Turnagain Pass Avalanche Forecast

With a break in the precipitation yesterday afternoon, there was an opportunity to see some of the avalanche activity from the storm. Evidence of large natural avalanches was observed across the forecast zone.  A few notable slides listed below:

• Seattle Ridge: one above Bertha campground and one just south of the moto lot.
• The south end of the west face of Magnum stopping before the power lines
• A 10′ crown on a lower slope of Twin Peaks.

Avalanche on Seattle Ridge observed from the moto lot. 1.11.21.

We finally have a quick break in the onslaught of heavy precipitation before the next storm starts early tomorrow morning. There is SO much new snow (6-10′) which is incredibly appealing but still potentially very dangerous. It’s a day to carefully evaluate terrain and consequences if a large avalanche does release.  Low angle slopes without steep slopes above are great ways to enjoy the new snow without worry. As the snow settles it may become easier to travel but may also mean the slab is becoming more consolidated and may still be sensitive to human triggers. The old snow surface before all the snow fell had a thin layer of weak snow. In addition, there were a few temperature fluctuations throughout the storm cycle that could have also created weak interfaces. There have been large natural and explosive triggered avalanches during the storm with crowns ranging from 2-15′ deep. These are not the type of avalanches you want to mess with. We are hopeful that the new snow will eventually bond well and that we can enjoy it. However, we need more data after the storm and the snowpack needs more time to stabilize. As said many times before the snowpack is guilty until proven innocent and it is still likely that a person could trigger an unsurvivable avalanche today. We are in the 48 hour window after a storm where this is most common.

Signs of instability to watch for today:
–  Recent avalanches
–  Whumpfing (collapsing) of the snowpack, sure sign to avoid avalanche terrain period.
–  Shooting cracks, likely to be seen near ridgelines and on slopes where the wind has formed wind slabs.

Avoid travel on or under cornices as they may be quite tender today and often break farther back than expected.

Turnagain Pass DOT snow stake, 1.12.21. The mountains have received a huge snow load in the past week. Please be patient and let the snowpack adjust.

Another view of the avalanche shown above in recent avalanches. Note the deep crown on the looker’s left. Seattle Ridge, 1.12.21.

There is another tricky element to this avalanche puzzle. We have been tracking a layer of faceted snow associated with the 12/1 rain crust, which is now buried around 8’ deep, and exists at elevations up to around 2500’. We are not sure if any of the large natural avalanches released at this layer. The majority seemed to be storm snow only but the 10′ crown on lower Twin Peaks is suspect. This end of the Pass gets less snow and a lower elevation crown fits into the elevation band where we have found this crust facet/combo. It is unlikely a person could trigger an avalanche on this weak layer at the depths it is buried in Turnagain Pass. However, as we head south towards Summit Lake the storm totals taper dramatically and this could be possible. This is another unknown that needs more data after this storm cycle.