Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

It is still possible to trigger an avalanche on weak layers in the upper snowpack. These weak layers are widespread and have a higher chance of being triggered in steep and open terrain. To avoid this problem and to find the highest quality riding, stick to sheltered terrain in the trees. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Currently there are a few persistent weak layers in the snowpack, and it remains possible that you could trigger one of them. Recently buried surface hoar can be found anywhere from 25-75 centimeters below the surface, and though it is not showing full propagation in stability tests, it should still be given a healthy dose of respect. This problem is likely widespread and can be found mostly in open areas around treeline. There is also a widespread rain crust layer that formed on February 19th that has facets above and below it. Yesterday this crust layer produced clean shears in hand pits and can be found across the Silver Valley Zone. The "lucky Friday crust" is now buried 2-4 feet deep. This rain crust formed in mid January, and has delivered variable results with its ability to propagate over the past month. Once facets developed above and below this layer, we started to see more reaction from it. Continue to be aware of what terrain you travel into. Areas near rock bands and shallow areas in the snowpack, primarily on south aspects, can become potential trigger points. 

Avalanche Discussion

On Monday, March 6th we ventured out to Tiger Peak to get tabs on the various layers we have in our snowpack right now. We had a nice hike up and experienced calm winds and light snowfall throughout the day.  Surface conditions were a bit variable on the ski down, and we felt a light sun crust on the surface that formed from Saturday's blue bird day. This light crust was most notable on solar affected S-SW aspects. Weaving through the trees proved to have the best skiing conditions and was the best bet at avoiding the sun crust. 

After some digging in the snow, we found buried surface hoar, the zipper rain crust formed on February 19th, and of course the Lucky Friday crust. Small surface hoar developed on Wednesday, March 1st and was buried the next day by the last storm cycle. We found the surface hoar buried 25cm from the surface on a south aspect, and about 70cm down on a northeast aspect that was wind loaded.  The buried surface hoar didn't produce propagation in our extended column test, but showed failure in a column test. The thin rain crust formed on February 19th can be found about 1-2 feet below the surface. This should still remain on your radar as quick hand pits showed the potential for failures both above and below the crust. The Lucky Friday crust that formed back in mid-January is still hanging around, and this particular layer is a "low likelihood of triggering, but high consequence" scenario. Athough none of these weak layers showed full propagation in stability tests, be cautious if stepping out into steep, consequential terrain. As spring brings about changing weather, be aware that these weak layers are lurking and could potentially act as a bed surface if a rider were to find the right trigger point, or a significant load was added to it. A significant change in weather such as a big rain event, significant snow or rapidly warming temperatures could potentially re-awaken any one of these persistent weak layers. 

Last week two avalanches were reported after Thursdays storm and both were triggered on northerly aspects below ridgelines. Both of these avalanches likely failed on the same weak layer. Before committing to steep and open terrain on north or east aspects, take the time to assess the snowpack stability. These slopes are likely to have buried surface hoar present and will also harbor thicker slabs as these locations were loaded by winds during the previous storm.

Expect low winds and temps hovering around the mid 20's on the mountain today with partly sunny skies the first half of the day, and clouds building in the afternoon. Our next opportunity for a shot of snow will be Friday. 

Regions covered