Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220756 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 356 AM EDT Tue May 22 2018 .SYNOPSIS...
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A warm front will pass through the region today and a cold front will approach from the northwest tonight before passing through Wednesday. High pressure will he front will return north as a warm front on Tuesday with a cold front expected to pass through the area on Wednesday. Weak high pressure will build over the area for the second half of the week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 07Z showers are moving through areas west of the Blue Ridge along a warm front. These showers are weakening as they move east but isentropic lift may develop additional showers east of the Blue Ridge during early this morning with some thunderstorms possible. The warm front will continue to lift northward through the day placing us on the warm sector of by this afternoon. South to southwesterly flow will advect additional moisture across our area allowing an increase in instability due to daytime heating. CAPE values could reach values around 1300 J/KG this afternoon with shear around 30 knots... therefore a few strong thunderstorms are possible this afternoon/evening. PWAT values above 1.5 inches will allow for heavy rain which could cause isolated floods due to saturated soils. SPC has placed our region in a Marginal Risk for severe thunderstorms. Max temps will range from the lower to middle 70s across northeastern Maryland to the middle 80s across central Virginia, and it will turn out humid behind the warm front. A cold front will move across our region tonight with a few showers and maybe a thunderstorm still lingering over our area. Coverage should remain isolated to scattered due to the loss of daytime heating.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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A weak cold front will pass through the area Wednesday. A north to northwest flow behind the boundary will usher in drier conditions. A couple showers and thunderstorms cannot be ruled out depending on the exact timing of the frontal passage. As of now, the best chance for a shower/thunderstorm will be across central Virginia into southern Maryland, but even across these areas much of the time should turn out dry and any coverage will be isolated to widely scattered. High pressure will build overhead for Wednesday night through Thursday night, bringing dry conditions along with low humidity.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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High pressure will remain in control of the weather pattern for Friday before building offshore Friday night through the weekend. A southwest flow will usher in a return of hotter and more humid conditions. The increased humidity may lead to popup showers and thunderstorms, especially during the afternoon and evening hours each day. As of now, it appears that convection coverage will be scattered, but still watching the potential for tropical moisture to get drawn into the area. As of now, it appears more likely that it would remain to our south and west during this time. For Memorial Day, tropical moisture may make a push northward toward our area. This may enhance the chances for showers and thunderstorms but confidence remains low this far out.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/...
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A warm front will pass through the terminals this morning. A southeast wind ahead of the front will allow for moisture to increase, and this moisture is likely to get stuck underneath the nocturnal inversion. Therefore, low clouds are expected to gradually develop early this morning, and it may take most of the morning for them to mix out. IFR conditions are possible during this time. Also, a few showers are likely along with a thunderstorm as warm front passes through. The best chance for precipitation will be across the northern terminals. Popup showers and thunderstorms will develop behind the warm front this afternoon, but cigs should lift a bit as well. Some thunderstorms will be capable of producing gusty winds, hail and heavy rains that can reduce vsbys below 2 miles briefly. A cold front will approach the terminals tonight before passing through Wednesday. A light gradient ahead of the front will allow for patchy fog to develop overnight. Any fog should lift by mid- morning Wednesday. VFR conditions are expected most of the time Wednesday afternoon through Friday. A few popup showers and thunderstorms are possible Saturday afternoon and evening.
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&& .MARINE...
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A warm front will pass through the waters through midday. A few showers are likely along with a possible thunderstorm. There is a better chance for thunderstorms behind the warm front later this afternoon into this evening. These storms will be capable of producing gusty winds, hail and heavy rain that briefly reduces visibility below 2 miles. A cold front will approach the waters tonight. A shower or thunderstorm cannot be ruled out, but coverage should be limited due unfavorable timing. A weak cold front will pass through the waters Wednesday. A north to northwest flow will develop behind the boundary. Winds may come close to SCA criteria, but have gusts capped around 15 knots for now due to the relatively cooler waters. High pressure will build over the waters Wednesday night through Friday before moving offshore during the weekend. A return southerly flow will develop during the weekend and this may result in popup showers and thunderstorms, especially during the afternoon and evening hours.
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&& .TIDES/COASTAL FLOODING...
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The latest water levels were below minor flooding thresholds for Washington DC. Freshwater continues to decrease upstream so that is having less of an impact. However, the southerly flow will continue today and the high tide this afternoon will be the higher of the two. Therefore, the advisory has been extended in time for the high tide cycle this afternoon. The best chance for minor flooding will be at the Washington Channel with Potomac River at Georgetown likely remaining below minor flooding thresholds.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Advisory until 5 PM EDT this afternoon for DCZ001. MD...None. VA...None. WV...None. MARINE...None.
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&& $$ SYNOPSIS...BJL NEAR TERM...IMR SHORT TERM...BJL LONG TERM...BJL/IMR AVIATION...BJL/IMR MARINE...BJL/IMR TIDES/COASTAL FLOODING...BJL

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