Area Forecast Discussion
Issued by NWS Sterling, VA

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933 FXUS61 KLWX 220159 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 859 PM EST Tue Feb 21 2017 .SYNOPSIS... High pressure will move off the east coast tonight. A weak disturbance will cross the area late tonight into Wednesday. High pressure will be located off the southeast coast of the United States late in the week. A cold front will pass through the area this weekend. && .NEAR TERM /THROUGH WEDNESDAY/...
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The weather this evening features a cutoff low moving across the southeastern United States and a northern stream disturbance pulling north into Canada with a trailing trough into the Northeastern US. The majority of the moisture associated with the cutoff low will remain well to the south of the region while the main forcing with the northern stream disturbance is well to the north. That being said, enough interaction will occur to bring a few light rain showers to the region late tonight and into Wednesday morning, mainly south of the DC Metro region. Otherwise, plenty of high cloud cover with cutoff low pumping warm, moist air in aloft. Lows tonight generally 40-45F. The upper-level disturbance will move off to the east by Wednesday afternoon and subsidence behind this system should allow for some sunshine, especially north. A southerly flow around high pressure over the Atlantic along with the sunshine will cause more unusually warm conditions. Leaned toward the higher guidance or even above based on temperatures aloft and mixing potential...but did tweak temps down a few degrees across central Virginia where cloud cover may hang on a bit longer. Max temps will be in the mid to upper 60s across most areas...but much cooler (50`s) along the shore of the Bay and along the ridge tops of the Potomac Highlands.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... High pressure will remain over the Atlantic Wednesday night through Thursday night while upper-level ridging builds overhead. A southerly flow along with sunshine will result in unusually warm condtions for this time of year. Max temps Thursday are expected to be well into the 70s for most areas...but cooler (50s-60s) along the shore of the Bay and in the ridges. Near record warmth is possible during this time. See the climo section below. Very mild conditions are expected for both Wednesday night and Thursday night...but with increased moisture there will likely be areas of fog. Some fog may be locally dense. A couple popup showers are possible Thursday afternoon due to limited instability from daytime heating. However...coverage will be widely scattered or isolated and much of the time should be dry. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Dry conditions expected for Friday with southerly flow over our region and high temperatures in the 60s and 70s. Deep low pressure moves across the Great Lakes and its associated cold front moves across the Mid-Atlantic on Saturday... showers and thunderstorms likely. Dry conditions return Sunday as high pressure builds behind the front. Shortwave trough could bring showers over our CWA on Sunday night, followed by dry conditions on Monday. Frontal boundary could increase PoPs again for Tuesday. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
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Predominantly VFR conditions expected for tonight into Wednesday morning. A few showers are possible...mainly KCHO. High pressure will build to our south and east for later Wednesday through Thursday night. Areas of fog are possible Wednesday night into Thursday and again Thursday night into Friday. Fog may be locally dense with IFR/sub-IFR conditions possible. Dry/VFR conditions expected for later Friday before a cold front approaches the area on Saturday... with showers and thunderstorms possible into Saturday. Sub-VFR conditions possible Friday night into Saturday at moments. Gusty winds expected Friday night into Sunday.
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&& .MARINE... High pressure will remain off the coast through Thursday night. A southerly flow is expected during this time...but wind speeds should remain below SCA criteria. Dry conditions expected for Friday before a cold front moves across the Mid-Atlantic on Saturday. Showers and thunderstorms possible. Gusty winds expected Friday night into Sunday, with SCA conditions likely. && .CLIMATE... Did a check to see how warm it has been both for meteorological winter and since Feb 1 at the three major airports in terms of ranking (average temp): The statistics below are from February 1st through February 20th. Since Dec 1 Since Feb 1 DCA 5th warmest 2nd warmest BWI 14th warmest 13th warmest IAD 2nd warmest 2nd warmest Unseasonably warm temperatures are expected during the second half of the week. Below are record daily high maximum and high minimum temperature values for the 22nd through 24th (Wednesday through Friday). February 22nd DCA 77 (1874) 60 (1874) BWI 74 (1874) 51 (1874) IAD 71 (1991) 52 (1981) February 23rd DCA 78 (1874) 51 (1922) BWI 78 (1874) 52 (1874) IAD 73 (1985) 51 (1975) February 24th DCA 78 (1985) 52 (1975) BWI 79 (1985) 55 (1985) IAD 79 (1985) 53 (1985) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BJL NEAR TERM...BJL/MM SHORT TERM...BJL LONG TERM...IMR AVIATION...BJL/MM/IMR MARINE...BJL/MM/IMR CLIMATE...DFH

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