Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221426 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1026 AM EDT Tue Aug 22 2017 .SYNOPSIS... High pressure is centered well off the North Carolina coast. A cold front over Michigan will track across the eastern Great Lakes today, before pushing across the mid-Atlantic tonight into Wednesday morning. The front could stall just offshore the Delmarva Peninsula Wednesday. Reinforcing upper level energy will help to push the front offshore and allow for high pressure to build in from the northwest Thursday into Friday. && .NEAR TERM /THROUGH TONIGHT/... THeat and humidity continue today. Dewpoints remain in the mid 70s. High temperatures are expected to reach the lower to mid 90s east of the Blue Ridge. We expect to see heat index values of 100 to lower 100s in a large area east of the mountains. Clouds will increase from northwest late this afternoon through tonight as a strong cold front pushes across the eastern Ohio Valley and into the mid-Atlantic region. Showers and thunderstorms will increase in coverage and intensity from western Maryland toward northern Virginia and the I-95 corridor late this afternoon and evening. There is a slight risk for severe thunderstorms in western Maryland and parts of the eastern West Virginia Panhandle. The marginal risk extends from the mountains of Highland County in western Virginia to DC/Baltimore. The main threats with the strongest thunderstorms will be damaging winds in wet microbursts. Given PWATs of close to 2" very heavy rainfall is possible with storms. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Wednesday begins with a cold frontal passage across our region. As we get into the midday hours, the front could show signs of stalling just to our southeast as clouds and widely scattered showers linger along the front and just to the north. With added daytime heating and some backing of winds with height with frontal passage, additional showers and a few thunderstorms could form and be scattered throughout the eastern Piedmont of Virginia, southern Maryland and a large portion of the Chesapeake Bay. At this time, there is a marginal risk of severe thunderstorms across lower Southern Maryland and south into the Tidewater of Virginia Wednesday afternoon and evening. High temperatures, along and north of the front, will be cooler with highs in the lower to middle 80s. Humidity will be lower as well with high pressure to the northwest building southward and ushering in lower dewpoint temperatures. Throughout the overnight of Wednesday, the front should move far enough southeast to allow for conditions to dry out with the building high pressure. High pressure will continue to build into the region Thursday and Thursday night. Some upper level energy will try to scoot over the ridge of high pressure but should be unsuccessful of producing any precipitation Thursday into Thursday night. && .LONG TERM /FRIDAY THROUGH MONDAY/... The weekend forecast still looks quiet as high pressure passes north of the forecast area. One minor change is that guidance suggesting there may be a few terrain circulations, for a stray shower or thunderstorm, coincident with daytime heating in the mountains. Otherwise, sunshine should be plentiful and temperatures should be slightly below normal...with dewpoints in the 50s. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... VFR conditions expected at all terminals through Thursday night. The biggest concern is the cold front entering the Ohio Valley. While the strongest activity is expected to be to our north showers and thunderstorms could reduce visibilities to IFR in heavy rainfall late this afternoon and evening. VFR conditions anticipated Fri-Sat under high pressure. && .MARINE... We are seeing gusts into the upper teens on the wider part of the Bay. SCA in effect there. Small craft advisories are also in effect from Noon today through 11 pm tonight. No marine hazards expected Wednesday through Thursday night. North/northwest winds will be in the 5-10 kt range Friday- Saturday under high pressure. && .TIDES/COASTAL FLOODING... Northwest winds will arrive Wednesday morning. We shall see if that will be soon enough to preclude another borderline situation at Annapolis/DC early Wednesday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ530>543. && $$ UPDATE...WOODY! PREVIOUS...KLW/HTS

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