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Avalanche: Turnagain

Location: NW shoulder of Magnum

Date:
Observer:
Route & General Observations

Skied up the Sunburst up track to 1800′ then crossed the Taylor drainage over to the NW shoulder Magnum to 2200′.

Avalanche Details
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Trigger SkierAvalanche Type Soft Slab
Aspect SouthwestElevation 3200ft
Slope AngleunknownCrown Depth 6in
Width 25ftVertical Run 500ft
Avalanche Details

A small skier triggered wind slab avalanche was reported yesterday off the top of the south face of Sunburst. Approximately 25 ft across with a 6 inch deep crown and ran ~500+ ft.

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)?No
Observer Comments

Small skier triggered avalanche off of the South face of Sunburst. Observed some older debris on the West face of Magnum from an avalanche that likely occurred during the 1/26 storm. No other obvious signs of instability but generally poor structure on the NW shoulder of Magnum.

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

Few very light snow showers at Sunburst/Magnum @ 3 pm driving N on Pass it was snowing at Eddies to around 700' where it changed to rain. Raining until Portage and then no precip into Girdwood
Moderate ENE winds gusting into the 40s
Recent winds have channeled down from Taylor Pass and cross loaded slopes on the S face of Sunburst and the N side of Magnum.
Temps in the 20Fs. 32 @ parking lot.

Snow surface

Below treeline to 1400 ft had a few cm of snow from the past 24ish hours. ~2 inches total from the past few days. Treeline into the Alpine had varying levels of wind effect from a few cm wind skin to 15+ cm wind crust. Wind scouring on northerly and easterly aspects with southerly and westerly faces/gullies loaded.

Snowpack

Pit # 1 @1030' on 29 degree north facing slope. Height of snow was 100 cm. The surface was ~6 cm of settles storm snow over a rain crust from the 1/26 rain event. The rain crust was either all one 10 cm crust or two (2 cm) crust with runnels connecting and 6 cm of dry snow between depending on where you dug. The crust was supportable until 1200' and then completely disappeared around 1400'. At 50 cm below the surface we found large ~1 cm buried surface hoar. Tests yielded CT12 and an ECTP16SP at the buried surface hoar.

Our high point for the day was 2200 ft and we dug Pit #2 on a 24 degree north facing slope. The height of snow in our pit was 100 cm. The surface down to 85 cm was a pencil hard wind slab. Below this was pencil+ hard winds slab down to 75 cm. 75 cm down to 50 cm was small 1F .5mm facets. 50 cm to the ground was 4F facets that grew in size further down the pack (10 cm of 4 mm basal facets). Our tests yielded a CT8 and an ECTN13 15 cm down from the top at the hardness interface between the pencil and pencil+ wind slabs. Height of snow on the NW shoulder of Magnum averaged about a meter but was scoured down to 30 cm and even to bare ground in some areas. The leeward side of the shoulder onto the W face of Magnum had been loaded by the wind and had depths to around 200 cm.

Photos & Video
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