Pictured at left, and big version linked here, silvery ice-covered trees against newly cleared blue skies in south Roanoke County.
UPDATE 1:30 PM: Winter weather advisories are canceled south of the Interstate 64 corridor, including the Roanoke and New River valleys. They continue for Alleghany, Rockbridge and Bath counties northward. Click here for latest advisories from the National Weather Service in Blacksburg. END UPDATE
UPDATE 12:20 PM: The sharply defined back edge of the precipitation shield is pushing through Roanoke, having cleared the New River Valley. Sunshine is even being reported behind the edge of the precipitation. This will end the bulk of wintry weather today, and should allow for improvement on area roads during the afternoon. END UPDATE
UPDATE 11 AM: There are several reports of rain/freezing rain/sleet changing to snow on the backside of the precipitation shield in the I-77 corridor and the western New River Valley. This may advance eastward through the New River and Roanoke valleys over the next few hours, adding to a winter weather event that is already exceeding most expectations. Slushy, icy roads are possible anywhere in Southwest Virginia today. END UPDATE
UPDATE 3:30 AM: Winter weather advisory replaces freezing rain advisory for most of Roanoke/New River valleys, taking into account snow/sleet mix that has been occurring, with freezing rain advisory expanded southward to North Carolina state line. Click here for latest advisories from National Weather Service-Blacksburg. END UPDATE
UPDATE 2:35 AM, 12/26: Snow and sleet are being reported in parts of the Roanoke and New River valleys, as temperatures have cooled just enough above the surface, and are above freezing for a thin enough layer at the surface, to allow some snow to reach the surface. At this time, thin slushy accumulation on grass and exposed objects is all that is expected — but we’ll see just how long it can last. END UPDATE
The image from the European model a few days ago that showed cold air trapped over western Virginia with a strong low-pressure system approaching from the southwest spreading moisture into it looks like it will prove not to be so far off, after all. Colder, relatively drier air is funneling southward along the eastern slopes of the Appalachians tonight as moisture from the extremely dynamic low over the south-central U.S. begins to stream in. The result will be temperatures dropping to near freezing as precipitation develops, leading to a confusing mosaic of precipitation types on Wednesday morning across western Virginia. Winter storm warnings are out for the I-64 corridor (Rockbridge, Alleghany counties) and northward, where a mix of snow, sleet and freezing rain could produce an inch or two of crunchy muck — with maybe as much as 4 inches in some spots that can say snow longest. Farther south, through the Roanoke Valley, as far south as Floyd, Pulaski and Montgomery counties, there are freezing rain advisories for patchy ice developing. With temperatures flirting right at the freezing mark, who gets ice and who doesn’t may vary over just a few miles or a few hundred feet of elevation — and how that evolves could even vary from place to place, with higher elevations more easily reaching freezing generally, but deeper rural valleys often trapping colder air in for longer. We’ve had a mild December and even some low 50s on this Christmas Day, so road surfaces are not likely to support solid ice on streets and sidewalks, but there could be patchy ice in more shaded spots, on bridges and overpasses, etc. Trees and exposed objects will develop ice much more easily, where it is 32 or lower with rain. Some sleet is likely in the Roanoke and New River valleys, and a few wet snowflakes aren’t out of the question either — if either sleet or snow gets heavy enough for several minutes, we could see some white grass at least in spots. As the day goes along, slightly milder temperatures will likely change things over to mostly rain, at least south of I-64 — but cold air sometimes stubbornly remains in protected rural valleys, so ice may linger longer in some areas. There can always be surprises just about anywhere in this kind of borderline winter weather situation, so we’ll just have to monitor how it develops on Wednesday morning.
Rainfall amounts of near to somewhat over an inch are still projected. As the low goes by, cold northwest winds late Wednesday into Thursday will start another round of upslope snow showers.
New storm systems are expected to arrive Saturday and again about the middle of next week, which will be the start of the new year. The system on Saturday, once again, looks to be just cold enough, and likely to take a track far enough inland, for another murky snow/ice/rain setup, while the one near the middle of next week is just too far out to say much about. I will venture this much: The chance of frozen precipitation in western Virginia seems to be increasing with each subsequent system.