Chugach State Park

Recent Avalanches: *Updated on December 23rd* Skier-triggered avalanche occurred on December 22nd on Flattop. Over the past week, there was one wind slab avalanche documented on the north side of Mt. Baldy. The observation was written on Saturday (Dec 16th). The observer thought the avalanche occurred naturally Friday night. At the end of last week there were a few skier-triggered dry loose avalanches in the Upper Rabbit Creek area. Several of the Alaska State Park employees patrolled Upper Campbell Creek and took photos of natural dry loose avalanches on the west side of Avalanche Peak.

Natural dry loose avalanches on the west side of Avalanche Peak. Photo taken by Ben Corwin on 12.21.2023

Weather Recap: In the past week, the Front Range has received roughly 12” of new snow with moderate to strong winds at ridgetops, predominately from the north and at higher elevations. The Arctic Valley weather station recorded gusts up to 82 mph on December 16th at 3pm. Temperatures ranged from 0F to 32F with an average of around 18F.

Starting tonight (Dec 22nd) a storm is moving in with increasing winds, clouds, and snow. Winds are forecast to average 15-40 mph from the SE with stronger gusts for roughly 24 hours with a possible lull Saturday late afternoon and evening. On Sunday the winds are increasing again to averages of 15-35 mph. Between 8-12” of snowfall is expected this weekend, with precipitation starting this afternoon and continuing through Sunday evening. Temperatures should rise from the low twenties to the high twenties F during the day Saturday and then into the low thirties on Sunday morning, and drop into the teens Sunday evening. The rain line might creep up as high as 500’ on Saturday afternoon, but the weather models are uncertain.

The overall snowpack depth is highly variable in the Front Range right now. In many areas, around 16″ of light, low-density snow is sitting mainly on the ground, with lots of rocks and branches hiding underneath. In areas that tend to fill up with snow, like gullies and alpine bowls, the snowpack is deep and potentially harboring buried weak layers.

With stormy weather forecast this weekend bringing between 8-12” of new snow and sustained moderate to strong winds from the southeast, wind slab, storm slab, and loose snow avalanches are all expected.  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. 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.

Storm Slabs: The weather models are uncertain about how much new snow will come in this weekend. If over 10” of snow occurs in less than 24 hours then shallow storm slabs may form. These would be the depth of the new snow and either release naturally or easily triggered by a person.

Blaine Smith with the Alaska Avalanche School conducting a shovel-tilt test in the top 16″ of the snowpack. Photo taken on 12.19.2023

There are two weak layers we are watching within the snowpack. One is a thin layer of facets about 20” deep which exists right above the Thanksgiving crust. This has been observed at lower elevations. The other is a layer of larger facets at the base of the snowpack, observed at higher elevations. Over the past week, we have not had concerning test results in snowpits and we don’t know of any avalanches that have released on those layers. However, we are still highlighting them because of their potential to cause very large and destructive avalanches. To manage persistent slab problems, we recommend sticking to lower angle terrain.

Photo of facets above Thanksgiving crust in Rabbit Creek area at 2,400’. Photo taken 12.20.2023 by Graham Predeger.

Thanksgiving crust  25″ deep in Eagle River at 2,800′. Photo taken 12.19.2023