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Observation: Turnagain

Location: Sunburst

Date:
Observer:
Route & General Observations

Ascended Sunburst to 3400 ft and skied back down the ridge. Our objectives today included: 1) looking at the snowpack and testing the structure, strength, and energy of thinner spots above 3000′, including areas that have previously avalanched 2) observing the reactivity of the New Year’s Eve buried surface hoar (BSH) above 2000′ 3) observing the reactivity of the Thanksgiving facets above 3000′ 4) inventory surface conditions

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Observer Comments

No red flags.

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

Strong inversion today complete with valley fog

1100 at Sunburst parking lot: 6 degrees, clear above valley fog, no precip, calm
1400 at 3400 ft: 26 degrees, clear, no precip, calm, warm solar radiation in sun on ridgetops!
1600 at Sunburst parking lot: 10 degrees, clear above valley fog, no precip, calm

We noticed scintillation looking up the valley towards Taylor Pass, evidence of heat leaving the snowpack under clear skies.

Snow surface

Widespread surface hoar. 3-5 mm below 2000', 1-3 mm above 2000'. Below surface hoar snow was faceting out and sitting on top of a breakable crust that transitioned to a stout crust at around 2000'. Below 2000' the faceting snow above the crust was ~ 5 cm. Above 2000' the faceting snow is 7-13 cm thick. At 3400' we noted the crust near the surface had disappeared and boot penetration was boot top high.

Snowpack

We conducted three handpit tests off the uptrack at 1780'. HS= 115-120 cm. One hand pit failed easy in a planar manner, down 30 cm on facets sandwiched between a breakable upper crust and a stout melt freeze crust. The other hand pits failed moderate and hard, 25 cm down on facets under the upper crust. Of note, the New Year's Eve BSH was found below these crusts 35 cm down.

At 3400 ft we dug two pits below the ridge on a SW aspect. Photos and video attached below. Below are the results:

Pit 1: HS=55 cm. Line of potential BSH found around 35 cm down. The BSH was very difficult to identify and mostly looked like facets. Shovel shears and tilts were failing on the BSH with hard force. CT14 SP on depth hoar at the ground. ECTP 14 x 2 on Thanksgiving facets above a dense layer of basal ice above the ground. ECTP 13 on depth hoar on the ground, below the basal ice.

Pit 2: HS=55-75 cm. BSH was found 35 cm down. ECTN 22 and ECTN 28 x 2. CT22 RP. PST 80/100 end.

Photos & Video
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