Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 290805 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 405 AM EDT Thu Sep 29 2016 .SYNOPSIS... An upper level low slowly drops south from the Great Lakes overnight through Friday. Meanwhile, high pressure builds well north of the region and steers a moisture rich airmass into the region tonight Through Thursday night. && .NEAR TERM /THROUGH TONIGHT/... Latest GOES water vapor imagery centers the anomalous upper low over southern Indiana. Upstream of the upper low, a plume of anomalous moisture is visible stretching from central North Carolina into southern Pennsylvania. At the surface, low pressure has developed over North Carolina with a weak frontal boundary extending northward into the forecast area. Strong high pressure remains centered over southeast Canada. Diffluent flow aloft in combination with anomalous moisture flux has resulted in ongoing showers over the region. Locally heavy rainfall still possible. Will keep categorical POPs in the forecast away from southeast Virginia and northeast North Carolina. The upper low continues to dig southward through the Ohio Valleys today into tonight. Meanwhile, upper ridging builds north of the Great Lakes across southeast Canada. This will focus increasing moisture flux and enhanced convergence north of the frontal boundary draped across central Virginia. However, a high precipitable water airmass (at or above 1.5 inches) remains over the local area today, resulting in a continued heavy rainfall threat across the northern half of the area into tonight. Afternoon convection will enhance the rain rates. Rainfall amounts could reach 2-3 inches across the far northern tier counties bordered by 1-2 inches from Emporia to the Maryland Eastern Shore. Flash flood watch remains in effect through tonight. Highs today generally in the mid 70`s inland to low 80`s southeast. Mild tonight, with lows 8-12 degrees above normal in the mid to upper 60`s. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... Unsettled conditions continue into Friday as the upper low lingers w of the area, but overall moisture transport should diminish, with the heavy rain threat diminishing. The upper low begins to fill and lift n by Saturday resulting in gradually improving conditions. The sky remains mostly cloudy to overcast through the period. High temperatures range from the upper 70s to low 80s, with lows generally in the 60s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Anomalous upper low will make its way through the eastern Great Lakes Sat night/Sunday and into New England by Monday where it becomes more of an open wave/trough. This feature then moves off the Northeast coast early next week. Based on the latest model guidance...have slowed the timing of pcpn exiting the FA with chc pops (30-50%) lingering across eastern areas Sat night...diminishing to slight chc pops across eastern areas by Sun eve. Will maintain dry wx Monday, then a lot of uncertainty develops by Monday night into the middle of next week. There`s the potential for the remnants of the upper low/trough to linger offshore (providing moist onshore/easterly flow locally) and also uncertainty with regards to the eventual track of TS Matthew. Will carry low end pops for now Tue-Wed. Highs through the period mainly in the 70s. Lows in the 60s. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... An east-west stationary front will continue to remain across Virginia through the period, serving as the focus for showers and thunderstorms. Heavy rain and thunder are still ongoing at RIC, added TEMPO group to account for this. Expecting the rain/thunder to mainly impact central Virginia and portions of eastern Maryland through the first half of the night. Introduced IFR conditions for later tonight at RIC and SBY which will remain closer to the stationary front. Lower chances for MVFR across the VA tidewater and NE NC as this region will remain further away from the front. Slowly improving conditions are expected across all sites later into the day on Thursday. Outlook: Unsettled weather persists into Friday with continued chances for showers and thunderstorms due to the frontal boundary remaining nearby. Improving weather conditions are expected this weekend. && .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 bring persistent ENE flow to the area Thu-Fri. Strongest winds expected for the northern areas, with minor tidal/coastal flooding becoming a concern for Ocean City/Chincoteague/Wachapreague by Thu evening and Fri morning high tide cycles. Also, some potential for flooding into the Bay (both lower and mid-upper Bay) by Fri-Sat, as seas remain elevated and water is expected to struggle to exit the bay for several days. No coastal flood watches have been issued as chance for moderate- severe flooding is low, but we may eventually need to issue Coastal Flood Advisories. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Flash Flood Watch through late tonight for MDZ021>024. NC...None. VA...Flash Flood Watch through this evening for VAZ048-060>062-064- 066>069-509>516. Flash Flood Watch through late tonight for VAZ075>078-083-085- 517>522. MARINE...Small Craft Advisory until 1 AM EDT Saturday for ANZ652-654. Small Craft Advisory until 6 PM EDT Friday for ANZ656-658. Gale Warning until 4 AM EDT Friday for ANZ650. Small Craft Advisory until 7 PM EDT this evening for ANZ632- 636-638. Small Craft Advisory until 1 AM EDT Friday for ANZ634. Small Craft Advisory until 1 AM EDT Friday for ANZ635. Small Craft Advisory until 7 AM EDT Friday for ANZ630-631. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...ALB/SAM SHORT TERM...AJZ/SAM LONG TERM...JDM AVIATION...AJB/SAM/MRD MARINE...LKB TIDES/COASTAL FLOODING...

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