THIS AVALANCHE ADVISORY EXPIRED ON February 14, 2018 @ 5:27 am
Avalanche Advisory published on February 13, 2018 @ 5:27 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

High winds have created isolated windslabs on leeward aspects near ridgelines and gullies.  Use caution in high exposed terrain, particularly in the East Cabinets. Anticipate a significant increase in avalanche danger as storm snow is predicted to return on Wednesday.  The current forecast is predicting up to a foot of new snow to fall, this new snow will likely be very sensitive through the week as it will be resting on a slick bed surface in many locations.

How to read the advisory

High winds have created isolated windslabs on leeward aspects near ridgelines and gullies.  Use caution in high exposed terrain, particularly in the East Cabinets. Anticipate a significant increase in avalanche danger as storm snow is predicted to return on Wednesday.  The current forecast is predicting up to a foot of new snow to fall, this new snow will likely be very sensitive through the week as it will be resting on a slick bed surface in many locations.

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.

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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There is a thin layer of light snow resting on a stout rain crust across the area.  High winds this past weekend have created windslabs on leeward terrain where there was snow available to be transported.  This problem is more significant in the East Cabinets which managed to pick up more snowfall at the end of last week.  These slabs are likely to be isolated and variable in thickness; although they were not proving to be highly sensitive yesterday, it would be wise to use caution directly below ridglines and gully features where this loose snow has been deposited onto a slick rain crust.

Avalanche Problem 2: Persistent Slab
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There is still some potential to trigger deeper layers in the snowpack in the highest terrrain of the East Cabinets above the melt freeze line the formed on February 4th and 5th.  This is also a possibility in the Purcell Range of the Yaak where the snowpack is much thinner than the Cabinet Mountains.  These layers are thick, stubborn and will likely take alot of force to trigger.  Continue to keep this in mind as a possibility when playing on open slopes above 7,000'.  These cohesive slabs could pull in adjacent, lower angle terrain terrain that would generally be considered safe.

advisory discussion

IPAC is offering a Level One Avalanche class for snowmobilers and snowbikes in Trestle Creek on February 21-24th.  This is a great opportunity to get some in depth avalanche knowledge from the pros!  For info call the Sandpoint Ranger Station at (208)263-5111.

recent observations

Looking at the snowpack 3 things are always at the forefront of my mind: Past, Present and Future.  I will start with the Past.  On February 4th and 5th the area was under a very warm and moist pattern that saturated the snowpack, yesterday we observed evidence of this warming and weakening up to 7,500'.  Small wet slides off of rock bands, cornice fall and even glide creeps have opened up on locations that are known to have a rock slab bed surface.  We then transitioned into a cool down which locked the snowpack together,  then picked up a few inches of fresh snow across the area with the Eastern Cabinets winning at 7" of new snow.  This new snow has been scoured off of exposed areas and deposited onto leeward slopes and depressions forming a smattering of wind affected snow across the higher terrain.  In many locations this new snow has developed a dense skin that also has some near surface facets developing underneath it as the cold air pumps the moisture upward.  Where we don't have this thin layer of wind affected snow and facets we have a thick, hard rain crust. Going into the Future this week we have a predicted storm that is likely to drop a foot of snow Wednesday on these existing surfaces.  The National Weather Service is also predicting another strong system this coming weekend that will bring us additional snowfall.  

Summary: Our situation is likely to change significantly as the rock hard surface you were skidding down yesterday will become the slick surface that tommorows snowfall will be skidding down this week.

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
440 AM MST Tue Feb 13 2018
DISCUSSION: We are starting off pretty cold this morning with
temperatures at or below zero across much of western Montana
mountains. Cold wind chills will begin to subside as wind diminish
through the day. The next 48 hours, through Tuesday evening will
be dry and generally clear. The weather becomes active again
Wednesday. A winter storm from British Columbia will move across
the entire Northern Rockies Wednesday through midday Thursday
where storm totals of a foot of snow are likely across the
mountains. Some arctic air is expected to move across the divide
and increase northeasterly winds.  Thursday afternoon and Friday 
scattered snow showers will persist.


This upcoming weekend another winter storm which looks to be a
little stronger will impact the entire Northern Rockies with
another round of snow and blowing snow thanks to another shot of
arctic air moving over the continental divide. Another foot or
more of mountain snow is likely next weekend. 


Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           45%          90%          95%      
Hi/Lo Temps           24 to 29     18 to 22     21 to 27 
Winds(mph)            SW 15G41     SW 18G36     SW 10G29 
Precip Chc            0            90           100      
Precip Type           none         snow         snow     
Liquid Amt            0.00         0.21         0.26     
Snow Ratio(SLR)       0            15:1         16:1     
Snow Amt(in)          0            3-4          3-7      
Snow Level            500          500          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.