With back-to-back mornings at or below freezing at Blacksburg (32 on Sunday, 31 on Monday), Roanoke’s coldest low on Monday since mid-May (36), a 25 low at Southwest Virginia icebox Burkes Garden in Tazewell County and several reports of frost each of the last two mornings across Southwest Virginia, there’s no doubt we have entered the cold season. That is only going to be reinforced over the next 4 days or so. A cold front pushing through Tuesday will mark the leading edge of the colder regime that builds in toward the latter part of the week. Highs will struggle to get past 60 on Tuesday, struggle to make 50 on Wednesday, probably won’t make 50 on Thursday (maybe not even 40 for a few spots west of Roanoke) and lows will be back in the 30s by Wednesday morning and gradually getting colder through the rest of the week. A region-wide freeze is possible by Saturday morning, and maybe a hard freeze (28 degrees for 3 hours or more) at many locations west of Roanoke. A few showers may be possible with the frontal passage late Tuesday, and by late Wednesday, snow showers may develop from upslope northwest winds over the Appalachians, mostly in West Virginia, though a few flakes may blow into the Old Dominion as well.
On or near Thursday evening, an upper-level disturbance with a weak surface reflection is expected to move near or just south of our region. Each of the major forecast models now show this occurring to one degree or another. It won’t have a lot of moisture to work with, but may kick up some showers as it passes by (the green at left). With the freezing line about a mile up (the blue line at left, as depicted on the Canadian forecast model) sinking well to our south, there would be a good chance that at least some of what falls would be snow, especially at higher elevations. The boundary layer — the layer of the air near the surface — may hold just enough daytime warmth to melt snow showers into rain at lower elevations, at least to start. If the precipitation continued for a few hours, there could well be a few flakes of snow even into the lowest elevations of Southwest Virginia. At this point, this is just something fun for snow lovers in Southwest Virginia to keep an eye out for, with just about zero chance of any kind of really substantial winter event. Some ground-whitening snow may be possible at higher elevations west of I-77, along the Virginia-West Virginia line (think Potts Mountain, Salt Pond Mountain where Mountain Lake is) and, of course, in West Virginia’s high country. Those areas will not only get effects from a couple of upper-air disturbances, but ongoing upslope effects from northwest wind flow for a couple of days.
One factor is missing to keep this cold blast in place more than just a few days — no really solid blocking high near Greenland remaining in place. So temperatures will moderate by next week, though there probably will be additional cold shots in the next couple of weeks.