Observation: Turnagain

Location: Tincan Backdoor, Center Ridge

Date:
Observer:
Route & General Observations

Three groups traveled from the Center Ridge parking lot to assess snowpack structure and stability. Group A dug pits at 934′ in the flats towards the base of Sunburst on a S aspect. Group B dug pits at 2 locations at Tincan Backdoor: 1400′ on a SE aspect and 1200′ on a NW aspect. Group C dug pits at 1320′ on a SE aspect at Tincan Backdoor.

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

Evidence of recent wind slab avalanches- mostly D1 on convex rolls. Seen on Tincan and Wolverine from the road. Collapsing around Center Ridge flats and on the skin up Tincan Backdoor, shooting cracks observed on convex rolls when tested.

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

Overcast, Mixed precipitation. Moderate east winds, though groups were more protected in the trees. 33 degrees F at Center Ridge lot.

Snow surface

Rain at lower elevations has made for some heavy and moist conditions.

Snowpack

Groups had variable pit test results between locations, but also within their groups. Group A at the base of Sunburst had results of CT16 SP and ECTP2 both 90 cm down, and a CT1 SP 85 cm down on facets between a facet-crust sandwich. This group also had a CT12 SP and ECTP10 SC both 45 cm down on BSH. Mixed with these alarming results were also a couple ECTX. We did two PST tests since we were getting interesting results, and got PST 25/100 Arr 45 cm down on the BSH and PST 47/100 End 52 cm down on a layer of facets between the new snow/old faceted snow interface.

Both groups B and C had CTs with Q3 shear qualities as they stepped into the 1300-1400' elevation bands. Group B had CT26, CT27, and CT15 all 85 cm down while group C had CT14 50 cm down and CT20 100 cm down. Group B at this elevation had ECTX and group C had ECTN30 55 cm down.

Once group B moved down in elevation to dig their second round of pits at 1200', things started to get interesting again. Group B had CTV, CT3, ECTP12, and ECTP17 85 cm down.

The lower elevation pits had more reactive results in our stability tests, showing both sensitivity to fracture initiation and propagation propensity. There was spatial variability with these results, making false stable results not out of the question for both the persistent weak layer crust-facet sandwich and the buried surface hoar. Though we didn't see the same reactive results in our pits around the 1300-1400' elevation band, we found the snowpack structure to be similar in these locations. The crust-facet sandwich was buried deeper in these pits and found closer to the 1m depth range, where ECT and CT test results are often not as accurate. This means it may already be difficult to test for this persistent weak layer in the upper elevation bands, and we might not get any feedback on this layer until something triggers it at a shallower depth unfortunately. Scary!

Photos & Video
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