Avalanche Forecast

Issued: Apr 8th, 2014 9:36AM

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

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

Fair - Timing or intensity of solar radiation is uncertain on Wednesday

Weather Forecast

An upper level ridge will keep the region fairly dry with a mix of sun and cloud through the forecast period. Wednesday/ Thursday: Mainly cloudy with some sunny periods and isolated flurries. Ridgetop winds light-moderate from the west. Freezing levels near 1300 m. Friday: Mainly cloudy with isolated flurries. Ridgetop winds light from the West. Freezing levels rising to 1600 m.

Avalanche Summary

On Monday, a natural cornice release size 3 entrained recent storm snow and ran for approx. 1300m. Natural wind and storm slab avalanches up to size 2 occurred in isolated areas and numerous size 1 loose wet avalanches were observed at lower elevations.

Snowpack Summary

10-20 cm of moist surface snow sits on top of 20 cm of dryer snow which fell before the weekend. Isolated wind slabs currently have a poor bond (especially on slopes with a buried crust) over a medley of old snow surfaces including surface hoar, facets and melt freeze crusts. Large sagging cornices are looming over slopes and pose a threat if they fail.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 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. Larger triggers like cornice fall may be significant enough to activate these deeper layers.

Problems

Wind Slabs

Strong SW winds have formed new wind slabs on lee slopes. 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 could fail with warming.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible - 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 consistent strong wind.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Loose Wet

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Apr 9th, 2014 2:00PM