Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 081835 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 135 PM EST Thu Dec 8 2016 .SYNOPSIS... Weak low pressure tracks along the Virginia North Carolina border Thursday morning through early afternoon...followed by a cold front later Thursday afternoon. Canadian high pressure builds into the area Friday and Saturday. The high slides offshore Sunday, ahead of the next cold front on Monday. Another strong cold front impacts the region during the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Latest GOES water vapor imagery depicts a broad cyclonic flow over the western and central US, with an anomalous upper low over eastern Canada. An embedded potent shortwave is currently tracking across the Midwest, with another shearing wave across the Mid- Atlantic. At the surface, the pressure pattern is rather nebulous locally but generally characterized by a trough over the Piedmont and weak high pressure immediately off the coast. Mid and upper level clouds continue to stream into the area in fast southwest flow aloft. Expect a mostly cloudy to overcast sky through midday as the shearing southern wave tracks across the area. The northern stream wave tracks into the Ohio Valley, reinvigorating the surface boundary over the Piedmont and pushing it across the local area. Subtle forcing for ascent provided by increasing winds aloft and the shearing wave will combine with modest moisture (precipitable waters of 0.5 to 0.9 inches) across the eastern third of the area resulting in patchy areas of light rain. Some local convergence near the Bay could enhance rain briefly, but overall expect only a few hundredths of an inch of rain. The front pushes offshore mid to late afternoon. Cold air advection and dry northwest flow will result in a clearing sky behind the front, but the strongest cold air advection will be delayed until tonight. Cloud cover should hold highs in the upper 40`s to low 50`s. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... Low level thicknesses plummet tonight as Arctic high pressure builds into the central US and nudges eastward into the Southeast. 850Mb temperatures drop to -8 to -10C (-1 to -2 st dev) late Thursday night. Lows drop into the mid/upper 20`s under a clear sky. 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. Strong 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 to keep wind chill values in the low to mid 30s. The high builds into the region Friday night into Saturday as the upper trough axis pushes offshore. By this point the air mass 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 west to northwest wind. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Sfc high pressure slides overhead Sat night and offshore by Sun morning. Winds become more southerly and breezy...especially as a weak coastal trough begins to develop along the Carolina and Mid Atlantic coasts Sun night. Meanwhile, another upper level trough digs across the Midwest and Ohio Valley Sun/Sun night...followed by a strong cold front pushing through the area Mon and a more progressive, westerly flow pattern aloft for Tue/Wed. A brief warm-up should be anticipated with the coastal trough Sun night into early Mon...along with increasing chances of precipitation Sun evening through Mon evening with the passage of a cold front. The Piedmont may remain wedged and keep cooler air in place prior to the initial onset of precip. This could result in precip starting as light snow showers Sun evening before quickly transitioning to all rain overnight. Precip should remain as rain through Monday, however if any precipitation lingers into Mon night, it could easily transition back to light snow showers as another round of cooler, modified arctic air and sfc high pressure return to the region Mon night through mid week. Temperatures generally at to slightly below normal throughout the period. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... Outside of IFR conditions at SBY, conditions are generally VFR across the region. Expect SBY to improve quickly after sunrise. Broken to overcast ceilings have lowered to 4-6k feet AGL. Previous MVFR ceiling trends have not verified thus far this morning, so have pushed back MVFR conditions inland. Winds are generally calm. A cold front pushes across the region late morning into the afternoon. Broken to overcast ceilings will lower to MVFR for a brief period along the front, with clearing skies post frontal. Isolated to widely scattered showers are possible, but rainfall amounts will be light. VFR conditions return all sites this afternoon as Canadian high pressure builds into the region. Surface winds become west to southwest around 10 knots this afternoon. High pressure builds into the area Thursday night through Saturday. High pressure slides offshore Sunday as another cold front approaches from the west. This cold front crosses the region Sunday night into Monday. with a chance for rain. && .MARINE... Update...SCA flags added for Ern VA Rivers. Ongoing SCA flags extended several hours into early Sat morning (except ocean). Wind speeds/gusts will warrant the aforementioned changes. Previous discussion... Weak high pressure remains centered over the area this morning, which has allowed the winds to relax over the region and as a result, the waves have finally dropped below 5 ft on the coastal waters. Therefore have allowed the SCA that had been in effect to expire. Meanwhile, a much stronger surge of cold air is poised to cross the mountains today. As this colder air arrives, it will lead to the development of a cold front which will sweep off the coast tonight. Behind this front, the winds will increase to 15 to 25 kt across the waters, and this strong nw flow will continue into Friday before gradually diminishing on Friday night as the surface high pressure system finally pushes into the region. The seas will linger again on the coastal waters, so have issued SCA flags through early Sat. On Saturday and Sunday, the surface high pressure system will be over the area and should provide light winds and lower seas. The high finally pulls east of the area on Sunday night and the flow turns southwesterly in advance of the next cold front that will move through the area on Monday. But at this point, conditions should remain below sca levels with this front. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 7 PM this evening to 10 PM EST Friday for ANZ635-636-638. Small Craft Advisory from 7 PM this evening to 4 AM EST Friday for ANZ637. Small Craft Advisory from 7 PM this evening to 7 AM EST Saturday for ANZ630>632-634. Small Craft Advisory from 10 PM this evening to 4 AM EST Saturday for ANZ633. Small Craft Advisory from 7 PM this evening to 4 AM EST Saturday for ANZ650-652-654-656-658. && $$ SYNOPSIS...AJZ/SAM NEAR TERM...AJZ/SAM SHORT TERM...AJZ/SAM LONG TERM...BMD AVIATION...SAM/LSA MARINE...BMD/ESS

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