Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 121332 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 932 AM EDT Thu Oct 12 2017 .SYNOPSIS... High pressure is positioned over Quebec while a warm front is draped along the Mason-Dixon Line. The high will slowly drift eastward while the front moves to the south. A cold front will push into the Mid Atlantic Sunday night followed by a return to high pressure early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure over New England will extend south toward our area through this afternoon. An onshore flow has allowed for low- level moisture to be trapped underneath the subsidence inversion...resulting in low clouds along with patchy drizzle/light rain this morning. Upper-level ridging will increase a bit this afternoon while a trough digs into the western CONUS. This will allow for the low-level flow to veer toward the southeast...causing warm and moist air to overrun the surface cool air in place. Therefore...light rain and drizzle are likely to increase in coverage...especially for locations along and east of the Blue Ridge Mountains into the eastern Panhandle of West Virginia and western Maryland. This is where there will be an upslope component to the low-level flow. Areas of light rain/drizzle are possible over the Shenandoah Valley as well but coverage may not be as widespread this afternoon due to a downslope flow off the Blue Ridge Mountains. A few breaks of sunshine are possible across these areas as well but most of the day will be cloudy. Max temps will hold in the 60s for most locations. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... Because of the position of the high to the northeast don`t expect to see much of the sun in the short term. Mid Atlantic will continue to experience plenty of trapped moisture in the form of low clouds. Some improvement may be possible by late Saturday, although history has shown that clearing may have to wait until Sunday when the cold front from the west draws closer. In spite of the cloud cover much of the time it will be dry, only light rain and drizzle will be possible. Highs 65-70 Friday, mid 70s Saturday. Lows in the mid 50s. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Strong mid-upper level ridge over the southeast and southern mid-Atlantic will move east on Sun as a strong shortwave-trough moves across the Great Lks Sun into Mon. An associated cdfnt will cross the area Sun evening with sct showers along and just behind frontal passage. Cool fall weather will follow in its wake as high pressure from the northern Rockies builds southeastward. Highs will be generally in the 60s and lows in the 40s all of next week. && .AVIATION /13Z THURSDAY THROUGH MONDAY/... Extensive cloud cover expected today through Saturday. Today/tonight will see ceilings at IFR/low MVFR levels. This may continue at least at MVFR levels through Friday with some improvement possible Saturday. Cdfnt will be crossing the area Sun evening with a few showers expected. && .MARINE... SCA in effect for all waters today/this evening due to easterly winds, continuing tonight for the lower Potomac and Bay south of Pooles Island. Small craft advzy conditions likely Sun into Tue. && .TIDES/COASTAL FLOODING... Water levels are expected to rise later today everywhere due to onshore flow with minor coastal flooding at most locations for the next several days. && .EQUIPMENT... The NWS 88D Sterling radar (KLWX) will be down during the day from 7 AM through 5 PM through Saturday this week. This is for nationally scheduled maintenance on the radome. Our surrounding 88D radars as well as FAA terminal radars will be operational during this downtime. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory from 6 PM this evening to midnight EDT tonight for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ531>534-537- 539>541-543. Small Craft Advisory until midnight EDT tonight for ANZ530-535- 536-538-542. && $$ PRODUCTS...BJL/WOODY!/LFR

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