THIS AVALANCHE ADVISORY EXPIRED ON February 1, 2020 @ 5:32 am
Avalanche Advisory published on January 31, 2020 @ 5:32 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Warm temperatures and rain up to 7,500' are being forecast for Friday afternoon. Anticipate avalanche danger to rise on Friday at all elevations. Avoid avalanches by avoiding be on or below steep terrain on Friday and Saturday. Natural avalanches may be possible and human triggered avalanches are likely on Friday.

How to read the advisory

Warm temperatures and rain up to 7,500' are being forecast for Friday afternoon. Anticipate avalanche danger to rise on Friday at all elevations. Avoid avalanches by avoiding be on or below steep terrain on Friday and Saturday. Natural avalanches may be possible and human triggered avalanches are likely on Friday.

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wet Slab
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Warm temperatures and .6 inches of water will fall on the existing snowpack Friday afternoon and cause the upper 18-24" of the snowpack to become wet, heavy and weak up to 7,500' in elevation. Natural avalanches will be possible and they have potential to run to drainage bottoms if they release in large start zones at upper elevations. This problem will be a concern until Saturday afternoon when a cold front is forecast to enter the area and lower the snowline. Avoid being on or below steep terrain while these warm, rainy conditions are present. 

Avalanche Problem 2: Wind Slab
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On Thursday wind slabs were our primary concern as we noted very obvious effects of southwest winds that blew across the area early this week. They were less reactive; but, still a concern. On Friday and Saturday this problem will remain a hazard as the warm temperatures and rain will stress these slabs and cornices on north and east facing terrain. On Saturday the snowline will drop and the winds will continue and raise the hazard of wind slabs above 6,000'.

Avalanche Problem 3: Loose Wet
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It's gonna get sloppy out there on Friday afternoon!! Expect to see "loose-wet" slides flow freely down the hill up to 7,500' in elevation. By Saturday this problem will mainly be a concern at Treeline and below as the temperature drops and the rain turns back to snow at upper elevations. These slides are often slow and harmless in appearance. If you find yourself in trees or cliffs they will hurt you. Give this problem some respect in steep terrain with trees and cliffs.

advisory discussion

We have a dynamic situation right now in regards to weather and avalanche hazard. Yesterday we observed a very stable and cohesive snowpack. Our primary concern was windslab on north and east facing terrain where the southwesterly winds have built large cornices and cohesive wind-slabs. There are a couple of weak layers in the upper snowpack but neither were showing a high likelihood of failing. We will see a big change by Friday afternoon with the incoming weather. Temperatures are starting to climb and mountain rain is on the way. Discussions this morning with the National Weather Service indicate that by Friday afternoon it will be raining to at least 7,500' or higher. This will cause our upper snowpack to become heavy and weak. I anticipate that we will initially see lots of loose-wet avalanche activity early on followed by the potential for slabs to release in the upper 18-24" of the snowpack.

By Saturday morning the rain/snow-line is expected to drop back down to 6,000' and strong winds out of the southwest will hammer the area. With this you can anticipate the problems above treeline to shift back to a storm slab and wind slab concern. At lower elevations below 6,000' expect "loose-wet" and "wet-slabs" to remain the primary concern until Saturday afternoon.

Weather and CURRENT CONDITIONS
weather summary 
Backcountry Forecast from NWS Missoula issued:
400 AM MST Fri Jan 31 2020

DISCUSSION: 

Northwest Montana: Light to moderate snow will continue for all 
elevations through the early morning hours. By late morning, into 
the afternoon, warmer air aloft will move into the region changing
snow to a rain/snow mix for elevations of around 5000 feet and 
below. Above that, all snow is expected to continue through the 
rest of the daylight hours. Strong gusty westerly winds are 
expected today as well, above 5000 feet. Wind gusts could be 
approaching 50 mph by early afternoon. Even stronger winds will be
moving through northwestern Montana for most of the day Saturday.
Gusty westerly winds in the Mission and Swan Ranges, as well as 
GNP and the Bob Marshalls, will be exceeding 65 mph by the 
afternoon. A strong cold front will move through the area by 
sunset, bringing heavy snow and continued strong winds to the 
higher terrain.
Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           90%          75%          90%      
Hi/Lo Temps           35 to 40     29 to 36     34 to 40 
Winds(mph)            SW 25G55     SW 36G64     SW 43G78 
Precip Chc            90           70           90       
Precip Type           sno/rain     sno/rain     sno/rain 
Liquid Amt            0.57         0.15         0.45     
Snow Ratio(SLR)       11:1         8:1          13:1     
Snow Amt(in)          1-6          0-2          5-7      
Snow Level            6000         6500         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.