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Avalanche: Summit

Location: Raven's Ridge (North of Butch)

Date:
Observer:
Route & General Observations

From the lower summit lake pull-out, we toured up behind the cabins and through the alders/hemlocks to treeline on the northern most ridge (Raven’s Ridge) of “Butch”. A friend had toured up lower Tenderfoot on Friday during the storm and said the snow had fallen wet and heavy, however significantly cooler outflow winds followed through this area over the weekend, bringing drier and much cooler air (single digits to low teens). As expected, the snow pack has dried and the new snow is now right-side up making for excellent skiing. However as I will discuss below, there is still significant instability in the layers below and we trigger a very large wumpf and a corresponding avalanche (easily visible from the road if you’re driving by).

Avalanche Details
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Trigger SkierAvalanche Type Soft Slab
Aspect West SouthwestElevation 2500ft
Slope Angle 35degCrown Depth 24in
Width 600ftVertical Rununknown
Avalanche Details

While skinning to our target, a small knob just above low-angle terrain on the treed ridge, a single skier was poking the snowpack with his pole and triggered a large wumpf. We could hear it propagate quietly up the northern aspect, and then very loudly around the west ridge to the west-south-west aspect, where the avalanche initiated and carried down through some small pine and into the alder-filled drainage. The layer that released was the soft storm slab. From farther down it appears that it stepped down into the older snow/wind-slab that likely provided the initial bed surface. The crown varied in thickness from 6" to over 30".

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)?Yes
Cracking (Shooting cracks)?No
Observer Comments

Two days ago on Mt. Eva a friend reported a large wumpf down low, so we knew there was potential and stayed on very low angle terrain. Across the small drainage between our ridge and the southerly aspect of raven ridge there was a slide that likely happened yesterday (3/11) before last night's 4-6" of added snow. Were it not for sun and clear skies this would not have been visible otherwise.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

19 deg F when we started. 20's when we finished around 2pm, but very sunny and warming quickly as we left. 5-10 mph outflow winds kept air temperatures cool, but the sun was having a significant effect on the snow surface at road level and lower elevations.

Snow surface

Amazing.

Snowpack

1-2' of right-side-up new snow. Thin wind slab underneath (1-6") with facets below. The thicknesses of the new snow and the underlying layers varied significantly across the slope as the recent storm snow was deposited with wind.

Photos & Video
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