Avalanche Forecast
Issued: Feb 28th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
swerner,
Avalanche Canada
Overnight winds from the northeast may form fresh wind slabs on unexpected slopes. Be particularly cautious in wind-loaded areas and continue to make conservative terrain choices while the storm snow settles and stabilizes.
Summary
Confidence
Avalanche Summary
On Monday, several natural storm slab and cornice failures were reported up to size 2. The cornice fall triggered a slab up to 50 cm deep from the slope below to size 2. Additionally, numerous explosive-controlled wind slab avalanches and cornices were reported up to size 2.
Last weekend, numerous natural and human-triggered storm slabs up to size 2 were reported from all aspects and elevations. Observations were limited due to visibility, but we suspect a natural cycle occurred in alpine terrain.
Looking forward to Wednesday, human-triggered storm slabs remain possible, especially in wind-loaded areas. Storm slab reactivity is expected to persist for longer than is typical due to the weak surface they are sitting on.
For a deeper dive into conditions leading up to last weekend's storm, check out this awesome South Coast Conditions Report posted by Zenith Guides.
Snowpack Summary
An additional 5-10 cm of new snow adds to last weekend's storm snow that brought 20-50 cm down to valley bottom. In some areas, this new snow has bonded poorly to the underlying surface consisting of stiff wind slabs and near-surface faceting formed by recent wind and cold temperatures.
There are two crusts with facets sitting above, which are buried in the snowpack down 60-180 cm in the alpine and treeline elevation bands. These crust/facet layers have been responsible for a few large avalanches in the past 2 weeks in the Brandywine and Pemberton Icefield areas.
The remainder of the mid and lower snowpack is well-settled, strong, and consolidated.
Weather Summary
Tuesday Night
Clear periods. Alpine temperatures -10 °C. Ridge wind northeast 10-20 km/h. Freezing level valley bottom.
Wednesday
Cloudy with flurries up to 5 cm. of accumulation Alpine temperatures reach a high of -10 °C. Southwest wind 35 km/h and freezing level valley bottom.
Thursday
Snow amounts 10-20 cm. Ridgetop wind 40-55 km/h from the west. Alpine temperatures reach a high of -9 °C. Freezing level valley bottom.
Friday
Cloudy with sunny periods and isolated flurries. Alpine temperatures near -11°C. Ridge wind southwest 25 gusting to 50 km/h. Freezing level 900 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Carefully monitor the bond between the new snow and old surface.
- Don't let the desire for deep powder pull you into high consequence terrain.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Problems
Wind Slabs
30-50 cm of recent storm snow continues to be reactive, especially in wind-affected terrain at treeline and in the alpine. A poor bond may exist to the underlying old snow surface and reactivity may persist for longer than is typical.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Two weak layers consisting of a crust with small facets above buried between 50 and 180cm deep, have been responsible for a few large avalanches in the past two weeks. This problem seems to be more of an issue west of the Sea to Sky highway corridor. These layers are of greatest concern with large triggers, such as a cornice fall, or by first triggering a smaller avalanche that could step down to this interface.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 1st, 2023 4:00PM
