A Special Avalanche Warning has been issued for this weekend. Now is an important time to exercise restraint and stick to low angle terrain.
Confidence
Poor - Due to the number of field observations
Weather Forecast
An Arctic high pressure system dominates the weather pattern for the weekend. Cold and dry is the theme for the next few days.Saturday: A mix of sun and cloud, treeline temperature around -15, light N alpine windsSunday: Sunny, treeline temperature around -20, light NW alpine windsMonday: A mix of sun and cloud, treeline temperature around -15, light SW alpine winds
Avalanche Summary
On Thursday, widespread natural avalanches up to size 3.5 were reported in the Rogers Pass area. Observations in the S. Columbia region are still very limited but it is expected that similar avalanche activity is occurring throughout the region.
Snowpack Summary
The storm produced a slab up to 1m thick which sits on the mid-November weak layer (facets, surface hoar, and/or a sun crust on steep southerly slopes). 20-30cm below this layer is a thick rain crust with weak facets on top. In the Rogers Pass area, the storm slab is poorly bonded to the mid-November layer and snowpack tests suggest it can be triggered easily with wide propagations possible. In some tests, the deeper crust/facet layer was also failing and it is possible that avalanches may step down to this lower layer. Recent strong and variable winds have created wind slabs in exposed terrain and resulted in variable snow distribution in the alpine. At lower elevations expect travel to be difficult and potentially hazardous as many early season hazards are exposed or lightly buried (stumps, logs, rocks, open creeks, etc).
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.