May 7, 2014 - By Katie Roenigk, Staff WriterA small-scale tornado swept through rural Fremont County on Tuesday afternoon, whipping up debris and dust over open country about 20 miles north of Riverton.
No damage has been confirmed as a result of the two-minute twister, mostly due to its remote location.
National Weather Service meteorologist Dave Lipson said the weather phenomenon formed south of the Owl Creek Mountains and north of Sand Mesa Road between Boysen Reservoir and North Portal Road.
"It was kind of in that no-man's land area there," he said.
If it had gone through a more-populated area, the tornado could have caused some problems. Lipson said wind gusts near the tornado would have reached about 52 mph.
"It maybe would have torn a few shingles off, maybe a bit of siding," he said. "And also with a tornado it's not just straight line winds --it's an upward swirl. So you have flying debris because of that. ... We would have seen blowing and drifting garbage cans."
Kelly Allen, the fire weather program manager at the National Weather Service in Riverton, posted photographs of the tornado taken by her husband, Josh Allen, at about 2 p.m. Tuesday. Lipson said the image showed the twister after it had weakened.
Marble vs. beach ball
In a press release, the NWS said the tornado likely would be rated an EF0 on the Enhanced Fujita Scale. Compared with the tornadoes wrecking havoc in other parts of the country, Lipson said Fremont County's was like a marble next to a beach ball.
"Farther east ... they have the perfect mix of Gulf air to the south, dry air from the southwest (and) the colder northwest air masses," he said. "They have the perfect mix for tornadoes to form. ... We usually don't have the higher dew points to support the bigger storms like (they) have."
Tuesday's twister was formed by cold air moving in behind a recent storm. Lipson said the cold air interacted with the warm air in front of the springtime weather pattern.
"So you have this very cold air pushing up this relatively buoyant air and rising up, so you have this strong upward convection," Lipson explained.
A tornado is formed when that updraft captures the air circulating within the storm.
"You have winds blowing away and toward the radar at the same time," Lipson said.
He doesn't expect more local tornadoes any time soon.
"Now we're in the colder, more stable air," Lipson said.
The weather should be warmer later in the week, with temperatures reaching the mid-60s on Friday.
By Sunday, however, Lipson said it will be cold enough to snow again.
Wyoming has averaged about 10 tornadoes per year since 1950, according to The Weather Channel severe weather expert Greg Forbes. In Fremont County, the NWS says only six previous tornadoes have been recorded since 1996, and five of the six did not cause any damage. The other, in 2008, caused a reported $10,000 in damage and one minor injury from broken glass in Dubois.
NWS officials say Tuesday's tornado also was unusually early for Wyoming, where peak tornado months typically are June and July.
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