Area Forecast Discussion
Issued by NWS Sterling, VA

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150 FXUS61 KLWX 190209 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 909 PM EST Wed Jan 18 2017 .SYNOPSIS... High pressure will build toward the region tonight before settling overhead Thursday. A warm front will move into the area Friday and stall out nearby through Saturday. Low pressure will affect the area to start the new week. && .NEAR TERM /THROUGH THURSDAY/... High pressure is centered over the Ohio Valley this evening. After breaking up somewhat, stratocumulus clouds have been re-expanding. Given sharp inversion shown on 00Z IAD sounding and little additional cooling expected aloft, these clouds will be slow to erode and may expand a bit more to the south with the continued northwest flow. In the near term, the clouds could keep the temperatures a little higher tonight across the north. Currently, it appears the clouds should gradually scatter out through Thursday morning. Elsewhere, low temperatures in the lower to mid 30s look on track. On Thursday, high pressure moves right overhead. High clouds will cross at times, though some puffy low cumulus or stratocumulus may linger in northern portions of the area as well. Temperatures aloft will remain mild for January so surface temps should rise back into the 50s in most of the area thanks to rather plentiful sunshine. Winds will be fairly light under the high. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... Warm front starts to lift back north towards us on Thursday night and enters southern Virginia before stalling out on Friday. Warm advection surge with the front will result in increasing clouds Thursday night, with a period of rain looking definite starting mid-late morning and lasting into early afternoon Friday. That rain should leave the area late in the afternoon, though lingering low level moisture and light southeast flow may result in patchy fog and/or drizzle which could linger through Friday night. Lows Thursday night will be in the 30s with highs Friday afternoon in the mid to upper 40s generally. Lows Friday night will drop back into the lower 40s with plenty of clouds and the potential for fog/drizzle. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Weak high pressure will be overhead Saturday into Saturday night. Temperatures will stay mild throughout the period. A separate area of high pressure over New England could aid in some cloud cover with an upslope flow. A few rain showers can`t be ruled out, mainly Saturday night. A storm system will develop over the Mississippi Valley and deepen as it pivots northeastward Sunday and Sunday night. This low could send additional energy into our region Sunday into Sunday night, bringing rain showers to the region. On Monday, the main low will move to the northeast a little further. The threat for showers and perhaps a rumble of thunder exist Monday into early Monday evening. Temperatures will remain mild. Drier air will push in behind the departing storm system Monday overnight. High pressure will usher in cooler and drier air Tuesday and Tuesday night. Clouds will break for sun, except for clouds and upslope rain and/or snow showers in the Potomac Highlands possible. An upper level trough of low pressure will sag from the Great Lakes region toward the mid-Atlantic Wednesday. A return of mild air from the south will evolve ahead of the trough with some sunshine giving way to some clouds. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... High pressure is building in from the west this evening, which has allowed northwest winds to subside. However stratocumulus is expanding again to the south under an inversion. MRB has dropped to MVFR, and it`s possible this could overspread the remaining terminals (except CHO) overnight. If these cigs do occur, it may take some time into Thursday morning before they lift/scatter out. Light winds with limited clouds for the remainder of Thursday. Cigs redevelop and begin to lower later THursday night with a period of rain and sub-VFR, if not sub-MVFR conditions looking likely on Friday. IFR looking possible with lingering clouds, drizzle and fog behind the system Friday night. VFR conditions Saturday. MVFR conditions Saturday night with a chance of a few rain showers, mainly at the CHO terminal. Winds light and variable Saturday. Winds easterly around 5 knots Saturday night. && .MARINE... While northwest winds have generally subsided this evening, there was a resurgence on the Potomac near Dahlgren with a few 18-20 kt gusts. Have covered these with a Marine Weather Statement, with expectation that gusts continue to subside as high pressure moves into the area. Should be sub-SCA for Thursday with high pressure overhead. Warm front approaches from south on Friday with rain and mist, but winds should stay sub-SCA. Drizzle and mist may linger Friday night, but still sub-SCA winds expected. No marine hazards Saturday and Saturday night. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...ADS/RCM SHORT TERM...RCM LONG TERM...KLW AVIATION...BJL/ADS/RCM/KLW MARINE...ADS/RCM/KLW

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