Regions
Kootenay Boundary.
If the freezing level does not recover overnight, expect the Below Treeline Danger to be Considerable.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Tuesday: Expect an unsettled day, with flurries and moderate southerly winds. Accumulations could reach 10cm and freezing levels could rise to 1600m. Wednesday / Thursday: A series of fast moving systems will bring short duration snowshowers under continued moderate south-southwesterly winds. Freezing levels could climb to 1600m each afternoon. 15cm are possible each day.
Avalanche Summary
We have reports of loose, moist avalanches being triggered by solar radiation on sunny slopes on the weekend. A fatal avalanche incident occurred in this region on Wednesday. We will post more details when they become available.
Snowpack Summary
The recent warm, clear weather has left us with an aggressive melt freeze crust on solar aspects well into the alpine while shady, dead north slopes have grown some small surface hoar and remain powdery. In some areas up to 15cm of new snow now overlies these surfaces. New windslabs are forming at ridgecrest under the increased winds. Large cornices loom in the alpine. In recent snowpack tests, the early February surface hoar remains well preserved down 100-180cm and continues to yield sudden results. Although unlikely, triggering this layer would yield a very large, destructive avalanche.
Problems
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.
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.
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.