Avalanche Forecast

Issued: Apr 17th, 2015 9:10AM

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

swerner, Avalanche Canada

Northwest Inland.

Cloud cover, warm alpine temperatures, localized solar radiation, and rain will deteriorate the snowpack. Use a conservative approach to terrain and watch for signs of instabilities.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

Most of the North Coast regions will see unsettled conditions through the weekend. A dominating ridge of high pressure over southern BC will push North by late Sunday keeping a well-organized storm offshore. Saturday will see mostly cloudy skies and ridgetop winds light from the SW. Alpine temperatures will rise to 0 degrees and freezing levels will be near 1500 m. On Sunday, light precipitation and moderate SW winds is expected. Alpine temperatures near 5 degrees and freezing levels rising to 2400 m. Influence from the upper level ridge will see freezing levels rise to 2400 m through Monday and rain up to 10 mm. By late Monday, the ridge starts to break down allowing a more seasonally westerly flow.

Avalanche Summary

Slab avalanches up to size 2 were reported in the Mt. Leach area on mostly north facing slopes. On Saturday, touchy wind slabs and storm slabs are likely, especially in areas that receive higher snowfall amounts. If the sun pokes out, solar radiation will be strong and deteriorate the upper snowpack. Watch overhead hazards like cornices, solar triggered loose and slab avalanches.

Snowpack Summary

Recent storm snow has likely formed touchy storm slabs. Strong westerly winds have redistributed this new snow and has formed wind slabs on leeward slopes and behind terrain features. Solar aspects may have a sun crust from recent localized solar radiation. The lack of bond between the new wind slabs and storm slabs over the older snow surfaces buried on April 9 th (surface hoar, crusts and facets) are the primary concern. The March 25th surface hoar / crust layer is reportedly unreactive, however; it should remain on your radar as it may re-awaken with the new load of snow, wind and effects from warming. Large ripe cornices are also of concern and will be a problem with additional loading, especially when the sun and warm temperatures come back.

Problems

Wind Slabs

Strong winds have redistributed recent storm snow into wind slabs on leeward slopes. They are especially touchy where they sit on buried facets, surface hoar and/ or crusts. Cornices are large and may weaken with solar radiation.

Pay attention to overhead hazards like cornices, especially if the sun is shining.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Additional snow loading on the mid- March persistent weak layer could bring it back to life. Smaller slab avalanches may step down to this layer, initiating large and destructive avalanches.

Dig down to find and test weak layers before committing to a line.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar, facets and/ or a crust.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Loose Wet

Solar radiation and warmer temperatures will deteriorate the snowpack quickly. Travel on sunny slopes early, and watch for signs of instabilities like avalanches, moist surface snow and snowballing.

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

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Apr 18th, 2015 2:00PM