Avalanche Forecast
Regions: Sea To Sky.
Reactive storm slabs continue to build at higher elevations and thicker slabs will likely exist on leeward slopes due to wind redistributed storm snow. At lower elevations, loose wet avalanches are likely as rain soaks the snowpack.
Confidence
Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.
Weather Forecast
Strong southwesterly winds result in an onshore flow of a cool, and unstable air mass. This brings moderate to heavy snow at upper elevations to a drying and cooling trend by Thursday.
Tuesday Night: 10 cm of new snow with strong southerly winds. Freezing levels 1400 m falling to 1000 m by the morning.
Wednesday: Another 5-10 cm of snow with freezing levels near 1300 m. Strong southwest wind continues.
Thursday: Drying and cooling trend with the freezing level dropping to 1000 m with light northwest winds at ridgetop and clearing skies.
Avalanche Summary
By early afternoon on Tuesday, a few small size 1 wet loose avalanches were reported at lower elevations. With more snow/rain and strong winds, I suspect natural avalanches will be seen on Wednesday.Â
On Monday, storm slabs were still reactive but less electric than Sunday. A natural cycle up to size 2 was observed through limited visibility in the Whistler backcountry. Explosive control work produced mostly size 1s with a couple size 2 storm slabs. On the other side of the 99, a size 1 wet slab was observed sliding on the crust on an east aspect at 1500 m.
On Sunday, skier and explosive control work produced size 1-2 avalanches, a number of them remotely or sympathetically triggered. This MIN report describes a remotely triggered size 1 on a convex roll in an open area below treeline.
Snowpack Summary
30-50 cm of wind affected, upside-down storm snow sits over a variety of surfaces including sun crusts on solar aspects, a thick rain crust in windswept terrain and facets in shady, sheltered terrain. The upper snowpack is moist or wet below 1400 m.
A crust/facet/surface hoar interface formed late-January is buried down 40-100Â cm. This layer was most reactive between 1700 m and 2000 m. While this layer has been dormant in most of the region lately, large loads such as heavy snowfalls and cornice falls could wake it up and produce very large avalanches.
Terrain and Travel
- Minimize exposure during periods of heavy loading from new snow, wind or rain.
- Watch for fresh storm slabs building throughout the day.
- Keep in mind that wet avalanches can be destructive due to their high density.
Avalanche Problems
Storm Slabs
Storm slabs will continue to develop throughout the day where precipitation falls as snow. Storm slabs are especially likely to be triggered in steep or convex terrain and in wind loaded areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2.5
Loose Wet
Loose wet avalanches will become increasingly likely as rain soaks the surface snow at lower elevations.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Likely
Expected Size: 1 - 2