South Coast

Watch for fresh wind slabs in unusual locations at and above treeline Tuesday.

Fair

Synopsis: Arctic air to dominate for a few days, then warming from the north. Outflow winds should reach their peak Tuesday morning. By Tuesday afternoon warmer Pacific air associated with the offshore upper ridge should move inland opening the door to a potential inversion or an above freezing layer between 1500 & 2500m.Tuesday: Freezing Level: Valley Bottom; Precipitation: Nil; Wind: Treeline: Light, NW | Ridgetop: Strong, NE.Wednesday: Freezing Level: Valley Bottom, potential AFL 1500 to 2500m; Precipitation: Nil; Wind: Treeline: Light, NE | Ridgetop: Light, N/NW.Thursday: Freezing Level: Valley Bottom, potential AFL 1500 to 2500m; Precipitation: Nil; Wind: Treeline: Light, NW | Ridgetop: Light, NW.

On Friday, several size 1 avalanches were triggered by snowmobilers below treeline in the Coquihalla area. These are likely to have failed on the mid-December surface hoar layer down about 50cm. On Wednesday skiers reported whumpfing in the Coquihalla area. A week ago, storm slabs up to size 2.5 being remote-triggered from flat areas up to 75 m away in the Coquihalla area between 1600 and 1900 m elevation. Slabs were 40-70 cm thick and were releasing on the mid-December surface hoar layer.

New wind slabs are developing above a layer of buried surface hoar. A deeper layer of surface hoar from mid-December is buried about 60 cm down. The mid-December surface hoar layer is becoming harder to trigger, but snowpack tests are still showing that it has potential for wide propagation. It appears to be most reactive in sheltered treeline locations and may not exist across the entire region. A thick rain crust exists lower in the pack.