Avalanche Forecast

On Monday the action continued with many professional operations reporting that a natural avalanche cycle was occurring, these slab avalanche were reported as large (size 2.5) . Further evidence of cracking and settling of the warm and moist upper snowpack provided good evidence of the new storm snow instability. Explosives work conducted on Monday produced some large ( size 2 ) avalanches that gained mass with the available moist snow.

On Sunday. In the alpine numerous remotely trigger very large avalanches (size 2.5) have been reported. These were described as failing on the December 22nd facet interface/ Persistent weak layer on north east aspects with crown depths averaging 40 cm and gaining significant mass and running far, upwards of 400 meters in length.

Past avalanche activity Friday reported several remote avalanches that were large (size 2). Wind loaded features stepped down to a persistent slab, failing on the December 22nd, December 17th or November 21st layers.

Read about their decision making after triggering the first avalanche here.

Mondays warm and wet cycle cooled overnight and a thin melt freeze crust has formed on the surface. Wind and storm slabs have accumulated over layers of either facets, surface hoar or a crust. Strong westerly winds have been redistributing snow into wind loaded features in treeline and alpine terrain.

The snowpack is becoming increasingly complex with several deeper instabilities that may persist through the season, and sustained past cold temperatures had continued to facet (weaken) the snowpack. Layers of concern in this snowpack:

• The latest snowfall sits on a surface hoar layer from late December. Recent reports indicate the storm snow is very sensitive to human and remote triggers.

• An early December layer of surface hoar in sheltered areas and a thin sun crust in open south-facing terrain is buried approximately 40-50 cm deep. This layer has recently produced surprising avalanches in upper treeline and lower alpine terrain features.

• The most concerning layer buried in mid November is made up of large surface hoar crystals, facets, and a melt-freeze crust and can be found up to 80 cm deep. This layer has been reactive at treeline between 1700 to 2200 m, on all aspects.

Tuesday Night

Heavy snowfall will continue with 10-25 cm expected overnight. Sustained strong southwesterly wind 70 to 80 km/h . Alpine temperatures warming to or above -1°C as freezing levels may for a brief period reach 2500 m.

Wednesday

Snowfall, 1 to 5 cm. Moderate southwest winds 30 to 40 km/h. Freezing levels maintain at 1000 m. Alpine temperatures -3°C

Thursday

Snowfall very light , with trace amounts. Freezing levels will descend to near valley bottom by days end Moderate to light south wind 20 to 30 km/h.

Friday

Snowfall, light 1 to 2 cm. Freezing levels near valley bottom. Light southwest winds 20 to 30 km/h.

More details can be found in the Mountain Weather Forecast.

• Use increased caution at all elevations. Storm snow is forming touchy slabs.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.