Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 241312 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 912 AM EDT WED AUG 24 2016 .SYNOPSIS... High pressure will continue to build offshore today and out to sea Thursday. A cold front will move across the area Friday and stall to our south over the weekend. High pressure builds to our north over the weekend, then offshore Monday. An area of low pressure may pass to our north Monday, bringing a front across the area Monday into Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Forecast on track. Will update hourly grids based on latest surface obs, but no significant changes will be made to the database. An upper-level ridge, stretched across the southern states, will have an extension on its northeastern side move across our region during the course of today. As this occurs, surface high pressure over the area will become more centered offshore. The pressure gradient is not all that tight, and therefore, the flow is on the weaker side. With ample heating of the boundary layer this afternoon, there should be sea breeze development. This will back the winds a bit more south-southeast along the coast. As the ridge expands northeastward some today, there will be some warming aloft as reflected by an increase in the thicknesses. This will result in a warmer afternoon for many places from what was observed yesterday. Overall a warm afternoon, however dew points while a bit higher are expected to remain below humid thresholds for much of the region. Despite some ridging into the area today, convection in the Midwest early this morning will send some high level debris clouds downstream some of which will move through parts of our area at times.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... The northeastern extension of the southern states ridge shifts offshore tonight as a weakening short wave trough slides across the Great Lakes region. This is accompanied by a surge in low-level warm air advection up the Ohio Valley. The southwesterly flow will also start to bring in some increase to the low-level moisture as we go through tonight, however this does not appear to be real robust. It looks like the best forcing remains well to our west more in the Ohio Valley due to the warm air advection with the aforementioned short wave trough, plus a wind shift is noted around 850 mb. As a result, we kept the forecast dry with the expectation that any convection associated with this remains well to our west. We are anticipating some high level clouds around at times, otherwise a bit warmer night due to some uptick in the dew points. This may also result in patchy fog in the valley areas as well as some rural spots. && .LONG TERM /THURSDAY THROUGH TUESDAY/... High pressure continues to move out to sea Thursday, which will lead to return flow around the western side of the high. This will allow temperatures to warm and moisture to begin increasing. There will be a chance of showers/thunderstorms Thursday into Thursday evening as a couple of short wave/vorticity impulses slide across the area. The return flow will continue into Friday ahead of an approaching frontal boundary. There will again be a chance for isolated showers to develop during the day, but overall chances are small at this time. 925/850 mb temperatures and thicknesses will continue to increase, making Friday the warmest and most humid day of the week. The frontal boundary will sag south of the area Friday night, and stall just to our south over the weekend while high pressure builds to our north. This high will keep dry weather in place across the area through the weekend. The high pressure will build offshore of New England by Monday, and a cold front will begin approaching the area Monday into Tuesday as an area of low pressure skirts to our north. There are a couple of short wave/vorticity impulses forecast early next week, so there will continue to be a chance for isolated showers or thunderstorms Monday into Tuesday. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR. Light and variable to calm will become southwesterly at 5-10 knots by midday. A turn to south or southeast at ACY and ILG should occur by late afternoon as a sea/bay breeze develops. Tonight...VFR overall. Southerly winds becoming light and variable at most terminals during the evening. Local MVFR visibility is possible toward daybreak Thursday due to light fog, mainly at RDG, ABE and MIV. OUTLOOK... Thursday-Friday...Generally VFR conditions expected. A chance of isolated showers and thunderstorms which may lead to temporary lower conditions. Friday night through Sunday...VFR conditions expected.
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&& .MARINE... High pressure at the surface eases more offshore through today and tonight. This will allow for the surface flow to turn more southerly today and continue tonight. While the flow is not forecast to be all that strong with the departing surface high, the southerly flow will increase especially by late this afternoon across the northern coastal waters. There should be some nearshore enhancement particularly this afternoon and early evening as a sea/bay breeze circulation occurs, however the speeds (also seas) are expected to be below Small Craft Advisory criteria through tonight. OUTLOOK... Thursday through Friday...Winds may approach Small Craft Advisory levels Thursday into Thursday night. Winds will begin diminishing Friday morning. Friday night through Sunday...Sub-Small Craft Advisory conditions expected to continue across the waters. RIP CURRENTS...For today, the risk for the formation of dangerous rip currents is low. However, conditions may reach moderate this afternoon and evening especially if the waves in the surf zone increase to 2-3 feet combined with the south-southeast winds increasing faster. This coming Sun-Tue...model ensemble guidance on every successive cycle continues to send 2-4 ft long period (15 to 17 second) east southeast swell into our waters from the central Atlantic. If that occurs, swimming and wading dangers will increase markedly. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Robertson Near Term...Gorse/MPS Short Term...Gorse Long Term...Robertson Aviation...Gorse/Robertson/MPS Marine...Gorse/Robertson is the U.S. government's official web portal to all federal, state and local government web resources and services.