Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 211720 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 120 PM EDT TUE JUN 21 2016 .SYNOPSIS... A cold front drops into the area late this afternoon and evening. The front then stalls across the Carolinas Wednesday. The front lifts back northward as a warm front Wednesday night as low pressure tracks into the Great Lakes. Low pressure tracks into New England Thursday with the front dropping back over the region Thursday night. && .NEAR TERM /THROUGH TONIGHT/...
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Severe thunderstorm watch 278 is now in effect along and north of a line from Fluvanna to Mathews Counties VA (not including the city of Richmond) to the Eastern Shore. The watch is in effect until 9 PM. Latest regional radar mosaic depicts an area of showers and thunderstorms developing along the cold front in northern MD and moving east-southeast. South of this line, isolated to widely scattered showers and thunderstorms have developed over the Central Appalachians. Thanks to a warm and very moist air mass, MLCAPE values have increased to around 1500 to 2000 J/kg across the northern local area. Effective shear also analyzed around 30 to 35 knots. Confidence is increasing for the area of showers/thunderstorms along the front to become better organized and drop toward the Northern Neck to the Eastern Shore through mid afternoon, reaching the area by mid to late afternoon. Damaging winds and hail remain the greatest threats. Heavy rainfall also expected due to an anomalously moist air mass. Back toward the Piedmont, activity expected to remain isolated to widely scattered. Cannot rule out gusty winds and hail under the strongest storms. Previous Discussion... Latest radar trends depict a line of dissipating light showers over central Virginia this morning. Observed and radar rainfall amounts have been a few hundredths of an inch at best. Main impact from the early morning showers is the cloud cover observed across the region. The cloud cover has briefly suppressed temps this morning, with many locales running slightly below model guidance. Even so, expect temperatures to warm into the upper 80`s to low 90`s this afternoon as the sky becomes partly cloudy and southwest winds increase to 10- 15 mph. Attention then turns to the convective potential this afternoon and evening as a cold front currently located over southern Pennsylvania slowly sags southward toward the forecast area. Precipitable waters have increased to around 1.5 to 1.75 inches per blended total precipitable water. A moist boundary layer and warm afternoon temperatures will result in a moderately unstable air mass, with MLCAPE values of 1000-1500 J/kg. Increasing winds aloft between the deepening trough over the northeast CONUS and anomalous upper level ridging over the Desert Southwest will result in effective bulk shear of 30 to 35 knots. However, forcing remains rather weak with deep layer westerly flow observed in the soundings. The overall lack of forcing is expected to limit coverage from the Piedmont into central Virginia, with better forcing along the frontal boundary providing better coverage from the Northern Neck to the Maryland Eastern Shore. Have maintained likely POPs northeast, tapering back to low end chance (widely scattered) southwest. SPC maintains a slight risk for the area with damaging winds and hail the main threats. WPC has also issued a SEE TEXT for heavy rainfall across the Delmarva thanks to better coverage. Precipitation chances decrease this evening as storms push ahead of the front and instability wanes. Sky averages mostly clear inland to mostly cloudy along the coast. Mild, with lows in the upper 60s to low 70`s.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY/... Mid-level trough axis pushes offshore Wednesday with northwesterly flow aloft prevailing. Tuesdays front stalls over northern North Carolina. Low pressure tracks across the Midwest Wednesday, which will lift the western extent of the cold front northward as a warm front into the central Appalachians. Precipitable waters drop to at or below 1 inch Wednesday afternoon with dewpoints near 60 northwest to mid 60`s southeast. Disturbance progged to drop along the lifting warm front Wednesday will result in a slight chance for showers/thunderstorms across the southwest local area. Dry elsewhere. Still warm with highs generally in the upr 80`s. Attention turns upstream Wednesday evening as models continue to indicate upstream showers/thunderstorms dropping along the frontal boundary into the local area. Moisture returns quickly Wednesday evening as low level flow returns to the southwest behind the lifting warm front. Will keep mention of chance POPs as the front lifts through the area Wednesday night. Mostly cloudy with lows generally in the upper 60`s to around 70. Low pressure tracks into New England Thursday with an east to west frontal boundary setting up over the northern Mid-Atlantic region. A warm, moist, and unstable air mass will be in place across the local area. Pressure falls on the lee side of the Appalachians will induce low level convergence resulting in chance POPs across much of the local area. Guidance indicating a hot day, but have undercut guidance several degrees due to cloud cover and precipitation potential. Highs in the upper 80`s to low 90`s. The front will slowly slide southward Thursday night. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Cold front will drop acrs the area Thu ngt resulting in chc pops (40%) for showers and/or tstms. Will linger sml chc (30%) or slgt chc (30%) pops mainly ovr srn portions of the region on Fri. High pres then blds in fm the NNE Fri aftn into Sat morng, then sits off the Nrn Mid Atlc cst Sat aftn into Mon morng. A cold front will slowly approach fm the W during Mon. Expect mainly dry wx Fri ngt into Mon morng, then will have a slgt or sml chc for showers or tstms mainly in the wrn half of the area Mon aftn/eveng. Lows in the mid 60s to lwr 70s Thu ngt, in the 60s Fri ngt and Sat ngt, and in the mid 60s to near 70 Sun ngt. Highs in the upr 70s to mid 80s Fri and Sat, in the 80s Sun, and in the mid 80s to near 90 Mon. && .AVIATION /17Z TUESDAY THROUGH SATURDAY/... Vfr thru the 12z taf period. A cold front approaches the area from the nw tda...with skies mainly sct-bkn ~8-10k ft. Chances for rain are greatest at ksby (where shra was included) and kric (where vcsh was included). Elsewhere...confidence is lower for late aftn/eveng shras/tstms so kept any mention of rain out of the tafs attm. Reduced cigs/vsbys likely in any tstms however coverage is not expected to be widespread. Otherwise...expect gusty sw winds tda ahead of the frnt...decreasing ovrngt as the frnt drops into the area. OUTLOOK...Drier weather returns Wednesday with a chance for showers/thunderstorms Wednesday night through Thursday night. Precipitation chances diminish Friday with dry weather returning for Saturday. && .MARINE... Extended SCA until 10am EDT over the lower Chesapeake Bay south of New Pt Comfort/Currituck Sound and Lower James R. for low-end SCA SW winds in association w/tightening pressure gradient ahead of approaching front as high pressure builds off the SE coast. This front will drop into the area tonight into Wed morning, bringing a chance for Sct showers and gusty T-storms late today and tonight. Have gone ahead and hoisted SCA through late tonight over the coastal zones, mainly for seas 5-6 ft offshore. Front will slip south of the region early Wed, partially washing out over coastal NC. Lighter winds aob 10kt expected post-frontal on Wednesday. predominate wind direction will be WNW. However, light flow will allow seabreeze effects to take over by aftn over nearshore S coastal zones. Boundary lifts back N as a warm front from late Wed night into Thu morn. Good model agreement taking sfc Low pressure east from the Eastern Great Lakes through the day Thursday, before sliding off the Northern Mid-Atlc/Srn New England coast Thu aftn and night. The trailing cold front drops across the region early friday morning, with another period of marginal SCA possible. 1020+mb sfc High pressure will the build in fm the NNW through the day Fri before pushing offshore Friday night/Sat. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT Wednesday for ANZ650-652-654-656-658. && $$ SYNOPSIS...MAS/SAM NEAR TERM...SAM SHORT TERM...MAS/SAM LONG TERM...TMG AVIATION...MAS MARINE...MAM

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