Turnagain Pass

A skier triggered a small but deeper avalanche failing on a weak layer of facets just above the Thanksgiving crust yesterday on Eddie’s. The skier triggered the avalanche remotely and nobody was caught in the slide. The slab was roughly 2 feet deep and 50 feet wide. This is the first human-triggered avalanche failing on that Thanksgiving layer that we are aware of.

Skiers also triggered shallow wind slab avalanches on Eddie’s and Tincan yesterday.

Photo at the crown of the avalanche that was remotely triggered from 50′ away by a skier on Eddie’s. Photo: Andy Moderow, 12.09.2023

An intense storm is approaching today, and avalanche danger will rapidly be on the rise as the weather intensifies. For most of the day, the biggest factor will be the strong easterly winds that will be picking up starting this morning. We should see speeds around 30-50 mph this afternoon, picking up to 50-60 mph overnight. We are also expecting some snow today- around 2-4″ this afternoon- but the bulk of the storm is expected to hit us overnight tonight. We will likely see 2-3 feet of snow in Girdwood and Turnagain Pass, 1-1.5′ in Summit, and 3-4′ at higher elevations in Portage, Placer, and Seward. Most of this is expected to fall between 3 pm tonight and 3 am tomorrow. Expect HIGH avalanche danger as the storm intensifies, and plan on getting out of the backcountry before things get wild.

Since most of the snow is falling after sunset this evening, our main concern for the day will be the touchy wind slabs forming as the winds ramp up. We started seeing some of this yesterday, with skiers triggering shallow wind slab avalanches on Eddie’s and Tincan, and we are expecting to see more today. Slabs will be getting thicker, making avalanches bigger through the day, and the chances of natural avalanches will increase as the winds continue to blow. Given the strength of the forecasted winds, we’ll be on the lookout for winds moving snow into sensitive slabs down into the low elevations as well as in the alpine. To make things even more interesting, the new slabs forming at the surface will also be adding stress to a weak layer of snow buried deeper in the snowpack, increasing the chances of triggering a large avalanche (See the additional concerns for more on this). We’re entering a stretch of dangerous avalanche conditions, so travel cautiously and be prepared to get out of the backcountry as the storm picks up later in the day.

This is looking like a proper storm, with 12-hour totals exceeding 3 feet for many areas within our forecast zone. Graphic courtesy of NWS Anchorage, 12.10.2023

This round of intense snowfall will be applying a heavy load to the snowpack in a very short time, adding stress to the weak layer of facets above the Thanksgiving crust that we have been tracking for the past few weeks. There is a lot of uncertainty with this weak layer, and it is hard to say if the new snow will be enough to push that layer to its breaking point. Yesterday a skier triggered a small but deep avalanche failing on this weak layer in Eddie’s, and we also saw a natural avalanche that likely failed on this weak layer on the back side of Seattle Ridge sometime within the past week. If we do start seeing more activity on this weak layer it has the potential to produce very large avalanches, propagating wide distances over multiple terrain features. This storm will be a good test to see how close the layer is to its breaking point.

The layer of concern is currently buried about 2′ deep on average, but could be 5′ deep or deeper after the approaching storm. 12.10.2023