THIS AVALANCHE ADVISORY EXPIRED ON December 21, 2019 @ 6:04 am
Avalanche Advisory published on December 20, 2019 @ 6:04 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Heavy and dense snowfall is stacking up on a slick and reactive snow surface. Expect avalanche danger to remain HIGH throughout the weeked as more snow and strong southerly winds pound the Kootenai region. Avoid riding on or below steep terrain above 5,000' this weekend

How to read the advisory

Heavy and dense snowfall is stacking up on a slick and reactive snow surface. Expect avalanche danger to remain HIGH throughout the weeked as more snow and strong southerly winds pound the Kootenai region. Avoid riding on or below steep terrain above 5,000' this weekend

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Storm Slab
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Heavy amounts of dense snow is falling on a very slippery surface at treeline and above. The new snow coming into the area will cause avalanche danger to rise throughout the weekend. Avoid being on or below all steep terrain at elevations above 5,000'. Up to 3 feet of snow is forecast to fall in the mountains of the Kootenai Region between Thursday night and Sunday.

Avalanche Problem 2: Wind Slab
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Current weather forecasts are predicting South and Southwest winds in the realm of 30+ MPH and gusts over 60 MPH. This combined with ample amounts of fresh snow will create dense and reactive windslabs on north and easterly terrain. Steep terrain below ridges and steep gullies will be loaded and reactive. Avoid them this weekend and live to ride another day!

advisory discussion

Yesterday we toured into the East Cabinets and found generally stable conditions. The deep weak layers buried in our snowpack continue to show improvements in strength.  We observed one older avalanche crown that likely released on these deep weak layers in very steep and rocky terrain. The most notable observation was the development of a denser wind packed layer forming a thin skin at the surface of the snowpack. Though thin and harmless yesterday this layer really provides the perfect ingredients for causing avalanches as we stack lots of dense, heavy snowfall on top of it. This combined with our strong predicted winds will create dangerous avalanche conditions at upper elevations. At lower elevation what precious little snow we have will likely melt in the rain as snotel observations show that the snow line is a ways up the hill today.

 

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
350 AM MST Fri Dec 20 2019

DISCUSSION: 
Snow will continue today in the mountains of northwest Montana.
Satellite imagery shows a steady plume of Pacific moisture pointed
directly at the Pacific Northwest. This particular flow pattern
will favor the Cabinets and Purcells. These ranges should see up
to a foot and a half today. The Flathead and Whitefish Ranges will
also do well, picking up about another foot today. Temperatures
have increased today with a warm front passing overnight. These
increased temperatures will drop snow-liquid ratios and raise the
snow line to about 5000 ft today. Valley locations will see
primarily rain. Strong ridgetop winds will continue from the
southwest. Snow will linger in northwest Montana through the
weekend. Expect a cold front to arrive on Sunday night or Monday
morning and cool temperatures back to seasonal normals.


Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           90%          90%          95%      
Hi/Lo Temps           32 to 38     29 to 35     32 to 38 
Winds(mph)            SW 37G71     S 32G66      S 27G56  
Precip Chc            100          90           90       
Precip Type           sno/rain     sno/rain     sno/rain 
Liquid Amt            0.99         0.54         0.34     
Snow Ratio(SLR)       12:1         11:1         12:1     
Snow Amt(in)          10-19        4-12         3-6      

Snow Level            4500         5000         5000   
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.