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THIS AVALANCHE ADVISORY EXPIRED ON January 15, 2020 @ 5:24 amAvalanche Advisory published on January 14, 2020 @ 5:24 am
Issued by
Ben Bernall - Kootenai National Forest
Kootenai
bottom line
Expect to easily trigger wind slabs on steep terrain below ridgelines and cornices. Storm snow from this past weekend is quickly settling and gaining strength but still has potential to fail at upper elevations. Expect avalanche danger to decrease through Wednesday as the new storm snow has time to settle out and bond.
Kootenai
How to read the advisory
Expect to easily trigger wind slabs on steep terrain below ridgelines and cornices. Storm snow from this past weekend is quickly settling and gaining strength but still has potential to fail at upper elevations. Expect avalanche danger to decrease through Wednesday as the new storm snow has time to settle out and bond.
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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The last storm snow came in with consistent south and west winds. Slopes facing north and east have been loaded in and will likely harbor sensitive slabs just below ridgelines. Be alert for cracking and density changes in the snow surface as these will be likely clues to the presence of wind slab. Avoid riding on steep slopes that are directly under cornices or steep rolls.
Avalanche Problem 2: Storm Slab
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Unlikely
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Area wide a storm delivered another hefty shot of snow to the mountains. This new snow fell on a wide variety of surfaces out there and some of those surfaces are easier to stick to than others! Yesterdays stability tests showed very little reactivity in the new storm snow but my observations were limited to Flatiron Mountain in the Purcells. Upper elevations in the West and East Cabinets recieved more snow and much of it fell on areas that had graupel layers and wind crusts near the surface. These areas will have potential to release on the old snow interface in the upcoming days.
advisory discussion
There's alot of ground out there and I obviously can't see all of it. Going up to Flatiron Mountain yesterday where are snow pack is fairly thin compared to the Cabinet Ranges revealed that there is still some deep weakness at the base of the snowpack. These deep weaknesses are something I am going to continue to monitor but I don't see them being a problem until we get a big "rain on snow" event or even spring when it warms up. In most locations these weak layers are well bridged by a thick snowpack and are continuing to show gains in strength.
The storm snow at Flatiron was well settled and showed very little reactivity in pit tests or under foot as I climbed up. Knowing that we had a wide variety of surface conditions prior to the last storm I believe there is still some potential for the last storm snow to slide in areas that I didn't visit yesterday and I would continue to give steep slopes a wide berth for a couple more days. The main concern in my eyes yesterday was the windslab issue that can be easily seen in the video. Lot's of snow transport on north and east aspects. It is easy to feel the change under foot and if you are close to the edge shooting cracks will make themselves visible in areas with windslab. The weather looks pretty calm in the upcoming days with cool temps, light snowfall and lighter winds. This should all give the storm snow a chance to settle out during the week.
Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued: 340 AM MST Tue Jan 14 2020 DISCUSSION: NORTHWEST MONTANA: Dense cold air remains near the surface (below roughly 4500 feet), with easterly winds present, mostly along the Continental Divide. Above 4500 feet, winds of a southerly nature prevail. This will continue today. Snow has begun to spread across NW MT, with snow expected to be light, fluffy, and persistent. SWE will be on the lighter side as a result of the low density snow, favoring right along the ID/MT border, and the southern Missions and Swans. Quiet conditions will then persist through midweek until the next snow- making system makes an appearance. As of now, the bulk of the moisture associated with this feature will remain well to the south of NW MT mountain ranges.
Kootenai:
--------------------------- 5000-7000 FT ----------------------------
Today Tonight Wed
Cloud Cover 95% 85% 60%
Hi/Lo Temps 9 to 17 -1 to 8 12 to 19
Winds(mph) W 10G23 SW 14G28 S 15G28
Precip Chc 90 50 0
Precip Type snow snow snow
Liquid Amt 0.09 0.06 0.00
Snow Ratio(SLR) 22:1 21:1 21:1
Snow Amt(in) 2-4 1-3 0
Snow Level 0 0 0
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.
