Issued: Apr 22nd, 2023 4:00PM
The alpine rating is Wind Slabs., the treeline rating is , and the below treeline rating is Known problems include
Check for signs of windslab instability in steep terrain at higher elevations, especially around ridgetops. Shooting cracks or fresh avalanches are signs that you should retreat to terrain that is not exposed to the wind.
Small avalanches could step down to a deeper weak layer and form large avalanches.
There are very few field observations coming from this forecast area. Remember that a lack of avalanche reports does not necessarily mean a lack of avalanche activity. We expect that riders could trigger wind slabs in steep lee terrain features at treeline and alpine elevations.
On Sunday in the Duffey Lake area, several small (size 1), naturally triggered loose wet avalanches were reported on steep, north facing slopes.
On Wednesday, riders triggered a few wind slabs in steep, leeward terrain on Wednesday (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 and a half ago (e.g., this MIN).
7-15 cm of new snow for alpine and treeline elevations. Changing freezing levels have left a mixed bag of surfaces below treeline.
Recent snow and southwest wind have likely formed wind slabs in leeward terrain features at high elevations. Underneath the recent snow is 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 buried in early April is found up to 60 cm deep at treeline and alpine elevations. This layer was the culprit of many large avalanches around April 12. It is suspected that this layer may have gained strength and bonded to the rest of the snowpack, but with limited field data from this forecast area, it remains an uncertainty for us.
The base of the snowpack remains faceted and weak. There are no reports 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.
Cloudy. 5-10 cm of snow expected. Snow/rain line around 1300 m. Treeline low around -2°C. Light southwest ridgetop wind, trending to moderate at very high elevations.
Cloudy. 2-5 cm of snow expected. Snow/rain line dropping to 1000 m by the end of the day. Light south or southwest ridgetop wind trending to strong at very high elevations, but easing through the day.
Mix of sun and cloud. Possible trace of snow/rain expected. Freezing level rising to 1800 m. Light southwest ridgetop wind.
Mostly sunny. No new snow/rain expected. Freezing level rising to 2000 m. Light southwest ridgetop wind trending to moderate northwest at high elevations.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- 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.
Wind slabs may be found in lee terrain features from recent snow and southwest wind. Small avalanches could step down to a layer of facets and crust buried 60 cm deep that could result in large avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Valid until: Apr 23rd, 2023 4:00PM