Turnagain Pass

Today marks the 8th day of sunny skies and frigid temperatures. In fact, the Granite weather station near Johnson Pass Trail Head is reading -24°F this morning, the coldest reading in our forecast zone. These cold temperatures have been turning the top foot of snow into recycled powder or faceted snow. The clear skies have paved the way for a new batch of surface hoar to grow. For folks headed out in the backcountry, this soft surface snow is providing some great skiing and riding conditions- but there is a dark side… Sitting 1-3 feet below the surface are old weak layers of buried surface hoar and facets. Although these layers are becoming harder to trigger with time, we can’t forget about them. The consequences of finding just the wrong spot and triggering a slab avalanche can be significant. Of note is a slab avalanche in upper Seattle Creek drainage that was seen yesterday, believed to have been triggered by a snowmachine. It is unclear how old this slab is (2-4 days old), but it did fail on buried surface hoar and emphasizes our concerns that slabs like this are still possible to trigger.

Things to remember with the avalanche problem are, signs of instability may not be present before a slab is triggered It might be the third or tenth person on the slope that triggers the slide and the avalanche could be triggered remotely. Shallow areas and rocks in the snowpack are likely trigger points. Consider the consequences if a slab does release, where will the debris end up? Is there a terrain trap under the slope (bad) or will the the debris fan out (better)? And as always, use safe travel techniques, such as exposing only one person at a time.

Slab avalanche that was seen yesterday and believed to have been triggered between January 6th and 8th in upper Seattle Creek drainage near Minus 3 Bowl. Weak layer was buried surface hoar and slab was around 2 feet thick. More details HERE. Photo: J Davis

Westerly ridgetop winds have increased overnight and are blowing in the 10-15mph range this morning with gusts into the 20’s. Similar to two days ago, shallow wind slabs could be forming in the lee of ridges and places the winds are transporting snow and loading slopes. Keep an eye out for active wind loading today and look for older wind slabs that could have formed a couple days ago. Any wind slab found should be suspect of triggering as they are likely sitting on the weak faceted snow.

By looking close, you can see where tracks walk into the bottom of a wind slab. The slab failed but moved only an inch or so then stopped and did not avalanche. Other slabs did avalanche for this party on the far southern end of Seattle Ridge two days ago – report HERE. 1.8.20. Photo: Matti Silta

Loose snow sluffs:  As mentioned above, the cold temperatures are turning the top foot of snow into very loose faceted snow. This is allowing sluffs to become larger on longer sustained slopes where sluff management is prudent.

Glide cracks are still showing their brown signs, which is keeping them on our radar. However, none of them have released into avalanches that we of for quite some time. Because these are so unpredictable it’s always good practice to limit any time spent under them. Check out the photo below from the upper Bertha Creek zone (Gold Pan).

Glide cracks litter the south facing zone of upper Bertha Creek (Gold Pan). 1.8.20. Photo: Billy Finley

Cornices:  Cornices are looming along ridges. Be sure to give them plenty of space and limit your exposure when passing beneath them.