THIS AVALANCHE ADVISORY EXPIRED ON March 7, 2018 @ 5:29 am
Avalanche Advisory published on March 6, 2018 @ 5:29 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

Mild temperatures and a lack of wind have stabilized the upper snowpack. Use caution in steep, high consequence terrain on all aspects where loose-dry sloughing could cause a loss of control. Also keep in mind the potential to trigger deep weaknesses in the Purcell Range where the snowpack is thinner and potentially more sensitive to triggers.

How to read the advisory

Mild temperatures and a lack of wind have stabilized the upper snowpack. Use caution in steep, high consequence terrain on all aspects where loose-dry sloughing could cause a loss of control. Also keep in mind the potential to trigger deep weaknesses in the Purcell Range where the snowpack is thinner and potentially more sensitive to triggers.

1. Low

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Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Loose Dry
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The upper layer of the snowpack is blanketed in 6-8" of low density powder that is likely to create loose, dry sloughing in the steepest terrain (slopes over 35°) on all aspects and elevations.  This sloughing will be more significant in areas that are harboring the upper crust layer that developed from the warm sunny weather that dominated the area on Saturday. The new snow will be poorly bonded to this crust and may create enough energy to knock a rider off his feet in steep terrain but is unlikely to pose a threat of burial.

Avalanche Problem 2: Deep Slab
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The weak layer that is resting on the February 4th rain crust in now about 4' below the surface which puts it well into a "deep slab" problem in most locations. This weak layer has ceased to show any reactivity in stability tests and is unlikely to cause riders an issue. We are keeping this layer on our radar for now as the potential for triggering this deeply buried weakness could increase when we get our next spring thaw.  It is also worth paying attention to this layer in areas such as the Purcell Mountains of the Yaak where the snowpack is much thinner and slower to heal with the consistently cooler temperatures. 

advisory discussion

Thursday March 8th the Cabinet Mountain Brewery will be hosting a "Brews for Benefits" event to benefit the Idaho Panhandle Avalanche Center.  Come and join us from 5-8 PM, $1 for every beer sold will go to benefit your local avalanche center that makes these forecasts possible.

recent observations

Yesterday we travelled into the Eastern Cabinets from the Bull River side of the world. As we travelled in we observed extensive evidence of Saturdays' warming trend. There was a thin melt-freeze crust under the new snow that could be felt under foot up to 5,000' and higher in locations with solar exposure. We also observed old wet debris piles at the bottom of multiple avalanche paths on the way in. Stability tests reaveled a few weaknesses in the upper snowpack; but, these are unlikely to pose a threat as the recent snow has fallen with little to no wind and has not formed any slabs that we could find. In the highest alpine terrain above 7,000' it is possible that this new snow could have formed some thin and isolated pockets of cohesive slab which is worth paying attention to if you venture into the alpine terrain. 

The recent mild temperatures and lack of wind have done a great job of stabilizing the snowpack. Now that it is March we are starting to enter into the potential "spring-like" problems that can be expected this time of year. If the sun comes out at all we can expect that our "loose-dry" problem will quickly turn into a "loose-wet" avalanche problem. The weather forecast is hinting at the potential for the sun to peek through on Wednesday so be alert to changing conditions associated with exposure to the sun.

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
400 AM MST Tue Mar 6 2018
DISCUSSION: Scattered snow showers will be present across the
Northern Rockies for another day today. Like yesterday, these
showers will be short-lived, and will be quite intense as they
move overhead. The Mountains of northwestern Montana, in
particular around the Glacier Park Region, will see the higher 
accumulations. Partial clearing is expected overnight tonight,
allowing for good radiational cooling. Our next organized weather
disturbance is still forecast to move through the region Thursday 
and remaining active through Saturday. Snow levels will rise each
afternoon, to above 4500 feet, and lowering to around 2500 feet 
in the overnight hours. Several more inches of snow for the 
mountains is expected during this period.

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           80%          50%          55%      
Hi/Lo Temps           26 to 33     13 to 20     30 to 38 
Winds(mph)            SW  6        SW  5        S  6     
Precip Chc            30           0            0        
Precip Type           sno/shr      none         none     
Liquid Amt            0.04         0.00         0.00     
Snow Ratio(SLR)       18:1         0            0        
Snow Amt(in)          0-2          0            0        
Snow Level            1500         2000         1500     
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.