Avalanche: Summit

Location: Tenderfoot and Summit Lake Road Obs

Date:

April 6, 2017 2:30pm

Observer:

H. Thamm Professional

Route & General Observations

We drove through Summit Lake and observed significant active wind loading along ridge tops. Large plume off of West facing slopes. New avalanche activity was seen on East facing slopes of Fresno Ridge, West side of Butch, SW facing Raven’s Ridge.
We attempted to go up Tenderfoot, but only made it just above weather station (~1600.) Experienced large collapsing and cracking while traveling through very the saturated (isothermal) snowpack.

Additional avalanche activity was observed yesterday, see April 5 Summit Observations.

Avalanche Details

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Trigger	Natural	Remote Trigger	0
Avalanche Type	Unknown	Aspect	Unknown
Elevation	unknown	Slope Angle	unknown
Crown Depth	unknown	Width	unknown
Vertical Run	unknown

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)?	Yes

Observer Comments

Large plumes of blowing snow/active wind loading
Recent avalanches
Large Collapses - could see alders shaking 60-70 feet away and it would leave thin cracks within the snow, all in very low angle terrain, not steep enough to slide.

Weather & Snow Characteristics

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

Weather

Partly Sunny
Strong Ridge top winds from the East
Temps along road were 44F

Snow surface

Wet snow, except in places shaded (very thin 3mm crust on surface)

Snowpack

Saturated snowpack!

We dug a pit at 1600' after experiencing a large collapse. HS =85cm. Layer of 'most' concern was very large grained depth hoar in the bottom 30cm of the snowpack. We also found two layers of large (1-2cm) buried surface hoar, but test results all failed on facets. (CT21, ECTX - but propagated with two additional arm swings.) We took snow temps every 10 cm and found it all to be 0C (isothermal.) Boot Pen was waist deep, could touch the ground when on in skies. Ski pen varied from ankle to knee deep.

Photos & Video

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