Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 210022 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 822 PM EDT Thu Apr 20 2017 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Update...Adjustments made to increase POPs/sky and show progression of convective line as it slowly moves eastward over the next 3-6 hours. Percentages diminish over time as the line falls apart with the loss of daytime heating. Temperatures cooling off with the rainfall as dewpoints rise at the same time and tried to reflect this in hourly temperature trends through the rest of tonight. Lows generally 60-65F. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... 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 ewd 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 SAN portions of the area. There is the potential for heavy rain over much of the region (1 to 2 inches), especially 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. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Latest 20/12z models continue to depict unsettled conditions for at least the first portion of the long term/Sun night through Tue. Deep/anomalous upper trough progged to be centered along the southern Appalachians by 00z/Mon, with sfc low along the SC coast and weakening sfc high pressure along the southern New England coast. GFS/ECMWF now in very good agreement with the upper low continuing to dive SE through GA/SC on Mon, while remaining as a closed low. The ECMWF is still somewhat stronger with the strength of the upper low and also farther NW with the widespread precip shield through the day Mon than the GFS. Will blend these solutions/slightly favoring the GFS as the ECMWF has been somewhat of an outlier for several runs. Overall though, the forecast has trended wetter and cooler for Mon, after the potential for some locally heavy rain lingers all areas Sun night, and mainly over southern and eastern sections for Mon. 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 30-40% chance PoPs E and 20% PoPs west. Highs Mon to avg 60-65 F with mid-upper 60s on Tue. Warmer/dry for Wed and likely turning much warmer by Thu as the low finally will be far removed from the region and ridging aloft begins to center off the SE coast. Lows mainly in the 50s with highs mid 70s inland to 65-70 F near the coast Wed, and highs 80-85 F Thu (70s near the coast). && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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As of 23z...A line of showers and diminishing thunderstorms extended north to south through the RIC area associated with a weak surface trough. As this line continues to the east...thunderstorms will likely end before reaching ORF and PHF. Maintained mention of VCTS at SBY from 03-05z. MVFR ceilings and fog are indicated at SBY from 09-13Z based on guidance. A cold front over the Ohio Valley will move across the mountains early Friday morning and slowly cross the CWA late Friday and Friday night. Scattered thunderstorms can be expected along and just ahead of the front potentially affecting the TAF sites toward the end of the 00Z TAF period and beyond. The front will stall near or just south of the VA/NC border during the weekend as a well organized low pressure system moves eastward along the front. This will bring widespread rain throughout the weekend with periods of degraded aviation conditions. Thunderstorms will also be possible southern portions. The chance of showers continues Monday and toward the coast Tuesday as low pressure lingers just east of the Carolinas.
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&& .MARINE... 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. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...TMG NEAR TERM...BMD/TMG SHORT TERM...TMG LONG TERM...LKB AVIATION...LSA MARINE...LKB

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