The tropics ruled in late September, but now the tundra is striking back.
Autumn weather at our latitude in Virginia is often a battle between the tropics and the tundra, a back-and-forth bounce between the stickiness and sogginess related to tropical influence and the cool, crisp pushes of air from the northern latitudes.
Just as our night skies looked more like those of Canada with the year’s second atypically vivid display of the aurora borealis on Thursday night, our nights and mornings during the latter half of this week will have a bit of seasonally premature chill thanks to an air mass imported from our northern neighbors. (To be clear, aurora displays are caused by ejections of solar particles and are not related to the hemispheric movement of air masses in our atmosphere.)
· More night-sky wonder: See the second section of this column for information on viewing Comet Tsuchinshan-ATLAS.
· Weather in history: Did a derecho help American Colonists defeat the British at Yorktown? Part of the Cardinal News 250 series.
The cold air was sufficient to allow for the first ground-whitening snow of the season in some of West Virginia’s highest elevations on Tuesday, with some snowflakes even blowing into some of the higher elevations along Virginia’s western fringe. By Wednesday morning, light snow accumulation had occurred on the state’s highest peaks at Mount Rogers and the appropriately named Whitetop in Grayson County.
If you haven’t already, now would be a good time to protect or move inside any tender vegetation.
Temperatures near or below freezing are expected across all of Cardinal News’ broadly Southwest and Southside coverage area on both Thursday and Friday mornings. Some locations west of the Blue Ridge will experience a hard freeze with temperatures 28 degrees or lower for at least an hour, which is generally seen as the end of growing season. Growing season may effectively be over in several other locations that record 29-32 temperatures each of the next two mornings, some of which may have been near or slightly below freezing on Wednesday morning as well.
Through Tuesday, Tazewell County icebox Burke’s Garden had already recorded eight days this meteorological fall (begins Sept. 1) with lows at or below the freezing mark of 32 degrees, as low as 24 on Saturday morning (Oct. 12), so the growing season is over there. The crater-like temperature sink ringed by Appalachian ridges fell to 31 degrees four consecutive mornings Sept. 8-11 and then went 32-31-25-24 for lows Wednesday through Saturday.
Although before some of our western localities might have done so Wednesday morning, not many other official weather stations in our region had fallen to the freezing mark so far this season. Clintwood in Dickenson County reached 32 on Thursday and Friday mornings (Oct. 10-11). Saltville in Smyth County dipped to 32 on Friday morning (Oct. 11).
While the urban floor of the Roanoke Valley and several locations east of the Blue Ridge might squeak out of this week without quite reaching the freezing mark, frost is likely to form on a scattered to widespread basis the next couple of mornings, as winds die out and skies are clear for maximum radiational cooling.
Frost forms even with air temperatures slightly above freezing because those readings are recorded at 6 feet above the surface, and colder air sinks to ground level, plus some plants and exposed objects cool off more readily than the air just above. Clear sky, calm wind, and 36 degrees is usually about where fairly widespread frost begins developing, with scattered frost developing in upper 30s lows.
The season’s first low of 32 degrees or colder happening any day this week would be pretty much right on time for modern averages at Blacksburg and Wytheville. Blacksburg’s first freezing date averages Oct. 9 since 1893, but over the past 30 years, that has moved all the way to Oct. 21. A freeze this week would just about split those dates. Similarly, Wytheville averaged Oct. 8 for its first freeze since 1930, but that has moved later to Oct. 14 since 1994. Freezing temperatures in the latter half of this week would be only slightly later than the average of recent decades.
Hitting the freezing mark, should it happen at Roanoke, Lynchburg, or Danville this week, would be significantly early compared to history.
Lynchburg’s average first freeze date since 1892 is Oct. 25, and that is exactly the same for the past 30 years. Roanoke averages a first freeze on Oct. 23, considering all data back to 1912, but that has moved seven days later to Oct. 30 just considering the last 30 years. Danville’s average first freeze date is Oct. 26, considering all data back to 1917, and has only moved a day later to Oct. 27 since 1994.
Besides a warmer global climate that has moved autumn first-freeze dates later at many locations nationally, each of these sites has various localized issues involved as well, such as various sensor locations at Blacksburg, a mid-1990s sensor move to a much cooler location at Lynchburg, and the warming effect of commercial growth that has surrounded a sensor site previously surrounded by more open agricultural land at Roanoke.
Burke’s Garden, incidentally, was almost three or four weeks early for its Sept. 8 first freeze, depending on if you use the Sept. 27 first-freeze average since 1896 or the Oct. 2 average in the past 30 years. It’s very convenient that what may be the coldest spot in our region also has more than a century of weather data recorded.
While the next few mornings will feel quite wintry, and even days will struggle to get above 60 at many spots until Friday afternoon, this is nothing close to winter setting in for good.
The atmospheric pattern is expected to shift for the latter part of October to one featuring high pressure aloft over the Eastern U.S., which would favor above-normal temperatures. At this point, it looks likely to be a primarily dry period as well, though we’ll keep an eye on the Gulf of Mexico and western Atlantic for any potential tropical trouble.
A prolonged warm, dry period could have one positive benefit for autumn lovers: Changing foliage would be slow to brown and fall off, which could lead to a prolonged color show.
A fall that has bounced between cool, dry air from the tundra and sticky, soggy air from the tropics may present a third personality as we approach Halloween.
Don’t miss a beat! Catch the brightest stories streaking across your screen! Sign up for Cardinal News’ FREE daily newsletter and stay in the orbit of the latest headlines. Our stories are out of this world—be the first to discover them!
The ‘Purple Mountain’ Comet
Clearing skies the next few nights should offer many Virginians the opportunity to see Comet Tsuchinshan-ATLAS, which is rising higher in the western sky each successive night, visible shortly after sunset.
The comet’s lengthy name comes from the two observatories that discovered it last year — the Tsuchinshan Observatory in China and an Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in South Africa. Tsuchinshan means “purple mountain,” which would be an attractive name for a comet itself, given our location near and amid Appalachian ridges and the “purple mountains majesty” line in “America the Beautiful.”
A comet has been described rather unattractively as a “dirty snowball” in space that emits a lengthy tail as solid particles in its rock and ice makeup sublimate into gas — skipping the liquid state altogether. That tail is lit up by the sun and the only reason we can see it at all.
Comet Tsuchinshan-ATLAS is the first to be visible without telescopes in our skies since Comet NEOWISE in 2020. Comet Tsuchinshan-ATLAS was originally believed to have a revolution period of 80,000 years around the sun, though NASA now notes that newer data suggests the comet will leave the solar system entirely.
Either way, this is your only chance to see it. Look just south of due west about 30 to 45 minutes after sunset, continuing a little later in the evening as the comet appears higher in the sky and sets later. (Sky map linked here). It has been reported to be visible to the naked eye and may appear like a contrail remaining stationary with a brighter white head a little like a cotton swab.
A year with a total solar eclipse, two highly visible auroras very far south, and a comet as our nation has experienced in 2024 might be considered ominous in much of human history. But for many skywatchers today, this space trifecta evokes wonder and awe.
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. Sign up for his weekly newsletter: