Avalanche Forecast
Issued: Feb 27th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
zryan,
Avalanche Canada
Be particularly cautious in wind-loaded areas and continue to make conservative terrain choices while the storm snow settles and stabilizes.
Summary
Confidence
Moderate
Avalanche Summary
During the storm on Sunday, 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 Tuesday, human-triggered storm slabs remain likely, 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 will accumulate throughout the day on top of Saturday night's 20-50 cm of new snow 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 60-180cm 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
Monday night
Cloudy with clear periods and isolated flurries, up to 5 cm of accumulation. Alpine temperatures drop to a low of -10 °C. Light ridge wind from the southeast. Freezing level at valley bottom.
Tuesday
Cloudy with flurries, 5-10 cm of accumulation. Alpine temperatures reach a high of -8 °C. Ridge wind light southeast. Freezing level at valley bottom.
Wednesday
Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -9 °C. Ridge wind southwest 15 km/h gusting to 40 km/h. Freezing level at valley bottom.
Thursday
Cloudy with snowfall, 5-15 cm of accumulation. Alpine temperatures reach a high of -7 °C. Ridge wind southwest 30 km/h gusting to 80 km/h. Freezing level 900 meters.
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.
- Carefully monitor the bond between the new snow and old surface.
- Seek out sheltered terrain where new snow hasn't been wind-affected.
- 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
Storm Slabs
An additional 5-15 cm will accumulate over Saturday night's 30-50 cm of storm snow. In many areas, this new snow may be bonding poorly to the underlying surface and storm slab reactivity may persist for longer than is typical. Deeper and more reactive deposits will exist in wind-loaded areas.
Aspects: All aspects.
Elevations: All elevations.
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: Feb 28th, 2023 4:00PM
