. These would be more diurnally driven and diminish around/after sunset. Our attention then turns to the potential track of tropical cyclone Jose. The official track from the NHC keeps the storm well off the coast through Monday evening. The long range guidance continues to keep the storm offshore of the Mid Atlantic region as it lifts northward. The GFS is far enough offshore that it would keep the weather mostly dry, but the ECMWF is closer to the coast which would bring a better potential for precipitation and gusty winds. The track of the storm will be depended on how strong ridging to our west takes place, and how quickly a trough to our north will get to the east coast to help pull Jose away from the area. Please stay tuned to the National Hurricane Center for the latest official track and forecast regarding Hurricane Jose. Remember, we are at the peak of hurricane season for the Atlantic Basin, so it is important to have a hurricane plan in place. For tips as to what to have in your hurricane plan, please check http:/www.nws.noaa.gov/om/hurricane/plan.shtml && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Remainder of this afternoon...Mostly VFR cigs except brief MVFR or IFR conds in any heavier showers. Small chance of a thunderstorm, especially NNJ but no thunder in the TAF attm due to low probability hitting our TAF sites. South to southwest wind may gust 15-20 kt this afternoon along and east of I95. Tonight...VFR but patchy IFR conds in st/fog may develop late. Tempo group for expected fog is in the 18z TAFS. Leftover evening showers. south to southwest wind becoming nearly calm late at night. Friday...VFR sct-bkn aoa 5000 ft. A small chance of showers in the afternoon but probability too low to mention in the TAF. Light west wind trend south late in the day. OUTLOOK... Friday night...Conditions vary between VFR and MVFR with a chance of showers possible. Chance of fog/stratus Friday night/Saturday morning. Saturday-Monday...Generally VFR. Patchy fog/stratus during the late night/early morning hours. Scattered showers also possible during the day.
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&& .MARINE...
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Winds and seas should stay below small craft advisory criteria through Friday. A few gusts near 20 KT will be possible this evening on the Atlantic Coastal waters. Outlook... Friday night...Generally sub Small Craft Advisory conditions expected. Seas forecast to be 3-4 feet. Saturday-Monday...Conditions may reach Small Craft Advisory levels as seas may build to 5-6 feet. Rip Currents... For the rest of today, we have forecasted a marginal moderate risk for the formation of dangerous rip currents. Long period (10 second) southeasterly swells from tropical cyclone Jose continue. Looking ahead...a low or moderate risk is expected Friday then slowly building swells from Jose arrive this weekend, reaching their highest values around next Tuesday before subsiding. It Looks like a moderate risk for Saturday and moderate or high risk Sunday, with HIGH risk Monday and Tuesday.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Drag/Robertson 208 Near Term...Drag 208 Short Term...Drag 208 Long Term...Robertson Aviation...Drag/Robertson 208 Marine...Drag/Robertson 208

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