UPDATE 10:15 AM, 4/9: Breezes, dry air lead to continued high fire danger Monday; more frost/freeze issues by midweek
UPDATE 10:15 AM, 4/9: The red flag warning has been expanded to include all of Southwest Virginia and much of southern West Virginia. There are actually come counties around Abingdon and westward that have both a red flag warning for today and a freeze watch for Tuesday night/Wednesday morning — there will probably be some more freeze watches/warnings and frost advisories issued for that time period. But for now, the big concern is a dry cold front that will whip up breezes into the 15-30 mph range as it blows through, causing the potential for fires to spread rapidly. END UPDATE
Unlike most other warnings and advisories issued by the National Weather Service, it may not be immediately clear hearing the words “red flag warning” what that means. Think of it as “fire danger warning.” A red flag warning has been issued for Monday afternoon and early evening generally from Blacksburg and Floyd eastward, including the entire Roanoke Valley. Counties farther west are under a “fire weather watch,” which is only a notch down in danger from a red flag warning. Our current weather pattern is driven by relatively cool, very dry air being pushed our way out of the prairies of central Canada. Another reinforcement of that air arrived at midday Sunday, and yet another is due near the same time on Monday. The latest “dry cold front” will again cause breezes to kick up from the northwest — generally 10-20 mph with 30ish gusts. Those breezes combined with very low relative humidity readings — below 20 percent at times — and some pretty dry surface fuels like leaves and grass that haven’t had much rain lately, will create the potential for rapid spread of any fires, as we saw Sunday in Alleghany, Botetourt and Craig counties. So, of course, outdoor burning is strongly discouraged.
With bright sunshine in dry air, and westerly winds blowing down the mountain slopes to compress the warmth, Monday’s highs may well reach the 70s in much of the region after near to slightly above-normal lows in the 35-45 range, depending on elevation and geography. The cold air behind the newest front will dig in a little more in the Tuesday-Thursday period, when we may see some more frost/freeze issues in the morning, and a day or two of below-normal highs not even reaching 60. West Virginia’s mountains may see those northwest winds squeeze out just enough of the meager moisture for some light snow — maybe enough for a white ground at 3,000-plus elevations in Greenbrier County — late Monday night and early Tuesday. A few flakes may drift into some of the higher elevations of Virginia, too, but borderline temperatures and very dry air will likely preclude any more widespread snow showers.
It’s looking likely that the high pressure system pressing the cold air southward later this week will shift east and turn the prevailing winds to the south and southwest by the weekend, which will start a warmup, and perhaps, a gradual re-moistening of the atmosphere that may lead to better chances of rain next week.