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Looking for deep weak layers
Location Name:
Forecaster Observation - southern Glacier Park
Observation date:
Saturday, January 15, 2022 - 17:45
Is this an Avalanche Observation:
Yes
Observation made by:
Forecaster
Tabs
Quick Observation
We toured on the west side of Marias Pass today.
Large avalanches this past week in southeastern British Columbia failed on a crust/facet layer from early December (
https://avalanche.ca/blogs/persistent-slab-avalanches-in-southern-interior
) We suspect that our region has this same structure. With the avalanche danger LOW at all elevations, we decided to dig into the snowpack to look for this potentially troublesome layer. Digging a pit on the NE aspect at 6868 feet showed the presence of this weak layer, 35 centimeters above the ground. We did not find this buried weak layer moving to a nearby south aspect. FAC forecasters will continue to look for the distribution of this layer.
After this week's rain and warming, it was no surprise to find crusts in every aspect. Melt freeze crusts on south aspects are well developed and 2 inches thick. Above 6200 feet, North and Northeast aspects only had an eggshell crust with soft snow underneath.
We saw evidence of recent cornice collapse on mid and upper-elevation slopes (see photo). We noted a 10 foot long crack in a sagging cornice in one location.
Winds were moderate today, with blowing snow on a few of the highest peaks in the morning.
The Avalanche tab will be filled out in the morning
Snowpack, Avalanche, Weather Images:
Travel Details
Region:
Glacier National Park - Southern Lewis Range
Activity:
Skiing
Snowpack Details
Snowpack and Weather Details:
Terrain
Elevation of observation:
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation:
NE
E
SE
S
Persistent Weak Layers:
Not observed
New Snow in the past 24 hours:
0.00in.
Total Snow Depth:
245 centimeters
More comments about the snowpack and weather:
With large avalanches this past week in southeastern British Columbia failing on a crust/facet layer from December 3, we decided to look at upper elevations for the presence of this structure in our snowpack. We choose to dig on a NE and S aspect, close to each other (6868 feet). Total snow height on our NE aspect was 245 centimeters. The upper 210 centimeter is right side up and appears quite stable. We encountered the December 3 crust/facet layer 35 centimeters above the ground. The crust here is 8 centimeters thick and knife hard. It sits on top of a 2 centimeter thick, one-finger hard faceted layer. Moving to a nearby south aspect, we did not find this layer. The total snow height here was 160 centimeters. Temperatures were mild today, and melting began at 1100 on the south slopes. Today, melting continued up to 6800 feet when clouds and moderate winds cooled the snow surface. This week's rain and warming temperatures have resulted in many types of crust. South aspects sport a stout melt-freeze crust. On shady aspects at upper-elevations, the crust is notably thinner, eggshell thick in some places.
Blowing Snow:
Light
Wind Speed:
Moderate (Small trees sway)
Wind Direction:
West
Air temperature:
Below Freezing
Snow line:
5800 feet
Sky Cover:
Mostly Cloudy (BRK)
