Avalanche Forecast
Regions: South Rockies.
A recent pattern of large avalanches warrants conservative terrain choices.
Confidence
Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.
Weather Forecast
TUESDAY NIGHT: Cloudy with some isolated flurries, 50 km/h wind from the west, alpine temperatures drop to -10 C.
WEDNESDAY: Cloudy with isolated flurries and trace accumulations, 50 km/h wind from the west, alpine high temperatures around -6 C.
THURSDAY: Scattered flurries with up to 5 cm of new snow, 70 km/h wind from the west, alpine high temperatures around -4 C.
FRIDAY: Mix of sun and cloud, 30 km/h wind from the northwest, alpine high temperatures around -6 C.
Avalanche Summary
Several notable large persistent slab avalanches (size 2-3) were reported in alpine and treeline terrain over the weekend. Most of them were triggered with explosives, but one was remotely triggered as a person walked on low angle terrain above the slope. These avalanches have run on buried crusts and weak layers ranging from 40-100 cm deep. This type of activity is indicative of a weak snowpack structure capable of producing large avalanches.
Smaller storm slab and wind slab avalanches were also triggered by humans over the weekend, and may still be possible to trigger in steep and wind affected terrain. A concern with triggering one of these smaller avalanches is the potential for it to step down to a deeper weak layer and produce a much larger avalanche.
Snowpack Summary
20-30 cm of snow from the weekend has been redistributed by the wind to form wind slabs in the alpine and near ridgetops at treeline. Weak snow can be found 40-100 cm deep around crust layers that formed in November and October. These persistent weak layers have recently produced large avalanches. We are uncertain about the spatial distribution of these layers, but suspect they are widespread at upper elevations where early season snow existed. We are also uncertain about how reactive these layers could be to human triggering. Overall, this concerning snowpack structure warrants a conservative approach to travel in avalanche terrain. Snowpack depths range between 50-100 cm at higher elevations and taper rapidly below treeline.