| Trigger | Cornice | Remote Trigger | Unknown |
| Avalanche Type | Soft Slab | Aspect | Northwest |
| Elevation | 4200ft | Slope Angle | 38deg |
| Crown Depth | 3ft | Width | 150ft |
| Vertical Run | 500ft |
Avalanche: Hatcher Pass
Location: Rae Wallace
Fishhook Lot > Marmot South Ridge > Weather Station > Rae Wallace North > Presidents
Avalanche Details
Estimated occurred on 2/21
Crown depth 1-3 feet
HS/mostlySS-NC-D2-O failed on 4F 1.5mm facets rounding
Appears cornice failed naturally at ridge line, bounced down slope, triggered this slab mid-slope
Obvious signs of instability
| Recent Avalanches? | Yes |
| Collapsing (Whumphing)? | No |
| Cracking (Shooting cracks)? | No |
Observer Comments
Recent avalanche triggered by cornice fall, see details in this report
Recent natural avalanche on Idaho peak, see pictures.
3-4 recent natural avalanches along the Arkose Ridge line above the Little Su River, see pictures.
Recent reports of collapsing in isolated locations, one report with shooting cracks, see observations.
No shooting cracks, collapsing or human triggered slab avalanches were observed today. Small and slow loose dry avalanches were touchy and easy to human trigger on slopes 40 degrees and steeper.
Weather
10am-5:30pm
Clear skies
4-9F at 4500'
5-11F at 3050'
Calm to no wind 2800-4500' most of the day, with wind speeds building at 5pm on Marmot ridgeline above Presidents, flagging on peaks up the Mint Valley.
Snow surface
2/20 3" of new PP
Widespread Rimed Stellars at 4500'
Snowpack
Large slab sitting on early January facets with rounding, which are gaining a little strength, slowly. 4F harndess, 1.4mm, some old striations.
Recent avalanche on RW took a large, natural cornice fall to trigger the deeply buried weak layer.
Stability tests have been indicating moderate to strong strength, with recent improvements in PST results, above 50/100. Structure is poor. Energy is lowering over time. Stubborn to trigger, requiring large loads, such as cornice failures, rapid wind or precipitation loading events.
Numerous Arkose Ridge natural avalanches, likely 2/17-19
Divide Ridge - Idaho peak showing one avalanche in the shade which is older 2/17-19, and once newer, likely 2/21ish.
2/24 - Pit Profile, adjacent to recent natural avalanche triggered by cornice fall in Rae Wallace, see more pictures below
Approx. 2/21 Rae Wallace, NW, 4200'. HS/SS-NC-D2-O on 4F 1.5mm facets with rounding, 1-3 feet deep. 150' wide, 500' vertical run. Cornice naturally failed at ridgeline, bounced down slope, triggering this persistent slab mid-slope. Probed debris 75-100cm deep, mostly soft debris, with some 1F hard slab chucks and ice hard cornice chunks.
Another view of avalanche on Rae Wallace.