Well here’s the little swirl of clouds crossing into Montana that’s going to be cause of a swirl of rumors, mayhem and confusion the next 3 days. This is the “vorticity maximum” or “vort max” or just “vort” that will dive southeastward into the Tennessee Valley and then curve east and northeast in the jet stream flow. As it does that, it will help deepen a surface low-pressure system in North Carolina that will trek eastward on Wednesday. Behind this low, a large area of snow is likely to develop over much of Virginia. The parameters and intensity of that snow area are what are difficult to nail down, and indeed, may not be fully deciphered until the event is ongoing. But we will do our best to keep up with some forecast trends here as they continue to develop (and my schedule allows).
A couple points:
* Forecast guidance on Sunday night generally leans toward snowfall of at least an inch or two, possibly more, maybe much more, occurring in the Roanoke and New River valleys northeastward on Wednesday. Most guidance keeps the heaviest amounts, some possibly topping a foot, along or north of Interstate 64, but some models extend them farther southward. South and west of the valleys — let’s say southwest of a Martinsville to Wytheville to Bluefield line — there appears to be less chance of significant snowfall, but this may change. I think the back edge of the wraparound snow on Wednesday will probably end up on the I-77 corridor.
* There will be two waves of precipitation to watch. The first arrives late Tuesday, mostly as rain, but possibly mixed precipitation. Overnight and early Wednesday, the back edge of this rain shield may change to snow as the upper levels cool and the freezing level lowers in the atmosphere. Later Wednesday, as the low deepens, a large area of snow will wraparound to the west. How far west that area extends varies on the models. This will be where any heavy snow will occur.
* I’m leaning toward this being a significant winter storm with numerous to widespread 4+ inch amounts in much of our region. But I’m still not quite fully convinced. I think it’s very possible that part of our region could get huge snow totals while others get little or nothing, maybe not in the geographic or topographic manner we normally expect.
Below is the weekly snow meter for Roanoke and Blacksburg.
Snow meter 3/4-3/10
(0 to 10 scale of likelihood of 1 inch of snow)
Roanoke — 7 snowflakes *******
Blacksburg — 7 snowflakes *******
Outlook: In the 14th week of 15 in the snow meter season, we finally have an obvious, well-organized winter storm in the first three days of the week. As a strong upper-level storm system dives south of us and a surface low deepens over North Carolina on Wednesday, moderate to heavy snow is likely to develop for several hours in much of Virginia. Forecast guidance on Sunday seems to suggest Northern Virginia will have the best chance of larger amounts, some over a foot possible, with Southwest Virginia’s prospects a bit fuzzy. But my charge here isn’t to guess whether Roanoke and Blacksburg get a foot or get 4 inches of snow this week, but only an inch. I think it’s likely, though not certain, that those two sites do get a least an inch in the upcoming storm system. I would be silly not to go for higher numbers this week after a winter of so many puny, borderline, mixed muck storm systems.
Looking back: Not enough fractions of an inch (0.2 on Thursday morning) for an inch at Blacksburg in a week when I picked six flakes, so the losing streak goes to seven weeks and clinches a losing season there. Meanwhile, I’m within a win of my goal of 10 for Roanoke, with a win this past week for no measurable snow and only picking four flakes. Guessing what minor systems will do five or more days out has proven even more difficult than I thought it would be. Let’s see how I can do with a strong storm only three days out.
Current records: 9-4 for Roanoke, 5-8 for Blacksburg.