Area Forecast Discussion
Issued by NWS Sterling, VA

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872 FXUS61 KLWX 171638 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1138 AM EST Wed Jan 17 2018 .SYNOPSIS... A cold front will cross the area early today. High pressure will build into the area later today, then shift south and east of the region later this week into the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1130 AM UPDATE: Have dropped the remainder of the Winter Weather Advisory as accumulating snow has ended and drier air continues to move in. A few flurries or spotty light snow will remain possible into this afternoon across southern Maryland into parts of central Virginia, but additional accumulation is not expected. 855 AM UPDATE: Extended the Winter Weather Advisory for Stafford and King George Counties until noon as steady light snow continues in these areas. Elsewhere, have dropped the headlines as accumulating snow is ending. A few flurries will remain possible as a left exit region of the upper jet crosses through about noon, but little or no additional impactful accumulation is expected. Gusty northwest winds will bring in colder temperatures but also drier air, which should allow many surface to dry out during the day. Previous discussion... Surface cold front is pushing across the Mid-Atlantic this morning while an upper level trough is located west of the Appalachians. The best moisture within the frontal zone is just arriving, but with that said, forcing is weak in our CWA. Expect intermittent light snow to continue to progress south and eastward through the early morning hours. It`s still looking like most areas will receive less than an inch, although locally slippery roads will be possible. Will make adjustments to the advisory based on observational trends. We`ll have to watch what, if any, banding develops across central Virginia to perhaps southern Maryland in the left exit region of an approaching jet max. It`s possible snow could linger well into the afternoon in these locations. Basically, our CWA will be right near the gradient of what will be a decent snow event south/west of Richmond. To the northwest, skies will gradually clear, and it will become a bit blustery with wind gusts up to 25 mph or so. Calendar day high temperatures may have already occurred in some locations. Daytime temperatures will hold fairly steady in the mid 20s to lower 30s, with teens in the higher elevations. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... As the upper level trough pushes east tonight, low pressure will develop off the Carolina coast. So the pressure gradient will remain fairly tight with cold air advection continuing. Low temperatures will be in the teens for most, with around 20 in the cities and single digits in the higher elevations. While it seems the highest winds will remain above an inversion, limiting wind advisory potential on the ridges, there will still be enough wind to cause wind chills to potentially drop below -10 at the highest elevations. A wind chill advisory has been issued for Highland, Pendleton, and western Grant Counties. Expect single digit wind chills across the rest of the CWA. Heights will begin rising Thursday with the airmass moderating due to warm advection aloft and downsloping westerly flow. There will still be a bit of a breeze, but highs will range from the mid 30s to mid 40s. High pressure will remain to the southwest on Thursday night, so decoupling will likely be localized. Teens will be possible in these areas with 20s elsewhere. A weak upper level trough will be passing early Friday but should have minimal impacts other than a few extra clouds. Otherwise high pressure will be building south of the area and winds will be turning south of west. Further warming will occur, with high temperatures in the 40s to around 50, and Friday night lows in the mid 20s to lower 30s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... High pressure will settle to the south of the region over the weekend, allowing a milder flow of air from the southwest to dominate. A warm front lifting to the north to the west of the region may bring clouds to the area, and some showers are possible in the westernmost portion of the region along the ridges, but further east it looks fairly dry. Highs will reach the 50s, with lows in the 30s and 40s. High pressure will slide east off the coast on Monday as a cold front approaches from the west. Showers look likely to stay west early on Monday, but should move east across the region later in the day and at night as the cold front crosses the area. Highs will reach the 50s again. Cooler air will move into the region behind the system on Tuesday, with a decreasing chance of rain as high pressure builds back into the region. Highs will be in the 30s and 40s. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... VFR has returned to all terminals. Expect continued clearing through the afternoon. Northwest winds will continue to gust to around 25 kt this afternoon. No cig/vsby issues are expected through Friday as high pressure builds south of the area. West winds could gust to around 20 kt on Thursday, with lighter southwest winds by Friday. Generally VFR over the weekend as high pressure to the south dominates. && .MARINE... Northwest winds have been established behind a cold front this morning. SCA conditions will commence shortly, with gusts of 25 kt possible through the day and perhaps through the evening. Have still allowed the SCA to drop at midnight on the narrower waterways where there will be some decoupling, but it`s quite possible sporadic 20 kt gusts continue through the night. It may be a little more marginal on Thursday, but there does seem to be enough potential for 20 kt gusts to include all waters in a SCA until 4 PM. High pressure will build south of the area on Friday, with winds becoming southwesterly around 10 kt. Winds will mostly stay below SCA over the weekend with a southwest flow on the north side of high pressure. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...Wind Chill Advisory from 7 PM this evening to 9 AM EST Thursday for VAZ503-504. WV...Wind Chill Advisory from 7 PM this evening to 9 AM EST Thursday for WVZ501-505-506. MARINE...Small Craft Advisory until midnight EST tonight for ANZ530-531- 535-536-538>540-542. Small Craft Advisory from 8 AM to 4 PM EST Thursday for ANZ530- 531-535-536-538>540-542. Small Craft Advisory until 4 PM EST Thursday for ANZ532>534- 537-541-543. && $$ SYNOPSIS...RCM NEAR TERM...ADS/DHOF SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/RCM/DHOF MARINE...ADS/RCM

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