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Avalanche on Snowshed Mtn
Location Name:
BNSF Avalanche Safety - Snowslip Mtn. GNP
Observation date:
Wednesday, December 23, 2020 - 22:45
Is this an Avalanche Observation:
Yes
Observation made by:
Public
Location
Tabs
Quick Observation
Toured up the ridge above Burnout and the Shed 4D/5 avalanche paths and then farther on into the upper starting zone of Shed 7 West to a highpoint at ~6600’. Then made road observations and checked manual weather stations on the Canyon floor.
Descended the Shed 5 Path.
Objectives were to look for any recent avalanche activity, determine the upper elevation limit of the Dec 22nd crust, assess the past 48-hour snowfall totals and recent wind-loading, and obtain a full snow pit profile in the Shed 7 area.
No avalanche activity observed in the Program Area, but noticed an avalanche crown from Hwy 2 on the SE face of Snowshed Mountain above Sheep Creek (photo) in the Flathead Range. This appeared to be at least D2 in size and likely failed on a more deeply buried persistent week layer. Estimating that it ran sometime during the Dec 21-22 overnight warm-up.
About 4-5” snow from yesterday on top of the Dec 22nd crust at the Canyon floor. The snowpack below the crust was moist at low-mid elevations.
Around 6500’ the Dec 22nd crust eventually disappeared and there was about 6-10” of new snow from yesterday and the snowpack became dry throughout.
Recent wind-loading was minimal with very little new wind slab development at all elevations we travelled through.
Snow profile conducted in the Shed 7 West Path at 6600’ on a southeast aspect. Dec 9th crust/facet combo was about 28” below the surface here. No propagation with an Extended Column Test (pit profile with more details in photo).
No shooting cracks, audible collapses, or any other signs of instability during the ski tour.
Mostly overcast skies with occasional breaks that allowed for some brief sunshine. Clearing skies by late afternoon/sundown.
Very light snow coming down as on again/off again showers with trace accumulations over the day.
Light and variable winds at all elevations.
Daytime high air temperatures reached the mid-20s °F on the Canyon Floor and the mid-teens °F at elevations above 6000’.
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:
Tuesday, December 22, 2020 - 02:00
Number of avalanches:
1
Avalanche Type:
Hard Slab
Failure Plane/Weak Layer:
Old snow
More information or comments about the avalanche:
Observed from HWY 2 and all details are rough estimates.
Trigger
Trigger:
natural
Terrain
Aspect:
Southeast
Starting Elevation:
above-treeline
Size
Destructive Size:
D2.5
Relative Size:
R2 Small
Crown Height:
3 ft
Avalanche Width (Average width):
300ft.
Avalanche Location:
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