The region has a potentially volatile snowpack structure which although atypical for this time of year, continues to produce very large human triggered avalanches.
Confidence
Fair - Freezing levels are uncertain on Wednesday
Weather Forecast
Wednesday: Light snow turning to rain as freezing levels begin to climb. The freezing level should be around 2500m by sundown. Moderate SW winds at treeline, strong to extreme SW winds at ridgetop.Thursday: Light rain. Freezing level starting around 2400m, rising to approximately 2800m by sundown. Light SW winds at treeline, strong SW winds at ridgetop.Friday: Light rain. Freezing level starting around 2500m, lowering to 2000m by dinner time. Moderate SW winds at treeline, strong SW winds at ridgetop.
Avalanche Summary
Over the past week, very large slab avalanches have been running to size 3, failing on the mid-March persistent weak layer. This interface remains very reactive, avalanches have been remote triggered by skiers as recently as Monday. See this observation for a good visual: https://bit.ly/1CS2Nld
Snowpack Summary
A few cm of fresh snow fell with almost no wind Monday night. This recent dusting should make for great riding, but the region has a very serious persistent slab problem just under the surface. A cohesive slab 40 to 120cm in depth rests on the mid-March persistent weak layer that consists of small grain facets on a crust. This interface has been quite volatile recently and remains sensitive to human triggering. At lower elevations, rain has saturated the snowpack. The mid and lower snowpack are generally well-settled and strong.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.