We are deeply saddened to report a fatal avalanche accident that occurred on Stanton Mountain in Glacier National Park yesterday (more below). Lingering wind slab instability exists throughout the advisory area particularly in locations where they formed on weak snow. The avalanche danger is MODERATE above 5000 feet where human triggered avalanches are possible. Carefully evaluate wind loaded slopes and keep in mind the potential for a small avalanche to step down in to deeper weak layers.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Strong winds early this week created slabs on multiple aspects including atypical slopes across the advisory area. Recent observations prove variability in these slabs in terms of hardness, thickness, and reactivity. In some locations these slabs have been slow to strengthen due to weak snow that they were formed on. In the past week we found hard slabs in upper elevations that fractured and propagated with easy force in stability tests (video 1, video 2). Remember, that even a small wind slab release can trigger deeper instabilities and produce a large avalanche. Though the obvious signs of instability like cracking and collapsing may not be present it is still important to carefully evaluate wind loaded terrain before committing to a slope.
Weak snow in the lower to mid snow pack exists in most locations across the advisory area. These layers include weak snow (facets) formed during the cold period in mid-December (image), facets surrounding an early December rain crust, and weak snow near the ground in areas with a shallow snowpack. These layers have been dormant for most of the season mainly due to the lack of a cohesive slab on top of them. Now that we have a slab in the equation in many locations uncertainty remains about the load this weak snow can handle before reaching a tipping point. To address this uncertainty avoid terrain where you are most likely to trigger one of these deeper slides like steep, rocky terrain, and areas with a relatively shallow snowpack. Erich wrote about this in the new Forecaster's Corner.
We are deeply saddened to report that a skier sustained fatal injuries in an avalanche accident on Stanton Mountain in Glacier National Park yesterday, Thursday, 01/05/2017. We extend our most sincere condolences to the family and friends. We don't know the details of the incident yet, but a member of our staff is headed to the site to complete an avalanche accident investigation. We will provide an update as soon as more details emerge.
Yesterday, Zach was in the Crystal Drainage in the Flathead Range. He found wind affected snow above 6000' that was minimally reactive in stability tests. He also noted facets developing in the upper snowpack at all elevations. He observed wind transporting snow on the surrounding high peaks.
Tuesday: Todd and Seth traveled to Noisy Knob in the Swan Range. Hard wind slabs on all aspects at upper and mid elevations were observed as well as some facets at the ground level in shallow pits. The wind crusts were variable in strength, thickness, and reactivity. On a northwest aspect an Extended Column Test produced a fracture with propagation using easy force (ECTP 4) in a thin (10 inch), hard wind slab.
See below for all observations this season.
The cold arctic air that infiltrated the area early this week will remain into the early part of the weekend. Currently, mountain temperatures range from 1-8ºF, and winds are out of the southwest at 6-10 mph with gusts from 10-20 mph. Today should see mostly cloudy skies with light snow showers possible. Winds will remain out of the southwest at 5-10 mph with gusts in the 20s.
| 0600 temperature: | -1-7 deg. F. |
| Max. temperature in the last 24 hours: | 5-18 deg. F. |
| Average wind direction during the last 24 hours: | SW |
| Average wind speed during the last 24 hours: | 5-10 mph |
| Maximum wind gust in the last 24 hours: | 5-15 mph |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 51-67 inches |
| Friday | Friday Night | Saturday | |
|---|---|---|---|
| Cloud Cover: | Partly cloudy. | Partly Cloudy and cold. | Partly Cloudy. Light snow begins late. |
| Temperatures: | 8-14 deg. F. | -15--1 deg. F. | 14-23 deg. F. |
| Wind Direction: | Southwest | South/Southwest | Southwest/Southeast |
| Wind Speed: | 6-8 | 5-6 | 3-4 |
| Snowfall: | 0 in. | 0 in. | 0 in. |
| Snow Line: |
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
