New snow, winds and the passage of a cold front are expected to increase the avalanche hazard. At the higher elevations new soft slabs are forming on leeward aspects. Strong gusty winds are expected in association with the passage of a cold front and will likely enhance the development of new wind slabs at the mid and lower elevations. These winds should increase the sensitivity of these slabs to human triggers and may cause some natural avalanche activity. These conditions will also be increasing the load on buried weak layers. Large persistent slab avalanches could become unstable due to this load and be easily triggered by humans or release naturally on steep avalanche prone slopes. There have been three close calls in the past two days. Monitor conditions for increasing hazards. A careful assessment of snowpack stability and conservative terrain choices are warranted.
New soft slabs could build to depths of one to two feet at the mid and upper elevations and to depths of 6 to 12 inches at the lower elevations. Rapid loading by gusty winds may increase the sensitivity of these slabs to human triggers.
Fresh snow and and gusty winds will be increasing the load on persistent weak layers. Large slab avalanches 2 to 4 feet deep at the mid and upper elevations and 1 to 3 feet deep at the lower elevations may become increasely sensitive to human triggers. Natural releases may be possible in areas with poor snow structure.
A cold front is forecast to move across western Wyoming from eastern Idaho this evening. Snowfall intensity has already increased on the west slope of the Teton Range. Grand Targhee Resort has received five inches of new snow since 5 PM. Snowfall will be heavy at times until midnight. Snowfall after midnight will be light with a lull during the morning hours before increasing again in the afternoon and evening. Forecast snowfall totals during the next 24 hours are 3 to 6 inches in the Togwotee Pass area, 6 to 8 inches in the Southwest Trails area, up to ten inches in the Teton area and two to three inches in the valleys. Temperatures will be in the single digits and teens. South winds will veer to the southwest and west and increase to 25 with gusts to 40 miles per hour. These winds will create areas of blowing snow. The general avalanche hazard will be on the increase in areas that have received the most new snow and experienced the strongest winds. These winds will form new soft slabs on leeward aspects which could build to depths of 1 to 2 feet. The new snow will continue to increase the load on persistent weak layers. Large persistent slab avalanches may become unstable on steep slopes that experience rapid loading during the passage of tonight’s cold front. Depending on the distribution of snowfall tonight and the veracity of the winds the general avalanche hazard is expected to be considerable in some areas of the Teton zone and possibly some areas of the Southwest Trails forecast zone. It is expected to be moderate in the Togwotee Pass area.
