Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 220113 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 913 PM EDT SUN AUG 21 2016 .SYNOPSIS... A cold front was moving through the area this evening. High pressure builds into the area Monday and remain over the area through Thursday. The next cold front approaches from the northwest on Friday. The front may dissipate over the area next weekend while the center of high pressure approaches from the Great Lakes. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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The large area showers with a few embedded thunderstorms was generally moving east and off the coast attm. There were some lingering showers over ern NJ and srn DE, and that should be about it for organized precip. However, there are a few scattered showers over nern PA and MD that could still move acrs portions of the area, if they hold together. The overall trend is for improving conds into the overnight hours. Therefore, have lowered pops acrs the entire region to basically zero, except for the extreme e and to account for these few shwrs elsewhere. Also, adjusted temps and wind where necessary. As drier air moves in on a more wly and nwly flow, any and all precip shud end and clouds should break later in the night as well.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... High pressure will begin to build towards the region Monday. This will be the beginning of a nice stretch of fair weather. The airmass will be cooler and much drier. High temperatures will only reach the 70s across the north and low/mid 80s elsewhere. Dew points will only be in the 40s/50s too...so this will be a big break in the recent stretch of sultry summer weather. Winds will be a bit gusty however with NW winds 10 to 15 mph and gusts around 20 mph. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Expansive high pressure system will build in from the west Monday night with the center of the high over the area Tuesday and Wednesday. The high will move offshore late Wednesday and retreat into the open waters of the northwest Atlantic Ocean through the end of the week. Southerly return flow around the western periphery of the high will become established along the eastern seaboard during this time. A very quiet stretch of weather is in store for the mid- Atlantic region through Thursday with the high firmly in control. Comfortable outdoor weather conditions can be expected with highs generally in the low 80s Tuesday and mid 80s both Wednesday and Thursday. It will be very dry midweek for August standards with dewpoints in the 50s. The humidity increases a bit by Thursday but it will still be at comfortable levels with dewpoints in the 60s. Each day should also offer plenty of sunshine. The heat and humidity increases further by Friday as a cold front approaches from the west. It doesn`t appear to be excessive heat but highs in the upper 80s to lows 90F and dewpoints near 70F will make it feel muggy again. In general, went a couple of degrees above WPC/Superblend guidance for highs on Friday as they appear to be too cool. The front should provide us with our first perceptible chance of precipitation in the period. However, we continue to advertise very low PoPs. The forecast area will be situated on the northern side of an anticyclone/upper ridge over the Southeast states. In this setup, there is a risk that the subsidence inversion underneath the ridge would put a lid on convective development on Friday, especially the farther south you go. Furthermore, the deeper lift will also be displaced from the front, remaining well to our north as the belt of stronger westerlies associated with the subtropical jet stream resides near the U.S.-Canadian border. The front may stall and then washout in the area or nearby during the weekend as it meets the downstream blocking on the northern periphery of the ridge. Exactly where this happens will determine if our region is positioned on the cool side of the front with highs in the lower 80s or warm side with highs in the lower 90s...or somewhere in between. Leaned toward the warmer range of solutions with the pattern favorable for heat to build underneath the ridge. At this time, it appears that next weekend should be mainly dry. However, if the front stalls over the area and there is still enough residual convergence along it, then an isolated pop-up shower or storm map develop during peak heating. && .AVIATION /01Z MONDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. All TAFs are now VFR except for KACY as the large area of precip is movg off the cst. The only locations currently seeing precip attm are extreme ern NJ and srn DE. Expect KACY to return to VFR in a few hours. There are a few scattered showers over nern PA and over the Delmarva that cud impact portions of the area, if they hold together, but any organized precip has ended. Wind will become more wly then nwly overnight which will bring in drier air. This drier air will, in turn, cause a decrease in cloudiness overnight and by morning. Wind speeds will genly be 10 kts or less. VFR conditions expected with gusty NW winds up to around 20 knots on Monday. OUTLOOK... Monday night through Thursday night...Mainly VFR and light winds. Friday...Low chance for showers and storms with a cold front approaching from the NW.
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&& .MARINE...
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An update was made earlier to raise the SCA flag for Del Bay where gusts around 25 kts had developed. We already were advertising SCA conditions for tonight, but decided to raise the SCA flag for the coastal waters earlier and put it into effect with the 330 CWF. Winds will likely gust into the low 20s kt range with the approach of the cold front and the tightening pressure gradient ahead of it. Seas will build to around 4 ft on the ocean and 2-3 ft across Delaware bay. Gusty winds should continue Monday with the arrival of the cooler and drier air. OUTLOOK... Monday night through Thursday...No marine hazards are expected. Friday...Winds and seas below SCA thresholds. The official NHC forecast for Tropical Storm Fiona is for it to track westward and then to weaken as it curves to the north near Bermuda late in the week. We may start to see long period swell arrive in our coastal waters by Friday or next weekend but unless the system becomes much stronger than forecast, seas will still be below 5 ft. RIP CURRENTS... Wind gusts from the southeast this afternoon coupled with wave heights of 3 to 4 feet are enhancing the setup for dangerous rip currents at the beaches. A moderate risk day was assigned to the New Jersey and Delaware beaches today. The probable risk for the development of dangerous rip currents on Monday is low with an offshore wind expected.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ430-431- 450>455. && $$ Synopsis...Klein Near Term...Nierenberg/O`Hara Short Term...O`Hara Long Term...Klein Aviation...Klein/Nierenberg/O`Hara Marine...Klein/O`Hara

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