Turnagain Pass

There were only a couple reports from the mountains during the storm yesterday, one was from John Sykes (forecaster) at Pete’s South and the other from a group in Placer Valley. Both parties reported storm slab avalanches that were easy to trigger. They stayed in the trees due to the stormy weather and avalanche concerns, but in the smaller terrain they could trigger slabs up to a foot deep at Pete’s South and over 2′ deep in Placer Valley where more snow has fallen.

Small storm slab avalanche on Pete’s South. Slab was skier triggered at 1700′ on a west aspect, about 12″ deep and 50′ wide. 1.28.22.

Wow, what a few days of snowfall. Light to heavy snow has been falling since Wednesday afternoon with the highest rates seen yesterday. Snowfall totals over the past 24-hours were 18-24″ for mid/upper elevations in Girdwood and Placer Valleys and 12-14″ for Turnagain Pass. Check out the table below for the storm totals since Wednesday. Ridgetop winds have been fairly moderate out of the east until last night when they took a jump for 6-8 hours blowing 40-50mph with gusts over 70mph. All this new snow with those winds last night will keep storm snow avalanche issues front and center, especially wind slabs!

Storm total estimates for 2,500′ beginning Wednesday afternoon through last night:

Turnagain Pass:  14-22″  (1.4″ SWE at Center Ridge 1,800′)
Girdwood Valley:  24-36+”  (2-3″ SWE)
Placer Valley:  24-36+” (~3″ SWE)
Summit Lake:  2-4″  (0.2 SWE)

For all those headed out today- the storm has just ended. We need to ease into terrain and not let powder fever get the best of us. Be sure to pay close attention to slopes with recent avalanches, and the other signs of instability (cracking in the snow around you and whumpfing). The deeper the new snow, the larger the potential avalanche. Safe travel practices are a must. Expose only one person a time, watch your partners, and have escape routes planned. Although the storm snow should be in the process of stabilizing, it can take a couple days.

Wind Slabs:  These are likely to be easy to trigger and could be larger and more dangerous than expected. They could be anywhere from 1-3+ feet deep. Watch for signs of wind effect and steer clear of slopes and cross-loaded gullies with wind loading.

Storm Slabs:  It will still be possible to trigger storm slabs similar to those yesterday on slopes out of the wind, including slopes in the trees. Storm slabs could be 1-2′ deep depending on how much snow fell in the area you are in. There is crust up to ~2,000′ under the new snow and this could slow the bonding in the mid-elevations.

Sluffs (loose snow avalanches):  On slopes out of the wind, expect to trigger sluffs in the new snow. These could entrain a large amount of snow in larger terrain.

Cornices:  Be extra cautious on ridgelines as cornices could be teetering on the brink of failure. They could trigger an avalanche below and potentially put others in harms way.

Cracking on a small test slope yesterday on Pete’s South. 1.28.22.

Persistent Slab:  In addition to the storm snow avalanche concerns, there is an outside chance that a person could trigger a larger avalanche on weak snow near the New Year’s crust. This would now be buried 2-6+′ deep. This is a tricky problem with high uncertainty and low likelihood. The only known activity on this layer was a large human-triggered avalanche on Tincan Proper over a week ago (details here). As we head into a clear period and the storm snow stabilizes, we need to keep this issue in our minds.