THIS AVALANCHE ADVISORY EXPIRED ON March 31, 2018 @ 6:08 am
Avalanche Advisory published on March 30, 2018 @ 6:08 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

The highest elevations of the Kootenai are harboring isolated wind slabs that could be triggered in steep terrain. Pay attention to density changes in the surface snowpack and look for "lens shaped pillows" when travelling above treeline. At lower elevations the snowpack is generally stable, the exception will be during Saturday when the sun may cause small, "loose-wet" avalanches on southerly and westerly aspects.

How to read the advisory

The highest elevations of the Kootenai are harboring isolated wind slabs that could be triggered in steep terrain. Pay attention to density changes in the surface snowpack and look for "lens shaped pillows" when travelling above treeline. At lower elevations the snowpack is generally stable, the exception will be during Saturday when the sun may cause small, "loose-wet" avalanches on southerly and westerly aspects.

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

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.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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During the past week the area has been hammered by strong and erratic mountain winds. This combined with modest snowfall at upper elevations has created thin and isolated windslabs above treeline in "extreme" terrain. These isolated slabs will be found primarily on northeast aspects; but, there is potential to find them on other aspects as well by Saturday as the predicted cold front brings a switch in wind direction. Use caution in areas where a small slab release will have high consequences if triggered. Our recent warm daytime temperatures and cold nights have been effective in bonding these slabs to the existing snowpack. In short, they will likely be stubborn and difficult to trigger; but, steep terrain with high consequences should be approached with caution before you ride or slide.

Avalanche Problem 2: Loose Wet
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With light amounts of fresh snow and the potential for partially clearing skies on Saturday there is potential for some small "loose-wet" slides on aspects exposed to the sun. These slides will likely be small in nature; but, pay attention if you find yourself in an area where the terrain has potential to increase the consequences (cliffs, trees, gullies-etc!).

advisory discussion

Observation from March 29th revealed a very stable snowpack at lower elevations with evidence of extensive wind effects at elevations above treeline. The only weakness observed in the snowpack was revealed in the upper 8" of new snow.  Stability tests performed on a north aspect at 6,000' revealed this weakness in the new snow failed with moderate force but showed a low likelihood of propagating into a slab avalanche. Evidence of this layer failing and creating small avalanches (approximately 50' wide) was observed in the steep and rocky terrain above Leigh Lake. No "loose-wet" avalanches were observed yesterday, so the potential for this problem is low, but possible. 

As we continue into spring I would like to remind my fellow backcountry travellers to keep in mind the potential for "spring-like" avalanche problems to rear their ugly heads with quick changes in temperature and solar activity. Good snowpack stability can decline quickly when the sun comes out or if it starts to rain. Pay attention to these changes as you ride this spring and come home in one piece. 

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
410 AM MDT Fri Mar 30 2018

DISCUSSION: Strong westerly winds are expected to develop over the
Northern Rockies this afternoon, ahead of a modified arctic cold
front. Winds through the afternoon will gust as high as 50 mph 
along the ridge tops. This evening, as the arctic boundary moves 
over the the Continental Divide, winds will switch out of the 
northeast, with gusts up to 40 mph. Significant amounts of 
mountain snow is also expected to accumulate starting this 
afternoon, through tomorrow morning. Snow levels will briefly 
lower to most valley floors overnight and Saturday morning. 
Scattered mountain snow showers will linger through the day on 
Saturday, however only light accumulations are expected. Winds 
will also remain breezy out of the east.

Kootenai:

--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Sat      
Cloud Cover           75%          60%          55%      
Hi/Lo Temps           34 to 40     10 to 19     29 to 36 
Winds(mph)            W 21G41      N 18G39      NE 12G28 
Precip Chc            60           50           0        
Precip Type           sno/shr      sno/shr      none     
Liquid Amt            0.11         0.02         0.00     
Snow Ratio(SLR)       15:1         15:1         0        
Snow Amt(in)          1-2          0            0        

Snow Level            4000         2000         500      
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.