This is our first storm in quite sometime. The avalanche hazard has risen as a result of strong winds and new snow load.
Weather Forecast
The pineapple express that delivered rain and snow yesterday is being pushed south by a high pressure ridge. Freezing levels will hover around 1500m with lingering flurries today and mainly cloudy skies. Gradual clearing into Monday with more cooling as the ridge over our region strengthens. No precipitation is expected until mid next week.
Snowpack Summary
15-20cm of storm snow above 1900m. A mix of rain and snow (~15.0mm) below this elevation with a light dusting over a crust/moist snow. Storm winds peaked at over 130km/hr, wind slab at tree line and above will be a concern. Top 50cm has a few buried crusts that lay beneath previous wind slab which were reactive to human triggering.
Avalanche Summary
A natural cycle of moist/wet avalanches yesterday in the highway corridor. Avalanches were observed to size 2.5. This cycle continued into the evening as rain, snow and wind continued. Two days ago on Dome Glacier, a size 2.0 wind slab was triggered by the 5th skier on the slope, running 130m to the bench below the headwall.
Confidence
Due to the number of field observations
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.