We are at the touchy upper end of Considerable trending toward High avalanche danger. Conservative route selection is paramount.
Weather Forecast
A large pulse of warm precipitation is coming at us from the SW bringing upwards of 40mm of precipitation by Tuesday afternoon. Freezing levels are expected to rise to over the 2000m level.
Snowpack Summary
We are closing in on critical loading on the weak Dec 2 surface hoar layer down anywhere from 25-50cm. The building storm slab will overload this layer resulting in a widespread avalanche cycle. Look for a steadily increasing avalanche danger.
Avalanche Summary
Natural avalanches and skier triggered slides in the 1-1.5 size range were reported yesterday. Numerous avalanches were recorded in the highway corridor. These slides all appeared to be releasing on the Dec 2nd surface hoar layer. Field tests on a SE aspect at 2000m on Grizzly Shoulder gave a Rutch block 3 full block 50cm down on a sun crust.
Confidence
Timing of incoming weather systems 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.
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.