Near the end of a Weather Journal column about Superstorm Sandy at the end of October, I wrote this line: “Roanoke’s winds peaked at 40 mph sustained and 60 mph gusts. We may have a cold front or two this winter with winds almost that strong.” We may be about to test the truth of that statement for the first time this winter. The National Weather Service has raised a high wind watch (likely becoming a warning on Thursday) from Thursday evening through Saturday afternoon for the potential of some 60 mph winds in much of our region. A strong Arctic front is going to slam through on Thursday evening, bringing with it a blast of cold air that will be a quite a shock after so many days of 60s this month (Roanoke’s high of 64 on Wednesday was the 10th 60+ degree day of December, the most since 11 in 2006.) The tightening pressure gradient around a strong low that will track to our west and north, and only poke eastward across New England, will keep us in strong northwest wind flow for about 36-48 hours. (This strong low is triggering a blizzard, severe weather risk and dust storms in various portions of the central U.S.) As these winds hit the mountain ridges, choppy waves will develop that bring stronger winds aloft to the surface. It’s one of the hazards that goes along with living in our lovely Appalachians — recall that many locations east of Roanoke in the more level terrain didn’t crack 50 mph with wind gusts on Oct. 29, while 60 mph gusts roared through our trees with Superstorm Sandy. I would not at all be surprised to see a 60 mph wind gust at Roanoke or other regional locations — 40 mph sustained winds probably won’t occur, though, at least anywhere below the 4,000-plus ridgetops, just because that’s usually not the nature of these Arctic cold frontal events. Do expect 20-35 mph sustained winds with 50 mph gusts, at least, during this time frame. There will likely be scattered power outages. And it will be cold wind, with highs probably not getting out of the 30s anywhere on Friday.
There will be some precipitation, too — a good chance of quick-hitting rain showers, perhaps accompanied by thunder or a gust of wind, ahead of the cold front on Thursday, then upslope snow showers with the northwest winds climbing the Appalachians overnight Thursday into Friday. Several counties of West Virginia remain under a winter storm watch with 5-plus inches expected on west-facing slopes and in higher elevations, areas that will keep getting pounded by snow squalls into Saturday. This appears to be a strong enough upslope event that there will be some spillover into western Virginia — expect to see off and on snow showers early Friday in the New River Valley and west of I-81, with perhaps a few snow showers blowing even farther east into the Roanoke Valley and even some of the western Piedmont. Just by having such strong winds, it’s going to be hard to keep at least a few snowflakes from blowing into Roanoke. As for the rain — the Hydrometeorological Prediction Center is only predicting 1/4 to 1/2 inch for most of our region, and it seems these predictions have been a category too high for the past several rain events. There may be some heavy downpours, but not long-lasting. Any rain helps the dryness, though.
On that score — here is the HPC’s new experimental 7-day precipitation product, which shows rather copious rains over the next week. This would be the result of the post-Christmas storm we have been talking about, and likely presuming a track west of us that enhances southeasterly upslope flow from the Atlantic to the Blue Ridge, and flushes in milder air for a couple of days after near-seasonal cold hangs in through Christmas or so. Some models have started to bring the storm farther east, a trend that needs to be monitored, especially with some evidence that blocking features in Canada could force a farther south/east track. If it ends up a coastal storm, snow potential would be high locally; a track west of us, mostly rain; and near or just east of us, perhaps some of both. And there’s always a chance we don’t get much of either. That seems to be the recent local luck with moisture.