UPDATE 12:30 PM, 11/18: Cold air wedge will keep abnormal November chill going, maybe lead to patchy drizzle/isolated freezing drizzle Sunday/Monday
UPDATE 12:30 PM: With a little more sunshine today than first thought, we may see temperatures higher in the 50s than expected. But the cool, damp wedge will likely build back tonight and Monday. END UPDATE
All but 4 of the first 17 days of November at Roanoke, and all but 3 at Blacksburg, have averaged below normal in temperature, as did the last 3 in October at Roanoke and last 4 at Blacksburg. This will be reinforced the next couple of days, as our region is put in the squeeze play between high pressure near Maine and a developing low-pressure system off the Southeast U.S. coast. The resulting east to northeast surface winds will bank chilly, damp air against the mountains, leading to low clouds, some fog and possibly even light drizzle at times late tonight through Monday in the familiar “wedge” or cold-air damming effect we often see. As is typical, locations west of I-77 won’t be affected as much, and will see more sunshine the next couple of days, and even parts of the New River Valley may see a few more breaks in the clouds that the Roanoke Valley or Blue Ridge and points east are likely to. Normals this time of year run upper 50s highs/upper 30s lows at Roanoke and mid 50s highs/lower 30s lows at Blacksburg. With cloud cover thickening, lows won’t be far off those norms, maybe even a tiny bit warmer, but highs will likely fall several degrees short. Highs may struggle to reach 50 in both Roanoke and Blacksburg on Sunday and Monday. There is a chance that a few patches of drizzle may occur in localized spots where temperatures reach the freezing mark or a little below early Sunday, especially in higher elevations along the Blue Ridge. So be careful when driving on Sunday morning, especially on bridges and overpasses at those higher elevations. It won’t amount to much or last long, but all it takes is one patch of ice driven over in the wrong manner to cause a lot of mayhem.
The low itself will stay offshore, with the coast of the Carolinas most affected by wind, some heavy squalls and more beach erosion from lapping waves. The cold air being wedged against the mountains is very shallow — neither the depth of cold air nor the depth of moisture will be supportive of snow. This setup will only slowly unwind, but milder air is likely to arrive by Thanksgiving into next weekend, with widespread 60s probable. A weak disturbance may trigger a few showers on Tuesday, but certainly not much. Thanksgiving Week looks to have relatively quiet weather in most of the East, but remain rather chilly early on.