Storm slab development

Location Name: 
Forecaster Observation - Noisy Basin, Swan Range
Observation date: 
Friday, February 16, 2018 - 14:00

Is this an Avalanche Observation: 
No
Observation made by: Forecaster

Location

Tabs

Quick Observation

Traveled along the west side of the Swan Range, and the Swan Crest, to observe storm slab development and wind loading.

  • At low elevations, there was up to 8" of low-density snow sitting on top of a 1" breakable rain crust formed 2/8. On steep slopes, this snow easily sluffed off the crust with ski cuts.
  • At mid-elevations, there was up to 10" of snow sitting on top of a 3/4" breakable rain crust formed 2/8. In sheltered locations, this snow was low density and sluffed readily. In open areas, this snow was dense and was adhering to the underlying slab.
  • At upper elevations, up to 12" of snow sat on top of a 1" crust formed 2/8. This snow was generally dense and was not adhering to the underlying crust in sheltered locations.
  • Despite poor visibility, I noted a handful of thin (<12") storm slabs that had failed recently on easterly aspects. Most of these crown lines had already filled in with recent wind and snow.
  • I was able to trigger several thin (<12") storm slabs on easterly aspects with ski cuts. 
  • Cracking underfoot was observed throughout the tour with shooting cracks up to 20' in length noted at upper elevations.
  • Moderate southwest winds transported snow throughout the day at mid and upper elevations.
  • Facets on top of the 2/8 crust were observed at all elevations in sheltered locations.
Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Swan Range - West Side (Flathead Valley access)
Route Description: 

Traveled up the switchback trail to the Swan Crest.  

Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation: 
NE
E
SE
SW
W
Red Flags: 
Shooting cracks
More than a foot of new snow or heavy snowfall rates (>1"/hr)
Blowing snow
Persistent Weak Layers: 
Buried
New Snow in the past 24 hours: 
0.00in.
Total Snow Depth: 
130
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Friday, February 16, 2018 - 20:00