Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 202022 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 422 PM EDT Thu Apr 20 2017 .SYNOPSIS...
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A cold front will approach from the northwest tonight, then push across the area late Friday and Friday night. The front will stall across North Carolina and offshore Saturday through Sunday. Low pressure will track eastward along the frontal boundary across Tennessee and into the Carolinas Saturday through Sunday.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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A warmer/more humid airmass was prevailing acrs the region late this aftn, under a partly to mostly sunny sky. Temps were ranging fm the mid 70s to mid 80s. Latest rdr showed sctd showers and a few tstms moving ewrd thru W.VA and into wrn/nrn VA. This activity will hold together, as it runs into the lee side trof, and moves acrs the CWA this evening into early tonight. So, will have 20-40% Pops during this time period. Otherwise, becoming partly cloudy tonight with lows only in the lower to mid 60s.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
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Warmer and slightly more humid on Fri, due to SW winds and at least a partly sunny sky in advance of a cold front. Highs in the lower to mid 80s. Sctd showers and tstms will develop right in advance of the front Fri aftn/evening, as the front slowly drops into/thru the area. Have maintained 30-50% PoPs over the region. At this time, SPC has the entire fcst area in a marginal risk for severe storms. The frontal boundary will sink into NC by 12Z Sat. Then, fm Sat thru Sun, will go with the latest GFS model fcst. The front will remain nearly stationary acrs NC and offshore Sat thru Sun. Low pressure will track ewrd along the frontal boundary acrs TN and into the Carolinas Sat thru Sun. This will result in an overrunning scenario over the CWA, with a mainly cloudy sky and high chc to likely Pops for rain/showers and chc of tstms acrs srn portions of the area. There is the potential for heavy rain over much of the region (1 to 2 inches), esply later Sat thru Sun. Lows Fri night will range fm the mid 50 to mid 60s, and range fm the upper 40s to upper 50s Sat night. Highs on Sat will range fm the lower 60s N, to arnd 70/lower 70s S. Highs on Sun will range fm the upper 50s to arnd 70.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Latest 20/00z models continue to depict unsettled conditions for at least the first portion of the long term/Sat night through Mon. Potent system gathers over the Tennessee Valley Saturday night and slowly lifts ENE across NC or far southern VA Sunday into Sunday night bringing widespread rain (some heavy), with tstms possible for mainly southern/SE portions of the area. PoPs have been increased to 70-75% N/NW late Saturday night as overrunning focuses well out ahead of the approaching boundary. Forcing is weaker across the S but will maintain 40-60% PoPs there. Sfc-based instability should remain S of the CWA Sat night/Sun morning, but models suggest there could be some elevated instability after 06Z over southern VA/northeast NC. Lows Sat night mainly in the 50s. For Sunday, as the sfc low tracks into northern NC or perhaps as far N as southern VA, the warm front will lift N/NW for awhile, before stalling as strong sfc high to the N will remain in place. As a result will have likely PoPs all areas. Highs Sunday will tend to show quite a large gradient, low 60s NW (perhaps upper 50s), with 70-75 F S/SE (and potentially around 80 F for areas along the Albemarle Sound). Tstms will be most likely in the aftn/early evening in southeast VA and northeast NC. Low pressure lingers off the coast Monday with a chance for showers (mainly E/SE) along and ahead of the upper trough axis. Low pressure slowly pulls offshore by Tuesday as high pressure builds in from the NNW with drier conditions returning, but still likely enough moisture for continued chance PoPs southeast VA/northeast NC. Highs Mon and Tue will avg in the mid 60s along the cost and upper 60s/around 70 F well inland. Warmer for Wed as the low finally will be far removed from the region with highs mid 70s inland to 65-70 F near the coast. && .AVIATION /20Z THURSDAY THROUGH TUESDAY/... Shwr exiting SBY attm with only SCT clouds expected behind it. Otw, VFR conditions expected to start forecast period with only SCT clouds. High res models are showing a line of convection developing across the Piedmont then moving east following I64 towards 00Z. Medium confidence that this will actually occur, so went ahead and indicated a BKN cloud group generally between 21Z-01Z. Best area that would see any convection would be at RIC so went ahead with VCTS there toward sunset. Kept thunder out of all other TAF sites. VFR conditions expected all areas by mid evening. SW winds aob 10 KTS. OUTLOOK... Scattered showers and thunderstorms are expected Friday afternoon and evening as a cold front tries to cross the area Friday. As the front stalls around or just south of the local area...low pressure will move out of the southern Great Plains and eastward along the front. This will bring widespread precipitation late Saturday through Sunday night with periods of degraded aviation conditions. && .MARINE...
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Relatively benign conditions over the marine area this aftn with pressure gradient weak enough allowing winds to turn onshore/SSE at around 10 kt on avg. SSE winds this evening become SW overnight and on Fri as a cold front approaches from the W. Winds to avg 10-15 kt during this period with seas mainly 2-3 ft and waves in the Bay/Rivers 1-2 ft. The front crosses the area late Friday with high pressure building N of the region Saturday. A SW wind will continue Friday and then shift to N Saturday behind the front. Low- end/brief SCA conditions are possible Saturday with CAA surge, though models show some timing differences. Overall best chance is the lower Bay/southern coastal waters. Low pressure approaches from the SW Saturday and tracks across the region Sunday into Sunday night. Still some uncertainty as to exact location of the boundary on Sun (the NAM now actually shifting the boundary well south with weak high pressure trying to build in from the N). The GFS/ECMWF is favored over the NAM solution and will therefore continue to forecast an extended period of NNE winds...and marginal SCA conditions at least for southern areas on Sunday, with more significant winds/strong SCA conditions likely Mon-Tue (potential for low-end Gales mouth of the Bay/southern coastal waters on Mon). This as the system moves off the coast with sfc high to the NE. This setup lingers into Tue. Winds should gradually diminish Tuesday as the low slowly pushes farther offshore. Seas to build to 6-8 ft and waves to 4-5 ft in the Bay for Mon.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...TMG NEAR TERM...TMG SHORT TERM...TMG LONG TERM...LKB AVIATION...MPR MARINE...LKB

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