Avalanche Forecast
Issued: Mar 12th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Cornices and Deep Persistent Slabs.
MH,
Avalanche Canada
Avalanche Danger will increase throughout the day, likely reaching HIGH by the afternoon as the storm intensifies.
The Deep Persistent Layer has been brought back as a problem for Monday's storm as 30-40cm of snow is forecasted to fall with rising freezing levels, which may be enough to overload this layer.
Summary
Confidence
Avalanche Summary
Avalanche activity will increase as the storm progresses through the day on Monday.
A close call occurred Sunday morning in MacDonald Gully 11 as a group on their way up narrowly evaded being hit by a size 2 avalanche that originated in the cliffs high above from extreme terrain. They saw the powder cloud coming down and quickly moved into the trees and out of the way. They made a good decision and turned around.
Snowpack Summary
The new snow has fallen on a variety of surfaces including wind-hardened snow in the alpine, a crust on solar aspects and surface hoar (~5mm) in sheltered shaded areas.
Although generally strong, the snowpack still sits on a deep persistent weakness of rounding facets and a decomposed crust near the ground. This layer has not been reactive since the last major snowfall (February 27th), but as the snow continues to fall, we might see some large avalanche activity on this layer.
Weather Summary
A storm front arrives late Sunday evening, persists until Monday night and is expected to drop up to 30-40cm of snow. Winds will be 50km/hr from the SW in the morning and gradually drop to ~25km/hr by the evening. The freezing level will rise to 1900m.
Cooler temps and light winds for Tuesday and Wednesday.
Terrain and Travel Advice
- Storm slab size and sensitivity to triggering will likely increase through the day.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Loose avalanches may start small but they can grow and push you into dangerous terrain.
- Caution around slopes that are exposed to cornices overhead.
Problems
Storm Slabs
The storm slab will grow throughout the day on Monday as 30-40cm of snow is forecasted to fall by the evening. Strong winds accompany the snow and will form deeper slab in wind loaded areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
With the possibility of rapid loading and rising freezing levels, cornices may become stressed/weak and collapse. A failure of this size may be the trigger needed to wake up our Deep Persistent Layer, which would result in a very large avalanche.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
After several weeks of not listing the Deep Persistent Layer as a problem, we are bringing it back as uncertainty surrounds what may wake this layer up. Mondays storm will likely drop 30-40cm of snow at higher elevations and rain at lower elevations as freezing levels could reach 1900m. An avalanche on this layer would be very destructive, likely run full path or further and be of high consequence.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 13th, 2023 5:00PM
