Confidence
Fair - Due to variable snowpack conditions
Weather Forecast
Tuesday: Fairly zonal flow with light precipitation. Ridgetop winds 35-50km/hr from the West. Treeline temperatures near -5. Freezing levels at valley bottom. Wednesday: Ridgetop winds 20-45km/hr from the West. Treeline temperatures near -8. Thursday: Dry conditions continue through to Saturday. A ridge over BC will bring a warmer air mass to the region. Freezing levels may rise to 1200m.
Avalanche Summary
On Sunday several size 2 natural slab avalanches were seen. On Monday skier controlled, and explosive controlled avalanches were initiated up to size 2 with crown depths being 30-40cms. Monday afternoon the sun poked out and sluffing occurred on steep, rocky south facing slopes.
Snowpack Summary
The freezing level was as high as 1500m Sunday, as a result, a lot of precipitation that fell on Sunday was rain. Sunday night the region received near 30cms of new snow. Strong SW winds created stiff, yet reactive wind slabs on lee slopes. Cross-loading, and wind slabs are also found lower on the slopes and in unsuspecting terrain due to the strong push of the winds. Storm slabs have also developed at all elevations, and are reported to be touchy to rider triggers. So far the new wind slab and storm slabs are only releasing in the upper 30-40cms of the snowpack, with nothing stepping down lower. Last week 40-60cm of snow formed soft slabs over a crust/facet/surface hoar combo which has settled remarkably quickly.Deeper in the snowpack, a surface hoar layer buried in early December remains a concern, as avalanches triggered on this layer would be destructive. There may have been releases on this layer post storm but at this time nothing has been reported. It should be noted that basal facets exist in many parts of the region too.
Problems
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.
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.