UPDATE 11:15 AM: Overnight and morning forecast guidance has moved strongly in the direction of increased snow potential for Southwest Virginia and many surrounding regions for Wednesday. I will cover this in more detail in a blog post this evening. The comments section on this blog entry contains many notes from me and other Weather Journal contributors about the potential snow threat. END UPDATE
While a lot of winter weather conversation has understandably shifted to the middle of next week, there is a disturbance sliding southeastward through the Tennessee Valley. The bulk of its energy and moisture will bypass our region to the west and south, but some additional snow may work into the areas west of Interstate 77 and the higher terrain from Grayson County into North Carolina, where winter weather advisories have been issued. The passage of this disturbance will also re-fire the upslope snow machine in West Virginia’s mountains, bleeding eastward at times, on Saturday, so don’t be surprised to see a few flakes fly by in the Roanoke Valley, and a ground-whitening skiff may not be out of the question in parts of the New River Valley if a snow squall parks just right tonight through Saturday night.
As much as you may want to say “Here we go again,” Wednesday’s potential situation is not anything like any winter weather setup that has “gone again” since maybe Christmas 2010. We have not in all that time had any storm system to watch within 5 days that had a solid chance of becoming a powerful East Coast low south of New Jersey that could become a widespread, and, at least potentially, historic winter storm. Model disparity is still pretty wide with respect to the mid-week storm, but there seems to be consensus at least that a deep low is likely to develop somewhere near the coast of the Carolinas or Virginia as a powerful upper-air impulse swings southeastward around an unseasonably cold (though not extremely cold) jet stream trough. So at this point, you could say the general forecast has become more sure, but the specific forecast for particular effects in particular locations is as muddled as ever. Friday’s forecast models specifically for Southwest Virginia for Wednesday’s storm ranged from rain/snow mix with little or no accumulation (GFS) to a moderate snow event of a few inches but much less than that of central and eastern Virginia (Euro — 12Z chart for Wednesday morning posted above) to a pretty solid hit of heavy snow extending even into West Virginia (Canadian, British models). Based on the trough location and likely track of the upper-air impulse, I’m leaning right now to something similar to the Euro, though maybe not as extreme as the Euro, in which the upper-air impulse triggers a period of snow (maybe mixed with rain or sleet for a time) and a few inches (guessing 2-4) of accumulation in Southwest Virginia, followed by a deepening low and heavier accumulations somewhere east or northeast of us. This is barely more than an educated guess, and could easily go way up or down to zilch with later data. The upper-end potential of this winter storm for the Eastern U.S. region is extreme — the Ash Wednesday 1962, and March 1, 1980, coastal storms, which produced large areas of 12-inch+ snow in addition to (especially in ’62) coastal flooding and strong winds, have been mentioned by some weather experts as storms somewhat similar to what is possible next week. (The Roanoke/New River valleys got 9 inches in the 1980 storm and about 6 inches in 1962, with much heavier amounts not far to the east, just for a frame of reference.) If you have travel plans anywhere in the Eastern U.S. from the Carolinas to Maine next week, inland as far west as the Tennessee Valley and eastern Ohio Valley, pay close attention to later forecasts as details on this storm become a little clearer.