The January thaw that began on Sunday brought higher temperatures and some light rain, but it has also triggered avalanches throughout northern Utah.
Avalanche forecasters are warning recreationists to stay out of the backcountry at least until cold temperatures return, expected to be Wednesday morning. So far, only minor injuries were reported.
About 11:30 a.m. Sunday, a Salt Lake area man was hiking up a steep, north-facing chute in Little Cottonwood Canyon, said Drew Hardesty of the Utah Avalanche Center. "The person was booting up this steep gully and an avalanche came from above," he said.
The slide was relatively small, but it "took him for about a 400-500-foot ride. He ended up on top but just had minor injuries, really — lucky."
On Monday, search and rescue crews from the Salt Lake County Sheriff's Office responded to three avalanches in Little Cottonwood Canyon and two in Big Cottonwood. In the latter, both avalanches crossed the canyon's main road.
No vehicles were involved and nobody was injured, said Peggy Faulkner of the sheriff's office. The avalanches weren't very big but could have damaged any vehicle in their paths.
Rather than waiting for the road to be cleared, several vehicles drove over piles of snow. That's extremely dangerous, as someone could have been trapped beneath.
"To drive over an avalanche is dangerous," she said. "Either stay put or turn around and then call and let us know what happened."
In addition to the five main slides, Faulkner said many other avalanches were reported in the backcountry Monday.
The same kind of danger is expected throughout Tuesday as the weather continues to be warm.
The recent warm temperatures have caused the snowpack in the canyon to weaken, increasing the risk of avalanches and snow slides.
UDOT spokesman Geoff Dupaix said because the softening snow has too much moisture, it precludes the use of explosives. "It's really just a wait-and-see situation," said Dupaix. Crews are waiting for the snowpack to either re-freeze or slide off before they open the roads again.
The last few avalanches have been widespread, at many elevations and at many aspects, said Hardesty, avalanche forecaster with the center, which is maintained by the U.S. Forest Service on North Temple. An "aspect" is the facing direction of a feature, such as a mountainside.
Avalanche danger is most pronounced between Ogden and Spanish Fork Canyon, but it extends to the north and farther south on the Wasatch Plateau as well.
The threat of avalanches has prompted state transportation officials to close the two main roads up American Fork Canyon until further notice.
U-92 and U-144 were closed to all traffic at noon Monday, according to the Utah Department of Transportation. The closures mean there is no access to Timpanogos Cave and that access to Sundance Ski Resort is limited to Provo Canyon.
"Rapid warming of the snowpack due to either ambient temperatures, direct solar radiation and/or rain will also create widespread instability in the upper layers of the snowpack, and that's what we've seen," Hardesty said.
Danger should begin to drop with cooler temperatures on Wednesday morning, he said. "That should at least drop the hazard somewhat. But warmer temperatures are expected later on in the week, so we'll have to see how that pans out."
The center regularly updates its recordings on the six advisory phone lines, which can be reached at 364-1581. It also reports live on three daily radio programs. In addition, Utah avalanche information is posted on the Internet at www.avalanche.org/~uac/.