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Observation: Turnagain

Location: Sunburst

Date:
Observer:
Route & General Observations

Standard skin track up West ridge and descended SW face. Surface hoar was found from the parking lot to ridge tops and averaged 5-10mm in size. The top 10″ of snow was faceting out due to cold temperatures over the last week, and we only found one area where the snow was stiff enough to fail on the 1/21 surface hoar in a hand pit at 3300′ on West ridge. Otherwise the top 12″ of snow was loose and poorly bonded. We dug a quick pit at 3500′ on the SW face of Sunburst in the old slide path from the avalanche that occurred in mid January (~1/16/17.) We still found intact basal facets on a melt/freeze crust near the ground, but this layer was un-reactive in compression tests. There was a natural slab avalanche on Basketball Chute that was reported last Saturday (1/27.) There are ski tracks on a lot of steep terrain and no signs of recent activity were seen.

Red Flags
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Observer Comments

No observed, other than sluffing from ski tracks on steep slopes.

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

Sunny
No precip
Temps in the AM (single digits at 1000' and teens at ridge tops)
At 2:30pm temp at 1000' in the sun 25F vehicle thermometer
Winds were light from the East this morning becoming calm by 11:30am

Snow surface

5-10mm surface hoar at road level.
2-4mm surface hoar at 2000'
5-10mm surface hoar along ridge tops
0.25-1mm near surface facets within top 10 inches of snowpack

Snowpack

We found one area along the W ridge at 3300' where the snow was stiff enough to be slab like in a hand pit, and it failed on the 1/21 buried surface hoar. See photo below. Otherwise we found mostly loose unconsolidated snow within the top 12"(last weeks snow) of the snowpack.

In a pit at 3500' on the SW face we could still find the basal facets near the ground, but were un-reactive in compression tests. (HS=105cm, 29* slope) These facets were 4F hard and sitting on a thin melt/freeze crust near the ground with about 2' of very hard snow on top. This pit was dug in the old slide path from 1/16/18 avalanche where most of the SW face of Sunburst released. We didn't find the 1/21 BSH layer within the new snow from last week, but there was about 10" of near surface facets (top layer.)

Skied to the bottom and found an old crown (very hard) at about 2900' - possibly where the 1/16/18 avalanche stepped down, but couldn't confirm. I dug a quick hole to the ground where there was still about 2' snow. No basal facets were found in this location, just very hard m/f snow sitting on the ground. Between this location and the debris below you could see old vegetation poking through the snow, likely pretty thin coverage, but with stout melt/freeze layer covering it.

Photos & Video
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