Layers of persistent weak snow lie hidden within the snowpack. These weaknesses were buried as long ago as December 11th and as recently as January 12th. Slab avalanches involving these layers could be human triggered today in steep avalanche terrain above 7500 feet where they could be small to very large in size. In this upper elevation terrain, shallow wind slabs could also be triggered in steep leeward deposit zones formed during Sunday night's snowfall. Below that elevation, activity is limited to very steep isolated terrain features. Careful snowpack evaluation is recommended to understand where these persistent weak layers still pose a threat. Yesterday, backcountry recreationalists triggered small slides on the South Teton and one larger slide was also reported for that area.
Skiers and riders have the potential to trigger slab avalanches involving faceted snow and surface hoar. At the mid and upper elevations, depending on the layer initiated, they could be soft or hard and have depths of two to five feet. At low elevations, where the snowpack is comprised mostly of sugary snow, slab depths of one to two feet are possible in isolated areas.
High pressure and clear skies will continue on Wednesday. Inversions will exist, and high temperatures at 9000 feet could reach the mid to upper twenties. Summits will stay cooler due to westerly winds with averages of 20 -25 mph. Valleys will start off well below zero and rise into the mid-twenties. No real change is expected in the avalanche forecast. The focus will be on the persistent weak snow that can be found in several layers at higher elevations while dominating the snowpack at the lowest elevations. These slabs remain most sensitive in the Southwest trails areas where the hazard will be Considerable above 7500 feet and slab depths could reach five feet. Although less likely, avalanches with similar depths could be triggered in the Teton area where the danger rating will be Moderate. At Togwotee Pass the rating is also Moderate where less load lies upon the weak snowpack. Slab depths at Togwotee could reach four feet. Below 7500 feet in all forecast areas, although the structure is poor, avalanche activity is not expected except for in isolated pockets in very steep terrain.
