Avalanche Forecast

Issued: Dec 29th, 2014 8:46AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Persistent Slabs and Wind Slabs.

ghelgeson, Avalanche Canada

South Coast.

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

Summary

Confidence

Fair

Weather Forecast

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.

Avalanche Summary

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.

Snowpack Summary

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.

Problems

Persistent Slabs

A touchy layer of buried surface hoar crystals has been responsible for numerous small avalanches over the past few days.

Avoid spots where you're more likely to trigger larger avalanches: thin spots, rock out-croppings, convex rollers and broad planar slopes without anchors like trees.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Wind Slabs

Modified outflow winds are likely forming recent storm snow into fresh sensitive wind slabs in unusual locations at and above treeline.

Travel on ridgetops to avoid wind slabs on slopes below.>Avoid travelling in areas that have been reverse loaded by winds.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 30th, 2014 2:00PM