Kootenai National Forest Avalanche Advisory – 3/7/2014

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 7, 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, March 11, 2014 by Jon Jeresek.


MOUNTAIN WEATHER 

WeatherGraphic

Since the Tuesday AM (March 4th) advisory, HEAVY amounts of rain/snow (SWE 1.2”- 4.2”) have fallen at Kootenai snotel sites (Banfield Mtn, Bear Mtn, Hawkins Lake, Poorman Cr).  Winds Tuesday through Thursday were from the southwest at variable speeds with NO snow transport due rain impacts to surface snow.  Temperatures at all sites have been above freezing for the last three days.  There is little soft snow available for wind transport at all sites in our Ranges due rain impacts.

FORECAST:  Mostly cloudy skies Friday through Sunday.  All daytime temperatures are forecasted to be above freezing in the upper 30s F, with night time temperatures in the upper 20s.  Winds will be out of the southwest at 8 – 16 mph with LOW probability of snow transport Friday through Sunday due to rain impacts to snow surfaces.  Chance of snow is 50% Friday AM with minimal accumulations.  Chance of rain 100% Saturday PM through Sunday PM, with 0.50” forecasted.  THIS COULD BE ANOTHER RAIN TRIGGERING EVENT CYCLE SIMILAR TO WHAT WE EXPERIENCED THURSDAY AM.


 RECENT OBSERVATIONS

RecentObservationsGraphic

We traveled to Bear Creek Basin in the East Cabinets located 16 air miles southwest of Libby on March 6th.  95 – 100 inches of snow was encountered on south aspects at 5,500 ft. elevation.  The top 14 inches of the snowpack consists of heavy new snow from Monday that was rained upon Tuesday morning through Thursday morning.  This soft slab releases with a single wrist tap using the compression stress test.  The next 18 inches layer is colder, lighter snow from Sunday that releases as a soft slab with three wrist taps.  Below these new 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 to drive change processes.

Rain triggered D3/R3 slab avy on south aspect Bear Creek basin. 3/6/2014.

Rain triggered D3/R3 slab avy on south aspect Bear Creek basin. 3/6/2014.


Bear Creek Avalanche. Crown line is just under trees at ridgetop. 3/6/2014.

Bear Creek Avalanche. Crown line is just under trees at ridgetop. 3/6/2014.


Bear Creek Avalanche. Crown line traversed the whole head of basin for more than ¼ mile. 3/6/2014.

Bear Creek Avalanche. Crown line traversed the whole head of basin for more than ¼ mile. 3/6/2014.


Rain triggered D3/R3 slab avy on north aspect Bear Creek basin. 3/6/2014.

Rain triggered D3/R3 slab avy on north aspect Bear Creek basin. 3/6/2014.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

  SNOWPACK DISCUSSION

Avalanche Problem #1

 

Storm Snow

We have experienced exceptional storm loading through 03/06/2014.  Rain triggered soft slab releases on old snow surfaces are common.  Normally storm slab problems persist for a couple of days, however, we have transitioned from one storm cycle to the next without break.  You can reduce your risk from storm slabs by waiting +48 hours before venturing out into the backcountry.  ALL avalanche terrain (starting zones, tracks, and run outs) should be avoided.

 


 

 Avalanche Problem #2 

Wind Slab

We have abundant wind deposits on both sides of our north-south trending ridgelines.  Over the weekend, west-northwest aspects were loaded by east-southeast winds.    Prior to that, southwest winds loaded the east-northeast aspects.  No wind transport occurred since Tuesday’s advisory due to rain impacts to snow surfaces to 6,000 feet elevation.  These locations should be identified and avoided.

 

 


TREND:  Storm loading (0.50 inches of rain) is the forecasted Saturday afternoon through Sunday.  Temperatures are forecasted to be above freezing daytime in the upper 30s, and night time in the upper 20s through Sunday. 

 


  BOTTOM LINE

The avalanche hazard in the West Cabinets, East Cabinets and Purcell Range continues to be HIGH.  This means that very dangerous avalanche conditions exist on many terrain features, such as steep semi open slopes.  Natural avalanches are likely, and human triggered avalanches are very likely.  Backcountry travel in ANY avalanche terrain is NOT recommended.

SPECIAL NOTE:  Thursday morning, rain triggered natural slab releases were common in the East Cabinets.  Approximately 60% of north aspect chutes released and 40% of south aspect chutes.  They started near ridgelines at approximately 6,000 feet and ran as D3/R3 avalanches.  This means they could bury/destroy a car and involve approximately 80% of the historic avalanche path.  There is still significant “hang fire” slab material left out there!  


 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.