THIS AVALANCHE ADVISORY EXPIRED ON January 6, 2018 @ 5:14 am
Avalanche Advisory published on January 5, 2018 @ 5:14 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

The Kootenai snowpack is becoming progressively stronger with moderate temperatures.  Stay safe this weekend by practicing safe travel habits such as commiting one rider to a slope at a time, watching your parters and parking in safe locations where you will be an asset rather than a victim if your partners triggers a slide.

How to read the advisory

The Kootenai snowpack is becoming progressively stronger with moderate temperatures.  Stay safe this weekend by practicing safe travel habits such as commiting one rider to a slope at a time, watching your parters and parking in safe locations where you will be an asset rather than a victim if your partners triggers a slide.

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.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    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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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
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Moderate temperatures have been slowly bringing the snowpack together over the past week.  The persistent weak layers such as facets and patches of buried surface hoar are still lurking out there; but, they are rounding out and coming together.  Backcountry riders are most likely to trigger a slide on one of these weak layers in an area with a thinner snowpack.  These weak layers are becoming stubborn, but they are deep and will result in large avalanches if triggered.

recent observations

This past week I have had the opportunity to travel into the deep snowpack of the Cabinets and up into the Purcell Mountians via Spread creek.  In the Cabinet mountains the snowpack is quite deep and the main avalanche concerns are arising from the surface layers brought in by the storm that left on December 30th.  This storm left us with a layer of dense snow 6-10" thick that sat on top of lighter and colder snow.  I also observed extensive evidence of battling winds that left thin slabs and pillows on all aspects.  With a couple of days to settle out these layers were already proving to be fairly stable in pit tests and showing very little reactivity to ski cuts as well.

In the Purcells the snowpack is much thinner, it is also growing another pretty layer of surface hoar up to 1cm tall.  The same structure and benchmark layers are there (Thanksgiving rain crust/facets/more crust) but the weak layers are not as deep.  Stability tests are showing good strength and the facets all appear to be rounding out and coming together with the moderate mountian temperatures at higher elevations.  Primary concern is that with this thinner snow a rider may be more likely to trigger one of these weak layers resulting in a slab that would be 2' thick.  Also, colder air has been trapped in the drainage bottoms which is causing these weak layer to heal at a slower rate.  So, just because you are at a drainage bottom you should still be giving steep terrain respect and practicing safe travel habits.

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
330 AM MST Fri Jan 5 2018

DISCUSSION: Observations across the region area already coming in
with above freezing temperatures at high elevations. This is
expected to continue through Saturday morning when a cold front
will drop snow levels back down to the valleys again. Rain and
snow are expected in the mountains through Sunday morning when it
will decrease to mountain showers. Next week the pattern
transitions back to more active and cooler.

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           85%          90%          80%      
Hi/Lo Temps           29 to 37     26 to 28     29 to 36 
Winds(mph)            SW  8        SW  8G20     SW  9G20 
Precip Chc            40           80           70       
Precip Type           snow         sno/fzra     snow     
Liquid Amt            0.02         0.06         0.05     
Snow Ratio(SLR)       10:1         11:1         13:1     
Snow Amt(in)          0            0-1          0-1      
Snow Level            3000         4500         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.