Area Forecast Discussion
Issued by NWS Wakefield, VA

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955 FXUS61 KAKQ 291956 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 356 PM EDT Thu Sep 29 2016 .SYNOPSIS...
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An upper level low lingers over the Ohio Valley tonight through Friday. Meanwhile, high pressure builds well north of the region and steers a moisture rich airmass into the region tonight into Friday. Slowly improving conditions are expected into the weekend as the upper low lifts back to the north.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Current GOES water vapor imagery depicts the center of an anomalous upper low nearly stationary near the IN/KY border. Upstream of the upper low, a plume of anomalous moisture extends from the coasts of NC/se VA to the Delmarva and into Ern PA/NJ. Blended TPW imagery shows pw values of 1.5-2.0", which is around 150- 200% of normal. At the surface, low pressure is centered over wrn NC with a trough off the NC coast. 1038mb high pressure is centered over se QB and is ridging sw through New England and into the nrn Mid-Atlantic. Visible imagery depicts cloud cover over most of the area. Showers and embedded tstms are expanding in coverage from se VA/ne NC nw through central VA in vicinity of a southeasterly LLJ. Farther to the ne, an area of rain continues to gradually push wwd over the Lower Ern Shore associated with a strong easterly LLJ centered along the nrn Mid-Atlantic Coast. This general pattern should continue through the evening producing some pockets of moderate to heavy rain. The latest data does depict that the LLJ structures begin to weaken overnight, and hence rain rates and areal coverage should diminish. The most sensitive areas with respect to heavy rainfall will be from central VA in vicinity of the RIC metro to the Nrn Neck, and over the Lower MD Ern Shore. These areas received 4-6" of rain last night, with localized amounts up to 8". The flash flood watch will remain in effect from the piedmont through the Lower MD Ern Shore. Otherwise, mostly cloudy to overcast tonight and breezy along the coast. Lows range from the mid 60s nw to around 70 se.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
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Unsettled conditions continue into Friday as the upper low lingers w of the area, but overall moisture transport should diminish and be shunted n, with the heavy rain threat diminishing. Secondary shortwave energy does rotate around the upper low resulting in 60-70% PoPs across the piedmont. Pcpn potential will be lower toward the coast and generally 20-40%. Highs range from the low/mid 70s nw, to the low 80s se under a mostly cloudy to overcast sky. The upper low begins to fill and lift n by Saturday resulting in gradually improving conditions. The sky remains mostly cloudy along with slight chc/chc PoPs. High temperatures Saturday range from the mid/upper 70s nw to low 80s se, after morning lows generally in the 60s to around 70.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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Anomalous upper low over the Ohio Valley during the short term will make its way slowly north and northeast early next week...allowing for high pressure to build into the Mid Atlantic States. A chance for showers remains Sunday over the Chesapeake Bay and portions of Hampton Roads and east and end all areas by Monday morning. A strong surface high will remain over southeast Canada which will increase its influence across the Eastern Seaboard early next week with its associated easterly flow. A chance for showers returns to the forecast Tuesday and Wednesday. Tropical Cyclone Matthew may have an influence late in the week...especially in the marine area. Uncertainty remains in terms of the timing and track. Refer to guidance from the National Hurricane Center and extended forecasts from the Weather Prediction Center for details. High temperatures from 75 to 80 Sunday and Monday lower to around 70 in the northern Piedmont to the upper 70s northeast North Carolina by Thursday. Lows will range through the 60s.
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&& .AVIATION /20Z THURSDAY THROUGH TUESDAY/... Low pressure remains west of the region today, with high pressure anchored well ne of the area. This continues to steer a moisture rich airmass into the region and showers and iso tstms are increasing in coverage this afternoon. Cigs are variable this afternoon, vfr at most sites, mvfr at orf, and ifr at SBY. Expect vsby to fall to 1-3sm in heavier rain. An ene wind of 8-15kt is observed across the region, locally gusting up to 25kt along the coasts of se VA/ne NC, and stronger at SBY with a sustained speeds ~20kt, and a recent gust up to 35kt. Areas of showers/embedded tstms should continue through the evening, before gradually shifting to the nw later tonight into Friday morning. Cigs likely remain ifr at SBY through tonight into Friday morning, with ifr cigs developing at RIC later tonight. Some fog is possible later tonight, with vsby generally 2-4sm. Unsettled conditions persist Friday afternoon and evening, before gradually improving Saturday through early next week as upper level low pressure lifts n of the region. && .MARINE... Latest analysis shows surface low pressure from the SC piedmont to VA, with strong/anomalous surface high pressure (1035 mb+) centered over eastern Canada. The pattern today and tonight will feature this strong high building over eastern Canada, ridging into New England and the northern mid-Atlc region. A persistent/strong E/NE flow will prevail over northern portions of the marine area and have upgraded far northern coastal waters to a Gale Warning for today/tonight based on pattern with the surface high building to near 1040 mb). Elsewhere, have added several more zones to SCA headlines as winds gradually taper off to the 10-15 KT in NC and for the upper James. NC coastal waters still expected to have seas build to 5 ft so only zones that will not have any headlines will be the upper James and the sound. Winds diminish from S to N tonight and for all areas on Fri as the surface low lifts N and pressure gradient weakens. Coastal seas will diminish but still remain elevated at 4-6 ft into Fri night and possibly Sat due to residual swell. SSE flow expected Sat leading to sub-SCA conditions elsewhere with 1-2 ft waves over the Bay. && .TIDES/COASTAL FLOODING... The synoptic pattern with strong High pressure centered over eastern Canada with a slow moving boundary/sfc low pressure inland over the Carolinas/Mid-Atlantic will continue to bring persistent ENE flow to the area today/Fri. Departures avg 1.0 to 1.5 feet for the most part. Have expanded Coastal Flood Advisories to now include all zones in adjacent to the Bay and the James/York/Rappahannock River...with ocean side of the eastern shore also included. Many areas in the lower Bay to fall a little shy of criteria with the high tide this morning, but should see departures rise a bit more by this aftn/tonight/early Fri and have the advisory to cover the 2nd high tide overnight/early Fri. Will likely need to extend these advisories into Fri night and possibly Sat as offshore seas remain elevated and water is expected to struggle to exit the bay for several days. Chance for moderate- severe flooding is low, best chance would be across ocean side of the Accomack VA and Worcester MD by Fri. && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...Coastal Flood Advisory until 11 PM EDT this evening for MDZ024- 025. Flash Flood Watch through late tonight for MDZ021>025. Coastal Flood Advisory until 8 AM EDT Friday for MDZ021>023. NC...None. VA...Flash Flood Watch until midnight EDT tonight for VAZ048- 060>062-064-066>069-509>516. Coastal Flood Advisory until 4 AM EDT Friday for VAZ075>078- 084>086-089-090-093. Coastal Flood Advisory until 1 AM EDT Friday for VAZ095>097- 523>525. Coastal Flood Advisory until 11 PM EDT this evening for VAZ099- 100. Flash Flood Watch through late tonight for VAZ075>078-083-085- 517>522. MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ652-654. Small Craft Advisory until midnight EDT Friday night for ANZ656-658. Gale Warning until 4 AM EDT Friday for ANZ650. Small Craft Advisory until 7 PM EDT this evening for ANZ636- 638. Small Craft Advisory until 1 AM EDT Friday for ANZ632-634-635. Small Craft Advisory until 7 AM EDT Friday for ANZ630-631.
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&& $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ SHORT TERM...AJZ/SAM LONG TERM...LSA AVIATION...AJZ MARINE...LKB TIDES/COASTAL FLOODING...LKB

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