A significant warmup and an already unreliable snowpack provide the ingredients for an avalanche cycle. Friday may start cooler but the danger will rise quickly, especially on solar aspects.
Through these fluctuating conditions, we will list the highest expected rating of the day.
50-90 cm of settled snow overlies weak facets above the Feb 3 interface, which is a crust in most areas. Many natural, human, and explosive-triggered avalanches have occurred on this layer in the past week, and the likelihood of avalanches will increase with high freezing levels and sun.
The sun's effect and overall higher freezing levels will be more pronounced on Friday, and the likelihood of these avalanches will increase as the day goes on, especially on solar aspects.
Some recent avalanches have stepped down to the weak facet and depth hoar layers near the base of the snowpack resulting in large avalanches. This seems to be most common in thin, steep, rocky terrain in the alpine, and will likely increase in frequency.
Friday: Valley bottom freezing levels in the early AM rising to 2600m (high +3C at treeline), light NW winds and sunny.
Friday night: Valley bottom freezing levels except for an above-freezing layer from 2300m to the alpine (aka no freeze!).
Saturday: 3000m+ freezing levels (high +6C at treeline), with light winds and sunny skies.
Sunday: Much the same, maybe warmer.
For more details on the weather, click here.
Many large natural avalanches (size 2.5 to 3.5) were observed today in the Lake Louise backcountry (Richardson Bowl, Redoubt), likely triggered by heat. They initiated on persistent layers and then stepped to the ground. Also, a remotely triggered avalanche was reported on the Observation sub-peak without incident today (photos below). It started on the Feb. 3 crust, stepped to the ground, and remotely triggered three size 3 avalanches spanning multiple features.
Moist snow in the valley bottoms on steep solar slopes, and variable crusts are forming daily on solar aspects and lower elevations. On shady aspects up high, there is still dry snow. 50-90 cm of settled snow overlies weaker facets above the Feb 3 crust interface, up to at least 2500 m. The base of the snowpack consists of weak facets. Deeper snowpack areas (west of the divide) are more settled and stronger.
