THIS SNOWPACK SUMMARY EXPIRED ON January 13, 2017 @ 11:00 pmSnowpack Summary published on January 13, 2017 @ 6:00 am
Issued by Ben Bernall - Kootenai National Forest
Avalanche Character 1: Storm Slab
Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize.
On Sunday January 8th a storm rolled into the Kootenai Region and delivered 12-15" of light, cold snow to the West and East Cabinet Ranges and 6-8" in the Purcell Mountains of the Yaak. This snow has had time to settle and bond well to the existing snowpack in most locations; however, this new snow may prove to be hazardous in very steep terrain and elevations above 7,000' were it was exposed to the general winds.
Backcountry travelers can mitigate this hazard by avoiding steep, leeward terrain at high elevations and areas exposed to the winds were this new snow has been transported and formed a more cohesive layer.
If you missed last nights' "Know Before You Go" Presentation at Troy Elementary you can join us at the Noxon High Library January 17th at 6 P.M. for 1-2 hour avalanche awareness class.
For those going to Idaho or riding near the border you can gather additional snowpack info by clicking the link below for the Idaho Panhandle forecast.
On Thursday January 12th, Nate and I traveled into the Smearl Creek drainage of the Eastern Cabinets. Snow stability tests revealed a very stable snowpack with 12" of light, fresh snow. The new snow was observed to be "sloughing" in the steep, rocky terrain of the Cabinet mountains. We observed a couple of small avalanche crowns where the new snow had released earlier this week on steep, leeward terrain. Although winds were very calm throughout the day we did observe some steady wind transport of surface snow at the highest elevations (above 7,000').
The most notable observations in the snowpack are not the current problems, they are however future problems. Clear and calm weather conditions have created excellent conditions for surface hoar development and we found this to be widespread on all aspects as high as 6,500' in elevation (see photo below). This may create very touchy conditions next week if the predicted weather holds true and buries this surface hoar with a layer of heavy snow. Stay tuned.
Surface hoar crystals on East Facing ridge at 5,500'. Wind transport in progress above Leigh Lake.
The other weakness of note is the faceting and depth hoar development in areas with thin snow coverage. Recent cold snaps have created a very bottomless and sugary snowpack on ridgelines and ribs where the snow has been stripped away resulting in a thin, sugary layer at the ground level. I have not observed any areas where this is causing a stability problem yet because there is no cohesive layer overlying this weakness; however, there are likely spots out there where this weakness is buried by a cohesive slab. I would also anticipate this to become a problem if the next storm buries this weakness with a heavy, cohesive layer of new snow.
Weather and CURRENT CONDITIONS
Backcountry Forecast from NWS Missoula issued:
Backcountry Forecast from NWS Missoula issued:
500 AM MST Fri Jan 13 2017
DISCUSSION: A dry atmosphere and sunny skies will occur through
Sunday. A few clouds Sunday may produce some flurries. Strong
valley inversions producing fog and low clouds will also continue
through Sunday. Expect a slight warm up by Sunday with highs in
the 20s. The next major change to a wet pattern for the entire
region will begin by Tuesday.
--------------------------- 5000-7000 FT ----------------------------
Today Tonight Sat
Cloud Cover 40% 55% 70%
Hi/Lo Temps 10 to 18 3 to 10 18 to 23
Winds(mph) W 7 SW 5 SW 4
Precip Chc 0 0 0
Precip Type none none none
Liquid Amt 0.00 0.00 0.00
Snow Ratio(SLR) 0 0 0
Snow Amt(in) 0 0 0
Snow Level 0 0 0
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
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