Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190800 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 400 AM EDT Sun Mar 19 2017 .SYNOPSIS...High pressure will build over the area today and tonight, before a cold front crosses the area Monday night. Strong high pressure then builds across the region during the middle to latter part of the week. && .NEAR TERM /THROUGH TONIGHT/...Light snow has been falling across Frederick and Carroll counties in MD since about 11PM with rain elsewhere except in the Shenandoah valley where it has remained dry. Over the next few hours, we`ll see rain/snow line shift southward as column continues to cool down beneath upper low. No snow accumulation expected outside Carroll and Frederick counties where an inch or two are possible mainly on grassy surfaces. Upper low and trof axis will shift east later today with precip ending by 15Z if not sooner. High pressure then builds overhead tonight with clearing expected by daybreak Monday. Chilly with temps in the low 30s east and upper 20s west. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...High pressure will then shift rapidly to the south with showers expected in the afternoon and night as cdfnt crosses the area. Low pressure developing along front across North Carolina Tue night will bring another round of rain Tue evening with rain ending by daybreak Wed. Some accumulating snow is likely across the higher elevs of eastern WV and Highland county. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/...Computer model guidance is in good agreement through Friday. By Wednesday morning, the precipitation should be over as the area of low pressure moves offshore. A secondary, but dry, front will push southward during the day as an upper level trough axis swings through the northeastern states. Colder air will rush into the area with below normal temperatures expected. Surface high pressure will build over the central Appalachians by 12Z Thursday, and favorable radiational cooling will result in lower 20s in outlying areas. Temperatures will moderate slightly for Thursday. The surface high will move offshore Friday while upper level ridging builds overhead. There will be some additional cloud cover due to warm advection aloft, but it will likely stay dry with milder temperatures. Guidance spread begins to increase Saturday as a low pressure center moves into the Great Lakes and drags a cold front toward the area. A faster solution (such as the GFS) would result in showers for Saturday. Unless the front moves through early in the day though, high temperatures could push 70F. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/...IFR conditions through 13Z with rain changing to snow after 09Z and ending by 13Z. Cigs improve to MVFR after 13Z and become VFR by 18Z. Next chance of rain is Mon afternoon and night with next frontal passage. VFR conditions expected Wednesday and Thursday as high pressure builds into the area. NW winds could gust to 25 kt Wednesday, with lighter winds by Thursday. && .MARINE...Solid SCA conditions today, then winds begin to diminish this evening. Possible SCA again Tue night. Secondary cold front passage on Thursday will result in gusty NW winds with SCA conditions possible. Winds will diminish heading into Thursday as high pressure builds overhead. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ530- 531-535-536-538-539-542. Small Craft Advisory until 6 AM EDT Monday for ANZ532>534-537- 540-541-543. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...ADS AVIATION...ADS/LFR MARINE...ADS/LFR

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