THIS SNOWPACK SUMMARY EXPIRED ON December 26, 2014 @ 12:00 am
Snowpack Summary published on December 25, 2014 @ 7:00 am
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: Storm Slab
Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize.

 This soft slab over time with additional storm loading could develop into a persistent slab atop the 2 inch buried surface hoar layer.  Currently boot penetration through this slab is very common and collapsing of this layer is common above 5500 feet. In my travels today, I ventured out onto several wind loaded slopes.  Here I found a 3-4 inch hard wind slab that was very cohesive over topping the storm slab described above.  The wind slab was easily penetrated with boots but supported a snowmobile.  It would be adviseable to avoid these wind slabs on lee slopes and where cross loading occured.

Avalanche Character 2: Persistent Slab
Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.

The old surface soft slab fails with easy force (wrist taps) on the buried surface hoar layer and propagates across the extended column.

Avalanche Character 3: Persistent Slab
Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.
recent observations

AVALANCHE WARNING in effect for the Kootenai region for today. Warning will expire or be updated by 7:00 am 12/26/2014.  From advisory 12/23/2014: Today I visited Chicago Peak (7018 feet) in the East Cabinet Range.  Enroute to my pit site I experienced collapsing. On a moderate southwest aspect protected from the wind, I found 37 inches of total snow.  The top 6 inches was very soft new snow from the last 36 hours.  Below that was 7 inches of 4 finger soft slab snow sitting atop a 2 inch layer of very soft snow containing buried surface hoar (2-4 mm size)

  (blue card and pit brush frame the buried surface hoar layer). 

Below these surface soft layers is the November benchmark rain crust layer of 9 inches.  Below the rain crust is another 9 inches of 1 finger hard slab snow and the bottom 4 inches is loosely consolidated basal snow.

The layer of surface hoar above the crust was able to propagate fractures with easy force in our Extended Column Tests.    

The remaining 22 inches of the snowpack is very cohesive and fails near the ground line with hard force in stability tests.

weather

A winter storm system moved through the area the past 36 hours. SNOTEL sites reported between 6-11 inches of new snow and 0.7 to 1.7 inches of snow water equivalent.  

Disclaimer

This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.