Area Forecast Discussion
Issued by NWS Sterling, VA

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881 FXUS61 KLWX 240801 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 401 AM EDT TUE MAY 24 2016 .SYNOPSIS... Low pressure off the Mid-Atlantic coast this morning will move northeastward towards New England today and then toward the Canadian Maritimes tonight. High pressure over the southern Appalachians this morning will settle off the southeastern coast by Wednesday and generally persist through the weekend. && .NEAR TERM /THROUGH TONIGHT/... System that has been affecting our weather for the last several days is finally shifting east of our area. Some clouds and a few showers remain early this morning but showers should clear the area by dawn. Where some breaks have occurred in the clouds...some patchy dense fog has been trying to develop. Will need to closely monitor observations through the next few hours in case a dense fog advisory becomes necessary...most likely for inland locations west of I-95. Otherwise...today should turn out mostly sunny with a warm northwest downslope flow. Threat of lingering showers developing this afternoon over the higher terrain appears lower than yesterday and have cut back on POPs. Highs should generally be near 80. Tonight high pressure shifts east but ridge with weak flow sits overhead. This will again promote patchy fog development. Otherwise...seasonal to a bit mild with lows in the 50s...60s in the urban core. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Wednesday high pressure will dominate with continued warming. Highs will reach the low to mid 80s. Southwest flow will continue milder pattern Wednesday night...but an approaching weak system will bring increased clouds and maybe even a stray shower late in the mountains. This threat will spread east during the day Thursday as weakening shortwave moves into the area. Have best POPs west given some terrain influence likely...but advection will likely carry activity east towards the metro. This will wane but not completely end overnight as the shortwave drifts overhead. Highs on Thursday will reach well into the 80s while lows Thursday night stay well into the 60s. && .LONG TERM /FRIDAY THROUGH MONDAY/... An upper level northern stream ridge will persist over the eastern CONUS Friday into Monday/Memorial Day. A southern stream low is expected to develop off the southeastern CONUS coast per 00Z global guidance consensus. Whether this low comes ashore or persists in the gulf stream is yet to be determined. Friday looks to be unstable with light sly flow and mainly terrain driven diurnal thunderstorms. Onshore flow and rain are possible at some point sunday into next week from the coastal low. The 00Z GFS and ECMWF both feature Memorial Day Monday into Tuesday as rainy. This would be a fitting end to a rainy month. Instability would be low in onshore flow Monday/Tuesday with showers the expected precip. Temperatures may be on steady cooling trend Friday into next week due to this coastal low. Friday may yet have 90F temperatures in the Balt-Wash metro where cloud cover should be less than farther west. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... Generally VFR thru Thursday night. Fly in ointment is patchy fog this morning which may cause a few terminals like MRB to go IFR. Same thing Wednesday morning. Thursday/Thursday night showers and thunderstorms may cause reductions. Light sly flow and diurnal thunderstorms Friday. ifr conds expected in heaviest activity. Forecast confidence drops this weekend through Memorial Day with a coastal low likely on SErn CONUS. Onshore flow and rain chances increase Sunday through Tuesday. && .MARINE... NW flow expected to mix some gustier winds down today so issued low end SCA for gusts up to 20 knots. Otherwise turning out sunny today. Lighter winds Wednesday and Thursday but shower/storm threat returns Thursday. Light sly flow continues Friday. Flow looks to become onshore over the weekend and persist into Tuesday. && .TIDES/COASTAL FLOODING... Water levels a half foot above normal early this morning. NWly flow should keep any rises limited. No coastal flooding is expected today. && .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 2AM EST on the 24th): 20 Most days in May with at least 0.01": 20 (in 2003) So far in 2016 (through 2AM EST on the 24th): 18 Highest May monthly rainfall: 10.69" (in 1953 and 1889) So far in 2016 (through 2AM 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 2AM EST on the 24th): 20 Most days in May with at least 0.01": 21 (in 1882) So far in 2016 (through 2AM EST on the 24th): 16 Highest May monthly rainfall: 8.71" (in 1989) So far in 2016 (through 2AM 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 2AM EST on the 24th): 21 Most days in May with at least 0.01": 21 (in 2003) So far in 2016 (through 2AM EST on the 24th): 17 Highest May monthly rainfall: 10.26" (in 2009 and 1988) So far in 2016 (through 2AM EST on the 24th): 6.07" && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from noon today to 6 PM EDT this evening for ANZ530>543. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...BAJ AVIATION...BAJ/RCM MARINE...BAJ/RCM TIDES/COASTAL FLOODING...BAJ CLIMATE...DFH/RCM

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