Wind slabs on Mt Brown

Location Name: 
Forecaster Observation - Mt Brown, GNP
Observation date: 
Sunday, March 3, 2019 - 15:15
Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

Traveled to Mt Brown to note signs from the recent northeast wind event.

  • Two recent wind slab avalanches were observed near the top of 2 of the steep NW gullies. Both of these were above 6500'. 
  • Terrain sheltered from the wind harbored up to 14" of low-density powder that is settling out.
  • Recent winds have left a 4-8" (thick) 4F to 1F (hard) slab on SE, S, and SW aspects above and below treeline with slabs found on W and NW aspects above treeline. In many locations, the slab was bonding poorly to the underlying snow surface.
  • Instabilities noted included cracking, shooting cracks, and intentionally triggered small wind slab avalanches.
Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Glacier National Park - McDonald Lake Area
Activity: 
Skiing
Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation: 
S
SW
W
NW
Red Flags: 
Shooting cracks
Persistent Weak Layers: 
Surface Hoar
On the surface
New Snow in the past 24 hours: 
0.00in.
More comments about the snowpack and weather: 
Up to 14" of low-density snow that is beginning to settle out in wind-sheltered areas. Wind affected areas had a 4F to 1F hard slab 4-8" thick which rested on low-density snow on NW aspects and either a sun crust or firm wind packed snow on south aspects.
Wind Speed: 
Light (Twigs in motion)
Wind Direction: 
Northeast
Air temperature: 
Below Freezing
Snow line: 
0
Sky Cover: 
Clear (CLR)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Friday, March 1, 2019 - 20:15
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
More information or comments about the avalanche: 

2 wind slab avalanches near the top of 2 of the NW gullies. Could not see how far down the debris ran. Both were triggered by wind loading by northeast winds that pushed through the Snyder Basin headwall/Little Matterhorn saddle. Crowns were 12-18" deep.

Hide Trigger
Trigger: 
natural
Hide Terrain
Start Zone Slope Angle: 
37
Aspect: 
Northwest
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D2 Could bury, injure, or kill a person.
Relative Size: 
R2 Small
Crown Height: 
1 ft
Avalanche Width (Average width): 
100ft.
Avalanche Location: