Lingering storm instabilities remain a concern, especially in the alpine. Avoid steep, wind loaded features and large, unsupported slopes. Use extra caution on sun-exposed slopes during the heat of the afternoon.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Light precipitation can be expected Tuesday overnight into Wednesday morning. There is currently some model uncertainty regarding amounts but the region could see 2-10mm with freezing levels around 1500m. By Wednesday afternoon the clouds should break and sunny periods are possible. Freezing levels should reach around 2000m Wednesday afternoon and alpine winds should be moderate from the NW. On Thursday, a warm storm system reaches the south coast. There is currently quite a bit of uncertainty regarding the timing and track of the system into the interior regions. For the South Rockies region, it is currently looking like unsettled conditions for Thursday with mainly cloudy conditions. Freezing levels should again reach around 2000m and alpine winds may be strong from the SW to W. On Friday, light precipitation is possible but amounts are uncertain. Freezing levels may climb to over 2500m.
Avalanche Summary
We haven't received any reports recently but this likely speaks to a lack of observers. In the Lizard region, a natural avalanche cycle up to size 2.5 was reported with slabs up to 80cm thick. Similar activity is expected to have occurred in the South Rockies Region. On Wednesday, human-triggering of storm slabs remains a major concern, especially in the alpine. Wind-loaded features and steep, unsupported slopes are the most likely areas to trigger an avalanche. Loose wet avalanches are possible during the heat of the afternoon, especially on sun-exposed slopes.
Snowpack Summary
Heavy rain (up to 60 mm) on Saturday soaked the snowpack. On Sunday the rain changed to snow as the freezing levels slowly dropped. Heavy snowfall (up to 50cm) combined with strong southwest winds developed new storm slabs on all aspects in the alpine and at treeline. The thick mid-February crust was 10-30cm below the surface before the recent storm and extends up to around 2200m elevation. Below this elevation the crust is effectively capping the snowpack, preventing riders from stressing deeper persistent weak layers. In high alpine areas where the crust is not present or is less thick, dormant persistent weak layers may still be lingering and could wake-up with heavy loading or strong warming.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.