Island Park

New snow and wind today could create a fresh round of wind slabs and add weight to buried weak layers. Watch for cracking as a sign fresh wind slabs are unstable. If snowfall or drifting snow is heavy, choose more conservative terrain. Slopes to be extra cautious of, where avalanches could break deeper on old weak snow, are those that had snow during the dry spell prior to Thanksgiving week.

Over the last two days we had reports of at least ten large avalanches (view list and details here), with five triggered by skiers or snowmobilers and multiple large natural avalanches (video of slide in Beehive near Big Sky, photo of large slide on The Fin near Cooke City). The recent avalanche activity highlights how rapidly the snowpack has changed, along with a significant increase in avalanche danger over the last 1-2 weeks. Mark wrote a short Blog about it here.

In areas with the most new snow, avalanches can break as storm slabs within the new snow, or persistent slab avalanches could break deeper on weak snow that was buried a couple weeks ago. Both of these problems will be more likely and larger on recently wind-loaded slopes. Slopes to be extra cautious of are those that had snow during the dry spell prior to Thanksgiving week.

Today, large avalanches can be triggered, and dangerous avalanche conditions exist in the mountains near Bozeman, Big Sky and Cooke City. Avalanche danger is CONSIDERABLE at middle and upper elevations in these areas. Generally, sticking to slopes less than 30 degrees steep, and not below anything steep, is a wise choice today.

Near West Yellowstone and Island Park, the same avalanche problems exist, but less recent snow makes them less likely and relatively smaller. However, new snow and wind today could create a fresh round of wind slabs and add weight to buried weak layers. Watch for cracking as a sign fresh wind slabs are unstable. If snowfall or drifting snow is heavy, choose more conservative terrain. The danger is MODERATE near West Yellowstone, Island Park and the southern Madison and southern Gallatin ranges.