Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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528 FXUS61 KPHI 231614 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1214 PM EDT Wed May 23 2018 .SYNOPSIS... Weak low pressure will track north of the region into this morning dragging a cold front south across the area. High pressure builds in tonight and Thursday before shifting offshore Friday. A cold front is forecast to move southward across our area later Saturday night through Sunday, then stall in our vicinity early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Weak cold front is through the region, and now some weak mid level shortwave energy is passing through behind it. Winds have shifted to the NW, and surface dewpoints will continue to fall through the afternoon. Low clouds are scattering out, and mid level clouds associated with the shortwave will scatter out after its passage late this afternoon. Winds will back to the west by late afternoon as well. A downsloping westerly flow should result in highs in the 70s in the mountains and right along the coasts, and otherwise generally in the low 80s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... High pressure will remain west of the area tonight. We will be in a much drier and somewhat cooler air mass. Under mostly clear skies, temperatures should drop into the low/mid 50s across the northern areas and upper 50s/low 60s across the urban areas and Delmarva. Winds will be light from the NW. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Thursday through Friday night... High pressure will maintain fair and dry weather across the area through this period with lots of sunshine. As this high moves over the area Thursday, it will bring sunny skies with light winds and low humidity. Highs will generally be in the upper 70s to low 80s except several degrees cooler over the southern Poconos as well as along the coast where a sea breeze will likely kick in by afternoon. Thursday night into Friday, the high will move offshore setting up a return flow from the SW bringing in warmer temperatures and increasing dew points as well...though still not too humid. Highs by Friday afternoon will generally reach the low to mid 80s except again, cooler near the coast and across the southern Poconos. Lows Thursday night will generally be in the 50s to low 60s but as dew points continue to creep up Friday night it will keep temperatures up as well with lows in the 60s. Saturday through Tuesday... SW flow ahead of the next wave continues to bring in warmer and more humid air Saturday with some scattered to isolated showers and thunderstorms possible in the afternoon, mainly north and west of the I-95 corridor. Highs should reach the mid to upper 80s away from the coast with 90 degrees not out of the question. Dew points in the mid to upper 60s will also make it feel quite muggy. Right along the coast as well as the southern Poconos it will still be cooler...generally in the upper 70s to low 80s. Saturday night and beyond, the forecast gets more complex. The GFS and the GEM both drag a backdoor cold front southward across the area Sunday as high pressure moves into eastern Canada while the ECMWF keeps this front to the north. Based on the models recent handling of these types of patterns, tend to favor the colder solution that brings the front south. At the same time, tropical moisture associated with a large low over the Gulf of Mexico will be pulled north into the area around high pressure in the western Atlantic. This looks to set up a more unsettled pattern Sunday into Memorial Day with increasing chances for widespread showers and thunderstorms, some of which could be heavy. Temperatures should be cooler with highs Sunday mainly in the 70s to low 80s and highs Monday possibly only in the 60s north and the 70s south. Again though, there is increasing uncertainty in the forecast through this time period...especially regarding the placement of the front which will have an impact on both temperatures and precipitation. By next Tuesday, the front may start to lift back to the north as the next wave approaches from Ontario and Quebec but tropical moisture looks to remain in the vicinity so we keep chances for showers and storms in the forecast. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...MVFR CIGs continue to scatter out, and mid level clouds will scatter out by late afternoon as well. Only KACY currently MVFR, and VFR expected 17-18Z. Winds will be mostly 320-340 at 10-15 knots into the afternoon. Tonight...Mostly VFR expected with clear skies. Winds will be light NW or calm. The air mass should be too dry to support much in way of fog tonight, perhaps some patchy ground fog in rural areas. It will probably mot be included in the 12Z TAFs with overall low confid in its occurrence. OUTLOOK... Thursday and Friday...VFR. Northerly winds around 10 knots early Thursday backing to light SW by late Thursday with SW winds increasing to near 10 knots Friday. Saturday and Sunday...Mainly VFR Saturday and Saturday night. Sub- VFR conditions may occur at times with developing showers and thunderstorms by Sunday afternoon.
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&& .MARINE... Sub-SCA conditions are expected and fair weather today and tonight with high pressure building in behind the passage of a weak cold front. Seas on the ocean will be mostly 2 to 3 ft. OUTLOOK... Thursday...The conditions are anticipated to be below Small Craft Advisory criteria. Friday and Saturday...Southwesterly flow increases allowing the seas to build some. It is possible that wind gusts approach Small Craft Advisory criteria at times Friday night and Saturday Sunday...The conditions should be below Small Craft Advisory criteria as a front settles southward. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Fitzsimmons Near Term...MPS/O`Hara Short Term...O`Hara Long Term...Fitzsimmons Aviation...Fitzsimmons/MPS/O`Hara Marine...Fitzsimmons/MPS/O`Hara

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