Avalanche Forecast

Issued: Apr 5th, 2014 9:42AM

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

swerner, Avalanche Canada

Sea To Sky.

What's going to happen to the snowpack if it warms up significantly over the next couple of days? Read a discussion here...

Summary

Confidence

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

Weather Forecast

Unsettled conditions, bringing light-moderate precipitation amounts, rising freezing levels and mostly cloudy skies through Monday. Tuesday will show the brunt of the frontal system and bring moderate-heavy precipitation.Sunday: Freezing levels rising to 1500 m. Mostly cloudy skies with possible sunny periods. Alpine temperatures near 1.0 degree. Ridgetop winds generally light from the SW with strong gusts. Monday/ Tuesday: Freezing levels rising to 2000 m with no re-freeze overnight. 15-20 mm expected each day and alpine temperatures near 2.0 degrees. Ridgetop winds remain strong from the SW.

Avalanche Summary

On Friday, a deep persistent slab avalanche occurred on a NE aspect at 2400 m. It is suspect that it failed on the mid-March interface. Additionally, numerous size 1 storm slab avalanches were easily triggered by the weight of a person on leeward loaded slopes and on slopes that have the recently buried melt-freeze crust.

Snowpack Summary

Higher elevation areas have recently received up to 20 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 melt-freeze 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.Persistent weak layers exist lower in the snowpack. The mid-March surface hoar/ crust interface now down 80-110 cm and is decreasing in sensitivity to triggering. 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 refreeze through the forecast period. These layers may re-awaken.

Problems

Storm Slabs

New snow and wind has set up storm and wind slab problems on leeward terrain features. They are easily triggered by riders, and could be naturally triggered if the sun shines through, even if its for a short period of time.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain and be weary of solar slopes if the sun shines through.>

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, but I would be concerned about an increased likelihood of a large destructive event during a period of intense warming.

Consider backing off steep, aggressive terrain if the temperature warms considerably or if the sun hits the slope you are riding.>Extra caution needed around cornices with current conditions.>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 6th, 2014 2:00PM