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Observation: Turnagain

Location: Tincan

Date:
Observer:
Route & General Observations

Standard route up West Ridge to 3100′ between Common bowl and Hippy Bowl

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)?Yes
Observer Comments

There were a few natural avalanches D1.5 - D2's - see photos
-Seattle Ridge - SE aspect
-Sunburst - North gully
-CFR ridge Tincan - cornice triggered storm slab
Shooting cracks on wind loaded unsupported features
One small collapse underfoot felt at 2300'

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

Overcast to broken skies from 11am to 3pm
Temp at 1000' were 37F
Winds were 5-25mph NE - SE
Light rain to moderate on the drive through Turnagain Arm and on Northern end of Turnagain Pass in the morning

Snow surface

1000 ' wet snow w/ ski pen 25cm. Thin rain crust from last week was still intact and by late afternoon was re-frozen
1500' - rain/snow line - 8cm wet snow
2000' - 20cm moist new snow
2500' - some patches of wind blown exposed rimed surface hoar to 30cm of new snow from the last two days
3000' - wind blown surfaces ranged from 20cm-40cm of new snow from the last two days

Snowpack

Dug many hand pits and found the 1/21 buried surface hoar in every location. The 1/21 BSH is sitting on a crust to ~2500'. Hand pits between 2000' - 2400' failed with moderate force on a density change above the 1/21 BSH layer. A thin crust was also noted just above the BSH, but it was still intact and standing up. In the alpine between 2700' and 3000' hand pits failed with easy to moderate force both on the 1/21 BSH and just below it on a density change.

Two test pits at 3100' on a SW aspect found the 1/21 BSH 35-40cm below the surface. All stability tests failed on this layer with moderate to strong force, 2 out of 6 ECT's propagated through the column. Shovel shear tests found 1/11 buried surface hoar 45-50cm below the surface, and two CT's failed with strong force, but no failure on ECT's. The 1/21 buried surface hoar was 6-10mm in size and sitting on a 1F- hardness. The slab was 4F with several wind packed 1F density changes. The slab broke under the shovel in several ECT's.

Photos & Video
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