THIS AVALANCHE ADVISORY EXPIRED ON February 17, 2018 @ 5:34 am
Avalanche Advisory published on February 16, 2018 @ 5:34 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Expect avalanche danger to change rapidly going into the weekend with strong winds and heavy snowfall forecasted for Saturday and Sunday.   This new snow will be falling on a multitude of weak layers that will take multiple days to settle and strengthen.

How to read the advisory

Expect avalanche danger to change rapidly going into the weekend with strong winds and heavy snowfall forecasted for Saturday and Sunday.   This new snow will be falling on a multitude of weak layers that will take multiple days to settle and strengthen.

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 plenty of loose snow available for transport and more on the way we can expect the strong southwesterly winds that are forecast to produce sensitive windslabs on leeward terrain.  These slabs will increase in sensitivity and depth throughout the weekend.

Avalanche Problem 2: Storm Slab
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The mountains of the Kootenai are begining to pick up light snow this morning as the first of a series of storms enters the region.  Storm snow totals are forecasted to be fairly light today and increase significantly throughout the weekend.  This new snow will be falling on two different weak layers that are overlying a thick crust.  This will create an ideal recipe for rising avalanche conditions going into the weekend.

Avalanche Problem 3: Loose Dry
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There is approximately 8-10" of loose dry snow overlying a stout crust.  This loose snow is breaking free with ease and creating small sloughs in steep terrain.  Although these slides are not dramatic they can cause you harm in steep, rocky terrain if they knock you off your feet.

recent observations

Yesterday we toured into the Keeler area where we found 8-10" of loose, dry snow overlying the stout rain crust that developed on February 4th and 5th.  Overall the snowpack was proving to be very stable. The surface layer was too loose to form a dangerous slab and the underlying crust is over 5" thick in most locations.  We revealed two weak layers near the existing surface that will be cause for concern if the storm materializes this weekend.  The first being a weak interface in the storm snow that sits 2-3" above the crust layer, this poor bond was the cause behind the extensive sloughing of surface snow in steep terrain.  The second weakness is the surface hoar that grew during the previous cold, clear night.  These two weaknesses overlying the stout crust bed surface will create an "avalanche sandwich" if the heavy snow load forecasted for the weekend materializes.

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
350 AM MST Fri Feb 16 2018

DISCUSSION: 
Increasing snowfall and strong west winds are forecast today into
Saturday as the first wave of moisture moves through the region.
By Saturday afternoon, a mild air mass will briefly return and 
snow levels will raise above 3500-4500 feet south of I-90. 
However, by Saturday night into Sunday it will rapidly turn colder
as an arctic front drops in from the northeast. This arctic front
will create strong gusty winds from the north and east as it 
tracks into western Montana. Overall, expect 1-3 feet (or more) of
widespread snow over the mountains during this 72 hour period. 
Snow will become lower density as the colder air mass takes over, 
and is expected to continue into Monday. 

Kootenai:

--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           95%          70%          95%      
Hi/Lo Temps           23 to 29     13 to 19     21 to 29 
Winds(mph)            SW 18G45     W 16G39      S 14G36  
Precip Chc            90           50           100      
Precip Type           snow         snow         snow     
Liquid Amt            0.16         0.05         0.61     
Snow Ratio(SLR)       18:1         18:1         18:1     
Snow Amt(in)          2-5          0-2          9-16     
Snow Level            1000         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.