Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Don’t let late season powder fever lure you into steep terrain today. Heavy snowfall and high winds have created dangerous avalanche conditions at middle and upper elevations. Human triggered avalanches are likely. Stick to sheltered slopes under 30º, where you’ll find safe skiing and superior snow conditions.

Avalanche problems

  • Wind Slabs

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

    Winds to 48 mph, with gusts to 66 mph, have been sustained for the past sixteen hours, transporting significant new snow to leeward aspects and increasing the size and destructiveness of potential avalanches. 

    At upper elevations, most snow surfaces are likely affected by wind. Easterly aspects and cross-loaded gullies could hold wind slab several feet deep. Wind slab could run long distances on the solid crust underlying all snow surfaces.

    Wind sculpted snow, wind lips, cornices, hollow-sounding snow, and broad drifts are all indications of wind slab.

    Keep it mellow today, stick to slopes under 30º, and avoid wind-loaded start zones. 

    Watch for red flags such as shooting cracks and natural avalanches.

  • Storm Slabs

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

    Between six inches and two feet of snow has fallen in the past 24 hours, accumulating on the solid crust at all elevations and aspects.

    Snow continues to accumulate, avalanche danger will increase throughout the day.

    Sheltered areas not affected by the wind, more likely at mid-elevations, likely hold storm slab. The combination of slick bed surface and fresh snow has created dangerous avalanche conditions.

    Storm slab avalanches large enough to bury, injure, or kill a person are likely.

    Avoid slopes over 30º and convexities. 

Avalanche Discussion

Since the last forecast, the mountains have received up to two feet of new snow. The central Bitterroot has received the brunt of the storm with 1.8” SWE at Twin Lakes. The Seeley zone has received 0.4” SWE, and the Rattlesnake 0.4” SWE. SNOTELS may not be showing full totals as observations in the Missions yesterday indicated more than 5” of new snow by midday. Winds reached 66 mph last night and have sustained above 30 mph for 16 hours. 

Winter has returned after a couple of weeks of disappointing conditions. Soft snow could await, but don’t let the anticipation of fresh turns lure you into dangerous situations. New snow sits on a solid crust throughout the forecast area, creating a slick bed surface for avalanches. 

During the previous week, 1 to 4” of snow  fell. It was drifted around by wind, and faceted by cold overnight temperatures. Small wind slabs over the weekend and sluffing on steep slopes show poor bonding to the crust. The facets may provide a failure plane for the new snow where they exist.

Strong to extreme winds for 12+ hours have likely done more than just drift snow. Windward aspects at upper elevations could be stripped of fresh snow. Snow surfaces could be very wind affected with wind lips and sastrugi, making skiing difficult. Wind slab could be multiple feet deep. Treed areas may have considerable branches and foliage down. The central Bitterroot is likely most affected with the strongest winds and the highest snowfall. 

For the most part, avalanches are not possible below 6000’ due to lack of snow. The exception is the Lolo Pass area, where the snowpack extends to lower elevations and sections of the Seeley Lake zone. 

Today the mountains could receive another eight inches of snow. Winds will be strong out of the west. Avalanche conditions will deteriorate further throughout the day. Now is not the time to push terrain. Conditions are touchy, and avalanches could run long distances. The new snow needs time to bond. Sheltered slopes under 30º are where you’ll find the safest skiing and the best conditions today. 

Please let us know what you see in the mountains. No matter how simple, all observations are valuable. You can submit them here.

Ski and ride safe

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