THIS AVALANCHE ADVISORY EXPIRED ON March 24, 2018 @ 5:56 am
Avalanche Advisory published on March 23, 2018 @ 5:56 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Cold temperatures have locked the upper snowpack together following Thursdays' warm and wet weather. Generally stable snowpack conditions will exist on Friday with the potential to find isolated pockets of wind slab at upper elevations on leeward terrain. Expect windslabs and stormslabs to increase in size and sensitivity going into the weekend.

How to read the advisory

Cold temperatures have locked the upper snowpack together following Thursdays' warm and wet weather. Generally stable snowpack conditions will exist on Friday with the potential to find isolated pockets of wind slab at upper elevations on leeward terrain. Expect windslabs and stormslabs to increase in size and sensitivity going into the weekend.

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: Wind Slab
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On Thursday night a cold front pushed out the rain and warm air with high winds and a trace of new snow. Area snotel sites recorded 1-3" of new snow with Hawkins Lake Snotel finally scoring a win at 5" of new snow accumulation. This new snow snow should bond relatively quickly to the warm and moist surface of the existing snowpack. The NWS mountain forecast for the area is calling for 2-3" of snow Friday night and 5-7" Saturday with more southwesterly winds. This will increase the size and sensitivity of these slabs moving into the weekend.

Avalanche Problem 2: Storm Slab
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With forecast calling for up to 10" of new snow in the mountains on Friday night and Saturday we can expect the development of small storm slabs by Saturday morning.  Take the time to observe and assess the bonding strength of this new snow on steep slopes before committing. It is difficult to predict at this point what the potential will be on Saturday. The potential for a storm slab problem and its sensitivity will vary, much of this will depend on the temperatures during the next storm and the variable surfaces that the new snow is landing on. At lower elevations this new snow is likely to fall on Thursdays slick melt-freeze crust. Again, best to assess individual slopes on Saturday before committing to steep terrain.

advisory discussion

Yesterday we toured into the Cabinet Mountains to test out the water resistance of our ski gear. At 6,000' in elevation we finally found the rain-snow transition line, I believe the operative word used by my partner was "yuck".  We travelled as high as 7,600' where we found new snow amounts of 3-4" that were extremely wet and sticky. We performed stability tests on a northeast aspect at 6,800' and the snowpack had no failures or propagation. At this location we were unable to find evidence of the surface hoar that has been prevalent in sheltered locations 10-14" below the surface. We also reaffirmed our theory that at this elevation the February 4th rain crust disappears. The most important observations taken from the day were the amount of moisture being absorbed by the upper 12" of snow, even at elevations above the rain line the top foot of snow is very wet. We also observed two "loose-wet" slides that released on a north aspect at 7,000' yesterday. This thawing and rain, followed by the cold temperatures that moved in on Friday morning will have the snowpack "locked-up" and relatively stable through Friday. Much of the forecast is based on the potential for new snow and strong southwesterly winds predicted for Friday night and Saturday. As I mentioned in the "Problems" section, there are multiple variables that will affect the potential of the storm slab problem on Saturday. Use caution on each aspect and elevation change until you have verified the bonding strength of the new snow Saturday.

Weather and CURRENT CONDITIONS
weather summary 
Backcountry Forecast from NWS Missoula issued:
350 AM MDT Fri Mar 23 2018

DISCUSSION: 
In the wake of last night's cold front, temperatures have trended
cooler and a few lingering snow showers will be possible
throughout today. However, only light accumulations are expected.
Another cold front will begin pushing into north-central Idaho and
western Montana by late tonight into Saturday. Snow showers and
gusty west-southwest winds will be on the increase, and showers
could be locally heavy at times overnight into Saturday. Snow
total accumulations in the terrain of northwest Montana could
reach 6-10 inches (locally higher). Saturday's max temperatures 
will struggle to get above freezing for most of the mountains. 
Northwest flow will set up Sunday and into next week, leading to a
few light showers and a gradual warming trend. 

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           50%          85%          85%      
Hi/Lo Temps           30 to 38     20 to 27     27 to 35 
Winds(mph)            SW 18G37     S 10G25      SW 18G61 
Precip Chc            40           70           100      
Precip Type           sno/shr      sno/shr      sno/shr  
Liquid Amt            0.02         0.14         0.33     
Snow Ratio(SLR)       16:1         15:1         15:1     
Snow Amt(in)          0            2-3          5-7      
Snow Level            1500         2500         2000
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.