Turnagain Pass

Yesterday’s clear skies gave plenty of opportunity to assess the extent of Friday’s natural cycle. The exact timing of some of the avalanches was uncertain, but we know there were some natural slab avalanches later in the day Friday that were triggered by loose avalanches when the sun came out in the afternoon. Almost all of the avalanches around Turnagain Pass were around 1-2′ deep, and are suspected to have failed on an interface from the beginning of last week’s parade of storms. Here are a few photos from the cycle.

Wide-propagation in Lynx Creek, as seen from the Center Ridge parking lot. Photo: Andy Moderow. 02.19.2020

Wide crown in the bowl just east of Pastoral. Photo: Pyper Dixon. 02.19.2020

Smaller loose avalanche in motion, overrunning the crown of another recent avalanche. 02.19.2022. Photo: Andy Moderow.

The storm from Thursday night fell onto some suspect surfaces, which are still giving us cause for concern today. Yesterday’s bountiful sunshine allowed us to get an idea of the extent of Friday’s natural cycle, and to assess the layering in the upper snowpack that facilitated that cycle. We are still investigating the potential weak layer that was buried on Valentine’s Day. Here is what we have seen so far:

Seattle Ridge: Groups have been finding near-surface facets and buried surface hoar about 1.5′ deep, which was propagating in some snowpit tests. (more info here).

Lipps: Yesterday we found a layer of decomposing stellar dendrites buried just over a foot deep that was giving mixed results in snowpits. We suspect this layer was the culprit for at least one nearby avalanche. (Details here).

Girdwood area: One group backed off an objective after getting propagating test results on a thin rime crust buried about 1.5′ deep just north of Girdwood.

So far we are not aware of any slab avalanches that occurred yesterday, but some of these details suggest we just buried a potentially dangerous weak layer. Needless to say, there is still a high level of uncertainty with this layer. Today, this uncertainty requires a heightened level of awareness, and careful terrain selection while we see how the layer is behaving in the long run. With another quiet day of weather on tap today, it will be important to keep this potential for human-triggered avalanches in mind and avoid big or consequential terrain.

For areas with a thinner snowpack at the edges of our advisory area (Crow Pass, Lynx and Silvertip Creeks), as well as outside of our area (Summit Lake), there is an additional concern for the weak snow associated with our New Year’s and Halloween crusts. We have consistently seen poor stability test results failing on faceted snow buried 2-4′ deep in these zones. This indicates the potential for large human-triggered avalanches, and is one more reason to reign in your terrain choices in the areas with a thinner snowpack.

Loose snow avalanches: If the sun pokes out again in the afternoon we can expect to see another round of loose snow avalanches, dry and wet.

Crown of a recent natural avalanche on Lipps. The avalanche was not huge, but it was big enough to bury a person and it seemed to be a similar depth to most of the rest of the activity around Turnagain Pass. It had been partially blown in after it released. Likely depth 1-2′, triggered by loose snow avalanches releasing up slope. 02.19.2022

Depth to the layer of concern (decomposing stellars) on Lipps. This depth corresponds with buried facets and surface hoar on Seattle Ridge, and a rime crust north of Girdwood. 02.19.2022