Something I will draw attention to again during the winter season is the National Weather Service’s experimental change in the wording for winter weather advisories. Blacksburg is one of several weather service offices in the northern and eastern U.S. participating in the project to gather input. Linked here, you can see side by side wording on the current advisory/warning system and the proposed change in wording. You can offer comments to the weather service at the bottom about whether you like it or not.
Overnight and Saturday morning there will continue being strong northwesterly wind gusts, perhaps reaching their crescendo on Saturday morning as (1) winds turn more perpendicular from the northwest blowing against and over the southwest-to-northeast angle of the Appalachians, creating more “crashing waves” of wind and (2) a layer of stronger winds aloft slowly moving downward, reaching near the ridgetops. Some 70 mph gusts are possible in elevations above 3,000 feet or so, with 40-60 mph at lower elevations. That’s why the high wind warning remains in effect through 6 p.m. Saturday, after which winds should finally subside.
There will also continue to be snow squalls overnight and Saturday in the mountains of West Virginia, far southwest Virginia west of Interstate 77 and the ridges along the Virginia-West Virginia border in Bland, Giles, Craig, Alleghany and Bath counties. Those areas remain under winter storm warnings or winter weather advisories. Snow showers and flurries will scatter east of there into the Roanoke and New River valleys and along the Blue Ridge, but any accumulations are likely to be minimal, scattered and likely blown away quickly by the strong winds. Occasionally in a prolonged upslope snow squall situation like this, an isolated narrow squall will extend several miles eastward from the main snow area and dump a quick half-inch to an inch in an hour or less, with other spots a couple of miles away seeing stars and having bare ground. Don’t but don’t be shocked if you happen to be driving tonight and encounter heavy snow blowing sideways for a few minutes, or even some slick spots on roads.
Let’s fast-forward ahead to the weather talker of the coming holiday week, the likely central/eastern U.S. winter storm system of Dec. 25-27. First, there will be a weak low tracking northeast to our west and north on Christmas Eve, drawing some moisture into our region. This may trigger some light rain — maybe some sleet, but I doubt we see any Christmas Eve snow with the way system is tracking. This low zips northeastward very quickly, out to sea. The combination of its backside rotation and high pressure building in behind through southern Canada and New England may trap enough cold air southwestward along the eastern slope of the Appalachians for a wedge of below-freezing temperatures just above the surface to develop — just in time for the stronger low to move northeastward from near the Gulf Coast. Today’s European forecast model (12Z) captured what would be a rather intense cold air wedge situation (note the blue colors through western Virginia, poking toward the east side of the low in Tennessee) on the day after Christmas. Such a setup would mean that just about all the moisture hurled ahead of the low would be frozen in our region, a good bit of it snow, taking this model run at face value. But, just as the forecast models still haven’t pinpointed the all-important track for the post-Christmas storm system (could actually start seeing some precipitation late on Christmas, as it looks now), the details of any wedge of cold air are still murky, too. Some level of it is likely to exist, but whether it will be as expansive or as intense as shown by the 12Z Euro is unclear. Most of the GFS (Global Forecast System) model runs do not show the wedge to cover as large an area or remain in place as long, with some highs to the north more easily moving out of position. I bring this up with regard to the midweek storm mainly to point out a second important factor, besides the storm track, that will have major implications for what kind of precipitation we get. A track to our west combined with a wedge of rather deep cold air could result in a significant to major winter storm for our part of Virginia — similar in many ways to the winter storms of Dec. 4-5, 2002, and Dec. 4-5, 2003 (not a misprint, similar storms on same dates in back-to-back years) that each left 4-8 inches of snow in our region topped by sleet and ice (thicker sleet and ice with 2002 storm). Both of those early 2000s storm systems transferred energy to a coastal low, and such a transfer appears likely to occur again IF the storm tracks this far inland. An inland track combined with a weaker wedge, more easily scoured out by easterly/southeasterly winds ahead of advancing low pressure, would result in a brief period of mixed precipitation or ice changing to rain in most of our region — so far, this is the forecast depicted on most GFS model runs, and the one the National Weather Service is buying into for its midweek forecasts, at least for now. Also still on the table — and depicted on the most recent GFS (18Z) – is a “Miller A” track that would carry the storm from the Gulf Coast up the East Coast, a path more likely to bring mostly snow to our region.
So for Dec. 25-27: A storm system is very likely to take a track northeastward from the Gulf Coast. How and where jet stream energy digs southward will determine whether this tracks inland or up the coast. How much wintry precipitation we get, and what kind, from an inland track will largely be determined by how much cold air is banked against the mountains. These are highly variable factors in play for what looks like a confusing and highly volatile Christmas week forecast with enormous implications for Christmas return-home and pre-New Year travel plans. Whether or not it’s a big wintry deal for us, it will be somewhere not far away. Stay tuned.