Kootenai National Forest Avalanche Advisory – 4/1/2014

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.

THIS ADVISORY HAS EXPIRED

Issued: April 1, 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 last scheduled advisory for the Kootenai National Forest area will be Friday, April 4, 2014 by Jon Jeresek.


MOUNTAIN WEATHER 

WeatherGraphic

Since the Friday morning (March 28th) advisory, heavy snow (SWE 1.3- 1.9 inches) accumulated at Kootenai SNOTEL sites (Bear Mtn, Hawkins Lake, Poorman Cr). Banfield Mountain in the southeast Purcell Range was the exception with 0.4 inches SWE.  Winds Friday through Monday were light from the southwest.  All sites have experienced melt-freeze cycles through Monday.  Night time low temps in the upper 20s F and day time highs in the upper 30s F.  

FORECAST:  Partly cloudy skies Tuesday through Thursday.  All daytime temperatures are forecasted to be above freezing in the low 40s F, with night time temperatures in the upper 20s F.  Winds will be variable in direction at 3 – 6 mph Tuesday through Thursday.  Chance of snow is 0-30% through Thursday with trace accumulations forecasted.


 RECENT OBSERVATIONS

RecentObservationsGraphic

We traveled to Twin Peaks in the West Cabinets located 30 air miles west of Libby on March 31st.  Total snow depth was about 105 inches on a west aspect at 6,000 feet.   One inch of new snow sits atop a sun crust.  Below these surface layers is a soft three inch deep graupel deposit overlaying a nine inch hard slab.  All of the above layers formed in the last four days.  Below these top layers, is a very complicated mix of knife hard crusts and hard slab material about 16 inches thick.  The upper 10 inches of the snowpack releases cleanly (Quality 1 shears) easy force in stability tests.  The mid pack hard slabs release cleanly with hard force.  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 to drive change processes.

 

Graupel of 2-4mm from a 3 inch thick deposit this weekend. 3/31/2014.

Graupel of 2-4mm from a 3 inch thick deposit this weekend. 3/31/2014.

 

Bear Mountain Snotel 5400’ with Rattle Mountain 6079’ in background. 3/31/2014.

Bear Mountain Snotel 5400’ with Rattle Mountain 6079’ in background. 3/31/2014.

 

 

 

 

 

 

 

 

 

 


 

   SNOWPACK DISCUSSION

Avalanche Problem #1

Wind Slab

Southwest wind events have transported snow onto east and northeast aspects.  From a distance these are quite obvious to the observer due their smooth, raised, rounded appearance.  Most of these slabs are hard and may have a hollow sound when traveled upon.  Wind slabs should be identified and avoided. 

 

 

 


Avalanche Problem #2 

CorniceCornice fall is the release of an overhanging mass of snow that forms when the wind moves snow over a sharp terrain features such as ridge.  Cornices range in size from small wind lips to huge overhangs of hard snow.  They can break off the terrain suddenly and trigger slab avalanches.  Cornice locations should be identified and avoided.

 

 


TREND: Light storm loading is expected Tuesday morning through Thursday with a trace of snow accumulations. Temperatures are forecasted to be above freezing daytime in the low 40s F, and night time in the upper 20s F through Thursday.  


 

  BOTTOM LINE

The avalanche hazard in the West Cabinets, East Cabinets and Purcell Range is MODERATE.  This means that heightened avalanche conditions exist on specific terrain features, such as wind loaded slopes.  Natural avalanches are unlikely, and human triggered avalanches are possible.  Evaluate snowpack and terrain carefully and identify features of concern.


 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.