Danger will elevate throughout the day as slope warm up. Plan on finishing early and minimizing your exposure to avalanche terrain once it heats up. Read more in this Forecasters' Blog.
Cornices are large and looming along many ridgelines. They will become weak with daytime heating and could trigger avalanches on the slopes below.
Wet loose avalanches will start to run naturally on steep solar aspects when the sun comes out.
Prolonged warming could increase the sensitivity of deeply buried layers in the snowpack. While these layers have not been reactive lately, you should practice increasing caution during this period of warm weather. Thin rocky slopes are most suspect.
A high pressure ridge brings clear skies and progressively warmer temperatures.
TUESDAY NIGHT: Clearing skies, light west wind, freezing level climbs from 1700 to 2000 m by the morning with treeline temperatures climbing to +2 C.
WEDNESDAY: Mostly sunny, light south wind, freezing level climbs from 2000 to 2700 m throughout the day, treeline temperatures climb to +5 C.
THURSDAY: Sunny, light south wind, freezing level steady around 2800 m, treeline temperatures around +8 C.
FRIDAY: Mostly sunny, light south wind, freezing level steady around 3000 m, treeline temperatures around +8 C.
Warm sunny weather this week will cause wet loose avalanches and cornice falls. Natural slab avalanches will become an increasing concern after several days of warm weather.
On Sunday and Monday there were many small (size 1) wet loose avalanches on south-facing slopes at all elevations and a few size 2-2.5 cornice failures on north and east facing slopes. On Saturday there were a few naturally triggered wind slab avalanches (up to size 2) on northeasterly aspects in the alpine.
Sunny skies and rising freezing levels will result in melting surfaces everywhere except north-facing alpine terrain. In the alpine 5-20 cm of snow is quickly settling and strengthening, although some wind slabs could linger on steep slopes. The recent snow has covered a variety of snow surfaces, including wind affected snow, crusts on solar aspects and at lower elevations, and soft snow on sheltered slopes at upper elevations.
The lower snowpack has been strong and settled over the past month, however the dramatic warming this week could potentially wake up weak basal facets. This is particularly a concern on steep, rocky slopes with a shallow or thin to thick snowpack.
Cornices are large, looming, and capable of triggering large avalanches when they fail.
