Avalanche: Turnagain

Location: Tincan

Date:

April 5, 2018 5:00pm

Observer:

H. Thamm Professional

Route & General Observations

Toured up to 3200′ above Common Bowl via the SW ridge and descended NW ridge. There was 15-20″ of new snow from a storm that ended this morning. Lots of obvious clues were present (recent avalanches, whumpfing, cracking.) Throughout the day the slab character was changing from with warming temps and solar radiation. Most of the activity happened between 3pm and 5pm and likely continued after were left. Sunset was at 9pm today.

Avalanche Details

If this is an avalanche observation, click yes below and fill in the form as best as you can. If people were involved, please provide details.

Trigger	Natural	Remote Trigger	0
Avalanche Type	Soft Slab	Aspect	Southwest
Elevation	3000ft	Slope Angle	unknown
Crown Depth	18in	Width	100ft
Vertical Run	300ft

Avalanche Details

Timing happened sometime after we left Hippy Bowl around 3:30pm and drove by on the road around 5pm. There was a lot of traffic on Tincan today along the ridge above Common Bowl, but the nearest tracks were 300+' away. Its unknown if this was remotely triggered or a natural event, but warming and solar radiation were affecting surface conditions in the afternoon. There were two small wet loose avalanches in Hippy Bowl on due South aspects by 2:30pm.

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 avalanche released in Hippy Bowl early evening
-Several small human triggered avalanches on W and NW aspects below 2500'. The first one observed was at 12:30pm (remote triggered from 100' away.) See photo.
-Small wet loose on South and SE aspects and started near rocks or from ridges around 2:30pm (Hippy bowl and Seattle Ridge)
-Numerous collapses at 2000' and 2700' when we broke our own trail.
-20+' long crack on North aspect above Common bowl slowly widened over a few minutes and opened up to about 1" wide. This occurred around 3pm after a dog ran onto the slope and returned to the ridge. Cracking was also observed on several steep features, including a supported slope, a distance from where groups skied down on gentler terrain.

Weather & Snow Characteristics

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

Weather

Partly cloudy becoming mostly sunny in the afternoon
Temps below 1000' - mid 30F's to low 40F's
Temps in the alpine - remained cooler ~low 20F's
Winds were light (5-10mph East)
No precip

Snow surface

15" new snow at 1000'
15-20" new - variable slab depths due to winds
*wet and sticky surfaces were observed on South aspects and more noticeable on slopes angles steeper than 30 degrees. On our descent at 5pm the lower elevation snow was much heavier and moister than earlier in the day.

Snowpack

We dug 4 pits and tried to get a variety of aspects and focused our stability tests on the new/old snow interface.

Pit #1- 2700', West aspect, 21* slope, HS=350cm - CT13 ECTN24 failed 50cm below the surface on near surface facets. A sun crust was not present in this pit location.

Pit #2 -2700', WSW aspect, 28* slope, HS=405cm - CT5, CT10, ECTP11, ECTP2 failed 45cm below the surface on 2mm near surface facets above a thin 2cm 1F hard sun crust. There were .5-1mm near surface facets below this thin sun crust and one of the ECT's failed on both layers. The sun crust was only 2cm thick and 1F hard. See video and photo below.

Pit #3 - 3200', SSW aspect, 22* slope, HS=260cm - CTV, ECTP24, ECTP26 failed 50cm below the surface on near surface facets below a 4cm knife hard sun crust.

Pit #4 - 2900', N aspect, HS = 140cm - CT17, ECTN19 failed 45cm below the surface on near surface near surface facets on pencil hard old snow. Also had a CT29 fail 70cm below the surface on the Jan.21 buried surface hoar/facet layer.

Photos & Video

Please upload photos below. Maximum of 5 megabytes per image. Click here for help on resizing images. If you are having trouble uploading please email images separately to staff.

Possible natural or remote triggered avalanche in Hippy Bowl. This was first seen by our group around 5pm, but may have happened within the last hour.