THIS SNOWPACK SUMMARY EXPIRED ON January 26, 2017 @ 9:00 amSnowpack Summary published on January 25, 2017 @ 4:00 pm
Issued by
Ben Bernall - Kootenai National Forest
Avalanche Character 1: Persistent Slab
Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.
I am using this "problem" to identify a number of different weaknesses that vary across the landscape of the Kootenai National Forest. The most threatening layer at this time would be the surface hoar layer buried below the rain crust. It is 8-9" deep and may be found on sheltered north facing aspects. Backcountry travelers can mitigate this hazard by using caution on steep(over 35 degrees), north facing slopes that are sheltered from wind and sun.
The other weakness of note is the faceting and depth hoar that has developed at the ground in areas with a thin and shallow snowpack. These sugary, angular grains are being found on southerly aspects, exposed ribs and shallow rocky areas. This sugary snow development is very extensive in the Purcell Range of the Yaak where the snow coverage has been thinner and the air colder. At this time we have not observed this weakness to be reactive in stability tests; but, it is something worth paying attention to as this weak layer is buried with more snow. Triggering an avalanche on this deep weak layer is low in likelihood but may be high in depth and consequence.
Avalanche Character 2: Loose Dry
Loose Dry avalanches exist throughout the terrain, release at or below the trigger point, and can run in densely-treed areas. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells.
Three to five inches of new snow is now lying on top of a slick rain crust. This new snow is loose, dry and poorly bonded. RIders may find this to be a problem in the steeper, gullied terrain where this loose snow could create enough force to cause one to loose control. Something to pay attention to before entering steep terrain as sloughing and thin slab releases are very likely with this layer.
Snowpack Discussion
ATTENTION!! THE NEXT SNOWPACK SUMMARY WILL BE ISSUED TUESDAY FEBRUARY 7TH AT 7 AM. DUE TO REQUIRED TRAINING I WILL BE ABSENT AND UNABLE TO ISSUE ANY SNOWPACK INFO FOR THE KOOTENAI N.F. FOR THE NEXT 10 DAYS.
Until then it would be advisable to visit the Idaho Panhandle website for information as thier snowpack weaknesses have been fairly similiar in stability issues and weather throughout the season. http://www.idahopanhandleavalanche.org/current-advisory.html
David Thompson SAR will Be offering a free Avalanche class on January 27th at 7 p.m. and resuming the next day at 7a.m. This class will take place at the SAR Barn in Libby. It is free and open to all. For additional info contact DTSAR Mt. Unit Leader Terry Crooks at 293-1618
recent observations
Yesterday obs were taken on Bear Mountain in the Keeler-Rattle drainage. Stability tests revealed multiple weak layers in the upper snow pack ranging in depth from 3" to 4" depending on location and aspect. The small amount of new snow has come to rest on a rain crust that we have observed at elevations well over 6,000'. This thin layer of new snow slides easily and is quite reactive; however, it is thin and soft at this time and poses minimal hazard. Some natural releases were observed in this thin upper layer. We are also finding a weak layer of buried surface hoar below the rain crust on sheltered north aspects. This layer is aproximately 8-9" deep and is a much greater concern. Test results are showing this layer to fail with moderate force and it produces clean and sudden shears.
On Saturday the 21st I recieved reports from friends skiing near Burnt Peak who found similiar conditions regarding these weak layers and depths. All reported a thick rain crust(1-1.5") up to 5,200'. Above this elevation the crust was between .25 and .5" thick, this rain crust will need to be watched closely when the next storm system adds a new layer to this slippery surface.
I traveled into the Eastern Cabinets on Saturday where snotel data showed high tempertures reaching up to 37 degrees during last weeks warm spell. The crust layer was over 1.5" thick at 5,000' and the snow was observed to have fallen off the trees as high as could be observed. There was also evidence of multiple small, wet slides that had released earlier in the week.
Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
210 PM MST Wed Jan 25 2017
DISCUSSION: Northwesterly flow will persist over the Northern
Rockies through Thursday. This flow pattern is conducive to
scattered snow showers and the mountains could receive a couple
of inches of new snow. The mountain ranges right along the
Montana/Idaho border and the Continental Divide have the best
chance of accumulations. A ridge of high pressure builds over the
region Friday supporting the continued development and
strengthening of valley inversions through the weekend and into
next week. Meanwhile frequent 'bluebird' conditions will be found
throughout much of the backcountry above the valley inversions.
Kootenai:
--------------------------- 5000-7000 FT ----------------------------
Tonight Thu Thu Night Fri
Cloud Cover 85% 80% 80% 90%
Hi/Lo Temps 13 to 20 24 to 28 14 to 19 25 to 28
Winds(mph) W 7 W 5 W 6 SW 7
Precip Chc 30 0 0 0
Precip Type sno/shr flurries sno/shr sno/shr
Liquid Amt 0.01 0.00 0.00 0.00
Snow Ratio(SLR) 18:1 18:1 16:1 15:1
Snow Amt(in) 0 0 0 0
Snow Level 500 0 0 500
Disclaimer
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.
