A few avalanches and buried surface hoar

Location Name: 
BNSF Avalanche Safety - Snowslip Mtn GNP
Observation date: 
Tuesday, January 7, 2020 - 19:45
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 avalanche paths to 5800 feet. Descended the same route.
  • Objectives were to observe the new snowfall totals from the current storm, acquire more detail on the snowpack structure above the rail at the east end of the Program Area, and look for any recent avalanche activity.
  • Path 1163 ran sometime earlier today. Visibility was limited, but the debris ran about 2/3rds path terminating above the rail. This appeared to be a soft slab and was a Destructive size 2 of 5 (could bury, injure, or kill a person).
  • Numerous small (Destructive size 1) sluffs were observed on steep cutbanks below 5000 feet.
  • We saw what appeared to be a crown from a recent slab on western side of Shed 5 but could not confirm due to low visibility.
  • Overcast skies with moderate snowfall for much of the day until about 1600 when snowfall rates began to taper off. Light to moderate SW winds all day with very little new wind-loading in our location. But we suspect wind-loading was more severe above 6000 feet.
  • Air temperatures rose to just above freezing on the Canyon floor this morning and hovered there all day. Temperatures above 6000 feet rose to the mid to high-20s °F.
  • Snowfall totals from the past 2 days ranged from 12-18 inches on the Canyon floor with about 1.2 inches of water equivalent. Above 5500 feet new snowfall has exceeded 20 inches.
  • From the Canyon floor up to about 5500 feet the new storm snow was “upside down” with heavier, more dense snow from last night and today sitting on top of a layer of lighter, lower density snow beneath. Above 5500 feet this layering structure dissipated and new snow density was more uniform.
  • Ski cuts on small test slopes resulted in only minor cracking (1-2 feet long) or no shooting cracks or slab releases at all.
  • We dug a snowpit and conducted a full profile in the upper reaches of the Shed 4D path at 5800 feet on an easterly aspect, 27° slope. Total snow depth was 70 inches with about 24 inches of new snow since yesterday afternoon (pit profile attached).
  • We found an obvious layer of buried surface hoar down 27 inches from the snowpack surface. This layer propagated in an Extended Column Test, ECTP14.
  • The Christmas crust was about 40 inches down and the November crust was not present at this location.
  • The faceted snow at the base of the snowpack was rounding and unreactive in large column tests. A deep tap test resulted DT17 with a non-planar break, just below the Christmas crust.
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, January 7, 2020 - 10:00
Number of avalanches: 
1
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Unknown
Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
South
Hide Size
Destructive Size: 
D2 Could bury, injure, or kill a person.
Relative Size: 
unknown
Avalanche Location: