Significant rain on snow events allow free water to percolate deep into the snowpack. This water breaks bonds betwween crystals causing widespread snowpack instability. With the amount of rain fallen (1.8 inches), and predicted rain to fall (+1.2 inches) coupled with our below normal (<70% of average SWE) snowpack, we anticipate wet slab natural releases Friday afternoon and Saturday. Given the amount of rain impacting a thin snowpack, we could see widespread deep wet slab releases.
Very dangerous avalanche conditions face any backcounrty travel. Travel in avalanche terrain is NOT recommended, this includes runout zones. Wet slab avalanche debris is very heavy and survivability if caught is marginal at best. Back country travelers could find their exit route from a basin cutoff by wet slab debris which piles high and has a very rough surface. Please use the good decision making that has served you well to date, realizing that wet avalanche cycles are a very different event to think through.
Since the Thursday February 5th advisory, weather in the Kootenai Region has been warm and very wet. All Snotel sites are reporting temperatures above 35ºF since Thursday afternoon, with most mountain temperatures pushing 40º F. Precipitation has been heavy with most coming in the form of rain. Snotel sites are reporting precipitation increases of 1.4 inches to 1.8 inches since Thursday afternoon. Forecasted weather through Sunday, shows continued above freezing temperatures and another 1.16 inches of rain on snow. Remember that significant rain on snow can be one of the most destructive forces on snowpack stability.
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.