Avalanche Forecast

Issued: Feb 25th, 2018 3:34PM

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

jlammers, Avalanche Canada

Purcells.

Expect new snow and strong winds to form wind slabs and grow fragile cornices. Cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface. Avoid wind loaded areas with pillowy or chalky looking snow.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Monday: Mix of sun and cloud / Moderate to strong westerly winds / Alpine temperature of -16Tuesday: Light flurries / Moderate to strong westerly winds / Alpine temperature of -12Wednesday: Light flurries / Light and variable winds / Alpine temperature of -13

Avalanche Summary

No new avalanches were reported on Friday, although smaller human-triggered wind slab avalanches should be expected in exposed higher elevation terrain.Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.

Snowpack Summary

Light amounts of new snow now cover storm snow totals from last week that range from15-30 cm, with closer to 50 cm in the very south of the region near Kimberley. Winds have redistributed these accumulations into deeper, reactive slabs in wind-exposed terrain. These accumulations sit on an interface that was buried mid-February consisting of; a mix of older wind slabs in exposed higher elevation terrain, a sun crust on steep solar aspects, and surface hoar on sheltered slopes. Several recent avalanches have failed on this layer in the past week.Within the mid and lower snowpack are several persistent weak layers that are beginning to show signs of improving but still remain suspect. Two surface hoar/ crust layers buried in January are now 80-120 cm below the snow surface. At least one of these layers can be found on all aspects and elevations.Deeper in the snowpack ( about 150 cm deep) is a facet/crust/surface hoar layer buried in December that is most prevalent at treeline elevations and below.Near the base of the snowpack is a crust/facet combo layer buried in late November.

Problems

Wind Slabs

Light amounts of new snow and strong winds will create wind slabs in many areas in the alpine, as well as open areas at lower elevations. These slabs may be especially deep and touchy in wind-loaded areas on the leeward side of ridges.

Be cautious as you transition into wind affected terrain.Stay off recent wind loaded areas until the slope has had a chance to stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Persistent Slabs

Buried weak layers exist in the snowpack and may be reactive to large triggers such as a cornice or step down from a wind slab release. Human triggering may also be possible in shallow or thin, rocky, unsupported terrain.

Avoid steep convexities or areas with a thin or variable snowpack.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Feb 26th, 2018 2:00PM