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Ridge Runnin'
Location Name:
BNSF Avalanche Safety - Snowslip Mtn GNP
Observation date:
Saturday, January 11, 2020 - 20:45
Is this an Avalanche Observation:
Yes
Observation made by:
Public
Location
Tabs
Quick Observation
Conducted road observations from Hwy 2 and toured up the SE ridge of Snowslip Mtn. and into the upper reaches of the Burnout and Shed 4D and on up to Shed 7 West at 6500 feet. Descended the same route.
Objectives were to observe new snowfall totals since Jan 7th, re-assess buried weak layers in this area, and look for any recent avalanche activity.
Two very small (Destructive size D1.5) storm/wind slabs ran on the steep slope right under the 7 West cornice (about 6700 feet, east aspect). Visibility was limited, but estimate the crowns at 6-8” thick and maybe 40-50’ wide (SS-N-maybe cornice triggered?-R1-D1.5-I). These ran a couple hundred feet down slope terminating well above the rail, entraining a fair amount of snow on the way down.
No other avalanche activity observed.
Could just barely make out the old crowns from the larger (Destructive size 2.5) avalanche that ran earlier in the week (photo).
Overcast skies with snow showers off/on all day (S-1 to brief S2). Light SW winds all day with very little new wind-loading in our location.
Air temperatures rose to just about freezing on the Canyon floor by this afternoon. Temperatures above 6000 feet rose to the low-20s °F.
4-5” of snow overnight with another 1-2” over the course of the day. There was about a foot of new snow since Jan 7th.
Ski cuts on small test slopes resulted in only minor cracking underfoot (1-2 feet long) with no shooting cracks or slab releases.
Re-dug our snowpit in Shed 4D at 5800 feet from the 7th to test the layer of surface hoar that is now buried 30” down from the surface. ECTP14 on this layer on the 7th, ECTN29 on the same layer today. A compression test yielded CT22 SP on this same layer as well.
Continued up into the uppermost starting zone of Shed 7 West and conducted a full profile there at 6500 feet, on a SE aspect, 27° slope. Snow depth was 51” (profile attached). No layers propagated in large column tests. A compression test did yield a sudden planar result on the buried near-surface facets sitting on top the Christmas crust down 28” from the surface.
The faceted snow at the base of the snowpack was rounding and unreactive in stability tests.
Snowpack, Avalanche, Weather Images:
Travel Details
Region:
Flathead Range/Glacier National Park - John F. Stevens Canyon
Route Description:
To 6500 feet
Activity:
Skiing
Avalanche Details
Avalanche Details:
Date and Time of Avalanche:
Saturday, January 11, 2020 - 12:00
Number of avalanches:
2
Avalanche Type:
Soft Slab
Failure Plane/Weak Layer:
New/old snow interface
More information or comments about the avalanche:
Maybe cornice trigger? Visibility was limited by clouds.
Trigger
Trigger:
natural
Terrain
Aspect:
East
Starting Elevation:
6700
Size
Destructive Size:
D1.5
Relative Size:
R1 Very Small
Crown Height:
Less than 1 ft
Avalanche Length (Vertical Run):
200ft.
Avalanche Width (Average width):
50ft.
Avalanche Location:
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