Regions
Banff Yoho Kootenay.
A widespread avalanche cycle is underway with many small and large avalanches observed on Tuesday. Avoid exposure to all avalanche terrain. We have published our forecast early today to get this message out there.
Weather Forecast
Strong westerly flow continues as another storm crosses the area starting Tuesday afternoon. By Wednesday end of day we should see 20 cm of additional snow. Freezing levels will remain near 2000m until Wed afternoon when the air will slowly begin to cool. Alpine winds are forecast to be moderate to strong through the period.
Snowpack Summary
Additional snowfall and warming temperatures have tipped the snowpack and an avalanche cycle is underway now. A 50 cm dense slab has overloaded two prominent weaknesses in the snowpack; one down 40cm and the other in facets near the base of the snowpack. We expect the cycle to persist while the temperatures remain warm over the coming days.
Avalanche Summary
Two skier triggered avalanches on the Wapta on Monday evening, and then a flight along the Bow Valley Tuesday morning revealed dozens of fresh avalanches ranging from size 1 to size 3. There is an avalanche cycle underway now.
Confidence
Due to the number of field observations on Tuesday
Problems
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.
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.