Avalanche forecast

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Sun’s out guns out! This weekend we begin the transition into spring avalanche problems. Loose wet avalanches will become likely today on slopes exposed to direct sunlight, while slab avalanches are still possible in the upper snowpack. Manage the hazard by tracking surface snow conditions and terrain management.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Snow from earlier in the week formed wind slabs that are still reactive on north to east slopes beneath ridgelines. At the same time there are several distinct sun/rain crust facet combos buried in the upper meter of the snowpack, underneath Monday’s dense storm slab.

    Even small avalanches can be dangerous as they can drag a rider through trees and rocks, or step down into deeper buried instabilities. Before stepping out into steep consequential terrain assess the stability of the snowpack by doing basic stability tests in a hasty pit.

    Small wind slab release on NE aspect.

  • Loose Wet

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

    Temperatures are forecast to climb well into the 30’s. The warm ambient air and solar radiation will weaken the upper snowpack with an injection of moisture that lubricates weak layers and the spaces between crystals. Small wet loose avalanches will become likely on steep solar aspects. Manage this by planning your day to avoid steep slopes that have been exposed to direct sunlight. Snow bombs falling out of trees, pinwheel roller balls, and snow that sticks to your skis and skins are all signs that the surface snow is moistening and losing strength, and it’s time to head to shaded north aspects or back to the truck.

    Small point release loose slides. Photo submitted on Obs page, thank you!

Avalanche Discussion

Breakout a Hawaiian shirt and put on your green socks today, spring skiing is upon us! Looks like the mild weather and partly sunny skies will hold through the weekend.

Yesterday was one of those glorious March days when you start to recoup some of your depleted vitamin D reserves. While Kyla and I toured up Rabbit Gulch from the Burke Sub-station we marveled at how not cold our fingers and toes were when we stopped to dig pits. Throughout the tour, we found variable ski conditions ranging from dust on crust to ample soft snow. Solar aspects tended to have a mostly supportable sun-crust under 2ish inches of low-density snow, while shaded and non-wind effected slopes held the softer and better riding snow.

We have reached the time of year when the diurnal cycle begins to dominate the avalanche discussion. The diurnal cycle is the day time warming and nighttime cooling of the upper snowpack. As the days get longer and the sun’s trajectory becomes more overhead, more solar radiation is absorbed into the surface of the snow, which results in liquid water infusing and lubricating the upper snowpack. Each night when the temperature drops below freezing the liquid refreezes and locks the snowpack up again. The key to managing this is planning your tour to avoid steep solar aspects from mid-day onward when wet snow hazards are elevated, and recognizing the signs that indicate surface snow has lost cohesion. Snow bombs falling out of trees, pinwheel roller balls, and snow that sticks to your skis and skins are all signs that the surface snow is moistening and losing strength. Wet loose avalanches on steep slopes are sure to follow. When you notice these signs occurring, it’s time to head to shaded north aspects or back to the truck for a La Croix and a Rainer.

Even though the sun is out, it’s not time to switch off your avalanche brain yet. There are still many distinct facet and crust layers in the upper meter of the snowpack. Even though we have not been finding propagation in our pit tests, I do not trust them completely yet. I am continuing to look carefully before sending into steep consequential terrain. Yesterday I kicked off a small wind slab on a NE aspect at 6600’ while assessing stability. I would hate for that to step down into deeper instabilities.

Thank you for posting observations. Enjoy the good weather and variable riding and stay safe.

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