THIS SNOWPACK SUMMARY EXPIRED ON March 10, 2015 @ 11:00 pm
Snowpack Summary published on March 10, 2015 @ 6:00 am
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Our temperature regimes are transitioning from very light early morning refreezing to potentially no refreezing through Wednesday.  Upper 40s to lower 50s temperatures will soften surface layers and introduce free water to underlying layers.  Free water in the snowpack can be very impactive to snowpack stability.  Loose wet avalanches normally initiate as a point release and entrain more snow as it moves down slope.  If enough material is involved, release of mid pack weak layers can occur.

Back country travel is advised when the snowpack is colder and stronger.  Avoid steep slopes in the afternoon especially above terrain traps.

 (Wet avalanche)       (Terrain traps)

Snowpack Discussion

Backcountry recreation and travel will occur where snow access is easiest.  Due to our below average depth snowpacks, especially in the East and West Cabinet ranges (44% SWE), we are seeing a decline in backcountry snow travel.  Mostly stable snowpack conditions will persist under colder temperatures.  With elevated day time temperatures, travelers will need to be cautious on steeper slopes especially with terrain traps below in the afternoon.  Good decision making will serve you and your party well.  Pay attention to signs of wet snow instability like rollerballs and pinwheels.

  (Western Purcell Range)

recent observations

The Kootenai Region snowpack sites we study are accessed first by snowmobile for 5 to up to 22 miles, then by skis.  Yesterday, I off loaded the snowmobile four times to access sites and was stalled all four times by vast stretches of bare road. I made two approaches on easterly aspects (Blacktail Ridge, Cabinet Divide) and two on northerly aspects (Allen Peak, Silver Butte Pass).  With the East Cabinet Range at less than 50% of average SWE, I fear I am going to have to avoid this range for the remainder of the 2015 season.  I know the West Cabinet Range is equally tough to access, but will try at least another time.  The only Range with assuredly accessible snow is the north and west portions of the Purcell Range (74% SWE).  Unfortunately, I was unable to access any sites today.  

weather

Since the Thursday March 5th advisory, weather in the Kootenai Region has been dry and warm with melt/freeze temperature cycles. All SNOTEL sites are reporting daytime highs in the mid 40s F with light refreezing occuring 6-8 hours prior to sunrise. SNOTEL sites are reporting snowpapack drainage on the order of  -0.2 to -0.3 inches SWE.  Weather yesterday in the Silver Butte basin was clear with southwest winds 3-7 mph, no new snow, and 42'F.  Forecasted weather through Wednesday is for increased (20%-85%) cloud cover, no night time refreezing, day time temperatures upper 40s to lower 50s, southwest winds 8-12 mph, no chance of snow, and 50% chance of rain Wednesday.  The SWE for the four SNOTEL sites (Banfield Mtn, Bear Mtn, Hawkins Lake, Poorman CR) we monitor is currently at 56% of average.

 (Poorman Cr SNOTEL 46%  of average SWE) 

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.