Avalanche Forecast
Issued: Feb 25th, 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
Conditions are trickier than what meets the eye. New snow is expected to bond poorly to the underlying surface and may form reactive storm and wind slabs. What won't be as evident underfoot is the buried hard slabs from this week's northerly winds. Both of these problems are most likely to be an issue in wind-exposed alpine and treeline terrain.
Don't let good visibility and the desire to ride deep powder lure you into consequential terrain. Sheltered terrain will offer the best and safest riding
Summary
Confidence
Avalanche Summary
A natural avalanche cycle occurred with heavy snowfall last Monday night and Tuesday. Avalanches were reported as size 2-3.5 wind slabs, storm slabs and persistent slabs on northwest, northeast and southeast aspects in the alpine and treeline elevation bands. The persistent slab avalanches were suspected to have run on the facet/crust layer buried in mid-January (outlined in the avalanche problem section).
As northerly outflow winds picked up on Wednesday, several natural and human-triggered wind slabs (size 1) were reported throughout the region. These slabs occurred on a variety of aspects in the alpine all the way down to below treeline terrain.
Looking forward to Sunday, a more widespread storm slab problem may exist, particularly in areas that receive 25 cm or greater in the overnight period. Riders should take a cautious approach and be on the lookout for signs of instability such as whumpfing, shooting cracks, drumlike or hollow sounds, and recent avalanche activity. Keep in mind that older, stiff wind slabs may now be hidden under the storm snow.
Please continue to post your reports and photos to the Mountain Information Network.
Snowpack Summary
Saturday evening's storm will accumulate 15-30 cm of new snow down to valley bottom. This new snow is expected to bond poorly to the stiff wind slabs and near-surface facetting formed by recent wind and cold temperatures.
A melt-freeze crust formed in mid-January is buried up to 90-140 cm deep. In some areas, small faceted crystals can be found above the crust. This layer has been reactive during the storm Tuesday night and Wednesday this week. The snow below this layer is well consolidated.
Snowpack depths are just below seasonal averages. Total amounts range from 150 to 300 cm at treeline, but decreases significantly below 1500 m.
Weather Summary
Saturday night
Cloudy with snowfall, 10-25 cm of accumulation. Alpine temperatures drop to a low of -6 °C. Ridge wind southwest 20 to 50 km/h. Freezing level 200 meters.
Sunday
Mainly cloudy with flurries, 5-10 cm of accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 25 to 60 km/h. Freezing level 400 meters.
Monday
Mainly cloudy with scattered flurries, up to 5 cm accumulation. Alpine temperatures reach a high of -3 °C. Light ridge wind from the southwest. Freezing level 800 meters.
Tuesday
Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -4 °C. Light ridge wind from the south. Freezing level 400 meters.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Good day to make conservative terrain choices.
- Use increased caution at all elevations. Storm snow is forming touchy slabs.
- Dial back your terrain choices if you are seeing more than 30 cm of new snow.
- Be careful to keep storm day fever from luring you out into bigger terrain features.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Storm Slabs
In areas that receive 25 cm or greater in the overnight period, storm snow may settle into a widespread storm slab problem. Expect deeper, more reactive slabs to exist in wind-loaded terrain. Start with small, low-consequence terrain and assess the snow surface on any aspect you are travelling on for clues of instability, like cracking, whumpfing or hollow drum-like sounds.
Keep in mind that older, stiff wind slabs from previous northerly winds may still be reactive to human-triggering and are now hidden under the fresh storm snow.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A crust formed in mid-January can be found down 80 to 120 cm. In areas around the Coquihalla, facets can be found sitting on the crust. This layer is 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 26th, 2023 4:00PM
