Turnagain Pass Avalanche Forecast

If you area venturing into the backcountry today it is important to keep in mind that triggering a large avalanche on the Solstice surface hoar/buried facets is a possibility and we are still in the 48 hour window after the New Year’s Eve storm. It is important to look for signs of instability but also remember they may not be present with this type of weak layer. Slowly progress into avalanche terrain and only expose one person at a time. With the improved snow cover it is possible to go to places in the advisory area that haven’t seen much traffic. Parts of the region with a shallower snowpack will be the most suspect i.e. Crow Pass, the southern end of Turnagain Pass including Lynx Creek and Summit Lake.  The weak layer is now buried from 1-4′ deep. Prior to the New Year’s Eve storm there had been reports of fairly widespread whumpfing (especially in the Treeline elevation band, including Seattle Ridge) and the Solstice surface hoar/buried facet layer was found to be reactive in some snowpack observations. Due to the highway closure we have limited snowpack data after the New Year’s Eve storm. What we do know is that it warmed up and then rained to 2200′-2500′. Some natural avalanches were observed around the region potentially failing on the buried weak layer but not that is not confirmed. It then cooled and rapidly switched to snow with 1-2′ ( or 4′ in Portage) of snow falling. There was not much observed avalanche activity associated with the colder part of storm or and temperatures have cooled down significantly since which should help the overall stability. However, it is important to remember today MODERATE does not mean LOW danger. The snowpack hasn’t had much traffic or testing.  Triggering a large, dangerous avalanche is still possible and whether you are traveling up, down or across avalanche terrain, caution is advised. Choose terrain wisely and avoid terrain traps.

Solstice buried surface hoar and facets are now buried by all the Dec 22-30 snowfall as well as the New Year’s Eve storm. The depth of the buried weak layer is variable across the region. Shallow snowpack areas are the most suspect. 

During the New Year’s Eve storm while the snow was falling, the winds were averaging in the 30s and gusting into the 60s likely loading leeward slopes and creating wind slabs just off the ridgelines and in cross-loaded gullies.  Look for drifting, cracking and hard snow over soft snow.  Avoid steep unsupported slopes with stiff snow. Remember even a small wind slab can be dangerous in high consequence terrain.

Cornices: Wet snow and wind in the Alpine during the warm part of the storm Tuesday likely added snow to the cornices already looming in the Alpine. Avoid travel on or underneath the cornices and pay attention to groups traveling above or below you.

Loose snow avalanches (sluffs): On the flip side if you are in protected steep terrain that is not wind effected watch your sluff. The cold temperatures will make the low density new snow even less cohesive and more likely move. Sluffs can be pushy and hazardous if you are in the wrong spot and get hit from behind. Some natural loose snow avalanches that occurred during the storm were observed yesterday.

Wind effect in the Alpine on Petes South, 1.1.20.

Corniced ridgeline, Petes North, 1.1.20