A stealthy inversion has recently slipped into the alpine, hastening the snowpack's transition out of the deep freeze. If there's one thing the snowpack hates, it's rapid change. Remember those basal facets? Be wary if they start to wake up...
Recent snow has been blown into soft windslabs in lee features at alpine and treeline. Keep avoiding thin or variable snowpack areas where a smaller wind slab could trigger a release on our weak basal snowpack.
As temperatures trend warmer in the alpine over the next few days, the deep basal facets may reawaken. Deep persistent slab avalanches on these layers are most likely to be triggered from shallow snowpack areas near rocky outcroppings, and propagate to areas of deeper snow.
Thursday night: Mostly cloudy with flurries bringing 5-10 cm of new snow. Light to moderate west winds. Alpine temperatures around -12.
Friday: Mix of sun and cloud. Light to moderate southwest winds, strong at ridgetop. Alpine high around -12.
Saturday: Mix of sun and cloud with isolated flurries bringing a trace of new snow. Light to moderate southwest winds, strong at ridgetop. Alpine high around -8.
Sunday: Mix of sun and cloud. Moderate southwest winds, strong at ridgetop. Alpine high around -3.
Avalanche reports from Thursday were predominantly skier triggered windslabs up to size 1.5. Our field team also reported a natural size 2 windslab avalanche that stepped down to the deep persistent basal facets below a rock band. This is the type of terrain where the deep persistent basal facets will typically be triggered. In the coming days, the warming period may provoke a resurgence in persistent slab avalanche activity.
Recent snow has been loaded into pockets of soft windslab in alpine lees, and is settling in the mild alpine temperatures. At lower, colder, calmer elevations it may remain unconsolidated. It sits over widespread windslab in exposed areas at all elevations.
A well consolidated mid-snowpack overlies a generally weak basal snowpack. The bottom 10-20 cm of the snowpack consists of facets and deteriorating crusts. This basal layer has gradually been gaining strength, but potential still exists for large triggers in thin, rocky areas to trigger avalanches at this depth.
