... Low pressure will pass to the south tonight. High pressure will return late Thursday through Saturday before another area of low pressure affects the region Sunday into Monday.
NEAR TERM /THROUGH THURSDAY/... The clouds are slowly but surely breaking apart. A mix of sun and clouds is anticipated through this afternoon as high pressure briefly noses toward the area from the Ohio River Valley, but the clouds will increase again this evening ahead of low pressure approaching from the Tennessee River Valley. This area of low pressure will move off the South Carolina coast by Thursday morning.
Although this surface low track is displaced well to our south, the parent upper-level trough forcing it will clip our area overnight into early Thursday morning. With cold temperatures through the atmosphere, precipitation will be mainly snow, and accumulating snow (albeit relatively light) is most likely along the Allegheny Front south of Canaan Valley, and across the foothills and surrounding valley/piedmont areas of west- central Virginia near and south of the I-64 corridor. A light coating of snow is possible during the Thursday morning commute for the far southern Washington DC suburbs, which could cause slippery roads and sidewalks. A few flurries may make it as far north as US-50, as well as areas along and west of the Allegheny Front north of Canaan Valley, but accumulation is not anticipated.
Some guidance has advisory-level snowfall (around 2 inches) along the Blue Ridge Mountains and atop Shenandoah Mountain, but the northwesterly flow (which is typically dry) plus the quick nature of the system have precluded the issuance of any Winter Weather Advisories for the time being.
Conditions will clear by mid morning Thursday, but it will be quite chilly despite the increased sunshine. Strong cold air advection will result in high temperatures generally in the 30s, and when coupled with wind gusts of 30 to 40 mph, wind chill temperatures likely hold in the 20s all day.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... The storm will only slowly move away Thursday night through Friday night, with gusty winds only slowly diminishing through this time. Cold air from Canada will also advect south across the region, with the potential for some of the coldest days and nights we've had so far this winter, though with the lack of real cold so far this year, this isn't really saying much. Widespread temperatures into the teens would have normally happened by now, and may at the end of this week, but haven't happened yet, so it could be the coldest of the season so far. Otherwise, dry conditions should prevail.
LONG TERM /SATURDAY THROUGH TUESDAY/... High pressure overhead will keep us dry and chilly Saturday. As the northern fringe of this high departs toward the northeast, the southern half will wedge along the eastern slopes of the Appalachians. This will likely keep cold air in place ahead of a developing low pressure system that could bring us a mix of rain and snow or all snow later in the weekend. Clouds will increase Saturday night before thickening with precipitation arriving Sunday.
As of now, the precipitation looks to arrive as some light snow late Saturday night into early Sunday from southwest to northeast. As an easterly flow increases ahead of the main storm system, we throw a factor of rain into the precipitation type mixture. By late Sunday evening and continuing Sunday night and through midday Monday, the easterly flow gradually becomes more northerly. This is due to a coastal low pressure system forming near the Outer Banks and intensifying as it moves toward the northeast.
By Monday night and into Tuesday, precipitation should taper off and end slowly from west to east as the coastal low moves away and high pressure becomes reestablished in the region. Temperatures will be near average during the lifetime of the storm system.