Turnagain Pass

Triggering a large and unmanageable slab avalanche 2-4′ thick remains our primary concern. Yesterday, a snowmachiner remotely triggered two slabs on Seattle Ridge from a meadow below the slope; it’s important to remember that these avalanches can be triggered from the flats. These slabs were on the North end of the ridge above the powerline trail. This longtime Turnagain rider noted that avalanches in this area are not often seen. Additionally, similar slab avalanches were triggered in Girdwood Valley in the Notch Mtn area. 

The avalanche activity yesterday was all in the mid to lower elevation bands. Various layers of old faceted snow sit under the 2-4′ of storm snow from Friday (photo of this below). The faceted layer has been overloaded by the new snow and is failing, creating the current ‘persistent slab’ avalanche problem. At the higher elevations, above 2,500′, the facets are not as pronounced, yet there are old layers of buried surface hoar that are a concern. How likely a slab is to be triggered in these weak layers at the higher elevations is uncertain at this time. Of note is very little to no traffic was seen in the upper elevation bands yesterday. 

If you are headed out into the backcountry today things to keep in mind are:

• The mountains are still adjusting to the several feet of new snow that fell two days ago
• Watch and listen for whumpfing (collapsing) in the snowpack. This was noted by many folks yesterday, including the rider/skiers that triggered slabs. This means the snowpack is highly unstable and will almost certainly avalanche if the slope is steep enough.
• Stick to slopes less than 30 degrees and ease into steeper terrain slowly – after careful snowpack assessment. Evaluate the consequences if the slope releases; where will the debris go?
• If the visibility turns poor, be extra cautious to avoid being in a runout zone 

Slab avalanches on East faceing Seattle Ridge (looker’s right of the up-track). Two of these could be the avalanches that were remote triggered from meadow below yesterday.

Loose snow sluffs on the West face of Magnum

 
Annotated photo of the storm slab bonding to the old snow surface, but the old snow surface is weak and failing. Hence, the new snow has ‘overloaded’ the older weak snow.

Three feet of new snow and wind effect on Tincan Ridge (left) and Seattle Ridge’s Repeat Offender and uptrack zone (right). It’s good to see the new snow, but slopes need time to adjust. 

Turnagain Pass flats – plenty of safe places to play that are out of avalanche terrain. (Photo: Allen Garrett) 

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Cornices have grown and are suspect for breaking while traveling along ridgelines. Give these an extra wide berth and minimize any time below them. Cornice falls can trigger avalanches on slopes below.