Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

In areas of the Bitterroot that received 8" or more new snow, you are likely to trigger windslab in upper elevation easterly terrain over 30º. Loose-dry avalanches are running far and fast and pose a risk in consequential terrain and features such as gullies that increase the depth. Choose slopes under 35º that are sheltered from the wind for the best riding conditions today. 

Avalanche problems

  • Wind Slabs

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

    It is likely for skiers and riders to trigger windslab on upper elevation easterly terrain over thirty degrees. Sun crusts on south and east aspects are a very slick bed surface for fresh windslab to run on. On northerly aspects, wind slab may sit on surface hoar. 

    Yesterday in the Rattlesnake windslab was very touchy, triggering easily from ridge top or to the side pockets. With continued winds and lots of low density snow available for transport, expect windslab to be larger and more consequential today.

    Areas of the Bitterroot that received 8" or more of new snow have a higher likelihood of consequential windslab.

    Cornices and wind lips indicate wind direction. Smooth pillows of stiffer snow that may be hollow sounding indicate windslab. Shooting cracks are a warning sign that conditions are touchy and avalanches are likely. 

    Avoid easterly wind loaded slopes in upper elevation terrain today.

     

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    Up to 13” of low-density snow sits on a variety of low-friction snow surfaces such as crust, facets, and surface hoar. Yesterday loose dry avalanches were readily running fast and far. Today it is likely to trigger them in terrain over 35º. 

    While mostly inconsequential, loose dry avalanche can push riders over and into hazards. Today’s are capable of burying a person if encountered in a terrain trap such as a gully that funnels debris and increases the depth. 

    Choose planar slopes free of hazards and terrain traps. Manage sluff by skiing to the side, out of its way, and letting it run. 

Avalanche Discussion

Yesterday winter temperatures and precipitation returned. In the Rattlesnake, snowfall was consistent all day Friday, with 6” by 11:00 am midstorm. Snowbowl reports 10” of storm total, but there is likely more accumulation outside the ski hill boundaries.  

The Central Bitterroot received up to 0.7 of snow water equivalent (SWE), and Lost Trail reports storm totals of 13”. However, observers yesterday noted just 4” of fresh at the North Fork of Lost horse. The Northern Bitterroot received less precipitation, with just 2” reported at Lolo Pass.

In the Seeley Zone The North Fork of the Jocko SNOTEL shows just 1” of new snow, but it is possible that more fell.

The weather stations seem to be having trouble registering this low-density snow, with reported totals not reflected in snow water equivalent (SWE); as a result, it is hard to estimate exact totals. If you find 8” or more new snow, step back to mellower terrain and increase your caution.

Temperatures have been cool, and the snow came in light. It remained unconsolidated yesterday, and likely remained so overnight. Slabby conditions were isolated to wind-affected and loaded areas, primarily upper elevation terrain just below ridges. 

The new snow sits on various snow surfaces, sun crust, near-surface facets, and surface hoar. All are low friction and slow to bond; instabilities could last longer, and slides run further. So far, windslab and dry loose are the main concerns in areas with enough new snow to increase the hazard. However, storm slab could quickly develop if the temperatures rise or the sun peaks through the clouds. Pay attention to the new snow density today and watch for signs of instability, such as shooting cracks. If the new snow is consolidating, stick to slopes under 30º and avoid convex rolls. 

Luckily all instabilities are isolated to the new snow. Areas that received minimal new snow such as Seeley, Lolo pass area, remain low danger. Pockets of small windslab can be expected just below the ridge line in upper elevations. Cloudy skies today will keep snow surfaces cool. If they do part and the sun breaks through loose wet slides are possible.

Please let us know how much new snow you find where you recreate today by submitting an observation.

Ski and ride safe

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