Human triggered avalanche remain likely in the wake of a heavy storm.
Isolated very large persistent slab avalanches during recent storm cycles have shown rapid loading can produce very large and destructive avalanches that fail much deeper than our storm snow depth. With another strong storm passing through the region, similar isolated persistent slab activity may occur.
Large reactive storm slabs continue to grow with another storm pulse crossing the region on Tuesday night. Natural avalanches are likely in the alpine due to strong wind throughout the day, while human triggering is a concern in steep terrain at all elevations.
TUESDAY NIGHT: Another frontal system passes through the region with 15-20 cm of snow, strong wind from the west and freezing level climbing to 1000 m.
WEDNESDAY NIGHT: Easing flurries as the front leaves the region mid-morning and another 5 cm of snow throughout the day, moderate wind from the west, freezing level drops to 700 m and alpine temperatures around -3 C.
THURSDAY: Cloudy with isolated flurries, 5-10 cm of new snow, light wind from the southwest, alpine high temperatures around -5 C.
FRIDAY: Mix of sun and cloud, light wind, alpine high temperatures around -8 C.
Storms over the past week resulted in several cycles of natural avalanche activity. Over the weekend there were reports of large (size 2-3) storm slab avalanches and Tuesday's storm is likely causing similar activity. While most of the activity has been storm slabs releasing in the new snow, there have been a few isolated instances of avalanches failing on deeper weak layers with crown fractures up to a metre deep. A few smaller (size 1) skier triggered soft slabs were reported on Monday.
Natural avalanche activity will likely decrease in the next few days as the stormy weather eases, but storm slabs will remain sensitive to human triggering.
A second frontal system will bring another 15-20 cm of new snow on Tuesday night bringing two day storm totals to 30-50 cm. At higher elevations moderate to strong wind will formed extra deep deposits, while lower elevations will settle rapidly due to mild temperatures and wet snow overnight.
100-150 cm of snow from the second half of January overlies a thin layer of facets that formed during the mid-January cold snap. Recent avalanche activity in the Bear Pass area and snowpack tests around Shames indicate this layer remains a concern.
A crust from mid November exists at the base of the snowpack. So far, we have only one observation from Saturday in the far north of the region showing this layer waking up during the storm. Previously, the last avalanche reported on this layer was on January 17. Potential still exists for large avalanches in surface layers to step down to this layer.
