Turnagain Pass

It was a fairly busy day in the backcountry with many folks doing their best to play it safe. Despite this, there were still many large and scary avalanches triggered. They were all remotely triggered and luckily the debris did not wash over anyone that we know of. Most of these were in Seattle Ck drainage (map). The other was in Skookum drainage near Placer Valley. We will be compiling additional photos and information today. Basic info here:

Seattle Creek (3rd Bowl):  Two snowmachiners near the bottom of the drainage triggered a collapse that then triggered two large slabs on the N and NW faces, shortly after another slab released on a SW aspect.

Seattle Creek (-3 Bowl, Triangle Bowl):  One snowmachiner lower on the slope in lower angle terrain also triggered a collapse (and small slab on a small terrain feature) that then triggered two larger slabs above and to the side, with another larger slab releasing out of view. These were on W to NW aspects.

Skookum lower drainage:  Possibly skier triggered – preliminary report here. Slab was extremely wide. Debris ran over snowmachine and possibly fat bike and xc tracks below. See photo below.

3rd Bowl. Northerly facing slab that was one of three slabs releasing in 3rd Bowl. Crown up to 8′ deep, maybe more in wind loaded areas. Photo by riders involved, 3.25.23.

3rd Bowl. The lower slab, which was the largest, that released behind the riders lower in the drainage and wrapped around to a more westerly aspect. Photo by riders involved, 3.25.23.

3rd Bowl: The smallest of the three slabs triggered (SW aspect). This one released last, likely sympathetically by the debris washing down from one on the other side. The debris from both slides ran together in the bottom on the drainage forming a ridge. Photo by riders involved, 3.25.23.

-3 Bowl/Triangle Bowl. These two slabs pulled out shortly after a rider dipped into a small terrain feature and triggered a collapse. Note the much larger slab (crown barely seen in the upper left of the photo) wraps around out of view. Tracks on slope were from another party earlier in the day. Photo by riders involved, 3.25.23.

Skookum drainage. Several slabs released near the same time to generate a very large avalanche with debris covering many tracks in the valley below. Unknown exact trigger, possibly skier triggered remotely. Photo from Henry Munter, 3.25.23. 

The photos above say it all. We are again in a period of dangerous avalanche conditions. It’s that setup where everything seems fine until it is not. Some slopes may in fact be fine, but there is really no way to know this 100%.

All that snow from March is not bonding well in many places. There was anywhere from 5-10 feet that fell from March 15 to the 22nd, which has settled to around 3-6′, more where the winds have loaded it. These avalanches are releasing under this snow, on the old early March ‘dry spell’ surfaces (facets/hard wind packed snow on shady slopes and sun crusts with areas of facets below the crust on solar aspects). The weak layer collapsing and creating these slabs is the faceted snow. Sunshine and warming of the upper snowpack is expected today, which can make it easier for us to trigger these slabs, and even in some cases may cause them to release on their own. Wet loose avalanches or cornice falls could also trigger a big slab.

We had a lot of uncertainty with this setup the past several days, but that has changed with one clear sky day and people out testing the snowpack. It’s clear we have a problem unfortunately. This layer is too deep to test, but we have all the evidence we need at this point to be conservative. Hence, staying away from large steep slopes and paying close attention to your location under slopes is recommended.

A warm day is on tap with light westerly winds (in fact temps have been warming overnight already). We are expecting to see rollerballs and moist to wet sluffs releasing through the day. Some could be large enough to run to the bottom of slopes. As is the case this time of year, the easterly slopes will see the first warm up and by 5pm the westerly slopes will be quite warm. Wet sluffs should be easy for people to trigger once the surface becomes moist and sticky.

Sunshine may also make the wind slabs that formed yesterday more reactive. Yesterday’s NW winds formed slabs on all aspects due to terrain channeling. It’s common for a wet sluff to trigger small pockets of slabs on its way down. The more concerning issue of course is if one of these triggers a deep slab discussed above.

Cornices may start warming and becoming closer to their breaking point. Not only is a cornice fall dangerous, but it could trigger a large slab below. Give these an extra wide berth along ridgelines.

Small wet loose sluffs releasing midday yesterday in Jr’s Bowl (2nd Bowl) on the backside of Settle Ridge. 3.25.23.

A quick THANK YOU to everyone who stopped by the motorized parking lot yesterday for our Turnagain Pass Avy Awareness Day!!