Avalanche Forecast

Issued: Apr 4th, 2014 9:30AM

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.

jfloyer, Avalanche Canada

Sea To Sky.

What's going to happen to the snowpack if it warms up significantly on Sunday/Monday/Tuesday? Read a discussion here...

Summary

Confidence

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

Weather Forecast

Synopsis: Moderate precipitation expected on Saturday before a ridge of high pressure builds for Sunday and Monday. Saturday: Approximately 10 cm new snow expected with freezing levels around 1200 m. Winds 30-40 km/h from the SW. Sunday: Scattered showers in the morning, becoming dry in the afternoon with some sunny breaks. Freezing levels around 1200 m. Winds 20-30 km/h from the NW. Monday: Dry. Sunny in the morning, becoming more cloudy in the afternoon. Warm, with freezing levels rising to 2200 m.

Avalanche Summary

No avalanches were observed on Thursday. I expect some relatively small storm slab avalanches occurred on Friday in response to the new snow.

Snowpack Summary

In most higher elevation areas, 15-20 cm of new snow sits on a mix of surface hoar, small grained facets and melt freeze crusts.Recent warm temperatures have helped to settle and strengthen the upper snowpack. Down 15 - 70 cm below the surface, snowpack tests are still producing hard resistant planar shears on the late March crust.The mid March surface hoar/ crust interface now down 80 - 110cm is decreasing in it's 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.The lower snowpack is strong and well settled.

Problems

Storm Slabs

New snow with strong SW winds has set up storm and wind slab problems on steep lee terrain features. Watch for sensitive storm slabs lee of both ridge crest and mid slope features like ribs/rock outcroppings.

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

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.

Be aware of the potential for large, deep avalanches due to the presence of buried facets and surface hoar.>Extra caution needed around cornices with current conditions.>Consider backing off steep, aggressive terrain if the temperature warms considerably or if the sun hits the slope you are riding.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Apr 5th, 2014 2:00PM