927 FXUS61 KLWX 100800 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 400 AM EDT Wed Oct 10 2018 .SYNOPSIS... High pressure over the western Atlantic will remain in control of the area through this afternoon. A cold front will cross the area late Thursday night. Hurricane Michael is expected to pass southeast of the area early Friday morning. An upper-level disturbance will pass through Friday night into early Saturday followed by high pressure for the rest of the weekend. Please refer to the National Hurricane Center for the latest on Michael. && .NEAR TERM /THROUGH TONIGHT/... Offshore ridging will begin to breakdown today in response to broad troughing approaching from the western/central CONUS. This will result in increasing southerly flow across the Mid-Atlantic. After patchy fog and low clouds burn off by late morning, scattered to broken cumulus will develop. The axis of a mid-level shortwave/vort max will approach from central Appalachians/Ohio Valley and pivot southwest to northeast across the region late this afternoon and evening, resulting in the development of scattered showers. A few heavier showers or isolated thunderstorms are possible mainly near and west of the Blue Ridge this evening. Continued PVA ahead of the approaching long wave trough and low- level moist advection likely causes showers to persist across much of the area overnight, with a rumble of thunder or isolated heavier downpour possible. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... The remnants of Hurricane Michael are forecast to move across the Carolinas and exit the east coast near the NC/VA border Thursday night. Meanwhile, the approaching longwave trough and attendant surface cold front will cross from west to east. Given the high humidity (enhanced somewhat by the presence of a remnant tropical system to the south) will result in the potential for heavy downpours. The main heavy rain shield at the moment looks to stay over mainly SE of I-95/US-50 (southeast of immediate DC area towards southern MD). Still, any heavier thunderstorms could result in an isolated instance of flooding. Although a few inches of rain is currently expected over southern Maryland, FFG here is higher so widespread flooding issues are not anticipated. Please consult the latest NHC forecast for updates on Michael. Following the frontal passage early Friday morning, a period of breezy conditions on NW cold advection is expected. Drier conditions will prevail with more fall-like temperatures. An upper shortwave will approach the higher terrain and could spark some showers again, though, by late Friday night. && .LONG TERM /SATURDAY THROUGH TUESDAY/... An upper-level disturbance will pass through the area Saturday morning through midday. At the same time, surface high pressure will be approaching from the Midwest and western Great Lakes. A northwest flow ahead of this system will continue to usher in much cooler conditions compared to the air mass that we are currently in. Latest guidance has trended a bit stronger and farther south with the track of the upper-level disturbance. This may trigger some showers across our area Saturday morning/midday, but drier air should advect in behind the departing disturbance Saturday afternoon. Also, there could be a few snow showers mixing in along the Allegheny Front for the ridge tops above 3500 feet Saturday morning. High pressure will build overhead for Saturday night before shifting offshore Sunday. Dry and seasonable conditions are most likely during this time. Low pressure and its associated cold front may pass through the area late Sunday or Monday, bringing the next chance for showers. Will favor the later solutions with the boundary passing through Monday since most of the guidance indicates this. High pressure will build in behind the departing boundary for Tuesday. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... IFR breaks by mid to late morning. Sub-VFR possible in scattered SHRA but too isolated to mention in the TAF ATTM. IFR likely returns tonight. SHRA likely Thu-Thu night with sub-VFR. VFR returns Fri-Fri night. Winds S through Thu, becoming NW and gusty Thu night-Fri. An upper-level disturbance may bring a few showers Saturday morning. VFR conditions are most likely, but a brief period of MVFR conditions cannot be ruled out. High pressure will control the weather pattern later Saturday into Sunday. Low pressure and its associated cold front may approach as early as late Sunday, but confidence is higher that this system holds off until Monday. && .MARINE... SCA tonight for most waters in increasing SE flow. Gradient relaxes for most waters before gales become likely on NW flow behind a cold front/remnants of Michael Thu night-Fri. High pressure will build toward the waters Saturday before settling overhead Saturday night and moving offshore Sunday. A Small Craft Advisory may be needed for portions of the waters Saturday. && .TIDES/COASTAL FLOODING... A south to southeast flow will continue around high pressure over the western Atlantic through tonight. A southerly component to the surface wind will continue for Thursday into Thursday evening. The southerly flow will cause elevated water levels during this time. Minor flooding is expected for sensitive areas with the high tide cycle this morning. A Coastal Flood Advisory remains in effect for Anne Arundel, ST Marys, Washington DC and Alexandria. Additional advisories may be needed for tonight as the southerly flow strengthens a little bit. More minor flooding is likely around times of high tide Thursday into Thursday night. A strong offshore flow will develop behind a cold front and also behind the departing tropical system (Michael). Anomalies will drop sharply Friday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until midnight EDT tonight for DCZ001. MD...Coastal Flood Advisory until 10 PM EDT this evening for MDZ014. Coastal Flood Advisory until 7 PM EDT this evening for MDZ017. VA...Coastal Flood Advisory until noon EDT today for VAZ054. WV...None. MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT Thursday for ANZ531>534-537>543. && $$ SYNOPSIS...BJL NEAR TERM...DHOF SHORT TERM...DHOF LONG TERM...BJL AVIATION...BJL/DHOF MARINE...BJL/DHOF TIDES/COASTAL FLOODING...BJL