Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190133 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 933 PM EDT Fri Aug 18 2017 .SYNOPSIS... A cold front will cross the region tonight. Surface high pressure will build in Saturday, but an upper level disturbance will cross the region Saturday night. A warm front will advance back north across the region early next week, followed by a strong cold front in the middle of the week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Heat Advisory, Severe Thunderstorm Watch, and Flash Flood Watch have all been cancelled. The line of thunderstorms that developed along a prefrontal trough and ahead of a shortwave trough aloft is now moving into southeast Virginia and the Eastern Shore. The surface cold front is now moving into western Maryland and the eastern West Virginia panhandle. Ahead of it, some elevated instability remains, so have left a slight chance of showers in the forecast for several more hours. A couple of showers recently formed near Hagerstown. The front will slowly push through the area tonight, but moisture will be slow to dwindle until it does. Have left patchy fog in the forecast, though have low confidence in its occurrence, particularly since mid level clouds seem to be forming in the frontal zone. Lows will be a bit cooler than last night, with 60s and low 70s expected. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... Other than patchy fog, Saturday should start out tranquil with some sun. Humidity will be lower, though temperatures will only be a few degrees less than today. However, potent upper level trough will move into the region late in the day and at night, and it appears enough moisture will remain to result in isolated showers and t-storms late in the day into the evening. High pressure dominates Sunday for the most part, with temperatures expected to drop a bit further once again - the most comfortable day of the weekend. However, warm front will start poking back north late in the day and at night, and that may result in a return risk of showers in central VA. && .LONG TERM /MONDAY THROUGH FRIDAY/... High pressure will move offshore Monday and settle into Tuesday, allowing for southerly flow to settle over our area. Moisture advection could enhance diurnally driven showers and thunderstorms Monday and Tuesday afternoon/evening. An upper trough and strong cold front will approach from the northwest on Tuesday night into Wednesday, bringing additional chance of showers and thunderstorms on Wednesday. The front should move across on Wednesday night with a high pressure returning Thursday into Friday. High temperatures Monday through Wednesday will be in the mid to upper 80s in Northern Maryland... to low 90s in Central Virginia at times... and 70s at higher elevations... highs in the 70s and 80s Thursday and Friday. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... The threat for thunderstorms has ended, though can`t totally rule out a rogue shower until frontal passage. The front is in western Maryland this evening and will progress east overnight. Have limited BR mention to CHO, where front will take longest to clear...although overall confidence in any fog is low. Otherwise, expecting VFR Saturday, though an isolated shower or t-storm is possible late. Mainly VFR again Sunday with high pressure dominant. VFR conditions expected Monday into Wednesday, with periods of sub-VFR conditions mainly Monday and Tuesday afternoon/evening and Wednesday due to possible showers and thunderstorms. && .MARINE... Line of storms will continue to move east of the middle Bay through late evening, ending the threat for Special Marine Warnings. There is a lull in winds behind the storms, but northerly channeling will be possible overnight as the actual cold front passes, so SCA continues for main channel until early morning. For balance of Saturday, should be sub SCA, but an isolated gusty t-storm is possible late in the day as an upper trough moves on through. Returning to tranquil conditions Sunday. Mainly dry conditions expected Monday into Wednesday, with periods of showers and thunderstorms possibly developing Monday and Tuesday afternoon/evening and Wednesday. Wind gusts are expected to stay below the small craft advisory threshold. && .TIDES/COASTAL FLOODING... Southerly flow will continue to cause elevated water levels through tonight. CFA for St. Mary`s through tonight. Most concern for an additional advisory is at Annapolis, but want to see how water recovers after sloshing from thunderstorms. Will keep an eye on DC and Baltimore as well. Cold front crossing late tonight will bring NW/N winds and decreasing water levels. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 3 AM EDT Saturday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory until 9 AM EDT Saturday for ANZ531>534- 537-539>541-543. Small Craft Advisory until 1 AM EDT Saturday for ANZ530-535- 536-538-542. && $$ SYNOPSIS...RCM NEAR TERM...ADS/RCM SHORT TERM...RCM LONG TERM...IMR AVIATION...ADS/IMR/RCM MARINE...ADS/IMR/RCM TIDES/COASTAL FLOODING...ADS/RCM is the U.S. government's official web portal to all federal, state and local government web resources and services.