Avalanche Forecast
Issued: Apr 21st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
bchristie,
Avalanche Canada
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.
Summary
Confidence
Moderate
Avalanche Summary
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).
Looking forward, we expect that riders could trigger wind slabs in steep lee terrain features at treeline and alpine elevations.
Snowpack Summary
Recent snow and southwest wind likely formed wind slabs in lee terrain features at higher elevations. These slabs have added 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.
Rising freezing levels on Saturday mean that the surface snow could get dense and moist at treeline and below.
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. 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.
Weather Summary
Friday Night
Cloudy. No new snow expected. Freezing level falling to 1200 m. Treeline low around -5°C. Light southwest ridgetop wind.
Saturday
Cloudy. No new snow expected. Freezing level rising to 1800 m. Treeline high around 0°C. Light southwest ridgetop wind, trending to moderate west at very high elevations.
Sunday
Mostly cloudy. 2-10 cm of snow expected. Snow/rain line between 1000 and 1500 m. Light south or southwest ridgetop wind trending to strong at very high elevations.
Monday
Mix of sun and cloud. 0-5 cm of snow expected. Snow/rain line between 800 and 1700 m. Light variable ridgetop wind.
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.
Problems
Wind Slabs
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.
Likelihood
Expected Size
Valid until: Apr 22nd, 2023 4:00PM
