Area Forecast Discussion
Issued by NWS Sterling, VA

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926 FXUS61 KLWX 231410 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1010 AM EDT Wed Aug 23 2017 .SYNOPSIS... A cold front will drop southeastward across the mid-Atlantic region today, before stalling over southeast Virginia tonight. Upper level energy will sweep southeastward tomorrow and push the front offshore tomorrow night. High pressure will quickly follow tomorrow night and persist right on into the weekend. && .NEAR TERM /THROUGH TONIGHT/...
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Northwesterly winds in the boundary layer suggest the surface front is through the area, although the airmass boundary (lower dew points) runs from north central Maryland to the Virginia Highlands. The mid level boundary remains overhead though, resulting in mostly cloudy skies and some light showers and sprinkles across central Virginia. HRRR has been over-developing this activity, so only expect some light showers across southern portions of the CWA through midday. Instability is expected to be confined from Charlottesville to southern Maryland this afternoon. Even so, the better forcing should be south of the area and a mid level stable layer will likely limit any updrafts. Have maintained chance POPs for this area. As we proceed into the overnight hours, clouds and precipitation chances decrease and slide to the east. Temperatures will be nearly 10 degrees cooler than yesterday across much of our region with humidity values on the downward trend as well. High temperatures will be mainly in the middle 80s with low temperatures tonight dropping down into the lower 60s.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Thursday will consist of two factors of weather. One of them an upper level disturbance dropping out of the Lower Great Lakes region into the mid-Atlantic region. This disturbance will help to kick the stalled front over southeast Virginia out to sea and could produce a couple of sprinkles in the northern Potomac Highlands. The other factor will be a firm ridge of high pressure that will build in from the northwest about the same time as the disturbance moves southeastward. The high pressure will strengthen behind the passing disturbance to give us a couple of periods of dry conditions and comfortable temperatures from Thursday right through Friday night. High temperatures Thursday and Friday will be near 80 with low temperatures Thursday night and Friday in the upper 50s to near 60. && .LONG TERM /SATURDAY THROUGH TUESDAY/... The weekend forecast will still be dictated by high pressure over northern New England. As has been advertised for a couple of days, temperatures/humidity levels will be almost fall-like. The only precipitation potential will come over the mountains at the end of the day...and that would be limited to a stray shower. Little will change for early next week, other than the center of the high will move offshore. That could lead to a bit more moisture flowing onshore, which may enhance diurnal/terrain showers. We`re still talking about a small chance, with isolated to perhaps at worst scattered coverage. And since water temperatures are in the upper 70s, forecast air temperatures wouldn`t change much. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
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VFR conditions expected at all terminals through Friday night. A shower or thunderstorm could develop in the vicinity of CHO near a stalled front through mid afternoon or so, but the chance for impacts is low. Winds have become northwest at 5 to 10 knots behind the front. Winds will be generally northwest to north 5 to 10 knots tonight through Friday night with typical diurnal fluctuations each afternoon. VFR conditions anticipated this weekend under high pressure.
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&& .MARINE...
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North to northwest winds today should remain below SCA criteria. A thunderstorm may affect the waters near southern Maryland this afternoon, but think the opportunity for strong storms will be farther to the south. Small craft advisories may be needed Thursday with diurnal heating during the day and cool advection aloft. No marine hazards expected Thursday night through Friday night. Winds this weekend should be light (at or below 10 kt) under the influence of high pressure.
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&& .TIDES/COASTAL FLOODING...
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Anomalies are falling now and should not pose a problem over the next few days with continued north/northwest flow. No flooding is forecast.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...None.
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&& $$ SYNOPSIS...KLW NEAR TERM...ADS/KLW SHORT TERM...KLW LONG TERM...HTS AVIATION...ADS/HTS/KLW MARINE...ADS/HTS/KLW TIDES/COASTAL FLOODING...ADS

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