Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240032 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 832 PM EDT Tue Aug 23 2016 .SYNOPSIS... High pressure remains over the region through much of the week with a cold front moving through on Friday. High pressure returns for the weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... High pressure will remain overhead tonight...bringing mainly clear skies along with light winds. Min temps will range from the mid to upper 50s in the valleys of the Potomac Highlands to the lower and middle 60s across most other locations. Patchy fog is possible in the favored river valleys and rural areas...but higher temp/dewpoint depressions this evening suggest that widespread fog is not expected. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Surface high pressure will slowly be working offshore Wednesday and Thursday. As a result, we should embark upon a warming trend. Upper 80s/near 90 for high temps seem likely again by Thursday. Dewpoints will start to creep upward too, but still at tolerable levels (lower 60s Tue, mid 60s Wed). As humidity increases, instability levels will rise as well on the back side of the ridge. NAM continues to place more emphasis on the westerlies across the northern half of the country. Consequently, more shortwave advection would be affecting area based on this solution, primarily Wednesday night and Thursday. GFS is far more reserved, and seems to be the more plausible scenario. Am keeping all areas dry Wednesday and Wednesday night, but with added clouds in the mountains. Although temps will be a little bit warmer, do not believe there will be adequate forcing for thunderstorms to develop. By Thursday, believe there will be a ribbon of instability, confined mainly west of the Blue Ridge. Going forecast has 30-40% chance of showers/thunderstorms in this area, which should address threat well. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A weak cool front is expected to stall across the region Friday and Friday night. A spotty shower cannot be ruled out along the boundary. Temperatures will be on the warm side too with highs reaching the lower to middle 90s. High pressure will build in behind the front Saturday and Saturday night. Drier and cooler air expected. Temperatures will be closer to normal. This high will move east and weaken Sunday and Sunday night. Dry conditions will prevail Sunday. We can`t rule out a shower or thunderstorm in the west Sunday night as the next cold front moves across the lower Great Lakes. Temperatures remaining near normal. The cold front will move across the region Monday and Monday night. A chance of showers and thunderstorms will ensue through the period. Temperatures normal. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... There may be patchy fog overnight, but air mass quite have limited fog in the forecast. Did allow for MVFR vsbys for KMRB and KCHO. VFR conditions should generally prevail Wednesday and Thursday as high pressure departs. Fog may be a little more pervasive by Thursday with added humidity. In addition, a few thunderstorms would be possible in the afternoon and evening, especially near MRB. VFR conditions expected Friday through Friday night. A brief period of MVFR or IFR is possible in any isolated thunderstorms near CHO, MRB, and IAD...mainly Friday evening. Winds southwest around 5 knots Thursday night becoming northwest around 5 knots Friday and Friday night. && .MARINE... Light south to southeast flow is expected overnight with the center of High pressure just to the south. Flow will become southerly over the next couple of days as the high pulls offshore. For the most part winds will be 10 kt or less. However, may have some gusts up to 15 kt due to channeling Wed and Thu nights. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...BJL/HTS SHORT TERM...HTS LONG TERM...KLW AVIATION...BJL/HTS/KLW MARINE...BJL/HTS/KLW is the U.S. government's official web portal to all federal, state and local government web resources and services.