The first full day of spring never saw the freezing mark at Blacksburg — 30, recorded at 1 a.m., was the coldest high for the date (previous March 21 record 31 in 1996) and also tied for the second coldest high on record for an astronomical spring day (tied April 7, 1982, with record of 29 on March 31, 1964.) Roanoke’s high of 37 (12:13 a.m.) was 2 degrees above the daily record of 35 set in 1914. Snow squalls combined with the arrival of the extremely cold air relative to the season led to some slick roads in parts of the New River Valley this morning. Lows in the upper teens to low 20s likely won’t set records tonight (if it gets a little colder, Blacksburg’s March 22 record of 15 from 1986 could be pushed), but will be about 15 degrees below normal. Temperatures will slowly moderate the next couple of days, but won’t get close to the mid to upper 50s that are normal for late March.
While the spring cold snap — which shows no signs of relenting significantly through the end of the month and perhaps into early April — is a significant to historic event in its own right, much more attention is being focused on whether or not Southwest Virginia reaps an infrequent widespread spring snowfall out of this unusual weather pattern. The approaching weekend storm system has some similarities in its expected general evolution to the one that affected Virginia with rain and heavy snow on March 5-6, with an inland storm to our west transferring energy to a coastal storm, what in weather geek talk is often called a “Miller B.” That storm left heavy amounts of snow — 10-20 inches — on much of the state from I-64 northward and along the Blue Ridge westward, but dropped lighter amounts in our region — 2-5 inches in the Roanoke Valley and just north, less than that in the New River Valley, zero to the south. Here are the important differences. (1) The overall pattern is much colder, even though it shouldn’t be climatologically three weeks later, because of the extreme high pressure blocking over Greenland and the North Pole. (2) The inland low is expected to be farther south, tracking east or northeast through the Tennessee River Valley,r ather than diving southeast through the Ohio Valley as on March 5-6. (3) The coastal low is expected to organize farther south, off the Carolinas, rather than off of the Virginia capes. (4) The storm appears to be not quite as wet as the March 5-6 storm. (5) The coastal storm is not expected to become as deep as the March 5-6 storm. Add these factors up, and the first three in particular lean a little more to snow for Southwest Virginia than March 5-6 ended up being. There will likely be a “front-end thump” of precipitation as the inland low throws Gulf of Mexico moisture into cold air. This may happen in the morning hours Sunday, which would mean the entire night would have allowed the air to cool from Saturday afternoon highs projected by the weather service in the 40s to low 50s, and most forecast models do show cold enough air to support snow wedging as far south as the Virginia-North Carolina border. It’s possible some residual warmth near the surface could limit the snowfall in lower elevations, and the higher spring sun angle is often a factor during daylight hours when precipitation is not especially heavy, so many forecasts will reflect a possible mix of snow, sleet and rain. Later, as the coastal low takes over, a back-end “deformation zone” of snow behind that low is likely to spread over the region late Sunday afternoon into Sunday night, perhaps even Monday morning. In between, there may be a lull in the precipitation, or even some light rain or sleet.
So here is the takeaway: It is probably going to snow Sunday, at least some. There will be some fine-tuning of details to determine a reasonable guess as to how much at any given location. On the upper end, I think it’s possible there could be a widespread 4+ event — so does NOAA’s Weather Prediction Center. It would be the first such event in spring since March 30, 2003. On the low end, it could just be some slushy snow giving way to rain/sleet/snow/ick mix, or the other way around, the ick mix giving way to a little wet snow at the end. I think it’s going to be difficult for the region to entirely miss snowflakes, but questions about the duration, intensity and surface temperatures leave accumulation projections very much in flux. My thinking now is toward the middle, a 2-5-inch type snow in the Roanoke and New River valleys, mixed with some sleet and maybe rain at times in the early to middle part of the event. Even that would be a notable event for late March. The higher up you are in elevation, and the farther north and west of Roanoke, the better chance of seeing several inches of snow Sunday into Monday; the reverse is true headed lower in elevation and south and east, though I think just about everyone sees flakes for some period of time.
There may be another system with snow potential around the March 31-April 2 period. Too far out to say that for sure, but a Palm Sunday/Easter doubleheader for snow would be some way to start spring after such a quirky winter.