Kootenai National Forest Avalanche Advisory – 3/28/2014

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: March 28, 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 Tuesday, April 1, 2014 by Jon Jeresek.


MOUNTAIN WEATHER 

WeatherGraphic

Since the Tuesday morning (March 25th) advisory moderate amounts of snow (SWE 0.2- 0.9 inches) have fallen at all Kootenai snotel sites (Banfield Mtn, Bear Mtn, Hawkins Lake, Poorman Cr).  Winds Wednesday through Thursday were strong from the southwest but with minor snow transport.  Temperatures at all sites have been above freezing during the day with brief freezing at night through Thursday.  There is a little soft new snow available for wind transport at all sites in our Ranges.

FORECAST:  Mostly cloudy skies Friday through Sunday.  All daytime temperatures are forecasted to be above freezing in the mid/upper 30s F, with night time temperatures in the upper 20s F.  Winds will be out of the southwest at 8 – 12 mph.  Chance of snow is 60-100% through Sunday with accumulations of 7- 12 inches forecasted.


 RECENT OBSERVATIONS

RecentObservationsGraphic

We traveled to Allen Peak in the East Cabinets located 31 air miles south of Libby on March 27th.  85 to 90 inches of snow was encountered on east aspects at 6,000 feet elevation.   Two inches of new snow sits atop a 1 inch sun crust.  Below these surface layers is a very complicated mix of knife hard crusts and hard slab material to a thickness of 12 inches.  There is no free water present in any layers of the snow column. The upper 14 inches of the snowpack releases cleanly (Quality 1 shears) with 3 – 5 wrist taps using the compression test.  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.

I also received a report of a hard slab wind deposit that released naturally to produce a D2/R3 slide in the West Cabinets near Twin Peaks.  This is just south of the popular Keeler snowmobiling area southwest of Troy.

   

 


 

  SNOWPACK DISCUSSION

Avalanche Problem #1

Wind Slab

Recent 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 (NOT RECOMMENDED!).  Wind slabs should be identified and avoided. 

 

 


Avalanche Problem #2

WetAvalRain on snow can also increase the chances of wet avalnaches. Be aware of changing weather conditions, specifically rain on snow or rapidly rising temperatures. If travelling on or below sun exposed slopes consider turning around or moving to shaded areas if the snow surface becomes wet, skis or boots sink deep into the snow, or pin wheels or roller balls start to form on steep slopes.  

 

 


 

Avalanche Problem #3 

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: Heavy storm loading is forecasted Friday morning through Sunday with 0.5 inches of rain and 7–12 inches of  snow expected.  We expect some wind transport (southwest winds of 8 – 12 mph) of new snow.  Temperatures are forecasted to be above freezing daytime in the mid/upper 30s F, and night time in the upper 20s F through Sunday.  The trend is for avalnache hazard to increase through this period.


 

  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 deposits.  Natural avalanches are unlikely, and human triggered avalanches are possible.  Evaluate snowpack and terrain carefully, identify features of concern.

SPECIAL NOTE:  Snowpack conditions have improved with melt-freeze cycles in the absence of storm loading, wind transport, or rain on snow events.  Next round of weather will include storm loading, possible rain on snow, and a little wind transport. The avalanche hazard is expected to increase through Sunday.


 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.