Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 301117 AFDAKQ Area Forecast Discussion National Weather Service WAKEFIELD VA 717 AM EDT Thu Mar 30 2017 .SYNOPSIS... High pressure becomes centered off the northeast coast tonight and Thursday. Low pressure and associated frontal boundaries track across the region Friday. High pressure builds over the area for the weekend. && .NEAR TERM /THROUGH TONIGHT/... Latest upper air analysis reveals a potent low pushing across the Central Plains toward the Middle Mississippi River Valley. Closer to home, downstream shortwave ridging has pushed east across the Mid-Atlantic into the southeast this morning. At the surface, latest analysis shows ~1034mb high pressure centered over James Bay, ridging south into the eastern Great Lakes and the interior Northeast. Resultant light ENE has allowed some sct low stratus to develop over the coastal plain this morning, with some more widespread mid level cloudiness across the piedmont. Temperatures this morning a bit chillier than the past few with temps mainly in the lower and middle 40s at 07z, with some upper 40s to near 50 hanging on with lighter flow and increasing cloud cover across the piedmont. Overall, relatively quiet weather-wise today. Upper ridge slides overhead today before pushing offshore tonight. Good model agreement with respect to increasing/lowering clouds through the day...first across the piedmont, then eventually spreading east to the coast by afternoon. Kept pops out of the forecast, but some patchy drizzle possible far west this afternoon. Otherwise, mostly cloudy to overcast inland, increasing clouds after a partly sunny start at the coast. Given weak/low mixing and the cloud coverage, generally accepted the cooler MET numbers, and accordingly took the forecasted maxima down a few degrees. Look for a cooler day with highs in the middle to upper 50s north...55-60 SE VA and interior NE NC away from the immediate coast...50-55 at the beaches. Overrunning moisture pushes across the area late this evening and overnight ahead of approaching upr level low. Will keep the evening dry for most with light rain showers overspreading the area by midnight far west...and after midnight east of i-95 midnight. Pops range from chc along the coast to likely across the Piedmont. Lows in the low- mid 40s. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... Models remain in good agreement with handling of the upper level low, which takes on a negative tilt as it lifts ENE across the OH valley on Friday. While the main low remains north of the local area, NAM and to a lesser extent the ECMWF key into weak meso low formation along the attendant frontal zone Friday afternoon, with the triple point feature lifting e-ne across the area Friday afternoon. This would present two distinct periods of rainfall; the first a strongly forced, quick moving line of showers producing rain Friday morning into early afternoon, with a second line of convection possible for the mid-late afternoon as the upper low and attendant surface cold front push across. PW`s in the 1.25 to 1.50 inches and strong lift argue for rain to fall heavily at times friday morning. However, showers should push through relatively quickly. Regarding the afternoon threat, SPC has now put the entire AKQ CWA in a marginal risk. Best thunder chcs remain confined mainly across the southern half of the area, with a slight chc across the north, where appreciable clearing and destabilization is least likely. Strong deep layer shear values would argue for at least a loosely organized convective line with any T-storms that do fire, and reasonably steep mid level lapse rates, LIs <-4 Deg C and CAPE maximized across South central VA and points south all argue for a narrow window for strong to severe storms Friday afternoon across the central/southern CWA, with the severe threat conditional upon breaks in the overcast and resultant destabilization. In that event, marginally severe hail, and damaging winds are the primary hazards in any thunderstorms. Highs mainly in the 60s to near 70 across the south, again dependant upon degree of clearing after morning into Midday rainfall. Likely to categorical POPS continue Friday evening with POPS tapering off after midnight as the low pulls offshore. Thunder chcs will be limited to the evening with forcing and instability waning quickly after sunset Fri night. Lows in the upr 40s-mid 50s. Trailing upr level energy tracks across the eastern shore with any showers tapering off before sunrise. Look for decreasing clouds w/highs in the low- mid 60s eastern shore, mid 60s-lwr 70s west of the bay. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Weak high pressure returns to the region Sat night/Sun with NW flow aloft. Mostly clear skies and cool temperatures anticipated with lows in the 40s Sat night and highs in the 60s Sun (upper 50s Atlantic beaches). High pressure slides offshore Sun night/Mon as the next low pressure system deepens over the Arklatex Region/Lower Mississippi Valley. The low continues to track NE into nrn OH/PA Mon night into Tue...dragging a cold front through the Mid Atlantic Region Tue aftn/evening. Increasing cloudiness late Sun night into Mon with similar temps to Sun. Lows in the 40s Sun night, and highs in the 60s Mon (upper 50s Atlantic beaches). Sfc pressure gradient tightens substantially late Mon night into Tue ahead of the approaching cold front. S-W winds gusting up to 25-30 mph will be possible. Widespread rainfall is anticipated during this timeframe with very low thunderstorm chances due to rain occurring primarily in the morning. Warmer temperatures Mon night/Tue as a warm front lifts north through the region. Lows Mon night in the mid-upper 40s far nrn counties (i.e. north of the warm front) and in the lower 50s elsewhere. Highs Tue in the 60s far nrn counties and in the lower 70s elsewhere. && .AVIATION /11Z THURSDAY THROUGH MONDAY/...
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E-SE flow allowing for some sct low stratus and patchy fog along and SSW of PHF/ORF this morning. Expect the Localized IFR/LIFR to mix out this morning. However, expect trend of lowering CU/Stratocu to continue today, albeit remaining in VFR range through this evening. Strong low pressure over the southern Great Plains will move northeast into the Ohio Valley later Thursday, resulting in increasing mid to high clouds over the Mid Atlantic region. Good model that ceilings will gradually lower through the day from west to east with warm air advection atop cool onshore flow at the surface. Mostly cloudy to overcast conditions (ceiling in the 5 to 7 KFT range AGL) expected through the day at RIC, reaching SE terminals at KORF/KECG by mid to late morning. OUTLOOK...Low pressure will move from the Ohio Valley across northern portions of the Mid Atlantic States to south of New England by Saturday morning. Widespread rain develops late tonight into Friday morning with a chance for thunderstorms Friday afternoon and evening. Periods of MVFR/IFR will be likely with Visibility restrictions possible by Friday morning and afternoon. Conditions improve quickly Saturday morning with high pressure rebuilding back over the area for the weekend. There will be a chance for showers western portions of the area by late Monday as the next system develops over the Mississippi Valley.
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&& .MARINE... Latest sfc analysis shows high pres stretching down through the Mid Atlc with a stalled frontal bndry over the SE states. Will maintain the SCA over coastal wtrs today for seas up to 5 ft out 20 nm. Mainly 10-15 kt NE/E flow today, with the high sliding offshore tonight and winds subsequently increasing late tonight and especially into Fri as the next low pres systm and associated cold front approach from the west. Marginal SCA conditions are psbl over the Bay and more likely over the cstl wtrs Fri with seas up to 6-7 ft, but will hold off on any headlines for now with this being third period and some headlines already in effect for today. The front crosses the waters late Fri night/Sat morning, with sub-SCA winds expected behind the front. Hi pres then builds in over the weekend. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ650- 652-654-656-658. && $$ SYNOPSIS...MAM NEAR TERM...AJZ/MAM SHORT TERM...MPR/MAM LONG TERM...BMD AVIATION...MAM/JEF MARINE...BMD/MAS is the U.S. government's official web portal to all federal, state and local government web resources and services.