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Friday may be climatically climactic.
This coming Friday, August 25, may well be the hottest day in all of 2023 at a few or many locations across Southwest and Southside Virginia. Even if it falls short of that, there’s a pretty good chance it will, at least, be the hottest day in the remainder of 2023.
(UPDATE FRIDAY MORNING, 8/25: A storm cluster moving southward into the western half of the region early Friday is taking some of the edge off the expected heat. Temperatures may still reach the 90s east of the Blue Ridge, but lingering debris clouds, showers and outflow breezes are likely to cut a few to several degrees off originally expected high temperatures, especially west of the Blue Ridge. END UPDATE)
The last five days have already seen quite a range across Cardinal News country, with some lows in the low to mid 40s – Burke’s Garden (Tazewell County) 42 and Copper Hill (Floyd County) 44 on Saturday morning – and highs reaching the lower to mid 90s – Roanoke tied its hottest temperature of summer thus far at 96 on Tuesday – at various sites. The next week to 10 days may see similar contrasts between heat to finish this week and cooler temperatures for several days beyond.
This week has been emblematic of the summerlong push-and-pull between the large and intense heat dome that has constantly been centered somewhere west of us and the repeating southerly dips in the jet stream over the eastern U.S. that have mostly kept us out of the extreme heat that has gripped many other parts of the nation.
After the cool weekend with comfortable humidity, the heat dome high-pressure system expanded enough over us for many 90s highs on Monday and Tuesday, before the circulation around the high brought down a cold front from the north to shave some numbers off the heat for Wednesday. But the heat will rebound over the next couple of days.
Friday, with an expansion of the heat dome overhead and some compression of the hot air ahead of another cold front, could well be the red-letter day for 2023 summer heat with mid 90s to near 100 temperatures expected in the lower elevations of our region (the urban floor of the Roanoke Valley and almost everywhere east of the Blue Ridge) and many lower 90s even in somewhat higher elevations from the New River Valley westward.
Then the cold front moves in over the weekend, with some scattered showers and thunderstorms, though moisture is pretty limited (perhaps enhanced a touch by Hurricane Hilary’s remnants from the Pacific). Behind that front, cooler than normal temperatures filter in for next week. We may have some days that don’t reach 80 across our region, and 40s-50s nighttime lows when it’s clear.
Although it may start giving some a craving for pumpkin spice, next week’s cooldown will not be the start of prolonged autumn-like temperatures. The heat dome will be slow to wither in September and may yet expand toward us again. But as the days shorten and the sun angle gradually gets lower, there will be a tendency for the hot periods to be not quite so hot or last as long, and the cool breaks to be a bit cooler and last longer.
We can’t say for absolute certain that Friday will be the climax of heat in our region this year and that there won’t be a relapse as strong or stronger in September (or early October, as was the case in 1941 and 2019). But, just as we would expect a late February Arctic outbreak to not be equaled in March or April even though we know it likely will get cold again, it would be a logical conclusion to think Friday probably will be the hottest day in what’s left of 2023.
Tropics come alive
We ended last week’s Cardinal Weather column with these words: “We are at that time of year when, in just a few days, the whole scene could change with respect to tropical systems.”
While Hurricane Hilary made a historic run out of the Pacific toward the U.S. Desert Southwest, the first system in decades to reach California as a fully defined tropical storm, no less than four named tropical storms popped up in the Atlantic.
Of those four, only Tropical Storm Franklin remains as of Wednesday morning, moving across Hispaniola with potentially flooding rainfall. Franklin may be able to drift north of the mountainous, tropical cyclone-shredding island and regain organization and strength over the weekend into next week, but it is not likely to be a threat to the U.S. beyond maybe stirring up some surf along parts of the East Coast.
Tropical storms Emily and Gert each met a quick demise over the Atlantic east of Franklin, stymied by shearing winds aloft and perhaps some Saharan dust. Tropical Storm Harold formed in the western Gulf of Mexico but ran of time and hot water for further development before running into south Texas.
Back to Hilary. Some media/social media reports about a hurricane hitting Southern California (it was a tropical storm at that point) and the arrival of a tropical system there being “unprecedented” (see two paragraphs down) were hyperbole.
But the event was certainly rare, and some of the rainfall amounts in typically arid desert regions were indeed unprecedented. Death Valley, California, received 2.20 inches in a day, which was a daily rainfall record and exactly what it receives in an average year. That may seem moderate by our backyard standards, but flooding was widespread in the region, as natural and manmade drainages can’t easily handle a year’s worth of rain falling in a few hours.
Previously, Hurricane Nora reached southwest U.S. as a tropical storm from the Pacific Ocean in 1997. Before that, a tropical storm made landfall at Long Beach, California, in 1939. San Diego was hit by a hurricane in 1858, the only known example of this occurring in California.
Cold water currents from the north Pacific moving southward along and just offshore of the western coast of North America typically weaken tropical systems moving northward from warmer waters off the Mexico coast, unlike the warm waters that move northward off the East Coast and continue to fuel hurricanes sometimes as far north as eastern Canada.
Some of what was once Hilary is being pulled into the upper-level trough that will affect our weather this weekend, but it will be unrecognizable, maybe just a dash more moisture than we might otherwise see with a low-pressure system and cold front not tapping the Gulf of Mexico or Atlantic much.
As of last week’s U.S. Drought Monitor map, there were small patches of abnormal dryness in parts of Lee, Wise and Scott counties in Southwest Virginia, a similar small patch in Hampton Roads at the southeast tip, and a bit more wide and intense area over Northern Virginia.
However, both the expansions of the heat dome from the west and the cooler northwest flow between hot spells will likely promote mostly dry weather, with no tap of the Gulf of Mexico or Atlantic for moisture. So, dryness and outright drought may start covering more real estate in Virginia in the next several days.
September and October have a strange feast-or-famine propensity with rainfall historically in our region, often either starved for moisture by cool but dry northwest flow from Canada or late-lingering summer heat domes, or else soaked by repeated tropical systems.
It remains to be seen which direction we may tilt for the entirety of the 2023 late summer and autumn, but early returns look dry. And as cold fronts get windier later in fall, dryness raises the risk of possible wildfires.
But we don’t know now if a yet-to-be-named tropical system has our name on it for a soaker.
Journalist Kevin Myatt has been writing about weather for 19 years. His weekly column is sponsored by Oakey’s, a family-run, locally-owned funeral home with locations throughout the Roanoke Valley.