Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251330 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 930 AM EDT WED MAY 25 2016 .SYNOPSIS...
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High pressure will build off the Carolina coast today and persist through Saturday. A cool front is forecast to settle across the Northeast Thursday before moving back to the north. Another cool front settles southward late Friday and Saturday, and as high pressure shifts around offshore this front should get pushed southward into our area later Sunday and Monday before lifting back north. The next cold front may slowly approach from the northwest later Tuesday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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High pressure located off the coast of the Carolinas will continue to influence our weather for today. We are anticipating a mostly sunny sky with a west to southwest wind around 5 to 10 mph. Temperatures were rising sharply this morning in response to the sunshine and we expect highs mainly in the middle and upper 80s. Readings are not forecast to get above the 70s in the elevated terrain of the Poconos and northwestern New Jersey, and along the immediate coast. The sea breeze front is expected to meet some resistance from the westerly synoptic flow. As a result, we do not expect the boundary to make much progress inland this afternoon.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
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The fair weather will continue tonight. Skies will be mostly clear with some high clouds expected late. Low temperatures will range from the upper 50s across the north and over rural areas...to the mid 60s over the Delmarva and urban areas.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
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Summary...A stretch of very warm/hot conditions. An increase in the humidity starts mainly later Thursday. A frontal boundary nearby Thursday into Sunday combined with instability should trigger some showers and thunderstorms mainly each afternoon and evening across the interior, then the front pushes south some later Sunday through Monday. There is less confidence with the temperature forecast later Sunday and Monday given the flow turning more onshore. The synoptic setup is comprised of a ridge in the east that amplifies with time though the holiday weekend. There will be several pieces of energy deflected around this ridge with a sharp trough possibly occurring in the vicinity of the Canadian Maritimes starting over the holiday weekend. This setup results in a frontal zone becoming draped from about the Great Lakes to New England. This front looks to meander north and south through Saturday before another front arrives. The upper air pattern may then support this front settling into our area more Sunday and Monday in conjunction with low pressure well to our south. Some energy along this front combined with plenty of heating to the south of it should result in mainly some diurnally driven convection Friday through the holiday weekend. Overall, a washout is not anticipated although there is still questions regarding the details for later Sunday and Monday. We used a model blend approach for Thursday through Friday night, then blended in the 00z WPC Guidance with continuity thereafter. Some adjustments were then made based on additional collaboration with our neighboring offices. For Thursday...The 925 mb temperatures are forecast to be between +20C and +25C. This combined with west to southwest flow will drive the temperatures well into the 80s for much of the area. The exception will be the coastal areas where the surface flow may back more southerly and allow some cooler ocean influence. We bumped up the temperatures some especially away from the coast. Low pressure tracking into the Great Lakes should provide enough of a downstream push to move a front back north. A few showers and thunderstorms may develop Thursday afternoon across mainly our western zones due to terrain circulations and local convergence, however much of the convection should reside to our west. In addition, the dew points will be on the rise especially at night allowing for a more humid feel to the air. The model guidance shows a rapid uptick in the 700 mb theta-e and PW values especially at night. For Friday and Saturday...The ridge axis builds nearly over our area. This will result in very warm/hot conditions along with a more noticeable increase in the surface dew points. Some mainly diurnally driven convection cannot be ruled out each afternoon and early evening. The PW values are forecast to increase to near 1.50 inches Friday and with the mid level flow more westerly this could result in a bit more cloudiness. If this occurs, then perhaps the temperatures are a little cooler especially Saturday. It appears given the rather warm air mass in place, some places especially in the urban areas of the I-95 corridor top out at 90 degrees Friday afternoon. An area of low pressure is forecast to be slowly approaching the Carolinas as the ridge aloft remains. Depending on the organization of this feature some additional moisture may eventually work northward toward our area. For Sunday through Tuesday...As the ridge axis shifts a bit farther north, high pressure at the surface near the Canadian Maritimes drifts southward. This will turn our winds from the east Sunday and Monday as a surface cool front gets pushed southward some. The forecast challenge is how strong this push will be as it will greatly impact the temperature forecast. As of now, we are still expecting some cooling given an onshore flow and more clouds. There should remain a corridor of instability especially in the interior for some possible scattered convection Sunday mostly in the afternoon, then possibly more showery Monday with the onshore flow. The low to our south should be slow moving however some of its moisture may enhance the convective potential across our area into Tuesday.
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&& .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. A great flying weather period expected today and tonight. Skies will remain mostly clear across the region with gentle w/sw winds. Tonight...skc with light sw winds at the terminals. Outlook... Thursday and Friday...VFR overall. A few afternoon and evening showers and thunderstorms especially Friday mostly north and west of KPHL may result in brief times of MVFR/IFR conditions. Southwest winds mainly up to 10 knots, however less at night. A sea breeze may turn the winds to the southeast at KACY each afternoon, and a bay breeze possibly affecting KILG. Saturday and Sunday...VFR ceilings at times. Some mainly afternoon and evening showers and thunderstorms are possible each day, however these look scattered.
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&& .MARINE...
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Sub-sca conditions expected today and tonight with a ridge of high pressure expected across the waters. Winds will be mostly w this morning and then back to sw this afternoon. Wind speeds will be mostly 5 to 10 knots today and 10 to 15 knots tonight. Seas on the ocean 2- 3 ft and 1- 2 ft across Delaware Bay. Outlook... Thursday through Sunday...A ridge over the area combined with high pressure at the surface to our south and east will allow for mainly a prolonged southerly flow across our area through Saturday night. Winds should then shift more onshore during Sunday. The conditions are expected to be below Small Craft Advisory criteria. Sea breeze circulations each day may allow for a period of increased winds near-shore during the afternoon and early evening.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Gorse Near Term...Iovino Short Term...O`Hara Long Term...Gorse Aviation...Gorse/O`Hara Marine...Gorse/O`Hara

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