The National Weather Service in Blacksburg has placed a winter storm watch this morning for much of Southwest Virginia along and west of the Blue Ridge and along and north of the U.S. 460 corridor for the threat of 4-8 inches of snow Wednesday and Wednesday night. The weather service has mentioned the possibility of adding more counties later as the situation develops — Franklin County and Lynchburg city would seem to be the two spots most likely for that. Weather doesn’t precisely follow political boundaries, of course, and so it’s not going to jump from Floyd County over northern Franklin County to southern Bedford County — don’t think there’s no chance of snow, possibly several inches of it, just because you’re a litle outside the current boundary.
Forecast guidance is in large agreement now that a surface low pressure system in the Gulf of Mexico will track northeastward through the Southeast and then up the East Coast, while a strong upper-level low feeds into the system from the west and southwest on Wednesday. As the surface low throws back moisture and the upper low both brings cold air throughout much of the atmosphere and strong lift to squeeze out precipitation, morning mixed precipitation will change to all snow in most areas around the middle of the day, and could be heavy at times into the evening. Snow will start to fall and accumulate at higher elevations first but should make it to all elevations fairly quickly once it starts in earnest. as the pull of cold air from aloft both from the storm dynamics and falling precipitation will be strong.
The weather service is going with 4-8 inches for most locations west of Roanoke (and southwest through Floyd County) and 4-6 inches for the Roanoke Valley, Bedford county and northward, east of I-81. These amounts are pretty close to my initial guesstimate yesterday of 5-9 inches west of I-81 and above 2,000 feet east of I-81, and 3-7 inches east of I-81 to a line from Stuart to Lynchburg. Be aware that there is some forecast model support for larger amounts. The Hydrometeorological Prediction Center has most of the region in a moderate risk of 4-plus inches and a slight to moderate risk of 8-plus inches. I’m not quite ready to go larger yet with the amounts but fully expect that at least some locations somewhere in our region will get double-digit snowfall amounts. Whether that’s isolated areas or a more widespread swath remains to be seen. I will be mointoring the forecast trends.