Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240800 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 400 AM EDT Wed Aug 24 2016 .SYNOPSIS...
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High pressure remains over the region through Thursday. A cold front will cross the region on Friday. High pressure will return for the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/...
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High pressure is centered near Delaware Bay this morning. Scattered altocu and cirrus are encroaching from the southwest, which may help mitigate fog development. It should be patchy and relegated to the typical western valley and Piedmont locations regardless. The high will become elongated as it moves offshore today and ridging aloft will expand eastward. With southerly flow established, there will be a minimal increase in temperature and humidity. Highs will reach the mid to upper 80s at lower elevations with dew points into the lower to mid 60s. Between minimal moisture return and strong ridging, think any terrain convection will be suppressed today, although the cu field will be more robust to the west. Several different layers of clouds may move in from the west tonight, but otherwise dry weather is expected. Lows should increase solidly into the 60s and perhaps staying at 70F in the urban centers.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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The NAM continues to offer the most suppressed solution for the upper ridge Thursday into Thursday night, allowing better shortwave forcing to enter the area. This will help determine how far eastward convection is able to make it. Along and west of the Blue Ridge will still be favored, as higher instability will be in place and the terrain will help with initiation. Some decaying showers could drift eastward during the early evening though. Some models actually depict increasing elevated instability overnight, but there doesn`t appear to be any forcing to tap into it. Temperatures/dew points will inch up another few degrees. A cold front trailing low pressure near the mouth of the St. Lawrence River will sink into the area on Friday. Mid-upper level forcing will be nearly non-existent with the strong upper ridge remaining in place. Low level convergence is also minimal. Therefore coverage of convection should be very minimal. It will get hotter ahead of the front though, with air temperatures reaching the lower to mid 90s for many. Combined with dew points in the lower 70s, this will result in heat indices of 100-105. The front will slip to the south Friday night. Falling dew points will result in a cooler night mainly N and W of DC, but it may remain somewhat muggy to the SE.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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Relatively good agreement remains in the long range guidance...through Tuesday at least...with the weak front dissipating just to our south over the weekend. This front will be so weak so to only slightly lower temperatures with its passage. High pressure at the surface will slide by to the north and bring a return southeasterly flow by Sunday...allowing moisture to increase again with rising chances of terrain-induced convection. The strong ridge aloft will gradually slide westward towards the middle of next week while weakening just a bit but not enough to allow any significant fronts to drop southward just yet. Overall...warmer and more humid than normal through most of the long term...but with a relatively low chance of rain.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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Scattered VFR clouds crossing the area this morning. MRB has the highest potential for BR, followed by CHO. High pressure moves offshore today, with VFR conditions and light winds continuing. While increased moisture may lend a better chance at patchy fog Thursday morning, the potential for clouds lowers confidence. Scattered thunderstorms may be near MRB Thursday afternoon, with perhaps a decaying shower reaching IAD/CHO. A weak cold front will drift south into the area on Friday; however thunderstorms look to be isolated at best. Mainly VFR through the weekend into early next week with only an outside chance of a thunderstorm or patchy fog...mainly at CHO and MRB.
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&& .MARINE...
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Southerly flow is becoming established as high pressure moves offshore. In general winds should be 5-10 kt today, perhaps increasing to 15 kt on the Bay this evening. Flow will increase Thursday to 10-15 kt, although it looks like any potential for SCA conditions should hold off to evening, as better channeling develops over the Bay. A cold front will move into the area Friday and Friday night, resulting in winds becoming westerly, then northerly. Any thunderstorms will be isolated at most with the front. SCA wind chance may linger early Saturday but generally light winds expected later Saturday into early next week. Little if any risk of t-storms over the weekend on the waters.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...ADS SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/RCM MARINE...ADS/RCM

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