Continued snowfall through Monday evening coupled with moderate variable winds will continue to form fresh and reactive wind slabs primed for human triggering on steep slopes across the region.
Recent new snow and variable winds will build wind slabs on south and east aspects over the next few days. Old wind slabs from previous strong southwest winds may still be lingering in lee terrain features on northeast-facing slopes.
A layer of large, weak facets sits near the base of the snowpack. This layer is most prominent in upper treeline and lower alpine elevations. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain.
Recent observations have shown a trend away from the very large persistent slab and deep persistent slab avalanches and toward surface instabilities such as wind slabs. We expect this trend to continue, however, the basal snowpack remains questionable and should still figure into terrain selection around steep features with shallow or variable snowpack areas where these layers may be more easily triggered by a person or machine as well as large wind slab or cornice releases.
Roughly 10 to 15 cm of new snow, coupled with winds shifting to the northwest may build new wind slabs on south and east-facing terrain from reverse loading. These new wind slabs will be developing over variable surfaces of soft snow in sheltered terrain and old wind slabs in open terrain features.
Several strengthening crust/facet/surface hoar layers can still be found in the upper and middle portions of the snowpack. The most concerning persistent weak layer, however, is at the base of the snowpack and composed of large and weak facets formed in November. This layer is strengthening slowly as well, remaining most likely to be triggered in thin, rocky alpine and upper treeline terrain.
Monday night
Cloudy with scattered flurries bringing another 5-10 cm of new snow. Northwest winds 20 to 30 km/h. Treeline temperatures -11°C.
Tuesday
Cloudy, clearing in the afternoon, 15 to 20 km/h northwest winds switching to the southwest and increasing throughout the day. Treeline temperatures -12 °C
Wednesday
Increasing cloud with isolated flurries, 20 to 30 km/h southwest winds, treeline temperatures -8 °C.
Thursday
Cloudy with 5 to 7 cm of new snow, 10 to 20 km/h southwest winds, treeline temperatures -5 °C.
More details can be found in the Mountain Weather Forecast.
