Yesterday's storm system brought 5 to 8 inches new snow with around a half inch of moisture to the mountains. Last night the Wyoming Department of Transportation triggered an avalanche on Teton Pass that ran to the roadway. Conditions are dangerous in steep terrain above an elevation of 8,500 feet. Large slab avalanches could be triggered by the weight of a single person. These slabs lie on persistent weak layers that formed earlier in the season and cannot be trusted. These dangerous slabs could be triggered on slopes that have been previously crossed by skiers, snowboarders or snowmobilers. Safe travel will require excellent terrain evaluation skills, restraint and a knowledge of the distribution of buried persistent weak layers. Avalanches are unlikely below an elevation of 8,000 feet.
The new snow has increased the load on weak faceted snow layers that persist near the base of the snowpack. In steep terrain humans could trigger dangerous slab avalanches up to three feet in depth. Yesterday's load has increased the consequences of being caught in one of these large slab avalanches. Understanding and identifying where the old weak snow is present is essential in avoiding this hazard.
At the higher elevations strong southwest to northwest winds have created new wind slabs on leeward aspects. These surface slabs could be triggered by skiers or riders in steep wind loaded avalanche starting zones. These slabs are 6 to 18 inches deep and could easily step down to faceted snow layers at the base of the snowpack and become a large and dangerous persistent slab avalanche.
( Discussion is generated from the previous day's afternoon forecast. )The snowfall will end late tonight as a cold front moves across the area. Favored areas may receive several additional inches of lighter density snow. Winds will veer to the northwest and decrease to around 10 miles per hour by sunrise. Skies will become mostly sunny on Monday. Temperatures will drop into the single digits tonight and rise into the teens in the mountain and into the 20s in the valleys during the day.The new snow has created dangerous conditions at the mid and upper elevations where the general avalanche hazard is expected to be considerable. Large to very large slab avalanches up to four feet deep could be triggered on steep slopes by the weight of a single person. These slabs lie on persistent weak layers that formed earlier in the season and cannot be trusted. These dangerous slabs could be triggered on slopes that have been previously crossed by skiers, snowboarders or snowmobilers. Safe travel will require excellent terrain evaluation skills, restraint and a knowledge of the distribution of buried persistent weak layers. Today's additional load on these problem layers have greatly increased the consequences of being caught in a large slab avalanche. At the higher elevations dense surface slabs one to two feet in depth formed by the recent southwest winds could also be human triggered in steep avalanche starting zones. These slabs could step down to the November drought layers. The general avalanche hazard is expected to low below an elevation of 7,500 feet.
