Avalanche Forecast

Issued: Mar 24th, 2013 8:06AM

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

danyelle magnan, Parks Canada

Glacier.

Afternoon cloud reduced the effects of the sun yesterday. Today should be mostly sunny- which will increase danger. Cornices are the biggest concern right now; they are large and weak, and likely to fail with the strong sun.

Summary

Weather Forecast

Lots of sun, warming temperatures, and calm to light SW winds are expected today and Monday. High cloud may form this afternoon and reduce solar inputs. Solar aspects, starting with easterly in the mornings, will receive strong solar. By Monday, air temps will be closer to 0'C and the effects of the sun will be greater. Clouds will increase on Tues

Snowpack Summary

Cool temps and clouds have reduced solar effects; a sun crust has formed only on steep, solar aspects. Elsewhere, 25cm of dry snow exists above 1400m. Tests on two surface hoar/crust layers in the top 1.5m indicate that they may be triggered by large loads (like cornices) in some areas (most likely on solar aspects). The snowpack below is strong.

Avalanche Summary

Natural avalanches were triggered during sunny breaks yesterday. 7 size 2 to 2.5 avalanches were observed mid day from solar aspects. Many were loose, with moist debris and a few triggered slabs. Very large cornice failures were reported throughout the Selkirks yesterday. One cornice failure was reported to be 120m long and triggered a size 4!

Confidence

Intensity of incoming weather systems is uncertain

Problems

Cornices

Look up lots today and avoid slopes with cornices above them. Cornice failures are expected due to daytime warming or by people traveling along ridges. A section of cornice hurtling down slope is a real concern, it may also trigger slab avalanches.

Do not travel on slopes that are exposed to cornices overhead.Stay well to the windward side of corniced ridges.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 4

Loose Dry

It may take a while for temps to warm up today, but when they do loose avalanches are possible due to strong solar. This is especially likely on steep solar aspects and around cliff and rocky outcrops. Loose avalanches may trigger deeper slabs.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. 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

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Isolated wind slabs in the alpine and near ridge crests have surprised a few skiers. These likely exist in steep, aggressive terrain where even a small avalanche could have severe consequences.

Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Mar 25th, 2013 8:00AM