Area Forecast Discussion
Issued by NWS Sterling, VA

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579 FXUS61 KLWX 191420 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1020 AM EDT THU MAY 19 2016 .SYNOPSIS... High pressure will build through Friday morning. Low pressure will approach the area Friday night from the Tennessee Valley and track to our south Saturday. High pressure will build overhead early next week...but an upper-level low will remain close by just off the Mid-Atlantic coast. && .NEAR TERM /THROUGH TONIGHT/... Stratus across the southeastern 4/5 of the CWA with cu developing in the nwrn sector that has cleared this morning. mixing across the area reduces cloud cover, but stratocu will develop in its place under subsidence. expect mostly cloudy to cloudy skies through the rest of the day. Conditions tonight will be favorable for fog development due to moist ground, light winds and clear skies. will continue to monitor areas that may see dense fog, continued patchy fog for now. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Dense high clouds will start advancing northeastward rather quickly ahead of low pressure over the TN valley Fri. Combo of height falls, moisture advection over cool air mass will lead to rain Fri night into Sat. Models continue to show a faster and weaker trend of upper trough crossing the area Sat. This leads to an earlier end of the steady rains Sat with lighter amounts of 1 to 1.5 inches total with heaviest over the southern portions of the CWA. At this time, flooding appears unlikely. Low pressure exits the area Sat night with mid-levels drying out, but additional shortwave-energy moving across the area as longwave pattern amplifies will keep the chance of showers in the fcst. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... The long term forecast will largely be influenced by a closed upper low. This low will form Sunday as a shortwave trough rotates into the mean troughing along the east coast after the departing coastal low on Saturday. Therefore expect a chance of showers on Sunday, particularly during the afternoon. Shower chances are a little more uncertain for Monday and Tuesday, depending on the location of the upper low and the placement of embedded vorticity maxima. The 00Z operational guidance doesn`t suggest any additional surface low development, which would point to light, showery activity focused on diurnal heating. Wednesday will have the best chance of being dry as the upper low pulls away far enough to have high pressure from the west to be the dominant influence. While temperatures (especially highs) will likely remain below normal due to the upper low, current layer RH forecasts suggest some breaks in the clouds will be possible. Thus temperatures should be closer to the 70F mark than some of our recent unsettled periods. Will have to watch Monday though, as low level flow will be from the NE. Assuming the low can move to the east by Wednesday, there is plenty of warm air available to spread eastward from the Plains. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... vfr conds through this evening with light north winds becoming variable this afternoon. Skies clear tonight which may cause fog development given wet soils and light winds...will continue to monitor this threat. Rain moves in after 00Z Sat and spreads northeast by 12z Sat. Mvfr/ifr cigs expected Fri night through Sat. Improving cigs Sat night. Widespread aviation impacts are not expected Sunday into Monday, although scattered showers will be possible at times due to upper level low pressure (highest chance Sunday). There is a chance sub- VFR clouds could develop Monday in NE flow. && .MARINE... North winds 5-10 kt expected rest of the morning. Variable flow less than 10 kt through Fri night. Winds strengthen Sat through Sun with small craft advisory conditions likely. Gusts to 30 kt possible. A trough axis will pass through on Sunday, and northerly winds may reach SCA criteria. The pressure gradient should relax enough Sunday night into Monday to keep NE winds in the 10-15 kt range. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BAJ/LFR NEAR TERM...BAJ/LFR SHORT TERM...LFR LONG TERM...ADS AVIATION...BAJ/ADS/LFR MARINE...BAJ/ADS/LFR is the U.S. government's official web portal to all federal, state and local government web resources and services.