Avalanche Forecast

Moderate

Riders triggered a few wind slabs in steep leeward terrain on Wednesday (e.g., as seen here and here). They were 10 to 30 cm deep, on west to northwest aspects, and varied between about 2200 m and 2700 m in elevation.

The most recent avalanches on the facet layer described in the Snowpack Summary occurred about a week ago (e.g., this MIN).

Loong forward, we expect that riders could trigger wind slabs in steep lee terrain features at treeline and alpine elevations.

Some new snow and southwest wind may form new wind slabs in lee terrain features at higher elevations. These slabs will build onto lingering 10 to 30 cm thick wind slabs that formed earlier this week. Underneath these wind slabs are a hard melt-freeze crust found on all aspects up to 1700 m and to mountain tops on southerly slopes or dry faceted snow on shaded aspects at high elevations.

A layer of facets and a crust from early April is buried up to 60 cm at treeline and alpine elevations. There's uncertainty in how this layer is bonding, but it was the culprit of many large avalanches around April 12.

The base of the snowpack remains faceted and weak. We haven't received any notes of recent avalanche activity on this layer, but the concern remains for steep and rocky slopes with a thin snowpack.

Cornices are large and looming at this time of year.

Thursday Night

Cloudy with snowfall, accumulation 5 cm, 20 to 30 km/h south wind, treeline temperature -7 °C, freezing level 1000 m.

Friday

Early-morning sun and afternoon clouds with no precipitation, 10 km/h southwest wind, treeline temperature -4 °C, freezing level 1500 m.

Cloudy with isolated snowfall, trace accumulation, 20 to 40 km/h southwest wind, treeline temperature -2 °C, freezing level 1700 m.

Cloudy with snowfall, accumulation 5 cm, 20 to 40 km/h southwest wind, treeline temperature -2 °C, freezing level 1700 m.

More details can be found in the Mountain Weather Forecast.

• Carefully evaluate steep lines for wind slabs.
• Use ridges or ribs to avoid areas of wind loaded snow.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• Pay attention to cornices and give them a wide berth when traveling on or below ridges.