Sunshine and daytime warming will increase the likelihood of triggering surface storm slabs. It feels like Spring in the valley, but it is still full-on winter in the alpine.
Weather Forecast
A mix of sun and cloud today, with isolated flurries, alpine highs of -3*C, freezing levels rising to 1600m, and light westerly winds at ridge-top. Flurries tonight and another day of mixed sun and cloud with flurries on Tuesday.
Snowpack Summary
30cm of snow fell in the alpine over the weekend, while the amounts diminish to 10-15cm around 1800m. Winds were strong from the S, but backed off to light on Sunday. This new snow lies on a firm temp crust and is reactive to light loads, especially where loaded in lee features. Deep persistent weak layers have not been reactive with the cool temps
Avalanche Summary
No new avalanches were observed in the highway corridor nor up the Illecillewaet drainage yesterday. Artillery control from Saturday produced surface slabs mainly size 2, some to size 3. All slabs were from the storm snow and were not observed digging down into the deeper layers.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.