Avalanche Forecast

Issued: Apr 8th, 2014 9:29AM

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

swerner, Avalanche Canada

South Coast.

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: Cloudy with 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 SW. Freezing levels rising to 1900 m.

Avalanche Summary

No new observations have been reported. On Sunday, small loose dry avalanches were seen from steep rocky terrain features. Loose wet avalanches were also seen on solar aspects. Natural avalanche activity may spike with solar radiation on Wednesday. Large, weak sagging cornices threaten slopes below if they fail.

Snowpack Summary

Up to 20 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. Surface snow has become moist on most aspects with the warmer temperatures and rising freezing levels. Large sagging cornices threaten slopes and could fail when the sun comes out. Snowpack tests have been producing hard resistant planar shears on the late March crust down 30-50 cm and the upper snowpack has strengthened.A couple persistent weak layers exist deeper in the snowpack. 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 large triggers like cornice fall.

Problems

Wind Slabs

Strong SW winds have set up isolated wind slab problems on leeward slopes, behind ridge crests and mid slope features like ribs/rock outcroppings. Sagging cornices may become weak with warming and solar radiation.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>Give cornices a wide berth when travelling on or below ridges.>

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 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

With warmer temperatures, limited overnight re-freeze and sunny periods on Wednesday, loose wet avalanches are likely.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid slopes when temperatures rise and the surface snow becomes moist or wet. Signs of instability are pinwheels and natural avalanches. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

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