Avalanche Forecast

The first arctic outbreak of the season brings outflow winds, modified cold air and additional snow falling to valley bottom through Tuesday. A blocking high pressure system will likely keep things cold and dry through the forecast period.Tuesday: New snow 5-15 cm overnight on Monday. Ridgetop winds blowing moderate from the N-NE and temperatures at treeline elevations hovering around -10.0.Wednesday/ Thursday: Freezing levels will remain at valley bottom with average treeline temperatures near -12.0. Light winds will continue from the N-NE direction

With new snow and wind, I suspect a natural avalanche cycle is happening as I write this. The new storm snow will need some time to settle out and adjust to the old snow surfaces. New snow, wind, weak layers and direct action avalanches are obvious indications for avalanche hazard to rise. However, the tricky part may be yet to come, when this storm settles out and people are chomping at the bit to get out. Rider triggered avalanches are possible-likely, but its the deeper, early season persistent weak layers in which my uncertainty lies due to lack of early season observations.

New storm snow amounts range from 15-25 cm. Initially, the storm arrived with strong southwest winds leaving lee slopes with deeper deposits. This new snow will likely have a poor bond to the old surfaces that comprise of surface hoar, crusts (potentially up to 2100 m) and some dry facetted snow above that. Forecast changing winds (outflow from the north) will likely redistribute the new snow on opposite slopes possibly building wind slabs that could catch you by surprise. Snowpack depths are highly variable across the region; however, slopes below treeline are below threshold for avalanche activity. Where the near-surface crust is robust (>1cm thick), the upper snowpack has gained strength and avalanches failing on deeper layers have become much less likely. I'd be extra cautious in areas where the near-surface crust is thin or has not formed (I'm thinking high alpine terrain or northern parts of the region). In these areas, deeper persistent weak layers may still be sensitive to human triggering.