THIS AVALANCHE ADVISORY EXPIRED ON February 13, 2019 @ 4:34 am
Avalanche Advisory published on February 12, 2019 @ 4:34 am
Issued by Ben Bernall - Kootenai National Forest

Kootenai

bottom line

CONSIDERABLE avalanche danger exists on all aspects and elevations. Expect the conditions to worsen throughout the day Tuesday as the latest storm rolls through. Heavy storm snow and sensitive wind slabs will create touchy conditions on all steep terrain through Wednesday. This week is a good time to make conservative terrain choices!

How to read the advisory

CONSIDERABLE avalanche danger exists on all aspects and elevations. Expect the conditions to worsen throughout the day Tuesday as the latest storm rolls through. Heavy storm snow and sensitive wind slabs will create touchy conditions on all steep terrain through Wednesday. This week is a good time to make conservative terrain choices!

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.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Storm Slab
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Heavy snowfall is predicted to fall throughout the day Tuesday and into Wednesday. This snowfall is predicted to come in warmer and will be of higher density than the cold, light snow below it. This will form a weak interface that will trigger easily in steep terrain (over 30°). Expect the avalanche danger to rise today through Wednesday and stick to lower angle terrain until this new snow has settled!

Avalanche Problem 2: Wind Slab
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Unless you live in a cave you have noticed the wind blowing this past week. Since last Thursday the wind has blown from the west, north to northeast through the weekend, then out of the southwest yesterday. This has formed wind slabs at all elevations and one may find windslab on any aspect particularly in steep, gully features where the snow has loaded in as the wind pushes snow across the slope.  Yesterday we observed some natural windslab avalanches and were able to easily release slabs with a stomp from the ski on north and east aspects. These windslabs are most likely to move at upper elevations where they are resting on firm, crusty bed surfaces. Again, with incoming weather this problem will become more sensitive and more dangerous. Short video of yesterdays windslabs⇒ https://youtu.be/DlDkP79sexE



Though they were thin on Monday; remember, this is what our new snow is landing on! 6,500' in E. Cabinets.

 

Avalanche Problem 3: Persistent Slab
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The buried surface hoar layer from mid-January may still be reactive between 5-6,000' in isolated locations. I would be most concerned about this weakness in the Purcell Range where the snowpack is thinner and observations from Flatiron last Thursday were still showing this layer to be propagating with moderate force. Pit results in the Cabinets have showed this weak layer to be non-reactive and difficult to find the past week. With the incoming storm snow there is the increased potential to "wake this layer up" with the added weight of the new storm snow.

advisory discussion

Today is a big weather day and we will be keeping a close eye on snowfall totals with the anticipation that the avalanche danger may rise to HIGH if the weather forecast manifests into a reality! What I observed yesterday was a snowpack that is fairly stable but has a lot of weakness near the surface that will make a poor resting place for the 1-2' of predicted snowfall. In gullies and near ridgelines we have thin and reactive windslabs, elsewhere the snow is very light, loose and cold. The new snow will likely come in at warmer temps and higher densities which will form an "upside down" scenario in the upper snowpack. So, continue to watch the weather and use patience with this new storm snow. Dial back your terrain selection and go play in lower angle timber away from the steep, wind loaded slopes.

Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
420 AM MST Tue Feb 12 2019

DISCUSSION: The Northern Rockies will continue to see temperatures
moderate today as a warm front moves through the region. Moderate
to heavy snowfall has developed across northwest Montana and the
higher terrain of central Idaho, and will continue in these areas
through tonight. A foot or two of snow will be possible in the 
higher terrain of northwest Montana, particularly for locations 
near the Idaho/Montana border. Winds will become southerly today,
becoming breezy at times.

It still looks like snow chances will shift southward once again 
Wednesday night into Thursday morning. Cold air from east of the 
Continental Divide appears to make a comeback over the Northern 
Rockies this weekend, particularly across western Montana, with 
widespread snow once again. A cool and active weather pattern will
remain in place in to early next week. 

Kootenai:
--------------------------- 5000-7000 FT ----------------------------
                      Today        Tonight      Wed      
Cloud Cover           100%         95%          85%      
Hi/Lo Temps           22 to 29     16 to 24     23 to 29 
Winds(mph)            S 20G49      SW 15G41     W  8G20  
Precip Chc            100          100          70       
Precip Type           snow         snow         snow     
Liquid Amt            0.68         0.34         0.09     
Snow Ratio(SLR)       18:1         17:1         18:1     
Snow Amt(in)          11-17        4-10         1-3      

Snow Level            2000         2000         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.