Two houses were destroyed by an avalanche Monday afternoon that slid down a hillside of burned trees and onto the Lower Board Ranch, west of Ketchum.
Responders were dispatched at about 2 p.m. to the area of Whipsaw Lane and Cross Cut Lane, on the south side of the residential area accessed by Warm Springs Road.
Large amounts of snow laden with downed trees ended up on the properties. The slides destroyed the homes and removed them from their foundations, according to the Sawtooth Avalanche Center. The avalanche debris was 40 feet deep, the center reported.
Ketchum Interim Fire Chief Tom Bowman said responders made contact with a caretaker from one of the homes, who said the owners were not there. Neighbors said the other home had not been occupied for months, so Bowman said the responders made the decision not to risk the danger of attempting to enter either structure.
He said a leaking propane tank posed the greatest hazard, but responders were able to access the tank and turn it off.
At about 6:45 p.m., a second avalanche came down on Warm Springs Road just west of the first one, about a quarter-mile after the end of the road’s pavement, according to the Blaine County Sheriff’s Office. The avalanche did not strike any homes, cars or people, but it did cover the road with snow, fallen timber and other debris, according to the Sheriff’s Office.
Neighbor Pam Franco said she was standing in her front yard with her husband, Ray, when they heard loud cracking, crashing noises on the hillside to the south.
She said they got in their car and drove down closer to the avalanche site, where they witnessed the slide come down over the period of three to four minutes.
She said she has lived in the area since 1977 and has never seen an avalanche take out homes before.
Franco said the combination of deep winter snowpack, warm weather and rainfall has made conditions ripe for avalanches at the Board Ranch. She said several have come down farther west along Warm Springs Road, though they have not hit her neighbors’ homes.
“We heard this huge crashing, cracking noise,” Franco said. “This is a perfect storm between warming and the rain. I’m just shocked from living here for so long and never seeing it take out a house. It’s the raw power of nature.”
The Sawtooth Avalanche Center rated the danger for avalanches in its entire forecast area as “Considerable” on Monday, which was the third-highest danger rating on its 1-5 scale. Following heavy rains Monday night with more in the forecast on Tuesday, the center’s forecast upgraded the risk to “High.”
The center posted two photos of an avalanche that came down in Warm Springs on Friday afternoon and evening. One photo depicted a wet slab avalanche that failed on a northwest-facing slope within the drainage, which wiped out several burned trees and left a 15-foot debris pile in its wake, according to the center’s website.
“Warm temperatures and rainfall will make both wet slabs and wet loose avalanches likely at middle and lower elevations,” the center reported Monday morning. “The size and likelihood of avalanches will increase throughout the day and overnight. Yesterday, the rain line rose to above 8,000-feet [elevation].”
The center reported that the avalanches in Warm Springs on Friday, as well as others in Baker Creek and in the Big Wood River drainage, are indicators of a wet snowpack.
“In lower and middle elevation terrain, the rain is falling on an already saturated and unconsolidated snowpack that hasn’t had a solid refreeze for many days,” the center’s website reported. “Wet slab avalanches … occur when weak layers in the snowpack are affected by liquid water. As the rain works its way down to these layers … this sort of slide will become increasingly likely. Wet slabs are destructive and unpredictable; it’s nearly impossible to estimate how much rain it will take to reactivate the weak layers in the snowpack.”
Board Ranch resident Wade Schilling said he has lived in the area for 25 years, and noted that other avalanches have come down in the area this winter but have only broken glass as they bumped up against homes.
He said temperatures exceeded 50 degrees Monday.
“This is way-above-normal snowpack,” he said. “This is the warmest day since last November. There were a few other avalanches that just broke some glass. That structure there is just gone.”