THIS AVALANCHE ADVISORY EXPIRED ON February 12, 2020 @ 4:55 am
Avalanche Advisory published on February 11, 2020 @ 4:55 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Human triggered avalanches are possible in steep terrain on north and east aspects that have been loaded in by southwest winds. Be on the lookout for snow that has drifted into pockets in steep chutes, steep convex rolls and below ridgelines. These will be your likely spots to find trouble in the next couple of days.

How to read the advisory

Human triggered avalanches are possible in steep terrain on north and east aspects that have been loaded in by southwest winds. Be on the lookout for snow that has drifted into pockets in steep chutes, steep convex rolls and below ridgelines. These will be your likely spots to find trouble in the next couple of days.

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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With a fresh shot of loose, light snow last weekend and strong southwest winds we now have pockets of windslab in the usual locations on leeward terrain. On Monday we observed that south and west aspects that were open and exposed to the wind have been stripped down to the crust layer. On the north and east sides there was plenty of snow loaded onto slopes below cornices and in terrain deppressions such as chutes and gullies.  These wind slabs have had some time to settle and were not highly reactive yesterday. In steep and unsupported terrain I would still avoid them, particularly in areas where a small slide may result in big consequences.

Avalanche Problem 2: Persistent Slab
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The snowpack held up well yesterday in stability tests and showed very little evidence of weakness as we travelled up the hill on all aspects. My primary concerns right now are the stout rain crust from February 1st, the snow is actually sticking to it well in most locations. We have observed a couple of weak interfaces above this crust in the past week that have not been reacting much or just difficult to locate. If you are committing to steep terrain take the time to dig a quick pit down to this crust layer and see if you are getting any propagation in the snowpack above this crust layer. We have observed small surface hoar and graupel just above this crust, check to see if it's on your slope before high-marking or jumping in to ski steep terrain. 

advisory discussion

On February 10th I travelled into Benning Mountain with Master Brewer and Engineer Grant Golden for a look at the snow. The obvious clues that jumped out on the way up were a couple of natural slides on northeasterly terrain both south and north of Benning Mountain. Both slides were small surface avalanches that appeared to fail in last weekends storm snow just below ridgelines. As mentioned above the Southwest winds had stripped the southwest aspects down above treeline and the northeast aspects were loaded in with pillows of soft snow. We also observed one large glide crack on Benning that was hanging precariously above a steep roll just waiting for some more warm and rainy weather.

Diving in for a closer look at the snow, our pit results were fairly promising and showed no weak points that jumped out and scared us. There is about a foot of snow on the February 1st rain crust which is 2-3" thick in the West Cabinets. In the Purcells and East Cabinets you will likely find less snow hiding this crust layer right now. There were a couple of weak storm interfaces in the snow above this crust but none showed a likelihood of propagation. At elevations below 5,200' we were seeing a second, thinner rain crust in the snowpack that was shearing off with a fair bit of resistance. I have not seen this second crust layer in the other mountain ranges of the Kootenai but it is another layer to keep an eye on in the West Cabinets for now.

 

 

Weather and CURRENT CONDITIONS
weather summary 
Backcountry Forecast from NWS Missoula issued:
410 AM MST Tue Feb 11 2020
DISCUSSION: 
Northwest Montana: A few weak weather systems will move through a
general light northwesterly flow aloft today through Wednesday. 
Scattered snow showers with little accumulation is expected. 
Thursday through Monday a couple of more organized and stronger 
weather systems will bring widespread mountain snow accumulations.
The period of best snow accumulations will be late Saturday 
through Sunday where a foot of snow is possible in the mountains. 
Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           85%          55%          40%      
Hi/Lo Temps           25 to 33     12 to 18     25 to 32 
Winds(mph)            SW 22G40     W 13G29      NW  8    
Precip Chc            40           0            0        
Precip Type           snow         none         none     
Liquid Amt            0.02         0.00         0.00     
Snow Ratio(SLR)       18:1         0            0        
Snow Amt(in)          0-1          0            0        
Snow Level            2000         2000         1000
Disclaimer

Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit.  For a recorded version of the Avalanche Advisory call (208)765-7323.