A few quick notes on the flooding/wind weather event just passed before we move to what’s next.
* A National Weather Service storm survey (linked here) has found that damage in and near Fairlawn and Dublin in Pulaski County was caused by straight-line winds — possibly briefly forming a “gustnado” or ground-based swirl of wind — and not a tornado.
* The New River’s 21.13-foot crest at Radford is the fifth highest on record and the highest since a 24.04-foot crest on Jan. 15, 1995. The Roanoke River’s peak crest of 12.44 feet on Thursday was the 23rd highest on record, and the highest since a 12.8-foot crest on June 27, 2006.
* The threat of failures at two New River dams led to the issuance of a flash flood watch for portions of Wythe, Pulaski and Carroll counties. The dam failure threat is now considered much less than before due to some intervention by American Electric Power, but the flash flood watch has remained in place.
Many of you saw snowflakes at times today, even into the Roanoke Valley. Some of you west of Roanoke even got a little white. This pretty much sums up what the weather is going to be like, off and on, for much of the next 4-7 days.
Alberta clippers — fast moving disturbances diving southeastward from Canada — and prolonged upslope snow events — when northwest winds squeeze out moisture crossing the Appalachians for days — have been largely non-existent this season. It appears we’re going to make up for this over the next several days. At least 3 Alberta clipper systems look to aim for the central/southern Appalachians and Mid-Atlantic, the first arriving overnight and early Friday, the second late Saturday, and the third about Tuesday … and there maybe another after that. In each case, the clippers will scatter snow showers southeastward out of the Ohio Valley. How much of that crosses over the Appalachians is always questionable, as the downslope flow on the east side of the Appalachian crest often dries out the moisture. But if there is enough lift, a clipper system can carry snow far east of the mountains, all the way to the coast in some cases, where clippers frequently trigger large low-pressure systems that move offshore. Snow amounts are likely to be light overnight and early Friday, an inch or less in most of the New River and Roanoke valleys, but more (2-3 inches) toward the West Virginia line and west of Interstate 77 (scroll down on this page for the weather service’s best guess at accumulations). Clipper systems sometimes surprise us with narrow paths of heavier snow, so it’s always something to keep an eye on, though the speed of the system will likely preclude any truly heavy amounts in our area. The systems Saturday night and Tuesday may be a bit stronger than this one, but the tracks they take remains uncertain. In between the clippers, northwesterly wind flow will keep the upslope snow machine going. That means that some of the West Virginia mountains are going to get several inches of snow from frequent snow squalls over the next few days, and that snow showers and flurries will be possible just about any time crossing into Virginia as well.
It is possible toward the mid to latter part of next week that a wetter system could develop in the central U.S., bringing some Gulf moisture back into play as it advances eastward. How much that interacts with cold air remains to be seen.