Avalanche Forecast

Issued: Apr 5th, 2014 9:39AM

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

swerner, Avalanche Canada

South Coast.

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

A mix of sun and cloud for Sunday. Unsettled conditions, bringing light-moderate precipitation amounts, cloudy skies and rising freezing levels through Tuesday. Sunday: Mix of sun and cloud. Freezing levels rising to 1600 m. Alpine temperatures near zero degrees. Ridgetop winds moderate from the SW.Monday/ Tuesday: Freezing levels rising to 1700 m with no re-freeze overnight. Up to 20 mm expected by Tuesday. Alpine temperatures near 2.0 degrees. Ridgetop winds remain strong from the SW.

Avalanche Summary

On Wednesday, a cornice fall on a steep north facing features at 2300m initiated a size 3 avalanche. It likely ran on the early March melt-freeze crust.Small loose dry avalanches were seen from steep rocky terrain features. Loose wet avalanches were also seen on solar aspects. I suspect natural activity will continue with the solar influence on Sunday and the warmer temperatures through Monday/Tuesday. Smaller surface avalanches may trigger deeper weak layers, especially in thinner snowpack areas.

Snowpack Summary

Up to 15 cm of new snow sits above a mix of surface hoar, facets and melt freeze crusts. The new snow seems to have a poor bond to old surfaces and isolated wind slabs likely exist. Solar radiation will likely weaken the snow surfaces and become moist or wet. Recent warm temperatures have helped to settle and strengthen the upper snowpack and snowpack tests have been producing hard resistant planar shears on the late March crust down 30-50 cm. The persistent weak layers from early March and early February continue to be a concern. The March melt-freeze crust/surface hoar is reported to be down 60 - 100cm. The February crust/facet/surface hoar layer is now deeply buried down 150 - 250cm. These layers are mostly inactive at this time, but could re-awaken with extended warming, solar influence and precipitation through the forecast period.

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.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

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, 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.>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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Loose Wet

The sun really packs a punch this time of year, so avoid and/or use caution and good timing on solar slopes if its sunny. A good indicator of weak snow is snowballing and wet or moist surface snow.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Apr 6th, 2014 2:00PM