THIS SNOWPACK SUMMARY EXPIRED ON December 17, 2014 @ 6:00 am
Snowpack Summary published on December 16, 2014 @ 6:00 am
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: Deep Slab
Deep Slab avalanches are destructive and deadly events that can release months after the weak layer was buried. They are scarce compared to Storm or Wind Slab avalanches. Their cycles include fewer avalanches and occur over a larger region. You can triggered them from well down in the avalanche path, and after dozens of tracks have crossed the slope. Avoid the terrain identified in the forecast and give yourself a wide safety buffer to address the uncertainty.

The rain crusts that formed since November 27 now dominate the snowpack.  Loose dry snow sits atop this deep slab. Walking, skiing, and riding do not penetrate this layer that firmed significantly with 36 hours of below freezing temperatures.  Below this deep slab is softer snow that we expect to firm up with additional below freezing temperatures over the next three days.

Snowpack Discussion

Avalanche risk has been downgraded from Moderate to Low since the Friday advisory.  Most of this improvemnet can be attributed to the below freezing temperatures.  Generally safe avalanche conditions exist. Watch for unstable snow on isolated terrain features.  Continue to use your proven safe crossing procedueres and good decision making.  Have fun and please be safe out there.

recent observations

Today I visited the South Cabinet Divide 6000 feet elevation in the East Cabinet Range.  On an east aspect I found 22 inches of snow.  The top 3 inches was very soft new snow sitting atop a knife hard 10 inch crust

  
10 inch raincrust is between pit brush and card consisting of multiple raincrusts originating from November 27 and after

This 10 inch layer had firmed up significantly with 36 hours of below freezing temperatures.  The bottom nine inches of the snowpack was four finger hard but firmed up immediately upon exposure to the cold 20º F air.  The Extended Column Test yielded no propagation.    

 

weather

 Weather since Friday afternoon has been the tale of two coins.  Friday to Saturday was warm (all SNOTEL sites reported above freezing temperatures) and wet with snow water equivalent (SWE) accumulation of 0.2 inches.  Sunday to Monday was cool (all SNOTEL sites were below freezing) and mostly dry.  Today's weather was dominated by dense mountain fog.

  
can you see the snowmobile at 100 feet? 

Temperatures were in the low 20º F with 2-3 inches of very soft new snow.  Forecasted weather is mostly cloudy with temperatures below freezing and winds switching from the southeast at 6 mph to southwest at 6 mph.  No new snow or substantial winds in the forecast through Wednesday.

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.