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Avalanche Forecast

Archived

Apr 8th, 2022–Apr 9th, 2022

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells.

Be mindful of conditions that change with aspect and elevation, like transitioning from ridgetop into a steep north-facing slope below.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

Friday night: Unsettled in the wake of the cold front with isolated and localized flurries, 5-20 cm by morning along with moderate to strong southwest winds. Freezing level dropping to valley bottom, overnight low -9 C.

Saturday: Blustery with alpine flurries, up to 5 cm. Light southwest winds. Freezing level near valley bottom, ridgetop high -5 C.

Sunday: A mix of sun and cloud with isolated flurries, trace to 5 cm. Light west winds. Freezing level remaining near valley bottom, ridgetop high -3 C.

Monday: Overnight flurries bringing trace to 10 cm. Light west winds. Ridgetop high -4 C.

Avalanche Summary

A loose wet avalanche cycle from solar slopes began late Thursday afternoon. Explosives also triggered several size 1 wind slabs, all about 20 cm thick.

On Wednesday, a size 3 natural wind slab was observed on a northeast aspect at 2300 m.

Over the past few days ski cutting has produced wind slab avalanches up to size 1.5. These avalanches have generally been on north and east aspects in treeline terrain. Explosive control has produced storm and wind slab avalanches up to size 2.5 on all aspects at treeline and above in the western part of the region where more storm snow was recorded. Several small cornice falls have also been observed.

Snowpack Summary

A crust has formed on all aspects up to 2200m and mountain top on steep, solar slopes. Variable winds have impacted dry snow at upper elevations and formed thin wind slabs in lee features.

A thick rain crust with facets above from early December is buried around 150 cm deep. Large avalanches were naturally triggered on this layer during the last significant warming event in western terrain near the Bugaboos. Avalanche activity on this layer will become unlikely as the freezing level falls.

Terrain and Travel

  • Avoid exposure to slopes that have cornices overhead.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Wind slabs may be poorly bonded to the underlying crust.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.