THIS AVALANCHE ADVISORY EXPIRED ON March 14, 2018 @ 5:16 am
Avalanche Advisory published on March 13, 2018 @ 5:16 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Warm afternoon temperatures will cause the snowpack to weaken as Tuesday is forecast to be another warm and sunny day. Avoid areas where "loose-wet" slides have the potential to injure you by pushing you into trees and cliffs. Cornices and glide cracks are also starting to weaken, the only way to manage this problem is to avoid being underneath them as temperatures rise during the day.

How to read the advisory

Warm afternoon temperatures will cause the snowpack to weaken as Tuesday is forecast to be another warm and sunny day. Avoid areas where "loose-wet" slides have the potential to injure you by pushing you into trees and cliffs. Cornices and glide cracks are also starting to weaken, the only way to manage this problem is to avoid being underneath them as temperatures rise during the day.

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: Loose Wet
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As the sun comes up and temperatures climb expect to see small, loose-wet snow slides begin to run down the hill. This problem was most prevelant yesterday on easterly slopes where last weeks storm snow was deposited onto steep terrain. These slides are often small and slow; however, if caught you may lose control and be pushed into objects or locations where you could be injured.

Avalanche Problem 2: Wind Slab
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On March 8th and 9th the area recieved a nice shot of storm snow that storm came in warm with strong southwest winds. This new snow bonded quickly but it also left some dense slabs on the northeast aspects above treeline. Yesterdays observations proved that these slabs are quite stubborn and resistant to movement. With mountain temperatures climbing into the mid 40's today these slabs could weaken and I would advise using strong caution before jumping onto a steep, northeast aspect above treeline at this time.



The upper layer of storm snow in a leeward location. Slab is 10-11" thick and showing low potential of propagation

 

Avalanche Problem 3: Cornice
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I am lumping a range of "unpredictable potentials" in this problem as we are starting to see a multitude of potential problems come into play with the spring weather. Large cornices are hanging over the leeward terrain, yesterday we observed one that is cracked and slowly pulling away from the ridgeline. There are also multiple "glide-cracks" opening up in steep terrain with rock slab bed surfaces below the snow. These problems will continue to increase and be tested as warm days and mountain rains become the seasonal normal.  We can't predict when they will cut loose; but, we can avoid being underneath of them when it is warm and sunny.

advisory discussion

On Tuesday March 12th we travelled into the Eastern Cabinets to check on the sensitivity of last weeks windslab. On the way in we had a good look at multiple aspects in the high terrain and I was quite surprised by the lack of "loose-wet" slide evidence despite the recent warm temperatures. It seems as though the high winds on Friday had stripped most of the new snow off of the southwesterly aspects down to the firmer layers below. For this reason most of the "loose-wet" slide activity was observed on easterly slopes where the new snow had been deposited, these slides where mostly originating below steep and rocky terrain. The recent storm snow and wind slab is showing a low likelihood of triggering in stability tests. We did observe some thin crowns in very steep, leeward terrain that appeared to be a couple of days old.

Climbing into the high terrain above treeline we are seeing an abundance of "glide cracks" opening up in areas where the snowpack is resting on rock slabs or smooth bed surfaces of bear grass. There is also some fairly significant cornice development hanging over the northeast aspects. The cold nights will help keep these issues locked together; but, as I mentioned earlier, expect them to start moving during the warm afternoon hours. If we get into a cycle of continuous warm weather or mountain rains the probability of these problems coming to life will increase. Again, the best way to deal with this problem is to avoid being underneath of it.

 

Glide cracks on easterly aspect at 6,500"                                                                        Cornices hanging off of ridge and glide cracks on face.                                                           

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
430 AM MDT Tue Mar 13 2018

DISCUSSION: Conditions will continue to be warm and dry across 
the Northern Rockies through this evening.

The next snow will arrive by late tonight, with snow levels 
initially rising near 6000 feet. Snow levels will steadily drop 
to near 4000 feet by Wednesday night, when snow accumulations up 
to 6 inches will occur across western Montana ranges above 6000
feet with the exception of far northwest Montana (e.g., Cabinet, 
Purcell Ranges and vicinity).

Another storm system appears plausible for late next weekend, with
accumulations most favored across north central Idaho and
southwest Montana. However, accumulations will likely be sub 6
inches and confined to 5500 feet elevation and higher.

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           5%           30%          80%      
Hi/Lo Temps           45 to 51     31 to 34     37 to 44 
Winds(mph)            SE  8        SE  7        S  5     
Precip Chc            0            0            70       
Precip Type           none         none         showers  
Liquid Amt            0.00         0.00         0.13     
Snow Ratio(SLR)       0            0            8:1      
Snow Amt(in)          0            0            1        
Snow Level            3500         5500         4500     
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.