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Observation: Summit

Location: Tenderfoot

Date:
Observer:
Route & General Observations

Toured to 2200′ on Tenderfoot to look at how much the snow from the last storm has settled, melt freeze crust formation on solar aspects, and how reactive persistent weak layers are in the snowpack.

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

Large human triggered avalanche triggered yesterday on Silvertip. Large slab avalanche on South aspect on gully sidewall below treeline (~1300'?) on Northern end of Summit Lake area on East side of pass. Several wet loose avalanches from ridgelines on steep terrain on Westerly aspects on Moose Mountain and Lonestar. (See seperate Summit Road Obs for photos).

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

Overcast turning to obscured skies in the afternoon around 4 pm. Calm winds becoming light around 3 pm and turning to moderate around 4 pm. Snowing less than 1 cm per hour starting at 3 pm, increasing to 1 cm per hour at 4 pm. Low 20s F at ridgetops and low 30s F increasing to upper 30s F at valley bottoms.

Snow surface

1" low density powder. A breakable 1" melt freeze crusts (MFCs) is present on Southerly and Easterly aspects. This all sits on settling snow from the last weekend's storm.

Snowpack

The snow from the last storm has settled from 45 cm (measured on Sunday the 11th) to 27 cm today. This slab sits over several different persistent weak layers that are failing in compression tests (CTs) and extended column tests (ECTs).

Pit 1 at 1900': NW aspect, 17 degree slope, HS & Test Depth (TD) = 120 cm. CT12 SC down 113 cm on 6 mm cupped basal facets. CT22 & 25 SC, ECTP29 down 58 cm on 2 mm facets on a decomposing MFC. ECTP22 down 90 cm on facets between decomposing melt freeze crusts. CT28 SC down 60 cm on facets between decomposing MFCs. This pit exhibited poor structure with weak layers reacting all the way to the ground.

Pit 2 at 2200': W aspect, 29 degree slope, HS & TD= 140 cm. Ski penetration to ankle. Boot penetration to knee. CT 22, 24 SC down 60 cm on facets over a MFC. ECTX. The Jan 21 buried surface hoar was found 47 cm down but was not reactive in tests. The lower foot of the snow was knife hard MFC.

Photos & Video
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