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Avalanche Forecast

Archived

Apr 7th, 2022–Apr 8th, 2022

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

Sea To Sky.

Overnight freezing level change, rain and snow leaves uncertainty over how the snowpack will react. 

During times of uncertainty lean on a conservative approach to terrain, cautious mindset and constantly make observations while you travel.

Confidence

Low - Uncertainty is due to rapidly fluctuating freezing levels. Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

THURSDAY NIGHT: Freezing levels fall from 2500 m to around 1200 m by morning. Precipitation begins as rain and transitions to snow. 30-40 mm is forecast with strong to extreme southwest winds. 

FRIDAY: Mostly cloudy with continued snowfall 10-15 cm. Freezing levels remain around 1200 m. Moderate westerly winds. 

SATURDAY: Mostly cloudy with flurries of up to 5 cm. Freezing levels around 800 m. Moderate westerly winds.

SUNDAY: Clearing skies with scattered flurries possible. Freezing levels remain below 1000 m. Light westerly winds. 

Avalanche Summary

High freezing levels and a mix of rain and snow overnight are expected to produce a natural avalanche cycle.

On Wednesday, several natural and rider triggered storm slab avalanches were reported on all aspects to size 2. Previous natural activity from the storm was observed to size 3. Several cornice falls were also reported, some triggered slab avalanches on the slope below. Most avalanches have failed on the buried crust from late March. 

On Tuesday, rider, natural and explosive triggered avalanches were reported to size 2.5. Small avalanches were also remotely triggered, indicating the sensitivity of the recent storm snow. 

Snowpack Summary

Up to 40 mm of precipitation overnight with falling freezing levels will create a mixed bag of conditions on Friday, as snow continues to accumulate.

High elevations can expect up to 40 cm of fresh wind affected storm snow, that will likely be redistributed into deeper deposits on north and east facing slopes over a crust or moist snow. Another widespread and supportive crust is buried 60-100 cm deep, below recent settling storm snow. This crust has recently been very reactive to human and natural triggers. 

Snow will transition to mixed precipitation and rain as elevation decreases. The lowest elevations will likely hold wet surface snow or a crust from heavy overnight rainfall. 

The middle and lower snowpack are generally strong and well bonded. 

Terrain and Travel

  • As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.
  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.