Snow and wind overnight Friday will elevate the avalanche danger.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Saturday
Weather Forecast
SATURDAY: Snow overnight Friday, accumulation 10-15cm then cloudy with flurries Saturday / Light to moderate southwest wind / Alpine temperature -3 / Freezing level 1500m SUNDAY: Cloudy with flurries, accumulation 5-10cm / Moderate north wind / Alpine temperature -2 / Freezing level 1300m MONDAY: Cloudy with isolated flurries / Light southwest wind / Alpine temperature -1 / Freezing level 1400m
Avalanche Summary
On Wednesday and Thursday there were numerous explosives triggered storm slab avalanches to size 1 and 1.5. Additionally there were explosives triggered cornice falls to size 2.
Snowpack Summary
20-25cm of new snow Friday has been redistributed by strong to extreme southwest winds. Reactive storm slabs and wind slabs built with continued snow and wind over the past 2 days. Ridgelines are heavily corniced and if they fail they would act as a trigger on the slope below. A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 120 cm down. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m. Below this, the snowpack is well-settled and strong.
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.