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UPDATE, 7:30 AM, 1/5/2024: The previous winter storm watch has been upgraded to a warning for localities along the Blue Ridge — Carroll, Patrick, Floyd, Franklin, Roanoke, Bedford, Botetourt, Amherst and Rockbridge counties, plus cities of Roanoke, Salem, Lexington and Buena Vista — with a winter weather advisory for many surrounding counties. The primary concern within the winter storm warning is the potential for damaging ice accretion on trees and power lines possibly exceeding 1/4 inch mainly in higher elevations, especially above those above 2,500 feet above sea level. A mix of snow, sleet and freezing rain is expected to spread across the region in the pre-dawn hours Saturday, becoming mostly freezing rain by mid-morning and then transition to cold but above-freezing “plain” rain in most locations across Southwest and Southside VIrginia by midday. Locations to the north nearer Interstate 64 and higher elevations along the Blue Ridge may hold on to colder air longer, allowing more accumulation of wintry precipitation types. Most of the precipitation should be over by sundown. Keep in mind on Saturday that there may be great variance in impacts across our region due to elevation, topography and minor differences in temperature, so wet roads or no apparent icing on trees at one location may not be indicative of what is occurring a few miles down the road. END UPDATE
A stripe of counties in the middle of Cardinal News’ coverage area has been placed under a winter storm watch from late Friday night through Saturday afternoon, as a mixture of freezing rain, sleet and snow is expected to cause travel problems and possibly scattered power outages.
Other than Grayson County for a narrow stripe of heavy snow on Feb. 12 last winter, this marks the first winter storm watch or warning issued by the National Weather Service for Southwest and Southside Virginia in almost two years.
Up to 2 inches of snow and sleet accumulation — less than 1 inch for most locations — followed by around two-tenths of ice accretion from freezing rain are expected in the winter storm watch area, which includes, from south to north, Carroll, Grayson, Patrick, Floyd, Franklin, Giles, Montgomery, Roanoke, Bedford, Craig, Botetourt, Amherst, Alleghany and Rockbridge counties plus the cities of Galax, Roanoke, Salem, Lexington, Buena Vista and Covington. The stripe of counties connects to winter storm watches in northwest North Carolina, for wintry mix and ice, and to those covering northwest Virginia from Shenandoah National Park to the West Virginia state line, where more snow is expected than in our region.
Locations both east and west of the winter storm watch are also expected to see a wintry mix on Saturday morning, but in lesser amounts before changing to rain. Winter weather advisories may eventually be issued for many of those localities, while areas now under a winter storm watch will likely receive either a winter storm warning or a winter weather advisory as later forecasts refine the extent of the wintry precipitation event.
A low-pressure system tracking northeastward just south of our region will spread moisture into marginally cold air on Saturday morning, leading to a mix of precipitation. Most locations will start as snow, sleet or a mixture of the two, but as milder air moves in aloft, precipitation will change to freezing rain, remaining liquid through the atmosphere until freezing on objects at the surface. By late morning, many locations, especially east of the Blue Ridge and south of U.S. 460 (Roanoke to Lynchburg to Farmville), will change to rain as temperatures rise above freezing.
It is the ice portion of the storm that has pushed it to a winter storm watch, as ice accretion of ¼ inch is typically considered sufficient for a winter storm warning. The current forecast for near two-tenths of an inch of ice accretion is very close to this mark and may be increased in some areas under the winter storm watch. Ice accretion of ¼ inch is generally considered the point at which damage to tree limbs and the expectation of at least scattered power outages begin.
Ice accretion is often uneven based on terrain and small changes in localized temperature, so it is possible some areas could receive heavy ice while others warm above freezing sooner and see very little.
Many streets will retain warmth from a thus-far fairly mild winter, so widespread icing of roads may not develop, but there may be some colder higher-elevation areas, shaded valleys and particularly bridges and overpasses where ice develops more quickly on roadways.
A slightly colder atmosphere aloft than expected could lead to more widespread or longer lasting sleet and snow to begin precipitation, reducing ice hazards on trees and power lines but collecting somewhat faster on road surfaces, while slightly warmer conditions aloft and/or at the surface could lead to temperatures rising above freezing more quickly in some areas, reducing the ice threat.
Whatever falls Saturday will not last long as temperatures reach the 40s to lower 50s by Sunday afternoon. Additional wintry precipitation is possible early Tuesday before warmth surges in to change all precipitation to rain, which could become quite heavy by Tuesday afternoon as the next storm system approaches.
Journalist Kevin Myatt has been writing about weather for 20 years. His weekly column, appearing on Wednesdays, is sponsored by Oakey’s, a family-run, locally owned funeral home with locations throughout the Roanoke Valley.
