The snowpack structure is complex and varies throughout the region. A conservative approach is essential.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Monday
Weather Forecast
The Interior will see generally dry, cool conditions under the current NW flow. A Pacific frontal system will arrive Sunday, bringing light- moderate amounts of precipitation and warmer temperatures.Sunday: Cloudy with some sunny breaks. Alpine temperatures near -11.0. Light NW winds.Monday: Snow amounts 10-25 cm. Alpine temperatures near -7. Strong westerly ridgetop winds. Freezing levels 1500 m.Tuesday: Cloudy. Alpine temperatures near -7. Ridgetop winds light from the West.
Avalanche Summary
On Friday, a skier triggered a size 2 slab avalanche outside of the ski area boundary in the Dogtooth Range. The person involved was fully buried and not wearing an avalanche transceiver. This slowed rescue efforts and unfortunately the person did not survive. The avalanche failed on the deep persistent October crust/ facet layer near the base of the snowpack. The depth of the crown was 40-80 cm and the width was near 70 m. Further south a size 2.5 natural slab avalanche was reported from a steep SE aspect.On Wednesday, a size 3 accidentally triggered slab avalanche was reported near Golden on Wednesday. This slide was triggered by a skier on a north-northeast aspect in the alpine and likely released on a persistent weakness near the bottom of the snowpack. The skier was uninjured. This type of avalanche activity may be a good indication of the potential for large avalanches during periods of loading.
Snowpack Summary
Average snowpack depths at treeline elevations are 100-130 cm. Low density new snow covers stiff, dense wind slabs in exposed lee terrain at and above treeline. In the upper 80 cm of the snowpack a couple persistent weak interfaces exist comprising of surface hoar and a facet/ crust combo. This interface has produced variable results with snowpack tests, and operators are keeping a close eye on them as the load above increases and/or a slab develops. At the base of the snowpack are weak facets and depth hoar combined with a crust from early October. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on steep, convex, north-facing slopes.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.