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Couple avalanches in JFS Canyon
Location Name:
BNSF Avalanche Safety - Snowslip Mtn GNP
Observation date:
Wednesday, January 1, 2020 - 18:15
Is this an Avalanche Observation:
Yes
Observation made by:
Public
Tabs
Quick Observation
Toured up the Shed 6/7 ridge to the weather station at 6100 feet, then descended Shed 5.
Objectives were to observe new snowfall totals, recent wind-loading, and any new avalanche activity.
Wet, windy, and warm weather. Snowline was pushing upwards of 4500 feet elevation (photo). Moderate snowfall most of the afternoon above this elevation with rain or rain/snow mix below.
Moderate SW winds above 5000 feet all day.
The day started with air temperatures just above freezing on the Canyon floor and warming into the upper-30s °F by the afternoon. Above 6000 feet daytime highs reached the upper-20s °F.
Below 5000 feet 24-hour snowfall totals ranged from 3-6 inches, but rain below 4500 feet had melted a lot of this new snow by late afternoon.
Above 5000 feet 24-hour snowfall totals ranged from 6-10 inches.
Recent westerly winds have wind-loaded easterly aspects above 5000 feet and thickened new storm/wind slabs to 15-20 inches in some locations.
The new snowfall is heavy and dense which somewhat limited the extent of blowing and drifting snow. At least at the elevations we travelled through.
The snowpack surface above 5000 feet pre-storm consisted of a few inches of weak, faceted snow and surface hoar sitting on top of a firm crust. The heavy and wet new snow is forming cohesive slabs over this weak structure and we observed a couple avalanches during our tour.
The first was an intentionally and remotely triggered slide in a location known as Test Slope 3, a SE-facing slope at about 5600 feet. Failure was in old faceted snow just on top of the crust formed/buried last week around Christmas. Debris ran a couple hundred vertical feet into the upper reaches of the Shed 6 path. Crown was 5-15 inches thick and about 100 feet wide (photo). Classified as SS-ASr-R3-D1.5-O.
The second was a naturally triggered avalanche in the Shed 5 path a SE-facing slope. The crown was located at about 5800 feet and debris ran to 5100 feet. We suspect the failure layer was the same as in Test Slope 3. Estimated the crown dimensions at 5-20 inches thick and 150-200 feet wide (photos). Classified as SS-N-R2-D2-O.
Snowpack, Avalanche, Weather Images:
Travel Details
Region:
Flathead Range/Glacier National Park - John F. Stevens Canyon
Activity:
Skiing
Avalanche Details
Avalanche Details:
Date and Time of Avalanche:
Wednesday, January 1, 2020 - 11:30
Number of avalanches:
2
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
Old snow
Trigger
Trigger:
skier
Trigger Modifier:
Intentionally Triggered
Terrain
Start Zone Slope Angle:
37
Aspect:
Southeast
Starting Elevation:
5600
Size
Destructive Size:
D1.5
Relative Size:
R3 Medium
Crown Height:
1 ft
Avalanche Length (Vertical Run):
200ft.
Avalanche Width (Average width):
100ft.
Avalanche Location:
Javascript is required to view this map.
Date and Time of Avalanche:
Wednesday, January 1, 2020 - 13:15
Number of avalanches:
1
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
Old snow
Trigger
Trigger:
natural
Terrain
Aspect:
Southeast
Starting Elevation:
5800
Size
Destructive Size:
D2 Could bury, injure, or kill a person.
Relative Size:
R2 Small
Crown Height:
1 ft
Avalanche Length (Vertical Run):
700ft.
Avalanche Width (Average width):
150ft.
Avalanche Location:
Javascript is required to view this map.
