Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 080843 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 343 AM EST Thu Dec 8 2016 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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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 stretching from the Southern Plains into the Tennessee Valley. At the surface, weak high pressure resides along the coast with a trough of low pressure/lingering frontal boundary located over the Piedmont. Mid and upper level clouds continue to stream into the area in fast southwest flow aloft. Expect a mostly cloudy to cloudy sky by daybreak as the shearing southern wave lifts along the Virginia/North Carolina border. 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 southeast half of the forecast area for isolated to widely scattered showers along the advancing frontal boundary. Best chances will generally be along and east of Interstate 95. Some local convergence near the Bay could enhance showers 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.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
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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.
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&& .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 /09Z THURSDAY THROUGH MONDAY/... A weak area of high pressure remains over the region early this morning, resulting in VFR conditions and light winds. Expect some patchy fog over the Piedmont through daybreak, with patchy ground fog closer to the coast. Increasing mid level clouds over the southern forecast area will limit any further fog development, so have only tempoed a few hours of IFR ground fog at the usual culprits of KPHF and KECG. A cold front pushes across the region late morning into the afternoon, with increasing low to mid clouds along the boundary. 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... A weak cold front crosses the waters late this aftn into this evening...with cooler air filtering down over the waters the rest of tonight into Thu. Winds generally nw-n aob 15kt during this timeframe. Seas have been slow to subside through today, and have therefore extended SCA flags for ocean through 500 AM Thu morning when seas finally drop below 5ft. Meanwhile, an upper level trough sits just north of the region on Thu...slowly sagging swd Thu night and then sliding across the area on Fri. Winds become more wnw as the day progresses with speeds remaining aob 15kt. Wind speeds increase to 15-20kt Thu evening for Bay/Ocean/Sound/Mouth of James River as a strong 125-150kt jet sags south over the waters in advance of the upper trough. A much colder arctic airmass arrives after midnight Thu night as the sfc pressure gradient tightens and speeds increase to 20-30kt (aforementioned areas) and 15-20kt (Rivers); still w-nw direction. SCA flags will likely be issued beginning with this initial surge in winds. Gale force gusts may still be possible (especially as skies clear with the strong jet streak overhead), however confidence is low at this time. The cold air begins to equalize and the sfc pressure gradient starts to relax late Fri night into early Sat as sfc high pressure axis shifts ewd and closer to the waters. Winds remain within solid SCA speeds through Sat morning before diminishing below 15kt all waters by Sat aftn. Seas build to 5-7ft north (possibly up to 8ft near 20nm Fri evening)/5-6ft south by Fri morning and are expected remain steadfast through early Sat morning before subsiding below 5ft by Sat aftn. The high slides overhead Sat night (light/variable winds) and offshore by Sun morning. Winds become more sly on Sun with a possible surge in speeds to 10-15kt into Sun night as a weak coastal trough starts to develop off the Carolina and Mid Atlantic coasts. The trough axis is expected to stall just offshore on Mon with winds becoming more sw-w aob 15kt. Seas average 2-3ft Sat night through Sun Night and may build to 4ft near 20nm on Mon. Waves 1-2ft. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 5 AM EST early this morning 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

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