Avalanche Forecast

On Tuesday numerous storm slab, wet loose and wet slab avalanches have been reported. These avalanches had been explosives triggered, skier controlled and natural. The sizing of theses avalanches varied, a few small (size 1) with many of them large to very large (size 2 to 3). The reports indicate that the avalanches gained mass as they entrained the moist snow below.

On Monday, explosive avalanche control produced a few avalanches with one very large avalanche (size 3) running up to 800 m in length. It was noted this avalanche stepped down to the the late November persistent weak layer and confirms suspicions that in specific terrain this layer of concern is reactive.

Over a week ago a natural size 2.5 persistent slab avalanche was reported. This avalanche occurred on a northeast aspect, 2000 m on a reloaded bed surface.

Monday's and Tuesday warm and wet weather cycle, has saturated the upper snowpack all the way up to 2200 m. During the past storm's precipitation amounts of 120 mm that totaled snowfall amounts of 20 to 40 cm were recorded. This new snow was redistributed by strong southerly winds. Larger deposits in east and north facing terrain can now be found and has formed new wind slabs. Slabs have formed over a variety of surfaces including; facets, surface hoar and a crust, Essentially they are moist and unconsolidated and not bonding very well.

Around 50 cm deep a layer of surface hoar at treeline and a thin crust on steep south facing slopes exists buried in early December.

The primary concern in the snowpack is the mid-November layer consisting of facets and surface hoar, buried around 80 to 120 cm deep. This layer is likely to become reactive as temperatures and the weight of snow and rain increase the load

The lower snowpack presents as primarily facetted combined with depth hoar. Ice has been reported to exist at the base in a few different locations.

The snowpack in the forecast region is quite variable with snowpack depths at treeline varying from 100 cm to 200 cm.

Wednesday Night

Cloudy with 1-5 cm of mixed precipitation expected. Moderate southwest wind 40 km/h. Freezing levels 750 m with a brief period at 1200m. Alpine high temperatures of -1°C.

Thursday

Cloudy with mid day clearing expected. Very light snowfall trace amounts. Moderate southwesterly wind 30 km/h. Freezing levels at valley bottom with a mid day rise excepted to reach 700 m. Alpine temperatures -3°C.

Friday

Cloudy with light snowfall 1 to 5 cm. Light to moderate southwesterly winds 20 to 40 km/h. Freezing levels at valley bottom rising to 1000m mid day, Alpine high temperatures -1°C.

Saturday

Cloudy with very light snow trace amounts. Light southwesterly wind. Freezing levels at valley bottom, alpine temperatures dropping to -9°C.

More details can be found in the Mountain Weather Forecast.

• Storm slab size and sensitivity to triggering will likely increase through the day.
• Watch for fresh storm slabs building throughout the day.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.