Avalanche Forecast

Issued: Feb 11th, 2018 5:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Cornices.

mgrist, Avalanche Canada

South Coast Inland.

Winds have formed pockets of reactive wind slab on leeward and cross-loaded slopes at upper elevations. Also keep an eye on what's above or below you. Cornices are large and may become fragile with warm temperatures or sun-exposure.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY: Mostly sunny. Ridge wind moderate, northwest. Temperature -5. Freezing level 500 m. Alpine inversion.TUESDAY: Mostly cloudy, light flurries. Accumulation up to 5 cm. Ridge wind moderate gusting strong from the west. Temperature -5. Freezing level 500 m. WEDNESDAY: Cloudy with some lingering flurries. Ridge wind moderate, northwest. Temperature -5. Freezing level 700m.

Avalanche Summary

On Saturday, skiers triggered a size 2 wind slab on a north east aspect near 2000m in the Duffey zone. See the MIN report for more details. Friday there were isolated reports of natural cornice triggered and wind slab activity up to size 2.5, as well as evidence of an older large, natural size 3.5, in high alpine terrain in the Duffey Lake area.On Thursday, the southern part of the region reported a natural slab avalanche size 3.5 from a NE-SE aspect near 1800 m and numerous wet slabs up to size 2.5. An avalanche control mission using explosives in the northern part of the region saw wind slab results up to size 1.5, only running in the surface snow and not stepping down deeper.

Snowpack Summary

Last week's snowfall totals are highly variable. In the south, up to 40 cm of new snow fell bringing the alpine totals up to 60 cm for the storm ending last week. In the north, new snow totals are half that and rapidly decrease below 1800m. This new snow remains unconsolidated in wind-sheltered, shaded areas at upper elevations but has formed wind slabs in open areas at treeline and above, and scoured areas at ridge crests. At lower elevations travel is rugged and some are recommending ski crampons below tree line (!) Below the snow surface, 80-150 cm down in the mid pack sits the mid- January crust. It generally shows signs of bonding to the overlying snow; however, I would remain suspect of this deeper layer while the snowpack adjusts to the new load. Thinner snowpack areas may have a higher likelihood of an avalanche failing on this layer. Large, looming cornices exist, they are fragile and demand respect.

Problems

Wind Slabs

Reactive wind slabs exist, especially on leeward slopes where more wind loading has occurred.

Be cautious as you transition into wind affected terrain.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Cornices

Recent snowfall and strong winds have created large fragile cornices. Cornices are unpredictable and demand respect. Give them a wide berth from above and below, especially during periods of warming or sun-exposure.

Give cornices a wide berth when traveling on or below ridgesFalling cornices may trigger large avalanches on slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3.5

Valid until: Feb 12th, 2018 2:00PM