Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 191344 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 944 AM EDT Thu Oct 19 2017 .SYNOPSIS... A dry frontal boundary will move toward the area tonight into early Friday. Otherwise, high pressure remains in control of the weather for much of the rest of the week into the weekend. A frontal boundary is forecast to affect the area early next week, bringing a return of unsettled weather. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Mid morning surface analysis shows a broad area of high pressure over the Southeast and mid-Atlantic states. This high was weakened and shifted south of our area over the past 24 hours. Meanwhile, a cold front was located over the Upper Midwest, stretching southwestward into the Central Plains. The cold front will approach from the west as it moves through the eastern Great Lakes/Ohio Valley this afternoon. GOES-16 water vapor satellite imagery (CHs 8-10) show a weak shortwave trough aloft passing thru the region this morning. Other than thin cirrus streaming across the area, this system will have no other impacts on our sensible weather today. The warm sector will clearly be established over the region today with southwesterly flow continuing ahead of the cold front. High temperatures were tweaked upward by a couple of degrees for the mid morning ESTF update and reflects a warmer solution than any guidance. Forecast highs are in the mid 70s across most of the area, except cooler in the higher elevations of NE PA/NW NJ and along the coast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Weak surface cold front passes through the region tonight. With a lack of moisture and no upper level support, conditions will be dry with its passage. Outside of some evening cirrus, skies should clear out after midnight. Surface high pressure reestablishes itself over the Appalachians after midnight. Some patchy ground fog is possible prior to the passage of the cold front. Dew points will fall behind the passage of the front. Lows tonight will be in the upper 40s to around 50. Lows in the Philly metro area will be in the low 50s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Quiet weather is expected for the end of this week into the weekend as high pressure will be in control of the weather through the end of the week before moving offshore for Sunday and Monday. Ridging aloft builds across the area late this week into the weekend, which will help keep temperatures several degrees above normal. As the surface high and ridge aloft moves offshore Sunday, return flow and southwest flow aloft develops. This will help increase clouds, but no precipitation is expected through Sunday. As we go into Sunday, an area of low pressure is forecast to develop near the Lower Mississippi Valley along a frontal boundary located across the central part of the country. It is then expected to strengthen as it moves northward along the frontal boundary and toward the Great Lakes Monday night into Tuesday. The front is expected to move toward our area Tuesday into Tuesday night, although there is some timing differences between the GFS and ECMWF. The GFS pushes the front through quicker, moving the precip through Tuesday into Tuesday night. The ECMWF slowly moves the front through slower, keeping precip across the area Tuesday night through Wednesday night. For now, we have the greatest chances for precipitation Tuesday and Tuesday night. && .AVIATION /13Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR through the TAF period. Patchy ground fog with brief MVFR VSBY is possible from around 04-12Z Friday. SW winds less than 10 KT, becoming less than 5 KT tonight. OUTLOOK... Friday-Monday...VFR conditions expected. Winds may gust around 15 knots Friday, Sunday, and Monday. && .MARINE... SW winds 5-10 KT, increasing to 10-15 KT with gusts to 20 KT this afternoon on the Atlantic coastal waters. Winds shift to the NW tonight after the passage of a cold front. Seas will generally be around 3 ft on the coastal waters and 2 ft or less in the Delaware Bay...predominately in a SE swell of 9 or 10 seconds. OUTLOOK... Friday-Monday...Conditions expected to remain below Small Craft Advisory levels through the period. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...Klein Short Term...MPS Long Term...Robertson Aviation...Klein/Robertson/MPS Marine...Klein/Robertson/MPS

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