Avalanche Forecast
Issued: Dec 12th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
ahanna,
Avalanche Canada
Southeast winds are forecast to pick up overnight into Sunday morning and at upper elevations there is plenty of soft snow to blow around. Watch for fresh wind slabs in lee features in the alpine and upper treeline.
Summary
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
Saturday night: Increasing cloud, moderate to strong southeast ridgetop wind, freezing level 500 m.
Sunday: Up to 5 cm new snow, moderate easing to light southwest ridgetop wind, alpine high -5C, freezing level 600 m.
Monday: 5-10 cm new snow, light southwest ridgetop wind, alpine high -7 C, freezing level 900 m.
Tuesday: 10-20 cm new snow, strong southwest ridgetop wind, alpine high -6 C, freezing level 1000 m.
Watch David Jones' Whistler Powder Picker weather report for the weekend here.
Avalanche Summary
Since Wednesday, both natural and human triggered avalanche activity has been mostly limited to small pockets of storm slab and loose dry sluffs confined to isolated features. On Saturday, a size 1.5 natural cornice fall was reported in this MIN from the Garabaldi area.
A widespread natural cycle occurred during the storm Monday night through Tuesday, storm slabs size 2-3 and loose wet size 1-2.
Have you been out and about in the mountains? If so please submit your observations to the Mountain Information Network (MIN). It doesn't have to be technical - photos are especially helpful! Thank you so much for all the great MINs submitted so far!Â
Snowpack Summary
At upper elevations, strong southwest overnight winds have likely redistributed 10-30 cm of dry snow sitting over a crust. A layer of surface hoar may be found within this recent snow.
At treeline and below, the crust continues to harden with cool temperatures but may still be somewhat punchy below 1900 m, with a moist snowpack below.
In the alpine, the crust is supportive. Sugary facets sit sandwiched between this surface crust ontop, and an ice lens 40-50 cm below the surface. The ice lens formed from the freezing rain that fell on the old snow surface at the beginning of the previous storm. Above 2100 m, it has been a failure plane for avalanches since the storm.
Snowpack depths change rapidly with elevation, with lower BTL barely at threshold, to 50-100 cm around treeline to over 200 cm in the alpine.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Wind slabs are most reactive during their formation.
- Keep in mind the crust offers an excellent bed surface for avalanches.
Problems
Wind Slabs
Strong southwest wind overnight has likely transported soft snow into fat pockets of reactive wind slab in leeward terrain features. The near surface crust offers a slick bed surface for avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 13th, 2020 4:00PM
