THIS SNOWPACK SUMMARY EXPIRED ON March 8, 2017 @ 1:45 amSnowpack Summary published on March 7, 2017 @ 8:45 am
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.
This "Avalanche Problem" is being put in here for the Purcell Range. Multiple weak interfaces exist in the snowpack of the Northwest Peaks/Buckhorn/Purcell Range that are not being found in the West and East Cabinets. These layers are tricky in distribution and have the potential to produce some fairly large and destructive avalanches. I will be revisiting this area on Thursday to see how things are coming together. In the meantime I would be very conservative with terrain choices when riding in the Purcell Range; choose lower angle terrain and pay attention to good travel habits by crossing steep or exposed areas one at a time.
Avalanche Character 2: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.
The West and East Cabinets have been getting relentless shots of new snow over the last couple of weeks with the occassional bout of high winds near the ridge tops. There are small and isolated pockets of wind slab that are forming at the tops of gullie features and right below ridgelines. Though they are small and isolated in nature they are worth taking seriously before dropping onto a slope where a small slide may push you into trees or cliffs.
Snowpack Discussion
Many are crying about winters relentless pounding this year! Embrace it and get out and enjoy the powder. Just be sure to check the weather forecast and avalanche conditions before heading out. There seems to be alot of winter weather activity heading our way in the next week. Lots of Snotel and mountain weather info can be found by browsing the weather tab on this page, it's a great resource so check it out!
Check out the Panhandle forecast by clicking the link below!
http://www.idahopanhandleavalanche.org/selkirks-cabinets/advisory#null
recent observations
Last week we travelled into the Hawkins Lake area of the Northwest Peaks where we found highly reactive surface hoar in our stability tests that was buried approximately 1' below the surface. Below that we found the snow is poorly bonded to the February 16th rain crust and facets/depth hoar on the ground. All are fairly serious weak layers and may be slow to heal. I would expect a large avalanche cycle to occur in this area when winter finally lets go and gives into spring temperatures and high mountain rains.
On Monday the 6th, we travelled into the Snowshoe Mine area of the Eastern Cabinets. We found deep snow and relatively stable conditions, the steady shots of new snow have not allowed any obvious weak layers to form in the upper snowpack. We did note some small density changes and wind slab development in gully features and near the ridgeline on the southwesterly aspects. The other notable observation would be some loose dry sloughing on very steep slopes, mostly benign but could be a problem on large steep faces and in steep chutes where a build-up of loose snow could knock you off your feet or sled.
Weather and CURRENT CONDITIONS
weather summary
Backcountry Forecast from NWS Missoula issued:
420 AM MST Tue Mar 7 2017
DISCUSSION: Beginning tonight, a prolonged period of heavy
mountain snow will take place across much of the Northern Rockies
through the weekend. Tonight's round of snow will drop a foot or
two of new snow, mainly focused across west central Montana and
north central Idaho mountains. Additional rounds of similar snow
totals will then occur Wednesday, Thursday, and Friday.
In addition, snow levels will gradually rise to about 5000-6000
feet for mountainous terrain south of the I-90 corridor by
Thursday and Friday (depending on exact timing, of course). There
is a high degree of uncertainty in the forecast Friday onward,
given model discrepancy on whether arctic air from east of the
Divide makes its way westward. One thing remains fairly certain
is that terrain across all of the forecast area will see heavy
snow amounts this week.
Kootenai:
--------------------------- 5000-7000 FT ----------------------------
Today Tonight Wed
Cloud Cover 80% 95% 90%
Hi/Lo Temps 24 to 30 17 to 22 25 to 31
Winds(mph) SW 11G25 S 8G31 SW 16G32
Precip Chc 80 100 60
Precip Type snow snow snow
Liquid Amt 0.05 0.38 0.10
Snow Amt(in) 1 6-9 1-3
Snow Level 500 1000 1500
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.
