THIS AVALANCHE ADVISORY EXPIRED ON December 18, 2019 @ 5:32 am
Avalanche Advisory published on December 17, 2019 @ 5:32 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Continue to be wary of steep and open terrain at upper elevations, it is possible to trigger a slide in the upper 12" of the snowpack in areas affected by the wind. The deeper weak layers will be very resistant to triggers but they are still there and will result in a destructive slide if you find that weak spot. Moving into the weekend expect the avalanche danger to rise as another storm brings heavy snow to the area.

How to read the advisory

Continue to be wary of steep and open terrain at upper elevations, it is possible to trigger a slide in the upper 12" of the snowpack in areas affected by the wind. The deeper weak layers will be very resistant to triggers but they are still there and will result in a destructive slide if you find that weak spot. Moving into the weekend expect the avalanche danger to rise as another storm brings heavy snow to the area.

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: Persistent Slab
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The primary concern harboring in our snowpack is a sandwich of crusts and weak sugary snow that is buried 2-3 feet deep. The good news, the sugary snow crystals are slowly gaining strength and trending upwards in stability and will likely be difficult to trigger. The bad news is that if you find that sweet spot and trigger an avalanche on this layer it will go BIG! Also, expect this layer to become more reactive during periods of drastic weather changes such as heavy new snowfall (predicted later this week) or rapid warming.



Photo taken on NW Peak, December 12th depicts weak layer of concern. This layer is found 3-4 feet below surface in the snowpack of the West Cabinets.

Avalanche Problem 2: Wind Slab
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Last weeks storm snow has bonded well in most locations; however, be alert to the possibility of triggering small pockets of windslab. This will most likely be a problem in steep and open areas at  elevations above treeline, below ridges and on convex (steep roll-overs) terrain features.

advisory discussion

If you have been reading the forecast or digging around in the snow you are likely aware of the deeply buried weak layer I mentioned above. It's not going away anytime soon but it is becoming more difficult to trigger. This is a good thing except for the fact that it often will give riders the impression that the stability is better than it actually is. There are still plenty of thin spots out there in our snowpack and it is possible to trigger this weakness if you find such a "sweet spot". This scenario would be most likely in very steep and rocky terrain above treeline. Yesterdays observations also showed that the storm snow from late last week was bonding well for the most part, I would use caution in steep and open alpine terrain and be very alert to the possibility of triggering the top 12" of snow in such areas. At elevations below 5,000' the snowpack is getting deeper but still lacks enough depth or layers to overcome the vegetation and cause an avalanche concern.

The big news moving forward is an "atmospherice river" moving into the area Wednesday night and delivering snow to the high country potentially measured in feet! This will be a welcome improvement to our snowpack coverage but expect the avalanche danger to rise going into the weekend with this storm. Lastly, avalanches can hurt or kill you; but, there are other concerns out there. Coverage is still pretty thin, and there are plenty of rocks, stumps and logs hidden in the snow that may wreck your machine or your body right now.

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
400 AM MST Tue Dec 17 2019

DISCUSSION: A few snow showers this morning from the Whitefish 
Range to the northern Mission Mountains and east will end mid 
morning. Snow accumulations are not expected. High pressure will 
strengthen this afternoon and result in clear and dry conditions 
through Wednesday. A pretty moist weather system will return 
Thursday and is expected to bring a couple feet of snow to the 
mountains of central Idaho, west central and northwest Montana 
Thursday through Saturday. Snow levels will rise to 4000-4500 
feet Friday morning.

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           70%          65%          55%      
Hi/Lo Temps           24 to 30     13 to 19     25 to 31 
Winds(mph)            SW 17G39     SW 17G33     S 13G29  
Precip Chc            0            0            0        
Precip Type           none         none         none     
Liquid Amt            0.00         0.00         0.00     
Snow Ratio(SLR)       0            0            0        
Snow Amt(in)          0            0            0        
Snow Level            1500         1000         500      
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.