Turnagain Pass

Several shallow wind slab avalanches were triggered yesterday. We also saw some evidence of natural small wind slabs from either Wednesday or yesterday.

North face of Cornbiscuit:  A widely propagating wind slab was triggered near the ridge; it is believed to have been human triggered. The slab was roughy 300′ wide and between 4-10″ thick. Debris was reported to be up to 3′ deep (photo below).

Northeast face of Groundhog Ck off the Johnson Pass trail:  Several small (not large enough to bury a person) wind slabs were triggered by snowmachiners (photo of one below).

Tincan Proper?:  We had a report of a crown visible from a distance. It was 200-300′ below the top of Tincan proper on the SW face. If you know anything about this avalanche, please send us a quick report/photo. Thank you!

Wind slab on the N face of Cornbiscuit that propagated fairly wide under the rocks. This is thought to have been triggered from the ridge in the upper left of the photo. 2.25.21.

Small wind slab, snowmachine triggered, around 3,800′, NE aspect, in the Johnson Pass area. 2.25.21. Photo: Travis Smith. 

While it is exciting that we could get a refresh of snow over the next couple days, it won’t be until later this afternoon that we are expecting light snow to start falling and a bump in east winds. Most of the daylight hours today should be fairly mild with cloudy skies, temps in the 20’sF and light ridgetop winds from the east.

The main concern today will be triggering a wind slab. Wednesday the mountains around Turnagain Pass saw strong easterly winds and yesterday strong northwesterly winds. Slabs have formed on a variety of aspects at the mid and upper elevations. These are up to a foot thick and were quite touchy yesterday. They are likely to be more stubborn today, yet something to really pay attention to. Be sure to consider the type of terrain you are getting into and the consequences if a wind slab is triggered.

Slabs should be fairly easy to identity. Look for signs of prior wind loading; smooth rounded surfaces and hollow/punchy feeling snow. Cracks that shoot out from you and a general stiffer feeling snow over softer snow are clues you have found a wind slab. These could be lower on the slope, in cross-loaded gullies, and on the steep side of rollovers.

Along ridgelines, be sure to give cornices a wide berth and limit travel under them. If you find yourself on a steep slope with soft snow and without wind effect, be sure to watch your sluff.

Wind transporting snow along the Cornbiscuit ridge and loading the North aspect. This photo was taken prior to the avalanche that is photographed above on the same face. 2.25.21.

Buried in the top three feet of the snowpack are a couple layers of buried surface hoar and/or facets. At elevations below 2,000′ a crust sits under the weak layers, making the lower elevations concerning as well. These layers are still showing signs of being reactive in some pits, yet not in others. This makes for a tricky situation and is reason enough to be cautious. The last known avalanche failing in one of these layers was five days ago on the steep SW face of Eddies Ridge. Slopes that have seen little traffic this winter and that have not been severely wind affected are the most suspect for triggering a slab.