6:30 Update to Treeline hazard
Temperatures are on the rise! Be alert to changing conditions.
Continually assess as you travel and avoid terrain with overhead hazards like cornices.
Cornices are large and looming. Strong winds and warming temperatures may increase the sensitivity. Cornices may trigger wind slabs or may step down to the persistent slab.
At upper elevations, where the crust is thinner or not present, it may still be possible to trigger persistent slabs on multiple buried weak layers of surface hoar and/or crusts in the top 120 cm of the snowpack.
Rising freezing levels and rain will soften surface snow. Steep terrain at treeline and below are likely areas to trigger.
On Monday, several small rider-triggered wind slab avalanches were reported.
On Sunday, a size 3 avalanche was reported in the Lizard Range below a steep headwall with a 2 meter crown. The avalanche was naturally triggered by a cornice.
On Friday, in the Flathead a naturally triggered size 2.5 on a north aspect below a steep headwall in the alpine. and a machine triggered size 1.5 Persistent Slab was reported in the Flathead.
Cornices are large and looming. Avoid traveling underneath them.
Strong winds are redistributing recent storm snow and developing wind slabs at all elevations.
A 1 to 10 cm thick crust on all aspects and is down 30 to 50 cm. The thickness of the crust depends on elevation.
At upper elevations, where the crust is thinner or not present, it may still be possible to trigger persistent slabs on multiple buried weak layers of surface hoar and/or crusts in the top 120 cm of the snowpack.
The mid/lower snowpack is well settled and strong in most areas.
Monday Night
Cloudy. 1 cm of snow at treeline. 80 km/h west ridgetop wind. Treeline temperature -3 °C. Freezing level 1900 m.
Tuesday
Cloudy. 1 cm of snow at treeline. 60 km/h west ridgetop wind. Treeline temperature 0 °C. Freezing level 1900 m.
Wednesday
Cloudy. 5 to 20 mm of rain at treeline. 60 km/h southwest ridgetop wind. Treeline temperature 2 °C. Freezing level 2400 m.
Thursday
Mostly cloudy. 2 to 5 mm of rain at treeline. 60 km/h southwest ridgetop wind. Treeline temperature 3 °C. Freezing level 2500 m.
More details can be found in the Mountain Weather Forecast.
