Avalanche Forecast

Issued: Feb 20th, 2015 7:38AM

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

Peter, Avalanche Canada

South Columbia.

A good dusting of fresh snow should improve the snow quality but watch for deep and touchy pockets of wind slab in wind exposed terrain.

Summary

Confidence

Good

Weather Forecast

The ridge of high pressure rebuilds and should result in clearing skies in most parts of the Province. However, there is a weak cold front sliding in from the east that could bring cloud and light snow to parts of the Southern Interior (particularly the east side of Purcells). By Sunday all regions should be enjoying sunny skies. The freezing level on Saturday is 500-1000 m and it bumps up a couple hundred metres each day. Ridge winds are light gusting to moderate from the NW to NE.

Avalanche Summary

Avalanche activity has gradually tapered off throughout the week. On Thursday there were a couple reports of natural cornice falls, but these did not trigger slabs. There were also a few reports of size 1 skier controlled wind slabs from East facing slopes. These were typically around 20 cm deep. Wind slabs could build and remain sensitive to rider triggering throughout the weekend.

Snowpack Summary

A dusting of new snow (around 10 cm) covers the previous variable snow surface of surface hoar, crusts, dry facetted snow, or wind affected snow depending on aspect and elevation. The "Valentine's Day" crust is just below the surface and is now strong and thick in most places. New wind slabs may have formed in lee terrain from recent W-NW winds, and cornices remain large and weak. The late-Jan crust/surface hoar layer (up to 100 cm deep) and the mid-January surface hoar (80-120 cm deep) continue to give variable results in snowpack tests. Chances of triggering these weaknesses have decreased, but triggering may be possible from thin or rocky snowpack areas; or perhaps with a cornice fall, or an avalanche stepping down, especially on sun drenched slopes.

Problems

Wind Slabs

A bit more snow than forecast fell on Thursday and was accompanied by moderate W-NW winds. Expect to find touchy pockets of wind slab on exposed lee slopes and cross-loaded gully features.

Give cornices a wide berth when travelling on or below ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Buried persistent weaknesses are largely dormant but could still be triggered by a large load (i.e. cornice fall) or from areas with a shallow or variable snowpack.

Avoid steep slopes below cornices.>Avoid common trigger points like convexities or areas with a thin or variable snowpack.>

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

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Feb 21st, 2015 2:00PM