Avalanche Forecast

Storm conditions continue.

Tuesday night: 50-80 mm precipitation falling mostly as rain. Freezing level 2500 m. Ridgetop winds in excess of 100 km/h from the southwest.

Wednesday: Wet snow mixed with rain; 30-40 cm. Continued strong to extreme southwest winds. Freezing level lowering slightly to around 2000 m.

Thursday: Cloudy with scattered flurries in the morning, some clearing in the afternoon. Moderate westerly winds. Freezing level dropping to around 700 m with treeline temperatures cooling to around -7 C.

Friday: Dry. Cloudy with some clear spells. Light northeasterly winds. Freezing level around 700 m.

Numerous natural and triggered avalanches, including large storm slabs avalanches (size 3 and 4) sliding on buried surface hoar and deeper buried crusts were reported during the last storm. We expect to see another widespread avalanche cycle during the current atmospheric river, with large, full-path avalanches.

At elevations up to around 2500 m, significant amounts of rain is falling on new snow from earlier in the storm. Until temperatures cool, this will result in a wet, heavy, unstable upper snowpack.

A layer of surface hoar has previously been reported that is buried between 60-100 cm deep. Slightly below this layer is a crust with facets. Surprising large avalanches sliding on these weak layers were reported during the last storm.

Average snow depths at treeline are now likely closer to 150-200 cm; 250+ cm in the alpine. Snowpack depths decrease dramatically below treeline and may still be below threshold for avalanches in some areas. Early season hazards such as rocks, stumps, and creeks are still a concern at these lower elevations.

• Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
• If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
• Be aware of the potential for large, deep avalanches to run full path or even longer.