Avalanche Forecast

Issued: Mar 20th, 2014 10:26AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Cornices and Deep Persistent Slabs.

jlammers, Avalanche Canada

South Rockies.

Watch the temperature and solar warming! Heat and cornices are two great ways to shake-up the snowpack over the next couple of days

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

Thursday night and Friday: Up to 20cm of snow overnight Thursday, becoming light on Friday / Light to moderate northwest winds / Freezing level at surfaceSaturday: Flurries with a mix of sun and cloud / Light to moderate northwest winds / Freezing level at surfaceSunday: Flurries with a mix of sun and cloud / Light to moderate northwest winds / Freezing level at surface

Avalanche Summary

On Wednesday a size 2 wind slab was accidentally triggered by a skier in the southeast corner of the region. The avalanche occurred on a northeast aspect at about 2600m. Although observations were limited, I expect there would have been a round of storm slab activity in response to new snow and wind on Thursday. Looking forward, continued snowfall will likely promote ongoing storm slab activity while intermittent sunshine may spark a loose wet avalanche cycle.

Snowpack Summary

At the time of publishing this bulletin up to 30cm of new snow had fallen and had been pushed by moderate to strong southwest winds into deeper deposits in exposed lee terrain. Below the new snow is a well settled storm slab which overlies a hard rain crusts. This crust exists on all aspects below 2000m and on solar aspects in the high alpine. North of Sparwood and in the Crow's Nest Pass area the buried crust seems more specific to previously sun-exposed slopes. The deep facet/crust persistent weakness buried at the beginning of February (now down up to 150cm) seems unlikely to trigger in areas where the hard, supportive near-surface crust exists. No matter where you are in the region, this weakness should stay on your radar as any activity at this interface would be large and destructive. Possible triggers include a large cornice fall, a large input in a thin snowpack area or solar warming.Cornices have also become large and unstable.

Problems

Storm Slabs

Significant snowfall and steady southwest winds have created a punchy new storm slab which exists at all elevations. Watch for triggering in wind-exposed terrain. If the sun comes out on Friday, the new snow may react as a loose wet avalanche.

Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

Cornices in the region are now very large and fragile. A cornice fall could be destructive by itself, and could trigger a large avalanche on the slope below.

Extra caution needed around cornices with current conditions.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

The deep weak layers that formed in early February may be more likely to trigger in the north of the region. Possible triggers at this point include a large cornice fall, a large force in a thin snowpack area or solar warming.

Caution around convexities or areas with a thin or variable snowpack.>Consider the consequences of the terrain if an avalanche steps down to a persistent weakness.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 21st, 2014 2:00PM