THIS AVALANCHE ADVISORY EXPIRED ON February 3, 2018 @ 5:17 am
Avalanche Advisory published on February 2, 2018 @ 5:17 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

At elevations above 6,000' there is the potential to trigger isolated wind slabs and thin storm slabs on all aspects with the incoming weather.  These smaller avalanches also have the potential to step down to weaker layers in the snowpack at upper elevations and create larger slides.  Below 6,000' the warm temperatures from Monday have bonded the upper snowpack under a thick, supportive crust layer.

How to read the advisory

At elevations above 6,000' there is the potential to trigger isolated wind slabs and thin storm slabs on all aspects with the incoming weather.  These smaller avalanches also have the potential to step down to weaker layers in the snowpack at upper elevations and create larger slides.  Below 6,000' the warm temperatures from Monday have bonded the upper snowpack under a thick, supportive crust layer.

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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Yesterday we observed battling winds that were blowing at a steady 12-15 MPH at the upper elevations.   Modest amounts of fresh snowfall has created the potential for isolated wind slabs to develop near ridgeline features on all aspects.  Very little cracking or reactivity was observed; but, this problem is expected to increase with the winds we observed yesterday as well as strong southwesterly winds predicted in the forecast.

Avalanche Problem 2: Storm Slab
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Mountain weather forecasts are predicting 2-5" of snow today and 2" tonight.  This snow may take time to bond to the existing snowpack.  Expect the potential to trigger thin slabs of fresh snow at tree-line and above this weekend.

Avalanche Problem 3: Persistent Slab
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At elevations above 6,500' the snow did not develop the stout crust layer that was formed under Mondays' warm spell.  The moderate temperatures did a great job of strengthening the snowpack at upper elevations; but, there are still some potential weaknesses in the upper 3' of snow.  These weaknesses consisted of multiple density changes that revealed high quality sheers under high force.  The only one that failed in stability tests was the upper 12" of snow.  Take-home message here: these layers are strong and cohesive and will be difficult to trigger.  Triggering them would likely take a lot of force but there is potential to step down to mulitple weak layers and create a large avalanche at the upper elevations.

advisory discussion

Help me and your fellow riders by submitting your avalanche observations!  You can do it via this site or email them to me at bbernall@fs.fed.us  They can be super simple and anonymous, just let me know what you saw, where (aspect/elevation), when and a quick line on the circumstances.  

Thanks!

Ben

 

recent observations

Yesterday I was able to get out into the Eastern Cabinets with my old friend Liz Figgins to check out the snow.  I was expecting to find nothing but bullet-proof crust and I was pleasantly surprised to find that light snowfall had actually made for decent conditions that improved as one gained elevation.  The new snow was sticking to the crust layer pretty well and pit results at 5,600' verified a very strong and cohesive snowpack.  As we climbed higher the stout melt-freeze crust slowly dissipated but the snow remained supportive and fairly dense under-foot.  Pit results on the north east aspect at 6,700' revelealed a failure in the top 12" with hard force.  This failure had a nice clean shear but was resistant to move much once it broke.  Below this layer I found multiple clean shears and density changes in the snow that fell late last week.  None of them failed in stability tests; but, I wouldn't be hucking off cornices at upper elevations.  The right force in the right spot could create a large slide on one of these layers.



Upper 12" of snow at 6,700' on NE aspect.  (ECTP21)

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
410 AM MST Fri Feb 2 2018
DISCUSSION: Snow will continue across Northern Rockies mountain 
ranges, particularly Clearwater, Bitterroot, Mission, and 
Whitefish/Glacier Region through this afternoon. Snow levels will 
steadily rise above 4000 feet by late afternoon. High terrain snow
totals will be in the 8-12 inch range near Glacier Park, with 4-8
inches elsewhere. Meanwhile some rain on snow activity will be 
found in the 4000-6000 feet elevation band for the Clearwater 
Range.

The next snow episode will develop on Saturday. Arctic air is now
forecast to move as far west as the Kootenai/Cabinet and as far 
south as the southern end of the Mission Range by Saturday evening.
Aside from along the Continental Divide near Glacier Park on 
Saturday (where SLR will increase from 10:1 to 15:1 over time), 
the remainder of the Northern Rockies will experience snow levels 
increasing to nearly 7000 feet by Sunday evening and SLR between
8:1 and 12:1. 8-12 inches accumulation is anticipated near Glacier
Park, however much lower accumulations will exist for points 
south and west. There is a significant amount of moisture 
associated with this storm system that will be falling as rain up
to 7000 feet outside of northwest Montana.

Storm systems will continue to bring precipitation to the region
through middle of next week, with a bit drier period thereafter.

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           95%          85%          75%      
Hi/Lo Temps           31 to 35     26 to 30     30 to 35 
Winds(mph)            SW 17G40     SW 11G31     W 17G36  
Precip Chc            100          70           70       
Precip Type           snow         snow         snow     
Liquid Amt            0.25         0.07         0.07     
Snow Ratio(SLR)       12:1         12:1         12:1     
Snow Amt(in)          2-5          0-2          0-2      
Snow Level            3000         4000         3500     
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.