Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 241405 AFDAKQ Area Forecast Discussion National Weather Service WAKEFIELD VA 1005 AM EDT Fri Mar 24 2017 .SYNOPSIS... High pressure remains offshore the Mid-Atlantic coast through Saturday. An upper level disturbance lifts over the region Sunday. A cold front crosses the region Tuesday night. && .NEAR TERM /THROUGH TONIGHT/...
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Radar shows an area of light showers that is dropping ESE around the upper ridge in the SERN US. The models do not have a great handle on this feature as it is faster and further south than the models indicated. So have adjusted the forecast for some chance pops moving across NRN portions of the CWA and went about 3 hrs faster than the models would indicate, which should allow the pcpn to exit the Delmarva coast by early to mid afternoon. The QPF with the showers should be light, mainly less than .10". Have left the temperature forecast in place, but may need to adjust the nrn tier down a few decrease as a result of the rain/clouds. Will take a look at that for the next update for early this afternoon. prev discussion... Latest GOES water vapor imagery depicts an active pattern across the CONUS. Upper trough that brought cooler weather of the past few days is pushing off the Canadian Maritime, with the next upper low over the Desert Southwest. The next upper low is just off the Pacific Northwest coast. Ahead of the desert southwest low, an upper level ridge axis is located over the Ohio Valley. At the surface, strong ~1036mb high pressure has centered just offshore. Not as cold this morning as modest return flow and warming dewpoints have kept temperatures generally in the low to mid 30`s. Upper ridge builds east over the eastern US today as the upper low tracks into the Southern Plains. A shortwave tracks across the northern Mid Atlantic region this morning, with some showers observed this morning over western Pennsylvania. Showers stay north of the local area with only an increase in cloud cover across the northeast local area. Return flow on the backside of the departing surface high increases as the gradient between the departing high and approaching low strengthens. Southwest winds gust to 25 to 30 mph this afternoon. Dewpoints continue to recover, warming into the 30`s to low 40`s this afternoon, resulting in minimum relative humidity values in the upper 20`s to low 30`s inland. While 850mb temps warm to +6 to +8C, a large subsidence inversion will prevent temperatures from reaching their full potential, even with a breezy southwest wind. Highs generally in the mid 60`s. Cooler Eastern Shore and along the coast. Temperatures expected to be warmer than yesterdays high by late morning. Westerly flow will send some mid to high level clouds over the region this afternoon, with generally partly cloudy conditions. Upper/surface low pressure locate over the Midwest today as the ridge axis pushes offshore. A southwest wind and partly cloudy sky results in a mild night tonight, with lows generally in the upper 40`s to low 50`s. Continued dry.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY/... Stacked low pressure weakens/fills Saturday, tracking into the lower Missouri River Valley late. A warm front extends eastward over the northern Mid-Atlantic region as the cold front tracks into the lower Mississippi River Valley. The result will be ongoing return flow over the local area. 850Mb high pressure slides offshore, with better moisture return expected, but conditions remain dry thanks to ridging aloft (warm temperatures and a lack of forcing). Warm, with highs in the mid to possibly upper 70`s under a generally partly cloudy sky. Mild again Saturday night with lows generally in the low 50`s thanks to southerly winds and increasing clouds ahead of the approaching low. The upper low continues to weaken into Sunday, lifting over the Great Lakes Sunday afternoon. A lead shortwave lifts into the Mid-Atlantic region Sunday afternoon, but the cold front remains well west of the local area. Moisture also remains limited with precipitable waters only rising to around 1 inch over the Piedmont. Dewpoints progged only in the low to mid 50`s. Have pulled back POPs Sunday afternoon given the limited instability due to warm air aloft and a general lack of dynamics, keeping only a slight chance to low end chance POP Sunday afternoon from the Piedmont into central Virginia. Dry elsewhere. Given the lack of instability, especially in the mixed phase layer, have removed any chance of thunder. Not quite as warm Sunday as Saturday given the extra cloud cover. Highs generally in the low to mid 70`s. Cooler Eastern Shore and along the coast. Lows Sunday morning start in the low to mid 50`s with some patchy fog possible. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Medium range period features a mild period, courtesy of surface high pressure oriented just off the Mid-Atlantic/southeast coast. Main weather features of note a couple of mid/upper level lows, which will bring scattered light precipitation late in the weekend and again by Tuesday. The first of these disturbances traverses across the central/southern Plains on Saturday, dampening as it crosses E- NE into the Ohio Valley and Eastern Great Lakes on Sunday and into the northeast on Monday. This feature will allow for some isolated to scattered showers Sunday night into early on Monday. QPF will be limited with this feature. Despite increasing PW values, minimal instability and steadily weakening dynamics/forcing remain maximized well off to our N-NW. Therefore, high end chc to likely pop is in place for Sunday night over our western/NW tier of the area for sct/numerous showers. Region remains mild in the warm sector with southerly flow bringing highs in the upper 50s to 60s Northern Neck and MD Lower Eastern Shore...with upper 60s to low 70s inland for early next week. For the middle of next week...attention turns to a second southern stream disturbance, which is expected to track east/northeastward from the CA coast...across the Plains and Mid-South Late Sat-early Monday. There remains some significant disagreement with the GFS/ECMWF, with the ECMWF and its member ensembles remaining more progressive and flatter. Will lean in the ECMWF direction with the GFS Parallel and GEFS seemingly trending in this quicker direction as well. Still, this system will be a bit stronger than the weekend system but it too will weaken as it pushes across the eastern third of the conus Monday through early Tuesday. So while would translate to another period of showers late Monday night into Tuesday afternoon, system will again be progressive. Given the timing, will mention slight chance of thunder Tuesday afternoon west of the Bay. Remaining mild, with highs in the 60s to near 70 Eastern Shore...mid 70s to near 80 South central VA/Interior NE NC. Shortwave ridging rebuilds behind this system for Wednesday. Highs remain mild through the period, with 50s and 60s over the northern neck of VA into MD, with highs well into the 60s to Mid 70s inland. Early morning lows mainly in the 40s to low 50s southern sections. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... High pressure/fair weather prevails over the region this morning, with SKC conditions observed. Surface winds are generally southerly at or below 10 knots. High pressure slides offshore today as a storm system tracks into the Midwest. Southwest winds increase this afternoon, with gusts to 25 knots across the region. A scattered deck of mid level clouds is expected this afternoon, with SKC conditions expected KECG. OUTLOOK...Dry weather continues into Sunday morning. Scattered showers are expected Sunday afternoon and night. Unsettled conditions are forecast to continue Monday and Tuesday. && .MARINE... Sfc hi pres remains just off the mid-Atlantic coast through the weekend. SSE winds starting off the today...mainly averaging 10-15 kt. SSW winds averaging 15 kt or less...lingering through Sat. Pressure gradient tightens by this afternoon as low pres develops invof central/srn Plains. While nearshore winds will become elevated/gusty this afternoon...and (to a lesser extent) Sat afternoon...cooler waters likely to cut down speeds and will undercut guidance slightly/keep waters below any SCA thresholds (though there may be a brief period of gusty/a bit higher speeds over the waters from the eve into the overnight hours). The next front crosses the waters early next week...w/ relatively benign marine conditions expected over the weekend in SSW winds mainly aob 15 kt. Seas averaging 2-3 ft...waves 1-2 ft. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...SAM NEAR TERM...ESS/SAM SHORT TERM...SAM LONG TERM...MAM AVIATION...SAM/LSA MARINE...ALB/MAM

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