Be ready to back off from avalanche terrain as danger increases over the day. Heavy snowfall, strong wind, and rising temperatures are expected to begin a natural avalanche cycle.
Heavy snowfall, strong to extreme winds, and rising freezing levels are a recipe for a dangerous storm slab problem. Avalanche danger, greatest on the west slope of the region, will increase over the day.
The rain line will climb over the day. Steep slopes at elevations receiving wet snowfall or especially rain on previously dry snow will become increasingly unstable.
On Friday, explosives control targeting buried weak layers with large explosives triggered one large (size 2.5) persistent slab near Pine Pass. This occurred on a south aspect at treeline.
The heavy explosives trigger doesn't suggest a wider problem exists, but this may change if heavy rain reaches high enough elevations.
A widespread storm slab problem is expected to form through Monday.
Roughly 30 to 50 cm of new snow should accumulate by end-of-day Monday. This adds to a settling 40 cm that accumulated since March 7, which sits on old wind effect at exposed higher elevations and on a crust that extends to ridgetop. Wind slab formation from easterly winds occurred with the earlier storm, now buried by either low density snow or more westerly wind transport. The crust becomes supportive at lower elevations and is 5 cm thick below 1400 m.
Another crust with faceted snow above, buried at treeline and below in February, is found around 100 to 160 cm deep. It's becoming well bonded to the surrounding snow and at lower elevations will be capped by more recent crust.
Sunday Night
Cloudy with increasing flurries bringing 10 to 20 cm of new snow. 30 to 70 km/h southwest ridgetop wind, increasing. Treeline temperature reaching -7 °C.
Monday
Cloudy with increasing snowfall bringing 20 to 35 cm of new snow. 80 km/h south ridgetop wind. Treeline temperature -2 °C with freezing level rising from valley bottom to 1500 m, rising to 2300 m overnight.
Tuesday
Cloudy with continuing heavy snowfall bringing 40 to 60 cm of new snow above 1800 m, including overnight, heavy rain below. 70 to 80 km/h southwest ridgetop wind, easing a bit. Treeline temperature 1 to 2 °C with freezing level 2100 m.
Wednesday
Cloudy with easing snowfall bringing 15 to 30 cm of new snow above 1600 m, including overnight, rain below. 60 to 70 km/h southwest ridgetop wind, easing. Treeline temperature 1 °C.
More details can be found in the Mountain Weather Forecast.
