Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Sat
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

Temperatures dropped below freezing last night at the upper elevations, locking in the upper snowpack.  With the cloud cover and precipitation today and this weekend, it will be slower warming up the slopes during the daytime.  Once you start seeing rollerballs or sinking in deep, it's time to head to the north or out of avalannche terrain for the day. When the surface is frozen and locked up, this will bridge over that buried persistent weak layer.  But when it gets soggy, a loose slide has the potential to step down and create a much bigger slide.  

Avalanche problems

  • Loose Wet

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

    Nights below freezing and daytime temperatures just barely above freezing with cloud cover and precipitation will keep this problem manageable this weekend.  As the day heats up and you start seeing rollerballs or sinking into slush when you jump off your sled, it's time to head to the north or to head home. Small, wet loose slides have the potential to step down and trigger a larger wet slab on the deep persistent weak layer.  This is low probability, but very high consequence.    

    (3/18/2021) When the rollerballs start getting big, get out of avalanche terrain!

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Our deep persistent slab problem has evolved!  On the north, where it is deep and dark and shaded and still acting like winter at the high elevations, it is the same problem we've been talking about for ages now. That buried surface hoar is still down there.  But where it gets interesting, from a geeky snow metamorphism perspective is how it has changed on our E-S-W aspects.  The warm weather has heated up the snowpack and water has percolated down through essentially melting the surface hoar out.  Think pouring water over sugar.  This water has continued down where it hits the top of the ice and can't easily get through.  So it runs along the ice, saturating the snow above it and creating a layer of liquid water on top of ice.  What does that mean in terms of avalanche danger?  Think of how slippery slightly melted ice is to walk on.  It's still buried down there deep, and the chances of us triggering it are unlikely, but the consequence is going to be high if we do.  A higher chance of triggering it is starting a smaller loose wet avalanche closer to the surface and having that step down. 

    (3/18/2021) Water accumulating on top of the 1/12 ice crust.

Avalanche Discussion

Ahh spring is in the air!  When I think of spring conditions, I think of questionable fashion choices, goggle tans, rocking a full face helmet and a t-shirt, dodgy ski runouts, and parking lots full of mud.  And all the warm weather avalanche problems that come with it!  The other two to keep in the back of your mind are glides and cornices. Glide cracks look like frowns on the hillside and are best to be well avoided as they can suddenly open up or slide.  When the weather heats up, the cornices start to get droopy.  If you aren't careful on the top of ridges, it is easy to get too close to the edge of one and that added extra weight might be the tipping point of cracking it off.  They have the potential to start a much bigger slide when they bomb into the slope below.  It's best practice to not hang out underneath them as well, wouldn't want a bus sized chunk of snow taking you out!

We have a couple small storms rolling through this weekend with the chance of a few inches of new snow at the high elevations.  This precipitation doesn't look likely to add up to enough to change the avalanche danger significantly.  

Let me know what you see out there this weekend, would appreciate some observations!  Where did you hit freezing line for the snow surface?  Where did the accumulation start? Liquid or solid?

 

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