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GNFAC Avalanche Advisory for Mon Apr 9, 2012

Snowpack and Avalanche Discussion

Some avalanche concerns to keep in mind:

1.    WIDESPREAD INSTABILITY

The greatest avalanche concern is new snowfall and wind-loading.  The likelihood of triggering avalanches spikes during and immediately after significant snow storms. Additionally, wind-loaded slopes are dangerous too. The good news is that any instability associated with the new and/or windblown snow can easily be found in the upper few feet of the snowpack. Instabilities associated with new snowfall will typically be short lived.

2.    WEAK SNOW NEAR THE GROUND

GNFAC Avalanche Advisory for Fri Apr 6, 2012

Snowpack and Avalanche Discussion

 BRIDGER / GALLATIN / MADISON / LIONHEAD 

New snow, cold temperatures, and winds forecasted to increase this afternoon will make fresh wind slabs the primary avalanche concern. In most places new snow rest on a thick melt-freeze crust and has not bonded to this crust very well yet. For today, new snow will sluff easily on the crust or produce slab avalanches on slopes where it was deposited by the wind.

GNFAC Avalanche Forecast for Mon Apr 2, 2012

Snowpack and Avalanche Discussion

 

The Bridger Range, Gallatin Range, Madison Range and Lionhead area near West Yellowstone: 

Spring is an erratic time for weather and snowpack conditions. This spring season seems more perplexing than most.  Buried depth hoar, above average temperatures, rain, sun and new snow have created an avalanche equation even Einstein would find challenging.      

This pit was dug on a northwest facing slope at 8,750' in Lionhead.  A dense, six foot thick pencil hardness slab is being supported by fist hardness depth hoar.  I scooped out some in my hand. The column broke on this layer and I was able to lay the pillar, intact, outside the snowpit. The deeper the depth hoar gets buried, the more difficult it becomes to trigger. But if you get unlucky and trigger it the avalanche will be large, destructive and deadly.  Photo: GNFAC

Lionhead Range, 2012-04-01