Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Very Likely
- Size
- 2–2.5
Big, deep, destructive avalanches will be easily triggered today. New snow and wind loading are overloading weak layers near the ground, and avalanches could also break in wind drifts. Avalanches are being triggered from long distances away and breaking wide and deep. Stay off of and far out from under all slopes steeper than 30 degrees.
Wind drifts may be found at all elevations, but will most widespread and likely thickest at upper elevations.
There is a big range in the avalanche conditions we expect today across the advisory area - primarily driven by how much it has snowed recently/overnight and how much snow will fall today.
Persistent Slab avalanches are the number one concern across the advisory area today. In places where the snowpack has been recently loaded, these avalanches are being triggered from a distance (Taylor Fork, Buck Ridge), breaking naturally (yesterday in Lone Lake Cirque), and breaking really deep and wide (Scotch Bonnet near Cooke City).
You could trigger a Wind Slab avalanche today anywhere you find a freshly drifted cohesive slab of snow. The deeper the drift, the more dangerous these slides will be. Based on new snow amounts, these slides will be more widespread, easily triggered, and very dangerous in the snowier regions (and at higher elevations) and more isolated, harder to trigger, and mostly harmless in places (and at lower elevations) without much new snow. Winds have been blowing hard, so watch out, because drifts may have formed at lower elevations and further down slopes than is typical.
Temperatures are back below freezing and it’s been snowing instead of raining, so wet snow avalanches are no longer a concern today.
Madison Range, Southern Gallatin Range, Lionhead, Island Park, and Cooke City areas
Big, deep, destructive avalanches will be easily triggered today in these areas. Avalanches could break in wind drifts or on the weak snow near the ground.
Slopes with the most recent snow, whether wind-drifted, or in areas favored by snowfall, will be the most dangerous. Avoid steep slopes today and with avalanches being triggered from a distance, make sure to give yourself a wide safety margin if you’re passing beneath them.
The avalanche danger is HIGH at upper elevations in the S. Madison and S. Gallatin Ranges and near Cooke City where there have been many large recent avalanches, the most snow fell overnight, the winds are blowing hard and it’s going to keep snowing today.
With slightly less new snow, conditions are very similar, but the avalanche danger is CONSIDABLE in the N. Madison Range, and Lionhead, Island Park areas.
Bridger Range and N. Gallatin Range
The mountains around Bozeman haven’t seen much recent snowfall and warm temperatures have helped promote bonding in the snowpack. At this point, any older wind drifts should be well bonded and unreactive. Any new drifts today will be extremely thin.
There is still the potential for Persistent Slab avalanches in these regions, particularly on higher elevation and shadier slopes. Dig down to check for weak layers near the ground before committing to steep slopes. The avalanche danger is MODERATE in the Bridger and N. Gallatin Ranges.