Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 070904 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 404 AM EST Wed Dec 7 2016 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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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, ~1001mb low pressure has centered offshore of the Eastern Shore with high pressure over the Northeast. A weak secondary boundary is located over the central Appalachians. Light rain still lingers along the coast of the Maryland Eastern Shore, so will keep chance POPs for that region through daybreak. Weak, secondary cold front pushes across the region this morning, stalling/washing out offshore this afternoon. The front will help kick the surface low farther offshore, with any chance of light rain ending for the Maryland Eastern Shore after sunrise. Northerly low level winds will be slow to scour out the lingering wedge air mass this morning, but expect dry air advection to erode the low clouds over the Piedmont by mid-morning. Clearing will spread eastward toward the coast through early-mid afternoon. 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.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY/...
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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.
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&& .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 /09Z WEDNESDAY THROUGH SUNDAY/... Widespread IFR conditions observed across the forecast area as low pressure centers just offshore. Ceilings are generally between 500 and 700 feet AGL. Surface winds northwest 5-10 knots inland and 10-15 knots with a few gusts of 25 knots near the coast. Lingering light rain persists along the Maryland coast, but dry elsewhere. Expect IFR conditions to persist through the overnight period, with some improvement possible over the Piedmont. However, any breaks in the clouds over the Piedmont into central Virginia will aid in fog development. Have brought some MVFR fog into KRIC late tonight, but main impact will remain the low ceilings. Ceilings will 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. VFR conditions return inland this afternoon. Northwest winds generally around 10 knots with a few gusts around 20 knots near the coast. 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...
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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.
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&& .EQUIPMENT...
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KAKQ radar is offline due to a pedestal dynamic fault. Techs will evaluate the radar first thing this morning. No return to service time is available.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 10 AM EST this morning for ANZ631>634. Small Craft Advisory until 10 PM EST this evening for ANZ650- 652-654-656-658.
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&& $$ SYNOPSIS...SAM NEAR TERM...SAM SHORT TERM...SAM LONG TERM...MAS AVIATION...SAM/LSA MARINE...ESS EQUIPMENT...AKQ

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