Avalanche: Hatcher Pass

Location: April Bowl Lower Roll

Date:

December 25, 2017 10:54

Observer:

Jed Allie Professional

Route & General Observations

IMB > winter road > HP proper. Hiked ridge > investigated recent avalanche > back to IMB. Hiked Marmot South ridge > descended SW face > Fishhook Lot.

Avalanche Details

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Trigger	Snowmachiner	Remote Trigger	0
Avalanche Type	Hard Slab	Aspect	North Northwest
Elevation	4100ft	Slope Angle	37deg
Crown Depth	3ft	Width	150ft
Vertical Run	350ft

Avalanche Details

December 22 or 23 - HS-AMr-R2D2-O, Likely occurred friday or sat. Likely snow machine remote trigger from below (50' from toe of debris). Previously wind loaded aspect. Crown depth varied from 6" to 3'. Debris depth 2-6' Largest blocks 3' X 6'. Debris piled into small terrain trap/depression. Alpha angle 22 degrees (Crown to toe).

Red Flags

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Observer Comments

Other recent avalanches Upper Willow Creek HS/SS?-AM-R2D2-O likely remotely triggered, and HS/SS-AM-R1D1.5-O both on SE, 4-4.5k'

Weather & Snow Characteristics

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Weather

Scattered skies am > broken pm
-8C
Calm

Snow surface

Small rounds 0.2mm at crown profile site

Snowpack

See profile image and pics

Evidence:
>Numerous human triggered avalanches this weekend, one remote, likely other remotes (unconfirmed)
>No reported/observed naturals.
>Most activity on this season's leeward slopes - west to north aspects
>Depth of PS 1-3 feet, one reported 4' unconfirmed

>Many reports of audible collapsing/whumphing

Assessment:
>Strong strength, poor structure, variable energy, moderate continuity (specific locations with avalanche results and instability test results)
>PWLs around MF crusts in mid-pack continue to cycle through inactivity/activity with cycles of rapid loading

Photos & Video

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