Bulletin d’avalanche

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Rain from recent storms has percolated into the upper portion of the snowpack creating weaknesses near the snow surface. The saturated snow surface can cause loose-wet avalanche conditions at all elevations.  Avalanches are most likely on steep slopes below rocks in isolated terrain features. Air temperatures above freeezing, which are forecasted for much of the zone today, will contribute to the likelihood of avalanches. 

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Loose-wet avalanches have been releasing naturally on all aspects in steep terrain below treeline.  There are many clues that loose-wet avalanches are possible. Monitor the snowpack surface for signs of instability. On small,  steep test slopes, the surface layers will slide easily. Fresh roller balls falling off trees and pinwheeling near cliff bands indicate that the snowpack surface is getting weak.

    (1/16/2023)

    New snow had fallen with little wind at treeline.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Above 4500', temperatures were cold enough that a couple inches of snow fell over the past 48 hours. The new snow  at high elevations fell on a newly formed rain crust, wich has created a slide plane that may become a problematic layer. Today, expect to see 4-6'' of snow on top of the crust. Snowpit tests on the new rain crust aren't indicating a likelyhood to fracture yet, but this layer will be worth keeping an eye on. Today, you can manage this persistent  slab by paying attention to terrain traps such as road crossings or creek beds and steering around them.

    Izzy managing the persistent slab problem

Avalanche Discussion

The Silver Valley has felt pretty wet over the past few days where rain from wet stroms has crept up into the treelines in most places. Relatively mild temperatures and very light winds have resulted in excellent skiing up top. However, they're pretty sticky down low, especially on flat run outs back to the car. After very subtle snow falls throughout various regions of the Silver Valley combined with the warm temps, snow may loosen up the surface of the snowpack and cause it to weaken. Take note of this on steep angle inclines, especially around rocks below treeline. 

Izzy Davis and Brian Hilland toured into the Stevens Lake Area near Lone Lake. They started at around 3700’ and it was a noticeably warm start to the tour. Although the temperatures were mild, they experienced snow starting at around 4200’ with no discernible accumulation. They had a pit oriented east at around 6200’. In their results they had seen a notable, thin rain crust around 15cm beneath the surface. Upon the isolated column test they found it to react on the CT8 but the shear surface was non-planar, uneven; it had jumped down 5 more cms with an irregular and rough break to another layer that had actually reacted on the same hit (CT8).  20 cms from the surface, it had a very stubborn shear and showed a lot of resistance. Their ECT produced no results. We will have to keep a eye on this layer, but it seems to be breaking into a melt freeze crust.  We'll have to see if the new snow bonds well with the current snowpack. While they reported that there was fairly decent skiing, there was evidence of some small, wet loose avalanches on steep pitches with high slope angle. The last push to the car felt quite sticky near the valley floor.

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