Avalanche Forecast

Issued: Feb 26th, 2017 5:12PM

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

shorton, Avalanche Canada

Purcells.

Watch for shallow snowpack areas where triggering persistent slab avalanches remains possible.

Summary

Confidence

High - Due to the number and quality of field observations

Weather Forecast

MONDAY: Continued light flurries with 2-4 cm of new snow, light southwest winds, alpine temperatures around -15 C.TUESDAY: Mix of sun and cloud with isolated flurries, light west winds with moderate gusts, alpine temperatures around -15 C.WEDNESDAY: Light flurries with 4-8 cm of new snow, moderate west winds, alpine temperatures around -12 C.

Avalanche Summary

No notable avalanches were reported on Saturday. On Friday, several skier triggered size 1-1.5 slabs were reported on steep convex alpine features. Several large natural persistent slab avalanches have been reported on the western slopes of the Purcells, including a cornice triggered size 3.5 avalanche on the November crust and two size 2.5 avalanches the February 3rd surface hoar. Last week, three larger skier triggered avalanches were reported including a remotely-triggered size 3 persistent slab near Golden.

Snowpack Summary

Flurries delivered another 2-5 cm of low density snow on Saturday night, bring recent totals from the last week up to 15-40 cm. A pulse of moderate winds from a variety of directions formed fresh thin wind slabs at higher elevations. The recent snow has buried the mid-February interface, which is composed of a thick rain crust up to about 2000 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. Several deeper weak layers remain a concern including the February 3rd interface (40-80 cm deep) in the southern Purcells and the mid-January interface in the northern Purcells (about 100 cm deep). Basal facets may still be a reactive in shallow rocky start zones.

Problems

Persistent Slabs

Several persistent weak layers buried 50-100 cm deep remain a concern (surface hoar, facets, and crusts). Slopes with thin or variable snowpack are the most suspect trigger points.

Be aware of the potential for large avalanches due to the presence of deeply buried weak layers.Avoid steep convexities or areas with a thin or variable snowpack.Avoid lingering in runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Watch for fresh wind slabs developing on lee and cross-loaded terrain.

Use caution above cliffs where small avalanches may have severe consequences.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 27th, 2017 2:00PM