Avalanche Forecast

Issued: Apr 9th, 2014 9:49AM

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

swerner, Avalanche Canada

Sea To Sky.

How does warming and solar radiation influence the snowpack? How do I manage cornice problems? Check out the new Forecaster Blog.

Summary

Confidence

Good

Weather Forecast

An upper level ridge will keep the region fairly dry with a mix of sun and cloud through the forecast period. Thursday: Cloudy. Ridgetop winds light from the SW. Freezing levels near 1300 m. Friday: Cloudy with sunny periods and isolated flurries. Ridgetop winds moderate from the West. Freezing levels rising to 1400 m.Saturday: A mix of sun and cloud. Alpine temperatures rising to 6.0 degrees. Ridgetop winds light from the West. Freezing levels rising to 2100 m.

Avalanche Summary

On Tuesday, numerous loose wet avalanches occurred up to size 2.5 on all aspects and elevations . Cornices have become weak and some have failed triggering storm slabs up to size 2 on slopes below. Warming and sunshine may be the name of the game in the forecast period. Natural cornice failure and loose wet avalanches will likely continue. Trip planning, and proper timing will be required to help mitigate these avalanche problems.

Snowpack Summary

A melt-freeze crust exists on all aspects up to 2200 m, and dryer snow can be found on high northerly aspects. The recent warmer temperatures have helped to strengthen and settle the upper snowpack, especially on solar aspects. Isolated wind slabs have formed and are sensitive to rider triggers, especially on slopes with a buried crust. Large sagging cornices are looming over slopes and pose a threat, especially when the sun comes out.Snowpack tests are producing moderate shears down 15 cm failing on surface hoar below the early April crust and hard resistant planar shears on the late March crust. Several persistent weak layers exist lower in the snowpack. The mid-March interface down 80 -110 cm, the early-March layer is down about 100-150 cm and the early February layer is now down close to 200 cm. These layers are largely dormant at this time; however, they should remain on your radar as we begin to transition into a warm-up with minimal overnight refreeze and intense solar output.

Problems

Wind Slabs

SW winds have formed isolated wind slabs on lee slopes. A poor bond may exist, especially on slopes with a buried crust and rider triggers are possible. Sagging cornices are fragile and pose a threat. A cornice failure could trigger the slope below.

Extra caution needed around cornices with current conditions.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Wet

Warm temperatures and periods of solar radiation will likely make the upper snowpack weak and cohesionless.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Watch for clues and avoid slopes if you start to see pinwheels, moist and/ or wet snow surfaces and natural avalanche activity.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Deep Persistent Slabs

Three buried weak layers exist in the snowpack. Deep releases have become rare; however, the weak layers could be activated by a larger trigger like a cornice fall, or a surface avalanche in motion.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for large, deep avalanches due to the presence of buried facets and surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Apr 10th, 2014 2:00PM