Ongoing snow and wind will keep avalanche hazard elevated. Avoid freshly wind-drifted areas and continue to make conservative terrain choices while the storm snow gains strength.
With continuing snow in the forecast, sustained southwest winds will have an ongoing supply of fresh snow to drift into wind slabs on lee slopes at upper elevations. These wind slabs will likely be reactive to human triggering.
30-60 cm of recent storm snow has formed a widespread storm slab problem that may remain possible to human trigger. Closely monitor how the recent storm snow is settling and bonding to the old surface.
Saturday night: Cloudy, 5-10 cm of snow above 300 m, moderate southwest wind, treeline temperatures near -4 C.
Sunday: Cloudy with sunny breaks, 5-10 cm of snow above 500 m, moderate southwest wind, treeline temperatures near -5 C.
Monday: Mainly cloudy, scattered flurries with up to 5 cm of snow above 500 m, moderate south wind, treeline temperatures near -4 C.
Tuesday: Mostly clear, light variable wind, treeline temperatures near -6 C, freezing level around 100 m.
We expect natural and human triggered avalanche activity to continue on Sunday.
A natural avalanche cycle likely occurred overnight during the storm. A MIN report from the Mt. Washington area on Saturday details widespread whumphing and has a great photo of a small (size 1.5) avalanche that was triggered remotely.
Intense bands of precipitation are forecast to bring another 10-30 cm of cold, light snow to the mountains in a highly localized pattern. Sustained southwest winds will have an ongoing supply of snow to drift into reactive wind slabs at upper elevations. Avoid freshly wind-loaded terrain features on Sunday (for example, down-wind of ridges and roll-overs).
A powerful storm on Friday brought 30-60 cm of new snow to the mountains with strong southwest winds. A gradual temperature rise during the storm created warmer denser snow over colder light snow. In many locations, storm accumulations sit on crust layers that formed in early December. This tricky combination of slab and sliding surface may require more time to recover and gain strength, and it warrants careful evaluation and cautious-route-finding.
Below the early December crust layers, the snowpack is generally well-settled. Recent indications of the region's snowpack suggest that snow depths at treeline are around 200 cm and taper dramatically below treeline. With this storm event, a greater number of areas below treeline may meet the threshold for avalanches. Check out this MIN report from Mt. Washington for a great visual of snow coverage just before the storm at these elevations.
