11-12

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

The Bridger, Gallatin and Madison Ranges, the Lionhead area near West Yellowstone and the mountains around Cooke City:

The Bridger, northern Gallatin and northern Madison Ranges, the Lionhead area near West Yellowstone and the mountains around Cooke City:

In the last 48 hours the following snowfall and SWE amounts were recorded:

 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.

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

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

The Bridger, Gallatin and Madison Ranges, the Lionhead area near West Yellowstone and mountains around Cooke City:

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

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

Today, a cold front will drop temperatures below freezing for the first time in days. This will create a tricky situation.  Although the snowpack surface may become firm with falling temperatures, the underlying layers will remain warm, moist and weak.