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Avalanche Forecast

Archived

Jan 21st, 2020–Jan 22nd, 2020

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

Regions

Sea To Sky.

Watch for slopes where thick deposits of new snow have accumulated, especially in wind-affected terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

TUESDAY NIGHT: 5-25 cm of snow overnight, moderate wind from the southwest, alpine temperatures drop to -5 C.

WEDNESDAY: Cloudy with scattered flurries and 5-10 cm of new snow, light wind from the southwest, alpine high temperatures around -3 C.

THURSDAY: Heavy snow with 30-50 cm of snow above 1800 m and heavy rain below, strong wind from the south, alpine high temperatures around -1 C.

FRIDAY: Scattered flurries with 5-15 cm of snow, moderate wind from the southwest, freezing level drops to 1200 m with alpine high temperatures around -3 C. 

Avalanche Summary

Recent storms have resulted in numerous small (size 1) slab avalanches triggered by riders on Sunday and Monday, while larger (size 2) wind slab avalanches have been triggered naturally and with explosives. Looking forward, continuing snowfall is expected to maintain similar conditions on Wednesday, with new snow and associated avalanche hazards increasing with elevation.

Snowpack Summary

Recent weather has created a mix of surface conditions. 5-25 cm of new snow will accumulate by Wednesday morning, but will likely be heavily wind affected. Extreme wind has scoured windward slopes in the alpine and formed thick wind slab deposits in lee terrain. A rain crust now exists up to treeline elevations, and moist snow exists below 1500 m. Overall storm slab hazards likely exist in areas where new snow has accumulated. 

Recent observation suggest it is now difficult to trigger surface hoar layers that formed in December (now buried 100 to 150 cm below the surface). However, weak faceted grains and crusts near the base of the snowpack continue to be a concern in inland parts of the region, such as the Spearhead Range. This layer will continue to be a problem when the snowpack is stressed by new snow or warming, and is best managed by avoiding shallow rocky start zones in the alpine and upper treeline.

Terrain and Travel

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Be especially cautious as you transition into wind affected terrain.
  • Use conservative route selection and resist venturing out into complex terrain.

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.