Four days after summerlike temperatures suddenly crashed 50 degrees into bands of snow and sleet, another season-bending day threatens severe thunderstorms, tornadoes, gusty winds and some snow on Monday.
The federal Storm Prediction Center has raised what for Virginia is a rare “moderate risk” for severe thunderstorms, or level four out of five, for areas of the commonwealth from Danville, Lynchburg and Charlottesville eastward on Monday. The third-level “enhanced” risk extends as far west as Roanoke and the Blue Ridge, tailing off to “slight” and “marginal” risk levels farther west.
Severe thunderstorms are those that produce wind gusts of 58 mph or greater, hail 1 inch or greater in diameter, or spawn a tornado. Storm Prediction Center risk levels increase as expected coverage of storms increases — a higher risk level indicates the potential for more locations to experience severe storm effects than lesser risk levels, where such effects are expected to be possible but more localized.
A strong cold front is plowing eastward into mild and moist air that has re-established after the last snow-bearing cold front on Thursday, though not nearly to the level of warmth experienced Wednesday when South Boston hit the 90-degree mark and several locations in Cardinal News’ Southwest and Southside Virginia coverage area were near midsummer norms in the mid to upper 80s.
A deep-diving jet stream trough is supplying strong winds aloft changing direction with height, and this will introduce some spin to any thunderstorm updrafts that build on Monday, increasing the risk that some of those strong winds aloft are translated to ground level in downdrafts or that rotating updrafts will tighten into a few tornadoes.
One or more clusters or lines of showers and storms are expected to march across Virginia on Monday, with storm intensity growing as it enters what is likely to be warmer air with greater upper-level wind dynamics east of the Blue Ridge. Generally speaking, the greatest risk of strong to severe storms is expected through midday west of the Blue Ridge, near midday along it, and in the afternoon to the east.
It is impossible to pinpoint exactly where the worst severe storm impacts and any possible tornadoes will occur hours ahead of time. Most occurrences of severe storms result in narrow but intense paths of damaging impacts while areas in between see weaker effects.
Tornado and/or severe thunderstorm watches encompassing large areas where ingredients will support severe storm development are likely to be issued Monday, with local National Weather Service offices issuing warnings for more targeted local areas once severe thunderstorm cells or potential tornadic circulation are detected on radar or observed.
It is advisable to keep up with watches and warnings on Monday via National Weather Service outlets on the internet, social media, or NOAA weather radio, or local broadcast television and radio stations.
Behind the front, gusty winds from the west and northwest will bring sharply colder temperatures by Monday afternoon over western Virginia, spreading eastward. The winds will be gusty enough, over 40 mph in many cases, and actually more widespread, to add some additional scattered power outages to whatever the storms cause.
Temperatures will drop off fast enough that some snow may again develop in the afternoon and evening, with possible streaky light accumulations west of the Blue Ridge.
Wednesday morning will bring a hard freeze with teens and 20s lows regionwide before a gradual warmup to end the week.
Journalist Kevin Myatt has been writing about weather for 20 years. His weekly column, appearing on Wednesdays, is sponsored by Oakey’s, a family-run, locally-owned funeral home with locations throughout the Roanoke Valley.
To submit a photo, send it to weather@cardinalnews.org or tweet it to @CardinalNewsVa or @KevinMyattWx. Please identify the location and date of the photo with each submission.
Sign up for his weekly newsletter: