Area Forecast Discussion
Issued by NWS Wakefield, VA

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890 FXUS61 KAKQ 071451 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 951 AM EST Wed Dec 7 2016 .SYNOPSIS... Low pressure pushes offshore this morning as a weak cold front pushes across the region. Weak high pressure builds into the area this afternoon. A reinforcing cold front crosses the region Thursday. Canadian high pressure builds into the area for the weekend. && .NEAR TERM /THROUGH TONIGHT/... Latest GOES water vapor imagery depicts broad mid to upper level troughiness over the central US, with a deep northern stream low over southern/southeast Canada. West to southwest flow is observed over the Mid-Atlantic region. At the surface, low pressure is now well offshore of the Eastern Shore with high pressure over the Northeast. A weak secondary boundary is located over the central Appalachians, and this will push across the area through midday and stall/wash out offshore this aftn. Some patchy drizzle is lingering over the Lwr MD Ern Shore (mainly east of Salisbury) and this should dissipate by noon. Otherwise, lingering low-clouds are dissipating quickly across se VA/ne NC, with much of the area becoming partly to mostly sunny late this morning, although a period of sct-bkn cu is expected by aftn. Little change expected in low level thicknesses compared to 24 hours ago, but still expect temperatures to warm into the mid 50`s across the region. Cloud cover will be on the increase again tonight ahead of the approaching central US trough and associated strong cold front. Lows forecast in the low to mid 30`s inland to upper 30`s southeast. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... Strong cold front quickly pushes across the forecast area Thursday morning into the afternoon. Associated anomalous upper trough digs into the Northeast. While the best height falls and dynamics lag behind the front, a shear axis and increasing winds aloft will provide subtle forcing for ascent along the front. The main limitations for precipitation will be downslope/westerly flow and marginal moisture return. Precipitable waters progged between 0.5 and 0.9 inches across the eastern half of the forecast area. Will continue the trend of a line of isolated to widely scattered showers along the convergence boundary Thursday morning into the afternoon. Will drop POPs to silent for the Piedmont due to the aforementioned downslope flow. Model QPF remains only a few hundredths of an inch at best. Clouds increase Thursday morning ahead of the front, with a mostly sunny to partly cloudy sky expected behind the front as mid/upper level moisture remains. The front pushes offshore mid-late afternoon as low level thicknesses plummet inland. Highs warm into the upper 40`s to low 50`s thanks to westerly flow inland and into the mid 50`s southeast. An Arctic air mass surges into the region Thursday night as the arctic high builds southward into the Midwest, nudging eastward into the Southeast. 850Mb temperatures begin to level off around -8 and -10C (-1 to -2 standard deviations) late Thursday night. Lows forecast generally in the mid to upper 20`s Thursday night under a quickly clearing sky. A cold/brisk day is in store Friday as the Arctic high builds from the Central Plains toward the southern Appalachians. 850mb temps drop to around -10C (-2 standard deviations) Friday afternoon. Strong cold air advection will prevent temperatures from reaching their full potential Friday afternoon, even with a sunny sky. Have undercut MOS guidance with highs generally in the low 40`s. Some Piedmont locales may struggle to get out of the 30`s. 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 30`s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Long term period starts off Fri night/Sat with dry weather as sfc high pressure builds directly over the Mid Atlc. Main story in the extended will be cold temps, with lows in the low/mid 20s Fri night and Sat night. High temps Fri and Sat avg in the low 40s both days. Next chance of pcpn arrives Sun night/Mon with an approaching cold front, with the best chance of rain being during the day Mon based on the 12Z GFS/ECMWF (40% pops). High temps Mon in the mid/upr 50s. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... Widespread IFR conditions persist early this morning, but latest IR satellite trends indicate clearing over the Piedmont. However, the low ceilings have been replaced with patchy fog. Patchy fog will quickly burn off after sunrise, but the low ceilings/IFR conditions will be slow to improve from central Virginia to the coast. Ceilings slowly lift/erode mid to late morning, but expect low to mid clouds to persist along the coast into the afternoon thanks to a moist northerly flow. North to northwest winds generally around 10 knots with a few gusts around 20 knots near the coast this afternoon. OUTLOOK...A strong cold front impacts the area on Thursday, with only a quick chance for showers Thursday afternoon. High pressure returns Friday through Sunday. && .MARINE... The coastal low that brought strong sca winds with some gale force gust is quickly moving to the east this morning nearing 70W longitude. On the back side of the low still seeing sca level winds over the waters out of the north and northwest. But as the low continues to exit the region, expect to see the pressure gradient continue to weaken and the winds should gradually weaken below sca levels later this morning. Have already seen then drop across the area rivers and northern portions of the Chesapeake Bay so have dropped sca flags there with this forecast package. Weak high pressure will nose into the area later this afternoon and evening allowing the winds to relax across the region, but the seas over the coastal sections will be slow to diminish so will keep sca flags up for seas through tonight. But should see the 7 to 10 ft seas drop to 5 to 7 ft this evening and eventually below 5 ft by Thursday morning. A surge of cold canadian air will arrive in the area on Thursday and will reinvigorate a cold front that is dissipating over the Central Appalachians today. This front will then push through the waters by Thursday afternoon. While there could be some showers with this front, expect strong NW winds to develop again with strong sca conditions. This cold air will allow mixing of the winds aloft to the surface and could keep sca conditions in place into Friday night or Saturday. The models are struggling some with the wave heights generated by these winds as the WNAwave guidance quickly reduces the seas on Friday while the NWPS guidance keeps seas in the coast areas up 7 to 9 Ft. FOr now have gone in the 5 - 7 FT range for now with the sca conditions. Finally by Saturday afternoon...with high pressure centered over the area, will see the winds relax and benign conditions returning through Sunday. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ650- 652-654-656-658. && $$ SYNOPSIS...SAM NEAR TERM...AJZ/SAM SHORT TERM...SAM LONG TERM...MAS AVIATION...SAM/LSA MARINE...ESS

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