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New snow and winds in the Program Area
Location Name:
BNSF Avalanche Safety - Snowslip Mtn. GNP
Observation date:
Friday, December 13, 2019 - 21:00
Is this an Avalanche Observation:
Yes
Observation made by:
Public
Tabs
Quick Observation
Toured through the upper elevations of Sheds 7 East, 6, and 5 today.
Objectives were to look for any recent avalanche activity, measure new snow accumulations, assess recent wind-loading, and continue to monitor snowpack structure and stability.
Overcast skies with light to moderate (S1 or S2) snowfall off and on throughout the day with moderate SW winds above 5000 ft. elevation.
Air temperatures hovered in the low to mid-20s °F above 6000 ft. elevation and warmed to low-mid 30s °F at the Canyon floor by early afternoon.
New snow accumulations from the past two days range from 8-11 in. on the Canyon floor to 12-18 above 6000 ft. elevation.
Above 5500 ft. the snowpack is about 1-2 ft. deep and above 6000 ft. deepens to 3-4 feet in wind sheltered areas. Wind loaded areas were deeper with up to 5 or 6 ft of snow in some locations.
Fresh wind slabs on easterly aspects were up to 1 ft. thick above 5000 ft. Ski cuts through these wind slabs resulted in some shooting cracks up to 50 ft in length (photo below).
Observed only one small avalanche in Shed 7 West, details below.
Revisited the same location in the Shed 7 East path where a full snow profile was conducted at 6300 ft. on a SE aspect on Dec 2nd. The snow depth here has doubled over the past 11 days from 24 to 50 in. No fractures during an extended column test on the layer of facets now buried 40 in. down in the snowpack. This facet layer was also moist from last week’s warm weather and had firmed to 4F+ hardness.
Dug another snowpit nearby at 6400 ft on an ENE aspect. Total snow depth was 40 in. with moist but weak facets making up the bottom 6 in. An extended column test resulted in ECTP21 on this weak basal layer (snowpit profile below).
One small (SS-NC-R1-D1.5) in the Shed 7 West path at about 6700 ft on an E aspect. Looked to be a cornice fall trigger that cut out a recent wind-slab just below the ridge crest. Estimated slab thickness was 5-10 in. with debris running only a couple hundred feet terminating well above the rail grade.
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:
Friday, December 13, 2019 - 09:15
Number of avalanches:
1
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
Within storm snow
Trigger
Trigger:
natural
Trigger Modifier:
Cornice Fall Triggered
Terrain
Aspect:
East
Starting Elevation:
above-treeline
Size
Destructive Size:
D1.5
Relative Size:
R1 Very Small
Crown Height:
Less than 1 ft
Avalanche Location:
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