Avalanche: Hatcher Pass

Location: Rae Wallace

Date:
Observer:
Route & General Observations

Fishhook Lot > Marmot South Ridge > Weather Station > Rae Wallace North > Presidents

 

Avalanche Details
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Trigger CorniceAvalanche Type Soft Slab
Aspect NorthwestElevation 4200ft
Slope Angle 38degCrown Depth3ft
Width 150ftVertical Run 500ft
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

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
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 & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
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.

Photos & Video
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