Kootenai National Forest Avalanche Advisory – 3/4/2014

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 4, 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 7, 2014 by Jon Jeresek.


MOUNTAIN WEATHER 

WeatherGraphic

Since the Friday AM (February 28th) advisory, HEAVY amounts of snow (SWE 0.7”- 2.3”) have fallen at Kootenai snotel sites (Banfield Mtn, Bear Mtn, Hawkins Lake, Poorman Cr).  Winds Friday through Saturday were from the east-southeast and strong with HIGH snow transport.  Temperatures at all sites have been below freezing for the last four days till noon Monday.  There is abundant soft snow available for wind transport at all sites in our Ranges.

FORECAST:  Cloudy skies Tuesday through Thursday.  All daytime temperatures are forecasted to be just above freezing, with night time temperatures in the upper 20s.  Winds will be out of the southwest at 10 – 21 mph with HIGH probability of snow transport Tuesday through Thursday.  Chance of snow is 80 – 100% Tuesday AM through Thursday, with VERY HEAVY accumulations of 19” – 29” forecasted.


 RECENT OBSERVATIONS

RecentObservationsGraphic

We traveled to Horse Mountain in the East Cabinets located 17 air miles south of Libby on March 3rd.  75” to 80” of snow was encountered on West aspects at 5,300’ elevation.  The top 20” of the snowpack consists of heavy new snow from Monday overlaying colder, lighter snow from Sunday.  Below this new snow is a knife hard suncrust from Tuesday-Wednesday that overlays a cold, soft snow layer. Below these surface layers are hard slabs which release cleanly with moderate 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.

Road to Horse Mtn showing roller ball activity. 3/3/2014.

Road to Horse Mtn showing roller ball activity. 3/3/2014.


Cable Mtn 6,000’ showing soft slab natural releases. 3/4/2014.

Cable Mtn 6,000’ showing soft slab natural releases. 3/4/2014.


Front of the East Cabinet Range. 3/3/2014.

Front of the East Cabinet Range. 3/3/2014.

 

 

 

 

 

 

 

 

 


 

  SNOWPACK DISCUSSION

Avalanche Problem #1

 

Storm Snow

We have experienced exceptional storm loading through 03/03/2014.  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 soft snow available for wind transport.  Over the weekend, west-northwest aspects were loaded by east-southeast winds.  Southwest transport winds of 12 -21 mph are forecasted through Thursday.  This will result in wind slabs and pillows on east aspects.  Our dilemma is that both sides of our north-south trending ridgelines have been recently loaded.  These locations should be identified and avoided.

 

 

 


 TREND:  VERY HEAVY storm loading (19” – 29”) in the forecast through Thursday.  We expect HIGH wind transport (SW 12 -21 mph) of available snow Tuesday through Thursday.  Temperatures are forecasted to be just above freezing daytime, and night time in the upper 20s through Thursday.  The trend is for RISK TO INCREASE through this period. 


  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.  Natural avalanches are likely, and human triggered avalanches are very likely.  Backcountry travel in ANY avalanche terrain is NOT recommended.

SPECIAL NOTE:  Last Tuesday-Wednesday we observed consolidation and some strengthening of the snowpack on solar slopes (south and west aspects).  This was followed significant wind transport Friday-Saturday with east-southeast winds loading west-northwest aspects.  This wind event was accompanied by very frigid temperatures.  Finally, Sunday-Monday produced significant storm loading with natural releases common.  This loading event came in cold and finished warm creating inverted snowpack densities.


 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.