Area Forecast Discussion
Issued by NWS Sterling, VA

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678 FXUS61 KLWX 271431 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1031 AM EDT Mon Mar 27 2017 .SYNOPSIS... A warm front will positioned over southern Virginia will track north through the Mid Atlantic through the afternoon. A cold front will cross the area late Tuesday. High pressure will build over the region Thursday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Dense Fog Advisory no longer in effect...as visiblities have been rapidly improving over the past half hour. Though, marine stratus layer with low ceilings will remain until warm front lifts through the area over the next several hours. As is often the case, guidance is struggling somewhat with the temporal evolution of the northward moving warm front and removes the CAD wedge along and east of the Blue Ridge a bit too quickly. Thus, low ceilings may remain in portions of the area through mid-afternoon (especially across N MD). Currently don`t think this will impact todays highs too much...as expecting a rapid warmup once front lifts through the area (highs M70s). CAPE gradient sets up this afternoon roughly from Montgomery County to the south...with ~500 J/kg of MUCAPE (250 J/kg ML CAPE) expected across central/northern VA into south central MD. Thus, could be a few scattered thunderstorms this afternoon with the differential heating boundary across these areas. 0-6 shear generally near 30-35 kts suggests a storm could briefly become somewhat organized. Though, lack of deep quality moisture coupled with long skinny CAPE profiles and relatively weak winds aloft likely limit any stronger thunderstorms. Gusty winds and small sub-severe hail the primary threats in any activity this afternoon. Thunderstorm chances rapidly decline after sunset. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... While we will be forecasting "chance of showers" overnight believe for the most part the nighttime hours will be dry. If it does the best chances will probably be late ahead of the approaching short wave. Lows generally in the mid 50s. Tuesday could see thunderstorm activity as the shortwave tracks through the Mid Atlantic. SPC has placed much of the forecast area east of the mountains in a marginal risk of severe storms. Neither the CAPE or helicity look particularly impressive for us. Chances for precipitation should be ending Tuesday evening as the shortwave moves off the coast. High pressure will return overnight and for Wednesday. Back on the roller coaster... temperatures Wednesday should be almost ten degrees cooler than the previous two days. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... High pressure will be building into the Northeastern United States Wednesday night, sliding east on Thursday. This will lead to drier and cooler weather, although still near climatological normals. Good radiational cooling night Wednesday night will lead to widespread lows in the 30s, with highs rebounding back through the 50s on Thursday. Meanwhile, a strong closed low will be moving northeastward out of the southern plains on Thursday, into the Mid-Mississippi Valley Thursday night, and towards the Mid Atlantic states by later Friday, becoming vertically stacked and gradually weakening. Model guidance is in relatively good agreement with this progression and timing. As the system makes its way to the eastern seaboard, some redevelopment off of the Mid-Atlantic coastline Friday night into Saturday morning is also projected. Therefore, chances for rain showers increase Thursday night into Friday morning with initial warm air advection, followed by bulk of the rainfall likely coming Friday and Friday night with main frontal push and any subsequent redevelopment. A drying trend should develop on Saturday, with the chance for some lingering showers as the low pulls away. High pressure will then build in for Sunday. Temperatures in the Thursday night - Sunday time period will be relatively seasonal, skewing slightly above normal. Lows will be mainly in the 40s. Highs coolest on Friday in the 50s with clouds/showers, rising into the 60s for the weekend. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Slow improvement expected over the next few hours as ceilings slowly rise. Conditions are expected to reach VFR this afternoon. Scattered thunderstorms are possible this afternoon. There will be chances of rain showers late tonight at all TAF sites..and then possible thunderstorms Tuesday afternoon. DCA has the best chance for strong gusty winds. VFR Tuesday night and Wednesday. VFR expected Wednesday night and Thursday, but chances for sub-VFR conditions increase Thursday night and Friday with rain and low clouds as next system moves into the area. Winds light Wednesday night into Thursday will increase out of the southeast later Thursday and Friday. && .MARINE... SCA currently in effect for the southern portion of the waters. An isolated thunderstorm with gusty winds is possible this afternoon into the early evening across the waters. Thunderstorms will be possible Tuesday afternoon, some of which could produce SMW level winds. This will need to be monitored. Sub-SCA conditions expected Wednesday night and Thursday. Potential for SCA then increases Thursday night and Friday with increasing southeasterly winds ahead of an approaching system. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ533- 534-537-541>543. && $$ UPDATE...MSE PRODUCTS...WOODY!/MJM

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