The warming trend is promoting slab development which may be reactive to skiers. Over the weekend, above freezing temperatures and sunshine are expected to trigger avalanches.
Weather Forecast
The warming trend that started yesterday will continue over the weekend, when a strong ridge is expected to develop. Flurries will taper off today and we may see some sunny breaks. Alpine temps of -3'C and light but gusty SW winds are expected. Fri will be similar. On Sat things heat up with alpine temps to +3'C and freezing levels rise to 2800m.
Snowpack Summary
Nearly 50cm of snow has fallen in the past 4 days. On southerly aspects, NE winds yesterday will have reverse loaded lees creating deeper pockets of soft slab. In exposed alpine areas and a ridge crest it will have buried old windslabs. The Jan 2 freezing rain crust is down ~90cm. The Nov 21st interface is now 1-2m in deep.
Avalanche Summary
Yesterday, 4 size 2.5 and one size 3 natural avalanches were observed from steep slopes. In the region, skiers reported triggering storm slabs. On Wed, skiers accidentally triggered a size 3.5 as they approached Camp West. The crown was 40cm deep where triggered and up to 1.5m deep. Width of the crown was well over 100m and ran over a kilometer!
Confidence
Timing or intensity of solar radiation is uncertain
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.
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.