A familiar theme of Southwest Virginia’s 2012-13 winter — moisture moving into a wedge of cold air — reprises its oft-repeated role overnight and early Monday, now almost three weeks into meteorological spring and just three days from the end of astronomical winter. Abundant moisture swept ahead of a low-pressure system moving into the Ohio Valley is overrunning cold air nearer the surface. The result is a wintry mix of snow, sleet and cold rain across much of Virginia, with more snow and sleet the farther north and higher up you go, the mountains west of Interstate 81 and north of Interstate 64 likely to again take the brunt. South of there, the closer you are to Interstate 64, especially at higher elevations, the more likely you are to see a few inches of snow/sleet mix overnight and early Monday as cold air continues to bank southwestward against the mountains. Winter weather advisories continue for Craig, Botetourt, Rockbridge, Alleghany and Bath counties, with winter storm warnings farther north. Farther south, the Roanoke and New River valleys, as well as the Blue Ridge south of those valleys, find themselves in the familiar position of riding the razor’s edge between frozen, freezing and unfrozen precipitation, as temperatures overnight drop through the mid 30s to near the freezing mark. Between midnight and 10 a.m., the temperature profile may become cold enough through the bottom mile of the atmosphere to support periods sleet and snow that could accumulate a slushy inch in some spots. Warmer air will be streaming in aloft, and this raises the specter of some freezing rain as well, more likely to collect on trees and exposed objects rather than road surfaces still holding in heat from Saturday’s sunny 70s.
As of this writing at mid-evening Sunday, it appears unlikely Monday morning’s mix will be a major travel problem in the Roanoke and New River valleys and anywhere south, but watch out for some patches of slush, especially in higher elevations. Any snow/sleet accumulation in the Roanoke/New River valleys is likely to be an inch or less, mostly in the grass — unless there is some kind of quirky 2012-13 suprise that would cause it to snow harder, longer. This could also very easily end up as primarily just a cold rain if the air temperature can buoy just above freezing in the lower layers of the atmosphere.
Watch the end of the week — the Thursday-Saturday time frame — for another possible winter event that may involve a lot of moisture and trapped cold air. The rest of March is likely to be one of the coldest late-March periods we’ve seen in many years. More on all this later in the week.