Although accumulations have not yet met expectations with this snow event, predicted heavy snowfall into the afternoon and accompanying strong winds will rapidly elevate the avalanche danger. New wind slabs are forming and will increase in size and sensitivity at the mid and high elevations. Weak faceted snow is a problem at all elevations. New snow is falling directly on a snowpack with poor structure at low elevations and adding load to buried weaknesses at higher elevations. Avalanche conditions will become more dangerous as the day progresses and conservative decision making is necessary for safe backcountry travel.
New snow and strong west winds are expected to rapidly form wind slabs on the snow surface this morning. These slabs are forming on crusts, surface hoar and faceted snow and given the predicted rapid loading are expected to be very sensitive with depths increasing to one foot later in the day.
At the mid and high elevations slab avalanches lying on weak faceted snow that was buried at Thanksgiving could fail to depths of three feet. These slabs could be triggered by backcountry travelers, by the initiation of a surface slabs or possibly release naturally if enough new snow loading occurs. At the lower elevations, new snow is falling on a weak shallow snowpack entirely comprised of faceted snow and slabs to one foot could be triggered this afternoon in steep terrain features where wind loading occurs. The size and sensitivity of these persistent slab problems will increase as the storm rapidly loads slopes today.
This storm is winding down and heading east. There could be some snow flurries in the mountains though Thursday, but amounts should be very light. Temperatures will be in the single digits tonight and rise into the teens during the day. Winds will be from the northwest to west and decrease to 15 miles per hour.Today’s strong winds and rapid loading event created new soft wind slabs that were very sensitive to human triggers. These surface slabs lie upon a layer of faceted snow. This new snow also increased the load on a buried layer of faceted snow that formed in November and is deeper in the snowpack. The general avalanche hazard is expected to be MODERATE on Thursday. Surface slabs 6 to 18 inches deep and larger slab avalanches up to 3 feet in depth could be triggered by humans on buried layers of faceted snow. Although these slab avalanches are expected to be less sensitive to human triggers than they were today, large slab avalanches could be triggered by skiers and riders on a variety of aspects on Thursday. A careful evaluation of the snowpack and conservative terrain choices are warranted. The strength and distribution of buried layers of faceted snow are difficult for even the most experienced backcountry users to assess and manage.
