Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 141038 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 638 AM 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. Hurricane Jose will be monitored for its northward progress off the East Coast later in the weekend into early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The rain showers and thunderstorms currently over western PA and N Central VA should continue to propagate east towards our region through the morning hours as the positively-tilted mid and upper level trough approaches our region. Although the main area of showers in western PA will miss our region, expect convective initiation to occur further south along the trough axis later today. A deep moist layer and the persistent cloud cover that should go with it may limit instability, but there is some chance for thunderstorms primarily along and east of the Delaware Valley. MOS guidance for the NAM and GFS was relatively close for highs, so stayed with a blend of the guidance with highs ranging from near 70 to the lower 80s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Surface trough axis should propagate through the region overnight, but expect little noticeable impact aside from a shift from southwesterly to westerly winds. As the mid and upper level trough fills, expect showers to dissipate through the eventing hours. However, this trough won`t completely dissipate, thus, expect persistent cloud cover to continue overnight. The temperature forecast (with lows generally in the 60s) reflects this as we should see limited opportunity for radiational cooling. && .LONG TERM /FRIDAY 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 Hurricane 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:/ && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Once visibilities improve to VFR (which should occur near or shortly after 12Z), mostly VFR conditions are expected for the remainder of the TAF period. However, there is a small chance for showers and thunderstorms across the region today. If any of these move over a TAF site, brief MVFR conditions are possible. Chance for thunderstorms is too low at this time to mention in the TAFs. Winds are expected to be mostly southwesterly and 10 KT or less through the TAF period. However, a shift to westerly winds is expected with a trough moving over the region after 06Z tonight. Though the KMIV ASOS is operational, our data link to the site is currently down. Therefore, appended AMD NOT SKED to that TAF until it is restored. We apologize for any inconvenience. OUTLOOK... Friday-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... Winds and seas should stay below small craft advisory criteria today and tonight. A few gusts near 20 KT will be possible this evening on the Atlantic Coastal waters. Outlook... Friday-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 today, we are forecasting a moderate risk for the formation of dangerous rip currents. Long period (10-14 sec) southeasterly swells from Hurricane Jose continue. Looking ahead...a low or moderate risk is expected Friday then another set of long period swells from Hurricane Jose should arrive this weekend and we expect moderate or high risk days from Saturday through at least next Tuesday with swells building to 5 to 6 feet and period lengthening to near 15 seconds. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...Johnson Short Term...Johnson Long Term...Robertson Aviation...Johnson/Robertson Marine...Johnson/Robertson is the U.S. government's official web portal to all federal, state and local government web resources and services.