Treat open slopes at treeline and below as suspect, new snow sits on a weak surface hoar layer. Watch for signs of instability like shooting cracks and whumpfing.
Wind slabs will continue to form at higher elevations as westerly winds strengthen..
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 northwest - expect wind slabs on most aspects.
Fresh snow sits over a large and sensitive surface hoar layer. Treat open slopes at treeline and below with caution - they may be more reactive and produce larger avalanches than you expect.
Arctic air brings cold temperatures, wind and little chance of snow until Friday.
TUESDAY: NIGHT: Cloudy with clear breaks. Moderate E winds. Freezing level at valley bottom. Isolated flurries
WEDNESDAY: A mix of sun and cloud. Moderate W winds. Freezing level at valley bottom. Alpine high of -18.
THURSDAY: Cloudy with sunny breaks. Moderate W winds. Freezing level at valley bottom. Alpine high -9.
FRIDAY: Cloudy with flurries, up to 7cm. Moderate SW winds, gusting strong. Freezing level 1000 m, alpine high of -5.
On Monday a natural cycle was observed to size 2.5 in many areas. Ski cutting and explosive control work also produced slab avalanches to size 2. A vehicle remotely triggered a size 1.5 slab avalanche, indicating sensitivity of the buried surface hoar layer.
A MIN report noted shooting cracks and whumpfing during their travel, showing reactivity of the January 18 crust (30-50cm) deep and the most recent surface hoar (20-30cm) deep).
A size 2.5 natural persistent slab avalanche was reported to have occurred on a path that had previously avalanched and reloaded bed the surface.
At lower elevations up to 30cm of storm snow sits over a thick melt freeze crust. In sheltered terrain, a widespread layer of surface hoar sits immediately above the crust, typically 10-20 mm but as big as 30 mm in places.
At higher elevations the storm snow is being redistributed by moderate to strong northwest winds, over a snow surface that was previously heavily wind affected. A thin melt freeze crust extends into the alpine on solar aspects. This crust may sit on the surface or below wind deposited snow.
The widespread January 18 rain crust is now down around 40-50 cm but has not been producing avalanches recently.
The mid snowpack is strong and well-consolidated above the early December facet/crust layer which is now down 100-200 cm. This layer has been dormant recently and is not currently a concern for the region but could still be a problem in the future. See the most recent forecaster blog for more details on this layer.
