A three-letter word beginning with “I” to describe the weather over Southwest Virginia Friday and Saturday could be “ice” for many … but “ick” might be more fitting. Snow and spring lovers are going to be equally put out riding the boundary between ice and cold rain for 24-36 hours.
The low-pressure system causing a large amount of weather mayhem across the country will be taking a track more or less along the old Route 66 … Texas Panhandle across Oklahoma, then northeast to St. Louis and Chicago. North and west of the low, a large snowstorm will occur, with many spots in Kansas piling up 1-2 feet — welcome news, in the big picture, considering the long-term extreme drought the Plains are suffering. A low getting its kicks on Route 66 is not remotely close to taking a path that would often cause a large winter storm in Southwest Virginia. But sometimes, a southwest-to-northeast moving low farther west like this one doesn’t scour out low-level cold air as efficiently as would a similar low taking a track through the eastern Ohio Valley. The cold air at the surface will be wedged much more strongly than it was on Tuesday. As moisture begins overrunning that cold air late Thursday night or early Friday morning, it will likely begin as period of snow/sleet mix, changing to more of a sleet/freezing rain mix and ultimately rain as temperatures gradually slip above freezing at the surface, generally from southwest to northeast. This will happen at different times in different locations, due to complex topographic factors, so it is possible that some areas will hang on to freezing rain well into Friday morning while others rise above freezing very early. Very generally, locations west and north of Roanoke, and at higher elevations, appear to have the best chance of substantial freezing rain in the first wave. Bent Mountain/Floyd County often seems to be a bullseye for significant ice in most of our freezing rain events. Typically, Roanoke city rises above freezing fairly early in similar situations, but some higher elevations around town get stuck at or below freezing longer. Most of you generally have an idea how your specific location behaves riding the edge of an icy situation … though each situation can present unique challenges that may or may not follow previous norms. The Hydrometeorological Prediction Center has painted most of Southwest Virginia in a slight risk of seeing at least one-quarter inch of ice — generally where tree damage and power-line trouble typically begins — in the 24 hours ending Friday evening.
Unlike with Tuesday morning’s brush of wintry weather, rising above freezing on Friday will mean floating into the mid to upper 30s, low 40s at best, not soaring into the 50s. The wedge of cold air will not break so much as it will modify. This leads us into a second wave of precipitation now expected to overrun the region on Friday night and Saturday morning. Temperatures will be nervously close to the freezing mark to start with, and may edge downward just enough for some locations to see another round of freezing rain. Again, generally speaking, locations north and west of Roanoke have the best chance of significant ice on Friday night and Saturday morning — these regions have been highlighted by the HPC with a slight risk of seeing at least 0.25 inch of ice. This is a rather touchy situation to keep abreast of, as the second wave of precipitation may be wetter than the first, so surface temperatures drifting below the freezing mark could have even more of an adverse impact.
Looking ahead — there will be yet another similar low tracking northwest of us early next week, with some amount of cold-air wedging ahead of it, again. I would not be surprised if there were another period of ice or sleet for some with this storm, but its track and the prevailing pattern make it unlikely to be a larger winter storm in Southwest Virginia. Down the road, however, the first week of March holds considerable interest for winter storm potential. It appears that high pressure building west over the North Atlantic into eastern Canada will trap a large bubble of colder than normal air over the southern and eastern U.S., further pumped into by building high pressure near the West Coast. This NAO-/PNA+ pattern may provide one or more shots at a significant winter storm developing somewhere over the southern or eastern U.S., depending on timing of various disturbances or shortwaves moving around the West Coast high and then under the East Coast trough. It’s impossible to say yet whether there is a large snow waiting on us shortly after the onset of “meteorological spring” on March 1, but it does appear very strongly that “winter is over” declarations that have been echoing off and on for weeks are grossly premature.