THIS AVALANCHE ADVISORY EXPIRED ON February 28, 2018 @ 8:16 am
Avalanche Advisory published on February 27, 2018 @ 8:16 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

New storm snow and strong Southwesterly winds have created sensitive slabs in steep terrain above 5,000' on all aspects.  Use caution on steep slopes until this new snow has had time to settle and strengthen.

How to read the advisory

New storm snow and strong Southwesterly winds have created sensitive slabs in steep terrain above 5,000' on all aspects.  Use caution on steep slopes until this new snow has had time to settle and strengthen.

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.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Southwest winds have been strong enough to transport the recent storm snow onto Northeasterly slopes which has created sensitive windslabs on these leeward aspects. Use caution and assess these aspects before committing to any steep terrain over 30° on wind loaded slopes.

Avalanche Problem 2: Storm Slab
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Many believed that winter was over in early February when the rain began to melt the snow and the dirt came shining through in the valley bottoms. Well,  mother nature continues to deliver the goods with yet another mountain storm that has left us with 12-15" of fresh snow in the high country.  This snow came in cool and gradually warmed up through-out the storm leaving a somewhat "upside-down" snowpack. Meaning, it's denser on top than the bottom. This new snow is showing poor bonding strength and is producing clean shears in stability tests. Give this new snow a few days to settle and bond before committing to any steep slopes above 5,000' in elevation. 



Storm snow layer. Poorly bonded to old snow and producing clean shears with consistent results.

Avalanche Problem 3: Persistent Slab
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There is still a weak layer of faceted snow crystals resting on the February 4th rain crust that is producing failures in stability tests.  These crystals are strengthening and bonding but should still be given some respect. Triggering this layer could produce a large avalanche and this possibility is increased now that we have a fresh storm slab stressing the upper snowpack. If an avalanche is triggered in the new storm snow the potential exists for it to "step down" to the deeper, persistant weak layer that is now over 2' deep in the snowpack.



Pit showing persistant slab layer on NE aspect at 5,700'.

advisory discussion

Thursday March 8th the Cabinet Mountain Brewery will be hosting a "Brews for Benefits" event to raise money for IPAC. Come and join us for the best beer in Lincoln County and help raise funding for your local Avalanche Center at the same time.

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
410 AM MST Tue Feb 27 2018

DISCUSSION:  

The next weather system will move from the northwest across
western Montana and central Idaho today into Wednesday. Light
precipitation will develop, with the main focus expected across
northwest Montana and in the Clearwater Mountains of Idaho.
Snowfall amounts will be relatively light, with generally 3 to 6
inches expected in the higher terrain over the next 24 hours.
Westerly winds will accompany this system at ridge top levels,
with gusts of 30 to 40 mph possible in exposed locations.
Southwest Montana will see minimal precipitation with this system.
An active patter is in store for the rest of the week into the
weekend as a large upper level low pressure system slowly moves
into the region starting Thursday. Initially southwest flow aloft
will usher in some warmer temperatures, increasing snow levels to
roughly 5000 feet. They will crash back down to valley floors by
Friday however as a strong cold front moves through. Continued
snowfall is expected, though certainty in where the heavier
precipitation will be located is low.


Kootenai:

--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           90%          85%          75%      
Hi/Lo Temps           21 to 28     15 to 20     25 to 32 
Winds(mph)            SW 15G28     SW 11G24     SW  7    
Precip Chc            80           80           40       
Precip Type           snow         snow         snow     
Liquid Amt            0.10         0.16         0.04     
Snow Ratio(SLR)       18:1         18:1         18:1     
Snow Amt(in)          1-5          2-8          1        

Snow Level            0            1000         1000     
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.