Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 280154 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 954 PM EDT Tue Jun 27 2017 .SYNOPSIS... High pressure over the Ohio Valley will build east across the mid-Atlantic region through Wednesday. The high pressure will move offshore for Thursday and Friday, returning our area to southwest flow. Another weak cold front is expected this weekend, bringing a chance of showers through early next week, especially if the front stalls. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Showers that developed across parts of the area this afternoon and evening have dissipated and outside of a very isolated shower, we should remain dry through the rest of the overnight period. Skies are already starting to clear out and we should see some drying occur as a more westerly flow is in place overnight. Some low level moisture may linger a bit in areas where rain fell through this evening, and some light patchy fog might develop towards daybreak. Light winds overnight combined with the clearing skies will allow for good radiational cooling to take place. Already starting to see some indication of this with 9pm temperatures already falling in Millville (65) and Somerville (63) and Andover (61). Overnight lows will fall into the 50s across the region with near 60 in the urban areas around Philadelphia and along the coast. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Northwest flow becomes established tomorrow on the upstream side of the shortwave trough moving through the area tonight. A surface high will build into the eastern U.S. This sets the stage for a very pleasant day, with skies mostly sunny and temperatures slightly below seasonal averages. With some fairly pronounced mixing, winds may gust to around 20 mph or so during the afternoon. May also see a cumulus field develop during the day, but subsidence above the boundary layer will keep these of the "fair weather" variety. MOS is in generally good agreement with highs tomorrow, but low- level cold air advection will cease during the morning, with ridging beginning to nose into the region as the day progresses. If this happens sooner, forecast highs may be a bit on the low side. For now, did not stray too far from a statistical MOS blend, given the strong consensus. Highs will be around 70 in the Poconos and near 80 southeast of the Fall Line. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... The long term starts out with surface high pressure just off the mid-Atlantic coast and associated fairly pleasant weather. However as the high moves farther offshore and low pressure moves into the Great Lakes, a more typical summertime SW flow will set up over the region. This in turn will cause increasing heat and humidity over the forecast area through the end of the week and into the weekend. At this point it appears that Saturday may be the most uncomfortable day with heat indices reaching the mid 90s along the I-95 urban corridor. Along with more heat and humidity will be gradually increasing chances for afternoon showers and thunderstorms. For Thursday and Friday it looks like any precip should remain well to the northwest of PHL. By Saturday an upper-level trof and associated cold front are forecast to approach the mid-Atlantic and also a surface trof is forecast to develop from eastern PA south to near the Chesapeake Bay. Enhanced low-level convergence is expected to result in more widespread afternoon convection on Saturday. For Sunday and beyond the forecast becomes more cloudy, as the models seem to disagree on whether a surface cold front can push through our area or whether it will stall out. Given the uncertainty, the forecast maintains at least a slight chance for showers/t-storms through early next week. Temperatures are expected to be near or slightly above normal at that time. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are expected to continue through the TAF period. Overnight...Skies will clear out through tonight with light westerly winds, less than 10 knots, across the terminals. Wednesday...VFR conditions continue. Winds will pick up out of the west/northwest between 14-16Z, becoming southwest around 10 knots with gusts up near 20 kts by late afternoon, Winds will lighten as we head into the evening. Skies look to be relatively cloud free but some cumulus may develop during the afternoon. OUTLOOK... Thursday and Friday...VFR conditions expected. Southwest winds gusting up to 20 kt in the afternoon both days. Saturday and Sunday...Mostly VFR conditions but lower at times in scattered mainly afternoon showers and thunderstorms. && .MARINE...
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Sub-advisory conditions are expected through the period. Winds should switch from southwest to northwest through the nighttime hours, with speeds generally 10 to 15 kts with gusts to 20 kts. Winds will switch back to southwest by afternoon tomorrow, generally remaining around 10 to 15 kts with higher gusts. May see gusts approach 25 kts by late afternoon, but predominantly winds should stay below advisory criteria. OUTLOOK... Thursday and Friday...SCA conditions may develop Thursday afternoon and continue into Friday due to increasing SW winds and building seas. Saturday and Sunday...Winds and seas are expected to be somewhat below SCA levels. RIP CURRENTS... The forecast is for a low risk of rip currents for Wednesday. However, southwest winds will increase to around 15 kts with higher gusts by late afternoon. With a 9-second period from a southeasterly direction, this may increase the rip current risk level, especially on the New Jersey coast.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...AMC Near Term...Meola Short Term...CMS Long Term...AMC Aviation...AMC/Meola Marine...AMC/CMS is the U.S. government's official web portal to all federal, state and local government web resources and services.