Avalanche Forecast
Issued: Mar 24th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Cornices.
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Avalanche Canada
Don't let the new snow lure you into consequential avalanche terrain, storm slab avalanches may be primed for human triggering.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
WEDNESDAY NIGHT: Cloudy with some lingering flurries delivering up to 5 cm, 30 km/h northwest wind, treeline temperatures drop to -8 C.
THURSDAY: Mostly cloudy with some light flurries but no notable accumulations of snow, 30-40 km/h northwest wind, treeline temperatures around -7 C.
FRIDAY: Cloudy with some light flurries but no notable accumulations of snow, 20-30 km/h west wind, treeline temperatures around -5 C.
SATURDAY: Cloudy with scattered flurries and 5-10 cm of snow, 30-50 km/h southwest wind, freezing level climbing to 1900 m, treeline temperatures around -3 C.
Avalanche Summary
The North Rockies field team reported rapidly growing storm slabs producing shooting cracks in the northern part of the region on Wednesday (check for an upcoming MIN report from Sugarbowl). While we do not have other recent observations, the sheer amount of new snow on Wednesday likely resulted in natural avalanche activity at higher elevations and has left the potential for large human triggered storm slab avalanches at all elevations on Thursday.
Snowpack Summary
By the time Wednesday's storm ends we can expect 30-60 cm of fresh snow across the region. The heaviest accumulations appear to be northern parts of the region along the Robson Valley. We expect a fair bit of variability in the density of this new snow including heavier powder at lower elevations, deep low density snow at higher sheltered terrain, and firmer wind slabs in open terrain. Slightly beneath this new snow is a widespread crust layer from the mid-March warmup. While we don't have recent observations of this layer, we suspect the snow is bonding to this interface.
It appears persistent weak layers have gone inactive in the past week. We had been concerned about a weak facet layer from the mid-February cold snap that is now 80-120 cm deep. This layer resulted in a few large avalanches triggered by cornice falls in the first half of March, but recent weather patterns have helped this layer heal.
Terrain and Travel
- Stick to well supported, lower angle terrain.
- Keep your guard up at lower elevations. Storms slabs have been reactive at all elevations.
- Avoid freshly wind loaded terrain features.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Storm Slabs
Any steep slope has the potential for storm slab avalanches on after 30-60 cm of snow fell on Wednesday. This snow has likely formed unstable slabs on wind loaded slopes at higher elevations. In steep sheltered terrain this snow may either result in dry loose or storm slab avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Where cornices exist they pose a threat both from the potential for them to collapse under your feet (or machine) and from the potential to send large chunks of snow far down a slope.
Aspects: North, North East, East, South East.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 25th, 2021 4:00PM
