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Avalanche: Turnagain

Location: Sunburst

Date:
Observer:
Route & General Observations

Sunburst to 2800′

Avalanche Details
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Trigger NaturalAvalanche Type0
Aspect WestElevation 2600ft
Slope Angle 40degCrown Depth 15in
Width 250ftVertical Run 300ft
Avalanche Details

Small storm slab on Magnums West Face - We saw it in the afternoon and it looked fresh. Most likely happened earlier in the day when temps were warm and there were no winds. Cloud cover was creating a greenhouse affect, until skies cleared a little and wind picked up between 2 - 2:30pm.

Red Flags
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Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?No
Observer Comments

We did not hear any collapsing or see any shooting cracks and only saw one recent avalanche on the W. Face of Magnum. Lots of point releases on all aspects.

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

Temps: 30F - 40F
Wind: Calm in the AM, blowing 10-20 mph in the afternoon
Sky: Thick cloud cover in the AM, and patches sun in the afternoon
Precip: Light flurries in the AM

Snow surface

1000'= 10" new snow, settled to 6" by afternoon, very saturated
2000' = 13" new snow, top 3" very wet and sticky by afternoon
3000'= 24" new snow, surface was moist

Snowpack

In general we found good bonding between the new storm snow and the older storm snow layers from the last two weeks. The new snow had a density of F-4F and the older storm snow below was 1F hard. We didn't find propagation potential within the new snow/older snow interfaces. Deeper in the snowpack we found several crust/facet/crust sandwich layers. Most of these crust layers were very strong. Only in one pit on a Northern aspect was the crust isolated, and it did propagate, but required a lot of force, more than 30 taps.

*Although we did not find any noteworthily instability within these older weak layers in these specific pit locations, it will be important to not forget about them should snowpack become saturated. Prolonged periods of very hot temperatures, multiple nights above freezing (32F), or a very warm and wet storm could re-active these older weaker layers.

Pit 1 - 2200', W aspect, 10* slope, HS=140cm, New snow was 13" (35cm) The only notable layers were 90cm below the surface. Several facet/crust layers, but crusts were very stout. No remarkable results in tests.

Pit 2 - 2200' NW aspect, HS=215cm, 19* slope, Facet layer was found 110cm below the surface with a 5cm Pencil hard melt/freeze crust below it and a 1F hard mixed rounds and melt/freeze layer above. No remarkable results in tests.

Pit 3 - 2700' N aspect, HS=155cm, 24*slope, Facets layer was found 88cm below the surface with a 5cm 1F hard melt/freeze curst above it and very stout pencil hard melt/freeze crust below it. This layer was isolated and failed at ECTP 30+ taps (SC)

Pit 4 - 2800' W aspect, 27* slope, HS=210cm, a 5cm layer of facets was found 150cm below the surface with a 20cm pencil hard melt/free crust above. A decomposing melt/freeze crust was found below it all the way to the ground. This layer was not isolated due to its depth. No results were found in the top 90cm of the snowpack.

Photos & Video
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