Chugach State Park

Recent Avalanches:  Over the past week, there have been no new known avalanches. The last known avalanches were the two large natural avalanches documented in the South Fork of Eagle River during the Christmas storm event. The slides appeared to be triggered naturally from cornice falls during the major wind events around Christmas and likely failed on the faceted layer at the base of the snowpack.

Weather Recap: In the past week, the Front Range has received roughly 3” of new snow with 20-60 mph winds at ridgetops predominantly from the north at higher elevations. Temperatures at Glen Alps and Arctic Valley ranged from single digits to mid-30s F, averaging around 20F. At the bottom of the South Fork of Eagle River valley temperatures dipped as low as -23F. Brr! The overall snow depth is highly variable in the Front Range right now. In many areas the winds have scoured the landscape and bare ground is visible. In areas that tend to fill up with snow, like gullies and alpine bowls, the snowpack is deep and potentially harboring buried weak layers.

Weather Forecast: Starting this afternoon (January 5th) a storm is moving in with increasing winds, high clouds, and snow. Winds are forecast to average 15-30 mph from the SE for roughly 12 hours with a possible lull late tonight and early Saturday morning. Saturday winds are looking to be around 15-30 mph, increasing to 40-60 mph through Sunday. Between 2-5” of new snow is expected this weekend, with precipitation starting this evening and continuing through Sunday evening. Temperatures are forecast to stay pretty consistently in the mid to low 20’s F this weekend. The rainline might creep up as high as 600’ today.

Flagging behind McHugh Peak. Photo taken 01.04.24

Photo of Peaks in Upper Rabbit Creek. Photo taken 01.04.24

Wind Slab: With stormy weather forecast this weekend bringing between 2-6” of new snow and sustained 20-60 mph winds from the southeast, wind slab, storm slab, and loose snow avalanches are all expected. Even if new snow amounts are only a few inches, wind slabs will still be a concern due to a foot of loose snow currently on the surface that could rapidly be deposited into slabs 1-3’ deep in exposed terrain. Both natural and human-triggered avalanches could occur this weekend.

To identify areas with wind slabs look for active wind transport and feel for firmer, hollow snow on the surface. Using small test slopes can be a good way to check whether wind slabs are reactive to human triggers in the area you are traveling. Wind slabs can be avoided by sticking to sheltered or wind-scoured areas. Keep in mind, given the weak snow layers buried deeper in the snowpack (Problem 2), a relatively small wind slab triggered near the surface has the potential to step down to a deeper weak layer.

Snow transport and flagging at ridgetops in the Upper Rabbit Creek Area. Photo taken 01.04.24

Persistent Slab:  There are three layers we are watching within the snowpack.  The most concerning is the layer of facets at the base of the snowpack at higher elevations. In the South Fork of Eagle River, two larger avalanches were observed on Swiss Bowl and Italian Bowl on NNW through NNW aspects that are thought to have failed on this layer around Christmas. The second layer is a thin layer of facets about 20” deep which exists right above the Thanksgiving crust. This has been observed at lower elevations. Lastly, we are also monitoring the interface between near surface facets and wind slabs ~6” down from the current snow surface. Over the past week we have not had concerning test results and we don’t know of any avalanches that have released on those layers. However, we are still highlighting these persistent weak layers because of their potential to cause very large and destructive avalanches. We also want to recognize that the flat light and a breakable wind crust on many snow surfaces over the past week was a perfect recipe for poor skiing and riding conditions. Therefore, we have not gotten as much traffic in the area as usual, and may not be getting the whole picture. To manage persistent slab problems, we recommend sticking to lower-angle terrain.

Thanksgiving crust observed at 2,900’ in Eagle River. Photo taken 01.03.24

Facets at the base of the snowpack in Eagle River at 2,900′. Photo taken 01.03.24

Photo of identifying layers of concern in the snowpack in Eagle River at 2,900’.  Photo taken 12.04.24