Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 090259 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 959 PM EST Thu Dec 8 2016 .SYNOPSIS...
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Canadian high pressure builds into the Mid-Atlantic overnight into Friday, and settles over the region Friday night into Saturday. The high slides offshore Sunday. Low pressure will push north of the area on Monday...with the associated cold front crossing the region Monday night. Another strong cold front impacts the region during the middle of next week.
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&& .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Mid-evening GOES WV imagery continues to feature broad cyclonic flow aloft over the east-central CONUS, in association w/a deep cold upper low situated over ern Quebec. The surface cold front is now oriented along the coast of SE VA back into eastern NC at 03z, and is primarily indicated by a sharp drop in dewpoints from the low to mid 30s to the upper teens to low 20s back in the piedmont (with dewpoints in the single digits to low teens just upstream). The primary CAA arrives late tonight as strong Canadian high pressure spreads ewd through the Ohio Valley and into the Mid- Atlantic. Temperatures have already dropped into the mid to upper 30s inland, upper 30s to low 40s Se coast. LAV and RAP have handled temps well thus far and have leaned in its direction for the overnight. Look for temps to eventually settle into the mid/upper 20s late tonight/early Friday morning, with low 30s for coastal se VA/ne NC.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... A cold/brisk day is anticipated Friday as the Arctic high builds from the Central Plains toward the southern Appalachians. 850mb temps drop to around -10C (-2 st dev) Friday afternoon. Steady CAA will prevent temperatures from reaching their full potential Friday afternoon, even with a sunny sky. MOS guidance continues to show highs generally in the low/mid 40s, but will trend toward cooler thickness regressions. Some Piedmont locales may struggle to get out of the 30s, with around 40/low 40s elsewhere. A brisk northwest wind of 10-15 mph inland and 15 to 20 mph near the coast is expected and will keep wind chill values in the low to mid 30s. The high builds into the region Friday night into Saturday. By this point the airmass will have modified enough to lose its arctic characteristics. Still cold and well below normal nonetheless, with lows Friday night in the upper teens to low 20s inland, to the low/mid 20s for se coastal locations. Limited mixing Saturday will keep highs in the upper 30s to low 40s despite some warming at 850mb. Sunny with a light westerly wind. Cold high pressure remains over the region Saturday night. Meanwhile, a nrn stream trough dives into the Great Lakes region, which could result in increasing high clouds late, especially across the north. There should still be several hours of rather ideal radiational cooling conditions and lows should once again drop at least into the low/mid 20s. The initial wave pushes north of the region Sunday with a secondary wave diving tracking into the Ohio Valley, with the surface high sliding offshore. Clouds should thicken and mixing will be limited, so highs will still be below normal and moderate only into the mid 40s to low 50s se. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Sfc high pressure slides offshore by Sun aftn and winds become more sly on Sun. The combination of a weak coastal trough developing off the Carolina Coast Sun night and a warm front lifting north through the area should bring rain up along the Mid Atlantic coastal areas Sun night into Mon morning with a brief period of drying during the day on Mon as the region becomes warm-sectored. A cold front associated with low pressure tracking along the St Lawrence River Valley is then expected to cross the region Mon night and exit the coast by Tue morning. Winds generally sw ahead of the front...becoming nly Tue. The cooler air behind the cold front is much more modified and what would be typical breezy conditions along the coast are not anticipated at this time. Sfc high pressure returns Tue/Tue night...followed by what could be a developing coastal low off the Southeast into Mid Atlantic coasts on Wed. A brief warm-up should be anticipated as the aforementioned warm front lifts through the region Sun night into early Mon. Areas north of the warm front should remain wedged and keep cooler air in place prior to the initial onset of precip. This could result in a rain/snow mix quickly transitioning to all rain overnight. Precip should remain as rain through Monday. Temperatures generally at to slightly below normal throughout the period. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Canadian high pressure will begin to build over the Mid Atlantic States tonight. Patches of high clouds early Thursday evening will clear overnight with the sky remaining mostly clear Friday. Winds will remain from the northwest through the 00Z TAF period. OUTLOOK...High pressure builds into the area through Saturday. High pressure slides offshore Sunday. There will be a chance for rain Monday as a cold front approaches from the west. Following the passage of the cold front Monday night...dry weather returns for Tuesday. && .MARINE... Have started all SCA flags for the waters with the aftn forecast issuance since winds are expected to increase in the next 3-6 hrs. A strong cold front will cross the waters this evening...followed by a rapidly tightening pressure gradient, strong cold air advection, and a strong 140-160kt jet streak impacting the waters in the post-frontal environment. Overall wind forecast over the waters is on track with w-nw winds increasing to 15-25kt this evening with gusts around 30kt over the ocean/Ches Bay overnight. Speeds stabilize Fri morning (still sustained 15-20kt), and a brief lull in winds to 10-15kt can be anticipated on the rivers during this time. This will be short-lived as a secondary surge in colder air/wind speeds is expected to occur Fri evening...with speeds/gusts increasing by roughly 5kt. Seas build to 4-6ft this evening and overnight... hovering around 4-5ft through early Sat morning. Waves will average 3-4ft during SCA and may also drop to a solid 3ft during the brief lull in winds Fri morning. The cold air finally begins to equalize and the pressure gradient slowly relaxes after midnight Fri night into early Sat as sfc high pressure builds across the OH/TN Valleys and inches closer to the Mid Atlantic Region. The high slides overhead Sat night into Sun morning with light and variable winds. The high then slides offshore by Sun aftn and winds become more sly aob 15kt on Sun. The combination of a weak coastal trough developing off the Carolina coast Sun night and a warm front lifting north through the area should bring rain up along the Mid Atlantic coast Sun night into Mon morning with a brief period of drying during the day on Mon. A cold front associated with low pressure tracking along the St Lawrence River Valley is then expected to cross the waters Mon night and exit the coast by Tue morning. Winds generally sw aob 15kt ahead of the front...becoming nly Tue. The cooler air behind the cold front is much more modified and SCA conditions are not anticipated at this time. Seas average 2-3ft Sat night through Mon and may build up to 5ft briefly on Tue. Waves 1-2ft. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 10 PM EST Friday for ANZ635-636-638. Small Craft Advisory until 4 AM EST Friday for ANZ637. Small Craft Advisory until 7 AM EST Saturday for ANZ630>632- 634. Small Craft Advisory until 4 AM EST Saturday for ANZ633-650- 652-654-656-658. && $$ SYNOPSIS...AJZ/LSA NEAR TERM...AJZ/MAM SHORT TERM...AJZ/SAM LONG TERM...BMD AVIATION...LSA/JAO MARINE...BMD

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