Avalanche forecast

Rattlesnake

West Central Montana Avalanche Center
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Avalanche danger

Sun
Alpine
1 · Low
Treeline
1 · Low
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Out of date — this forecast expired 4 years ago.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

The snowpack in the Rattlesnake is generally stable. However, there may be small isolated pockets of reactive wind slab in steep easterly terrain. Carefully evaluate the snowpack for signs of instability, such as shooting cracks, before committing to slopes over 35º.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Stay diligent for pockets of reactive windslab in the Rattlesnake. While observations the past two days have indicated unreactive windslab, it is possible that you could find the one pocket that will slide. 

    Snowmobilers may be more likely to find the trigger point because they can affect the snowpack deeper than a skier. 

    Wind lips and cornices indicate wind loading. Styrofoam-like, hollow-sounding snow is an indication of wind slab. Shooting cracks are a warning sign to stay off steep slopes. 

    Carefully evaluate the snowpack before committing to wind loaded terrain over 35º.

    Cornices are large and will grow weaker with today's sun and warmth. Stay well back from the top edge, as they can break unexpectedly, further back than anticipated. Avoid spending time in the fall line below them. 

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Yesterday, warm temperatures and clear skies resulted in solar warming and moist snow at all elevations on south and west aspects. Last night's refreeze will limit the extent of loose wet activity today. However, with warm temperatures and clear skies today, wet loose slides are possible. These pose little risk to skiers and riders unless encountered in a terrain trap where they could push you into or over hazards. If the snow is wet and rollerballs start, it's a sign to move to lower angle slopes or shadier aspects. 

Avalanche Discussion

Since the last forecast, the weather has mellowed out considerably, with high pressure, mild days, and light winds. Conditions have settled out considerably, with the Rattlesnake dropping to low hazard at all elevations. The Seeley zone and Bitterroot remain moderate at upper elevations due to lingering wind slab instabilities. 

Yesterday on the west side of Seeley, snowmobilers triggered a small avalanche near ridgeline in wind slab. Both were carried downhill; luckily, neither rider was buried and escaped without injury. The slope had been heavily ridden before the slide, but these riders hit the trigger point for this particular pocket. In the central Bitterroot yesterday, a small slab broke loose, pointing to the continued possibility of avalanches. Both these underline the fact that the mountains are never without some risk of avalanches, and continual diligence is required. 

Several glade cracks have opened near Marshal Lake, and a glide avalanche released in the northern Swans. I expect that some glide cracks are peppered through the Bitterroot as well. These aren’t widespread enough to be listed as a problem, but they should be given a wide berth if encountered. Warm days and direct sun may accelerate the opening of glide cracks. They can release unexpectedly as glide avalanches, running full depth to ground.

A crust facet combo has been noted in the North Fork of Lost Horse and Bass Creek on upper elevation south aspects.  It may be present in other areas of the Bitterroot. It is worth investigating before you commit to steep south facing terrain. Stay alert for whumpfing or cracking. 

Today, clear skies, warm temperatures, and light wind should make for a great day in the mountains. The hazard will continue to trend lower over the weekend. Stay diligent despite the increasing stability. Watch for red flags and practice safe travel, such as skiing one at a time. Low hazard doesn’t mean no hazard. Pockets of unstable snow are lurking, as the Seeley and Bitterroot slides yesterday demonstrate. 

Please let us know what you find out there by submitting an observation. We love to hear about stable conditions and great skiing as much as we love hearing about instabilities. 

Ski and ride safe

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