Tetons

Yesterday, a skier triggered a 12 inch deep soft slab on an east facing aspect around an elevation of 8,000 feet in Grand Teton National Park. Backcountry travelers could trigger similar slides in steep, avalanche terrain at the mid and upper elevations. Although small, these slides could easily sweep skiers or riders over cliff bands or into terrain traps. While difficult to trigger, large to very large persistent slab avalanches, which exist on a variety of aspects above 7,500 feet, carry much higher consequences. Careful evaluation of the terrain and snowpack continues to be warranted. Below 7,500 feet, any avalanche activity is expected to be limited to isolated terrain features.

In the morning, expect generally cold temperatures with mild inversions in place. A weak system with little moisture will provide for increasing clouds during the day and a chance for isolated light snow showers with little accumulation. Like today, temperatures in the mountains should rise from near zero degrees to the mid-teens. Winds are to be light. In the Teton’s, the danger rating on Tuesday will be on the lower spectrum of Moderate. The avalanche problem types are not a great fit for the current situation and will, at least temporarily, be removed from the forecast. At higher elevations where snow depths are the greatest, weak layers exist within the snowpack although triggering them has become unlikely except for a slight chance of large triggers finding a weak spot. As elevation lowers weak layers become more prominent but both snow depths and slab cohesiveness also lessen. In short, the chance for human triggered avalanche activity is becoming possible only in isolated areas that involve very steep terrain in avalanche starting zones and cliff areas. This is not the case for the Togwotee Pass or Southwest Trails areas. Although they will also be rated as Moderate, it is good to remember that the Moderate danger rating covers the widest range of conditions. Both of these other areas have weaker snowpacks and avalanches are more likely to be triggered by humans. This is particularly true in the Southwest Trails areas where sizeable cohesive slabs lie over well-preserved weak layers and the chance for human triggered is the most likely. However, it is also the case at Togwotee pass where, although less snow has loaded the weak layers and unstable snow is harder to find, a remotely triggered slide was reported near Mount Leidy just the other day.