Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250120 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 920 PM EDT TUE MAY 24 2016 .SYNOPSIS... A ridge of high pressure will build south of the region through the remainder of the week and into the weekend. A low pressure system may affect the region late in the weekend and into early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... High pressure will build overhead tonight...bringing mostly clear skies along with light winds. Patchy fog is likely in a few areas...dewpoint depressions this evening appear large enough to prevent widespread dense fog. Lows will range from the mid to upper 40s in the colder valleys of the Potomac Highlands to the 50s across most other locations. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Mostly sunny, warm, and dry weather will be the theme on Wednesday as ridge of high pressure dominates. Will be a weakening remnant vort/shortwave approaching from the west during the day, but instability will be lacking as moisture return is slow to occur, so only have a slight chance in the higher elevations of the far western counties. Highs will be in the mid 80s pretty much area- wide, with relatively low humidity as dew points hold in the 50s. Wednesday night will also be dry, lows upper 50s to mid 60s. Thursday will see more in the way of moisture return with dew points rising back into the low/mid 60s. This will lead to the development of some isolated to scattered showers/thunderstorms, especially in the higher terrain. Very weak wind field aloft though, so organized severe not expected. Temperatures warm a few more degrees with highs in the mid/upper 80s. A few showers/storms may linger into Thursday night. Mild night in store with lows in the 60s for all. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Remaining hot (U80s) and humid (U60s Tds) Friday with chances for isolated afternoon thunderstorms in the moderate instability, very low CAPE environment. Thunderstorm coverage will be greatest where orographic forcing helps with convective initiation. With weak steering flow, activity will have a difficult time moving off the higher terrain, though there could be a storm or two east of the Blue Ridge that develops due to localized influences. Saturday looks dry across most of the area, as poor mid-level lapse rates develop, with mid/upper ridge extending further north into the area. This keeps any shower and storm activity confined to the west over the higher terrain. Temperatures/dewpoints cool a few degrees from Friday. Changes begin to develop late Saturday into Sunday as low over the Atlantic approaches the eastern seaboard from the SE. While ultimate track of the system is uncertain at this time, precipitation shield ahead of system could begin to impact the area as early as Sunday and continue into early next week. Onshore flow and cloud cover ahead of system will also help to cool temperatures back below normal. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... Predominantly VFR through at least Thursday night. Some fog may bring some reductions late tonight, early Wednesday morning, but have left VFR for now as coverage will be patchy. Will also be some isolated-scattered showers and thunderstorms around on Thursday which may bring some brief reductions...but coverage will be scattered at best. Winds out of the northwest this afternoon with gusts up to about 17 knots become light and locally variable tonight, before turning light south/southwest Wednesday through Thursday night (less than 10 knots). While most of Friday will end up VFR, could be a few isolated storms with sub-VFR possible in and around any activity. Uncertainty increases Sunday as coastal low approaches the eastern seaboard, though rain chances (and associated sub-VFR) possible as early as Sunday. && .MARINE... Winds will continue to diminish this evening due to the loss of mixing from daytime heating. Lighter winds are expected through Thursday night. May be a few isolated- scattered thunderstorms on Thursday. Flow remains sub-SCA Friday and Saturday, though there is a low- end chance for a thunderstorm over the waters Friday. && .CLIMATE... We put together some records (preliminary) of how this month compares to rainy Mays on record for our area. Washington, DC (records since 1871) Most days in May with at least a trace: 25 (in 1952 and 1943) So far in 2016 (through 4PM EST on the 24th): 20 Most days in May with at least 0.01": 20 (in 2003) So far in 2016 (through 4PM EST on the 24th): 18 Highest May monthly rainfall: 10.69" (in 1953 and 1889) So far in 2016 (through 4PM EST on the 24th): 5.22" Baltimore, MD (records since 1870) Most days in May with at least a trace: 25 (in 2003) So far in 2016 (through 4PM EST on the 24th): 20 Most days in May with at least 0.01": 21 (in 1882) So far in 2016 (through 4PM EST on the 24th): 17 Highest May monthly rainfall: 8.71" (in 1989) So far in 2016 (through 4PM EST on the 24th): 4.92" Dulles, VA Most days in May with at least a trace: 23 (in 2003) So far in 2016 (through 4PM EST on the 24th): 21 Most days in May with at least 0.01": 21 (in 2003) So far in 2016 (through 4PM EST on the 24th): 17 Highest May monthly rainfall: 10.26" (in 2009 and 1988) So far in 2016 (through 4PM EST on the 24th): 6.07" && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...MM NEAR TERM...BJL/MM SHORT TERM...MM LONG TERM...MSE AVIATION...BJL/MM/MSE MARINE...BJL/MM/MSE CLIMATE...DFH is the U.S. government's official web portal to all federal, state and local government web resources and services.