Avalanche Forecast

Issued: Apr 7th, 2014 9:42AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs, Deep Persistent Slabs and Loose Wet.

swerner, Avalanche Canada

Sea To Sky.

Check out the new Forecaster Blog to gain insight of how to manage cornices, and how warming influences the snowpack.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

Precipitation and strong SW winds will prevail as the cold front moves across the region Tuesday. Tuesday: Snow amounts up to 25 cm. Freezing levels 1900 m then dropping overnight to valley bottom. Ridgetop winds moderate from the SW. Wednesday/ Thursday: Mainly cloudy with possible sunny breaks in the afternoon and some flurries expected. Ridgetop winds light from the West. Freezing levels near 1200 m.

Avalanche Summary

Numerous size 1 wind slab, loose dry and loose wet avalanches were reported on Sunday. One size 2.5 slab avalanche was also reported and the failure plane was a buried crust, no other details noted. Cornices are sagging, with one failure a couple of days ago. With new snow and strong winds forecast for Tuesday, I suspect natural avalanche activity will be on the rise.

Snowpack Summary

Higher elevation areas have recently received up to 25 cm of new snow which sits on a variety of old snow surfaces including surface hoar, facets and melt freeze crusts. Isolated wind slabs have formed and a poor bond seem to exist, especially on slopes with a buried crust.Recent warm temperatures have helped to settle and strengthen the upper snowpack and tests are producing hard resistant planar shears on the late March crust. Below 1800 m a spring-like melt-freeze snowpack exists.Persistent weak layers exist lower in the snowpack. The mid-March surface hoar/ crust interface now down 80 -110 cm. The early-March crust/facet 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 re-freeze.

Problems

Storm Slabs

New snow and wind will form new slabs. A poor bond may exist, especially on slopes with a buried crust. Natural avalanche activity is possible for tomorrow and rider triggers are likely. Sagging cornices are a concern with warming.

Extra caution needed around cornices with current conditions.>Use extra caution and be conservative if you transition onto leeward slopes. Recent wind loading have created touchy wind slabs.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

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 cornice fall, a surface avalanche in motion, or intense loading from snow, and wind.

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

Loose Wet

Rising freezing levels, warm temperatures and an insignificant overnight re-freeze 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 - 3

Valid until: Apr 8th, 2014 2:00PM