Kootenai National Forest Avalanche Advisory – 3/11/2014

THIS ADVISORY HAS EXPIRED.

The avalanche information for the Kootenai National Forest is provided by Kootenai National Forest personnel. The Flathead Avalanche Center hosts this information on its website for the Kootenai National Forest.

Issued: March 11, 2014 at 7:00 a.m. by Jon Jeresek
Expires: 11:59 p.m. of issue date

This advisory applies only to backcountry areas outside established ski area boundaries. The next scheduled advisory for the Kootenai National Forest area will be Friday, March 14, 2014 by Jon Jeresek.


MOUNTAIN WEATHER 

WeatherGraphic

Since the Friday morning (March 7th) advisory, heavy amounts of rain (1.6”- 5.4”) have fallen at Kootenai SNOTEL sites (Banfield Mtn, Bear Mtn, Hawkins Lake, Poorman Cr).  Tuesday through Thursday winds were from the southwest at variable speeds.  Temperatures at all sites have been above freezing for the last four days except early Saturday morning.  

FORECAST:  Partly cloudy skies Tuesday through Thursday.  All daytime temperatures are forecasted to be above freezing in the upper 30s F, with night time temperatures in the mid to upper 20s F.  Winds will be out of the southwest at 4 – 9 mph.  No new snow is expected Tuesday through Thursday.


 RECENT OBSERVATIONS

RecentObservationsGraphic

We traveled to Libby Creek Basin in the East Cabinets located 20 air miles south of Libby on March 10th.  80 to 85 inches of snow was encountered on southeast aspects at 5,300’ elevation.  The top 16 inches of the snowpack consists of heavy wet snow that was rained upon Tuesday morning through Friday as well as Sunday morning through Monday.  This wet surface snow releases with moderate force in stability tests.  The next 20 inch layer is colder snow without free water present.  This slab releases cleanly but with moderate force.  Below these snow layers is the old snow melt-freeze crust.  The base of the snowpack shows depth hoar development as a result of the severe temperature gradients during the first week of February.  Currently, there are no significant temperature gradients in the snowpack.

 

Rain triggered wet slab release from Monday AM.  Slide is just NW of the Montanore adit site. 3/10/2014.

Rain triggered wet slab release from Monday AM. Slide is just NW of the Montanore adit site. 3/10/2014.


This is a D3/R3 release that we saw so much of last Thursday.  Debris pile is 12-15 feet high of super dense material. 3/10/2014.

This is a D3/R3 release that we saw so much of last Thursday. Debris pile is 12-15 feet high of super dense material. 3/10/2014.


This is a D4/R4 wet slab from last Thursday.  D4s can destroy rail cars, big trucks. 3/10/2014.

This is a D4/R4 wet slab from last Thursday. D4s can destroy rail cars, big trucks. 3/10/2014.

 

 

 

 

 

 

 

 

 

 

 

 


 

  SNOWPACK DISCUSSION

Avalanche Problem #1

 Wet SlabWe have experienced exceptional rain on snow loading through 03/10/2014.  Rain triggered slab releases on old snow surfaces were common last Thursday morning and again Monday morning.  You can reduce your risk from wet slabs by waiting for the rain to cease and cooler temperatures to arrive before venturing out into the backcountry.  ALL avalanche terrain (starting zones, tracks, and run outs) should be avoided.

 


 

 Avalanche Problem #2 

GlideWith abundant rainfall on snow since last Tuesday morning (03-04-2014), steep snowpacks over bedrock and smooth slopes have developed glide cracks.  Nearly every drainage within the East Cabinets exhibits several of these slides to the ground.  These locations should be identified and avoided.

 

 


TREND:  NO rain or storm loading is forecasted Tuesday morning through Thursday. Temperatures are forecasted to be above freezing during the day reaching the upper 30s F, and night time temperatures in the upper 20s F through Thursday.   


  BOTTOM LINE

The avalanche hazard in the West Cabinets, East Cabinets and Purcell Range is CONSIDERABLE.  This means that dangerous avalanche conditions exist on many terrain features, such as steep semi open slopes.  Natural avalanches are possible, and human triggered avalanches are likely.  Careful snowpack evaluation, cautious route finding, and conservative decision making are essential.

Tuesday morning several rain triggered natural slab releases were observed in the East Cabinets.  They started near ridgelines at approximately 6,000 feet and ran as large avalanches.  This means they could bury/destroy a car and involve approximately 80% of the historic avalanche path (see attached photos).  We believe this activity will gradually decrease when the rain stops and cooler night time temperatures arrive. 


 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 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.