Avalanche Forecast

Issued: Mar 19th, 2012 10:06AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Another Pacific frontal system begins to track inland from the Coast late tonight into Tuesday. This will bring more snow, wind and rising freezing levels. Tuesday: Snow amounts near 5 cm overnight, another 10-15 cm during the day. Ridgetop winds strong from the West. Treeline temperatures near -2. Freezing levels 1100-1300 m. Wednesday: Convective weather pattern, cloudy with flurries. Ridgetop winds through the day up to moderate from the West. Treeline temperatures near -5. Freezing levels valley bottom. Thursday: Moderate to heavy snow amounts expected. Ridgetop winds strong from the SW. Freezing levels may spike up to 1300 m.

Avalanche Summary

No new reports on Monday. On Sunday, a size 1.5 avalanche released naturally on a north aspect. On Saturday, a recent avalanche was observed on a north aspect in the southern Elk Valley, suspected to have started as a wind slab and ending in moist snow. Evidence of a previous natural cycle was also reported. On Friday, explosives produced size 1-2 avalanches.

Snowpack Summary

Unsettled weather has brought snow and wind through most of the week, creating variable wind slabs and storm slabs. On Saturday, snowpack tests in the Elk Valley, east of Sparwood, showed a couple of shears in the top 20cm of storm snow. A rain crust is buried about 1m down. Two surface hoar layers, buried in February and now 1-2m deep, exhibited sudden planar results, which have been repeated in a number of locations. This means they still have the potential to produce widely-propagating, destructive avalanches if triggered. Most likely triggering mechanisms are a person traveling on a thin snowpack area, or a storm slab, wind slab or cornice stepping down. Basal facets may still exist, particularly in shallow snowpack areas with steep, rocky start zones. Cornices have grown large and threaten slopes below.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs can be found behind ridges and terrain breaks. Large cornices also threaten slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Storm Slabs

An icon showing Storm Slabs
New snow will continue to build storm slabs. Storm snow may release naturally with the first blast of sun. It's possible for surface avalanches to step down to a weak persistent layer, initiating large destructive avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 6

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Persistent weak layers, now buried 1-2m deep, still have the potential to produce large and dangerous avalanches. They could be triggered by cornice fall, smaller avalanches stepping down, and under the weight of a snowmobile and rider.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

4 - 8

Valid until: Mar 20th, 2012 9:00AM