Expect fresh wind slabs to form as westerly winds strengthen, navigate carefully around wind loaded terrain features and ridgelines.
Approach sheltered slopes at treeline and below carefully, buried surface hoar may produce larger avalanches than you expect.
Fresh reactive slabs may form over a smooth crust, and on a weak surface hoar layer in sheltered terrain features.
The snow came with southwest winds, and winds have now shifted to the norwest - expect wind slabs on most aspects.
Arctic air brings cold temperatures, wind and little chance of snow until Friday.
TUESDAY NIGHT: Clearing skies with scattered cloud. Moderate norwest winds. A chance of flurries. Freezing levels at valley bottom.
WEDNESDAY: Cloudy with sunny breaks. Moderate to strong westerly winds. Flurries bring up to 5cm to the west boundary of the region late in the day. Freezing levels at valley bottom. Alpine high of -12.
THURSDAY: Cloudy with sunny breaks. Moderate to strong westerly winds. Chance of flurries. Alpine high of -7. Freezing level valley bottom.
FRIDAY: 10cm of snow with strong southwest winds. Alpine high of -5.
On Monday, a natural avalanche cycle was observed mid storm producing storm slabs to size 1.5. Storm slabs were also triggered from ski cutting and explosive control work size 2.
All avalanches reportedly failed within the storm snow, or on the buried surface hoar layer immediately below. Avalanche activity occurred at treeline and above, mainly on North through East aspects (lee to the southwest winds).
At lower elevations up to 30cm of storm snow sits over a melt freeze crust. In sheltered terrain a widespread layer of surface hoar sits immediately above the crust, typically 5-15 mm but as big as 30 mm in some areas.
At higher elevations the storm snow is being redistributed by moderate to strong westerly winds, over a previously wind affected snow surface. A thin melt freeze crust extends into the alpine on solar aspects. This crust may sit on the surface in exposed terrain, or below wind deposited snow in sheltered features.
The upper snowpack then consists of several crusts and surface hoar layers, 30-60 cm deep. Recent reactivity has appeared limited to the storm snow and most recent surface hoar.
The early December crust/facet persistent weak layer is buried down 100-200 cm and has been responsible for sporadic avalanche activity throughout the first half of January. The layer has been mainly dormant in the region for the past couple weeks but still remains a concern. See the most recent forecaster blog for more details on this layer.
