Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210220 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 920 PM EST Mon Feb 20 2017 .SYNOPSIS... High pressure will build overhead through tonight. Cooler air will seep south tonight into Tuesday. A weak disturbance will cross the area Tuesday night into Wednesday. High pressure will be located off the southeast coast of the United States Thursday through Friday. A cold front will pass through the area during the weekend. && .NEAR TERM /THROUGH TUESDAY/... Backdoor cold front is shifting southwestward through the area this evening, noted by wind shift to the northeast and falling dew points, as ridge of high pressure builds over New England. At the same time, a highly amplified upper level ridge is building into the region from the west. High clouds will gradually increase across the area tonight as they spill over the ridge axis. A broken deck of lower clouds is also possible overnight across the Shenandoah Valley into the Potomac Highlands. precipitation is expected. Lows tonight mainly in the 30s to near 40F. The surface high will move off the New England coast Tuesday...but it will continue to wedge into the Mid-Atlantic. The upper-level ridge will also gradually move off to the east. An onshore flow around the high will cause cooler conditions compared to recent days...but max temps will still be above climo. An upper-level disturbance will approach from the west...bringing some clouds to the area but it should remain dry. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... An upper-level disturbance associated with the northern stream of the jet will pass through our area Tuesday night into Wednesday...but it will be weakening as it moves through. Cutoff low pressure will develop in the southern stream of the jet...but that should remain well off to our south. A couple showers are possible Tuesday night into Wednesday...but with our area split between the northern and southern stream of the jet most areas may end up dry. The best chance for showers will be in the Allegheny Highlands due to an upslope component to the low-level flow. High pressure will build offshore for Wednesday and Wednesday night...allowing for unusually warm conditions to return. Max temps Wednesday will once again be well into the 60s and 70s. && .LONG TERM /THURSDAY THROUGH MONDAY/... Dry conditions expected for Thursday with southerly flow over our region and high temperatures in the 60s and low 70s. A frontal boundary will be approaching the region from the north allowing for some showers Thursday afternoon into Thursday night. Warm air advection continues Friday into Friday night with an increase in PoPs as cold front approaches from the west. Deep low moves across the Great Lakes and a cold front moves across the Mid-Atlantic on Saturday... showers and thunderstorms likely. Dry conditions return Sunday into Monday as high pressure builds behind the front... high temperatures will be in the 50s and 60s, and in the 40s and 50s at higher elevations. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Predominantly VFR conditions expected through Tuesday. Winds light out of the northeast tonight will turn southeasterly for Tuesday, generally less than 10 knots. Will see an increase in high clouds overnight that will persist through Tuesday. A strato-cumulus deck will also likely develop on Tuesday, but generally expected to remain at or above VFR. An upper-level disturbance will pass through the terminals Tuesday night into Wednesday. A couple showers cannot be ruled out...but most areas will be dry. A light south to southwest flow is expected during this time. Areas of fog are possible Tuesday night and again Wednesday night. Dry/VFR conditions expected for Thursday before a front approaches the area on Thursday night... showers possible into Saturday, when a strong cold front moves across the Mid- Atlantic. Sub-VFR conditions possible Thursday night into Saturday at moments. Gusty winds expected Friday night into Saturday, reaching up to 20 kt. && .MARINE... Winds have turned to the northeast this evening and will continue through the overnight. A weak pressure surge is expected over the waters this evening, and gusts may approach SCA criteria, but should generally stay below. High pressure will build over the Atlantic for Tuesday and Wednesday. Southeast winds Tuesday will turn to the south or southwest Tuesday night through Wednesday night. Wind speeds should remain below SCA criteria. Dry conditions expected for Thursday before a front approaches the area on Thursday night... showers possible into Saturday, when a strong cold front moves across the Mid-Atlantic. Gusty winds expected Friday night into Saturday, reaching up to 20 kt, therefore small craft advisory possible. && .CLIMATE... 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 is the U.S. government's official web portal to all federal, state and local government web resources and services.