Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 271959 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 359 PM EDT Sun May 27 2018 .SYNOPSIS...
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Cold front over southern New Jersey and the Delmarva will continue to sag southward this evening, then will become nearly stationary over the Mid-Atlantic and stretching back to the south and west for much of the new week. Weak low pressure passes through the region tonight. High pressure begins to build in from the north on Monday, and then will push a back door cold front through the region late Tuesday as the high settles over Cape Cod on Wednesday. Meanwhile, what is currently Subtropical Storm Alberto will lift north and push the stationary boundary north as a warm front on Thursday. These remnants look to affect the Northeast and Mid-Atlantic for the end of the week and through next weekend.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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Convection continues to develop just to the north of the back door front across northern Delmarva into the Delaware Bay. This shallow boundary will continue to move slowly south through this evening, paralleling the mid-level flow, with additional rounds of showers and thunderstorms expected to develop and move across Delmarva through tonight. With an anomalously moist tropical air mass in place, rainfall rates up to 2 inches per hour and up to 5 inches within a few hours, will be favorable for flash flooding. Further north across Chester and Delaware counties in PA and eastward into far southern NJ, some of this heavier rainfall may propagate over this area. Therefore, the Flash Flood Watch remains in effect thru 4 AM Monday for extreme southeast PA, far southern NJ, the eastern shore of MD, and Delaware. With greater instability across the eastern shore of MD, cannot rule out isolated strong wind gusts and small hail with any thunderstorms that occur there through this evening. With the region to the north of the front tonight, expect areas of drizzle and fog to develop. While some of the fog could be locally dense, do not expect widespread dense fog. Winds out of the east to northeast may gust up to around 20 mph this evening, and up to 30 mph closer to the coast.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
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With the front nearby and residual onshore flow, areas of drizzle and patchy fog may linger through mid-morning under mostly cloudy skies. A few lingering showers are possible across Delmarva and far southern NJ during the early morning. A weak flow in place at the low-levels will lock in the clouds during the morning, but some subsidence will work in during the afternoon, especially northwest of the fall-line. Expect some breaks to develop in the overcast across this area, especially during the afternoon. High temps will be slightly below seasonal norms. Winds will be light and variable.
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&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
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A prolonged period of unsettled weather is on tap for much of the long term. This includes potential impacts from the remnant low of what is currently Subtropical Storm Alberto late this week and through next weekend. A warm and soupy airmass will be in place Monday night. Can expect warm and humid conditions as southwest flow ushers a tropical airmass into the region that will be in place through the week. Stationary boundary remains south of the Delmarva, and weak low pressure passing along that boundary may result in a few showers in the evening, but precip will end by midnight or so. Patchy fog should develop. High pressure over central Canada builds to the south and east on Tuesday, will pass north of New York state Tuesday night, and then will park itself over Cape Cod on Wednesday. This will allow a back door cold front to drop through the region Tuesday night. Meanwhile, the remnant low of Subtropical Storm Alberto lifts north through the Tennessee Valley and into the southern Great Lakes and Ohio Valley. This pushes the stationary boundary north as a warm front Tuesday night. The warmest day of the period looks to be Tuesday, as very warm and humid conditions on tap with highs in the mid and upper 80s and surface dewpoints well in the 60s. This will yield a heat index around 90 for most inland locations. A few showers and thunderstorms are possible Tuesday afternoon and evening as that warm front lifts north, mainly over western zones. From there, unsettled weather possible each day depending on the track and placement of the remnant low of Alberto. The low lifts through the Great Lakes and tracks into eastern Canada Thursday and Friday before dropping back into the Northeast and Mid-Atlantic over the weekend. Best chances for precip currently look to be Thursday, but will carry at least chance PoPs into the weekend. With low agreement among the global models, feel it is best to keep with chance PoPs for now. But it is important to note that there will be a tropical airmass in place with surface dewpoints well in the 60s to near 70 ahead of the remnants of Alberto, and given the tropical origins of Alberto, there could be a prolonged period of heavy rain next weekend.
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&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Widespread IFR conditions will develop this evening if they have not already. Potentially some LIFR as well, especially at ACY and MIV. Low ceilings will be the main driver of IFR, although some fog is possible as well. Thunder is possible until around midnight at PHL, ILG, MIV, and ACY. Winds out of the east-northeast with gusts up to 20 kts at times. Monday...Expect IFR conditions to gradually improve to VFR from northwest to southeast at all TAF sites, except MIV and ACY. This improvement may not take place until mid-late afternoon in the I-95 corridor. Winds will variable, generally less than 5-10 kts. Outlook... Monday night...IFR/LIFR CIGs/VSBYs in fog and stratus. S-SW winds 5 kt or less. Tuesday...Mostly VFR. Potential for afternoon SHRA/TSRA. W-NW winds less than 10 kt. Wednesday...Mostly VFR. Light East winds become SE 10-15 kt. Stronger winds possible at KACY. Potential for SHRA/TSRA late in the day and SHRA at night, mainly at terminals south and west of KPHL. Thursday through Friday...SHRA/TSRA possible throughout the period. SE winds 5-10 kt Thursday become SW on Friday.
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&& .MARINE...
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Tonight...The SCA was extended southward from Sandy Hook NJ to Cape Henlopen and now includes the lower DE Bay, and is in effect through early tonight. Across this area, east-northeast wind gusts of 25 kts with seas building 3 to 6 ft, except around 2 ft in lower DE Bay. Monday...Sub-SCA conditions expected at this time. Outlook... Monday night...VSBY restrictions possible in fog. Wind/seas below SCA thresholds. Tuesday through Friday...Winds and seas below SCA levels. Rip Currents... Through this evening...The risk for the development of dangerous rip currents is moderate for the NJ beaches and low for the DE beaches. Monday...A residual moderate risk for the development of dangerous rip currents is expected along the Monmouth and Ocean County beaches. For the rest of the NJ shore and DE, a low risk for the development of dangerous rip currents is forecast. Remember, a low risk of rip currents does not mean no risk! Life threatening rip currents often still occur near jetties, reefs, and piers. The vast majority of rip current victims swam at unguarded beaches. ALWAYS SWIM IN THE PRESENCE OF A LIFEGUARD.
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&& .TIDES/COASTAL FLOODING...
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A Coastal Flood Advisory has been issued for the northern New Jersey coastline from Ocean county northward through Middlesex county, as well as all of the tidal Delaware River and the upper portions of the Delware Bay. An east to northeast flow has continue to pile up water along the northern portions of the northern New Jersey coast today, and has also not allowed much water from the tidal Delaware River and Delware Bay to evacuate efficiently. Another factor that may lead to elevated water levels is the runoff from earlier rainfall across portions of the area may exacerbate any localized flooding in these areas. This may especially be true for the northern portion of the tidal Delaware River from Philadelphia northward, and Middlesex and Monmouth counties were the heaviest rainfall fell earlier. It is possible for the remainder of the New Jersey and Delaware coasts to approach or just reach minor flood levels, but we do not expect them to reach levels high enough for an advisory. This looks to be the only high tide that will need an advisory at this time, with the exception of possible the upper portions of the tidal Delaware River which may continue to have elevated water levels Monday night.
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&& .EQUIPMENT... The Sandy Hook NOS tide gauge (SDHN4) remains out of service. CORMS is addressing the problem. There is currently no estimated time for a return to service. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...Flash Flood Watch through late tonight for PAZ070-101-102. Coastal Flood Advisory from 11 PM this evening to 3 AM EDT Monday for PAZ070-071-106. NJ...Coastal Flood Advisory until midnight EDT tonight for NJZ012>014-020-026. Flash Flood Watch through late tonight for NJZ016-017-021>024. Coastal Flood Advisory from 7 PM this evening to 1 AM EDT Monday for NJZ016. Coastal Flood Advisory from 11 PM this evening to 3 AM EDT Monday for NJZ015-017>019. DE...Flash Flood Watch through late tonight for DEZ001>004. Coastal Flood Advisory from 7 PM this evening to 1 AM EDT Monday for DEZ001-002. MD...Flash Flood Watch through late tonight for MDZ008-012-015-019- 020. MARINE...Small Craft Advisory until 1 AM EDT Monday for ANZ452-453. Small Craft Advisory until 5 AM EDT Monday for ANZ450-451. Small Craft Advisory until 10 PM EDT this evening for ANZ431- 454.
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&& $$ Synopsis...MPS Near Term...LF Short Term...LF Long Term...MPS Aviation...LF/MPS Marine...LF/MPS Tides/Coastal Flooding...LR Equipment...MPS

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