Front Range
AvalancheJonah Seifer · Apr 18, 2021 · Front Range
Weather
Weather was a mix of classic Colorado springtime conditions. Our party had skied the east face of Frosty Mountain around 11:30am and enjoyed clear blue skies and light wind. Our ascent of Radiobeacon's east face began around 12:30 or 1pm, at which point the weather deteriorated. The sun intermittently poked through clouds, but otherwise we experienced increasing winds and snowfall. During our descent, the summit of Radiobeacon was enveloped by clouds and visibility deteriorated further.
Snowpack
Earlier in the day we had noted thin winds slabs on top of soft snow between 11,200' and 11,400' below Frosty Mountain's east bowl. The wind slabs were discontinuous and eventually disappeared above 11,400'. Around 11am, the snowpack around 11,700' began to show signs of warming, however it skied great and was not yet hot enough to form rollerballs. Later in the day as we were climbing Radiobeacon, the increasing cloud coverage, snowfall, and wind appeared to halt the warming trend. We had also transitioned to a more northeasterly aspect around 11,000' which likely contributed to the colder, drier snow we observed. As we ascended, our party noted much firmer, isolated wind slabs ranging from 4" to 6" deep. I dug a few hand pits and conducted shear tests which showed that the slab was poorly bonded to the underlying, smooth crust which formed during the hot weather in early/mid April. Following these tests, our party decided to descend and skied through dense, slabby snow with pockets of cold, soft snow.
Avalanche
During our descent on the lower east face of Radiobeacon, we crossed a 30º NE facing slope around 11,200' with isolated pockets of wind slab. Our party of 4 traversed / ski cut this slope one by one, with all members undercutting an isolated terrain feature which was about 35º and had some partially buried vegetation and rocks. The fourth member to cross this area skied about 1' above the other member's tracks, triggered the slide, and skied to the safe zone. The slide was an R1 D1 with a estimated crown depth of about 8". It likely could have caught and carried a skier, however the debris field did not appear deep enough to bury a skier. The avalanche broke about 70' wide and ran for about 200 vertical feet. The bed surface consisted of a smooth, pencil- to knife-hard crust which formed during the warm weather earlier in the month.