Fresh deep slab on Penrose

Location Name: 
Forecaster Observation- Flathead Range
Observation date: 
Friday, February 21, 2020 - 18:15

Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

We found a variety of avoidable avalanche concerns on today’s tour into the Middle Fork.

  • We spotted 4 recent cornice falls from alpine ridgelines. Two of these triggered slab avalanches (D2-D2.5). One appeared to be a deep slab.
  • About a dozen loose wet avalanches had run recently on southerly aspects starting at mid-elevations. A few of these grew to D2 in size and ran to low elevations. At least a few more D1s ran today.
  • Strong winds above 7000’ were blowing snow and forming thin but hard wind slabs that cracked under our skis in a few locations. We could identify them by noting where the snow surface got dense, hard, and smooth. The winds were also destroying near surface facets and preventing loose wet concerns. 
  • We traveled on steep southerly aspects early in the morning and late in the day when surface crusts were frozen, and felt comfortable skiing steep, wind protected, shady terrain where the snow quality was softest, while limiting our time below cornices.
  • Surface hoar formed at low elevations and near surface facets continue to develop on wind protected shady aspects. Sun crusts are prevalent on southerly aspects.
Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Flathead Range - Middle Fork Corridor
Route Description: 

To 7600'

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: 
NE
E
SE
S
Red Flags: 
Blowing snow
Rollerballs / pinwheels
Persistent Weak Layers: 
Surface Hoar
Facets or Faceted Crust
On the surface
New Snow in the past 24 hours: 
0.00in.
Blowing Snow: 
Moderate
Wind Speed: 
Strong (Whole trees in motion)
Wind Direction: 
Southwest
Sky Cover: 
Clear (CLR)
Highest Precipitation Rate: 
No Precipitation (NO)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Thursday, February 20, 2020 - 15:30
Number of avalanches: 
1
Avalanche Type: 
Hard Slab
Failure Plane/Weak Layer: 
Old snow
More information or comments about the avalanche: 

Crown observed from Hwy 2.  Could only see the start zone.  D size estimated with limited vantage.

Hide Trigger
Trigger: 
natural
Trigger Modifier: 
Cornice Fall Triggered
Hide Terrain
Aspect: 
Northeast
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D2.5
Relative Size: 
unknown
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, February 20, 2020 - 15:30
Number of avalanches: 
1
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Unknown
More information or comments about the avalanche: 

Viewed from Highway 2. Crown looked to be a few feet thick.

Hide Trigger
Trigger: 
natural
Trigger Modifier: 
Cornice Fall Triggered
Hide Terrain
Aspect: 
Northeast
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D2 Could bury, injure, or kill a person.
Relative Size: 
R2 Small
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, February 20, 2020 - 13:30
Number of avalanches: 
2
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Within storm snow
Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
South
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D2 Could bury, injure, or kill a person.
Relative Size: 
R2 Small
Avalanche Length (Vertical Run): 
1500ft.
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, February 20, 2020 - 13:30
Number of avalanches: 
10
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Within storm snow
More information or comments about the avalanche: 

These likely ran 2/20. Maybe 2/19 though.

Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
South
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R1 Very Small
Avalanche Location: 
Date and Time of Avalanche: 
Friday, February 21, 2020 - 13:30
Number of avalanches: 
4
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Within storm snow
More information or comments about the avalanche: 

SE aspects a bit more active today, perhaps because they were wetting for the first time, whereas south has been in the action now for a day or two.  

Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
Southeast
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R1 Very Small
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, February 20, 2020 - 13:45
Number of avalanches: 
2
Avalanche Type: 
Cornice
Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
Northeast
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D1.5
Avalanche Location: