Avalanche Forecast

Issued: Apr 6th, 2012 10:19AM

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

swerner, Avalanche Canada

South Columbia.

Summary

Confidence

Good

Weather Forecast

A very benign weather pattern will bring little precipitation, convective cloud, light winds and sunny periods over the next few days. Saturday: Scattered convective cloud cover, accompanied by light precipitation before lunch. Ridgetop winds light from the W-NW. Alpine temperatures near zero. Freezing levels 1800m falling to valley bottom at night. Sunday/Monday: A dominating ridge with diurnal temperature swings, freezing levels rising to 2000 m, and light ridgetop winds continue. Monday the ridge will start to break down and bands of cloud cover may exist later in the day.

Avalanche Summary

On Thursday reports from the region indicated many natural loose, and loose slab avalanches up to size 2 that are either wind slabs or moist loose slides due to solar warming. In the North Westerly areas of the region, an operator reported a couple skier remote slab avalanches up to size 2. These occurred on E-S aspects, above 2000 m, on the March 27th layer. Previous reports from last weekend or early in the week include remotely triggered size 3 and a natural avalanche with a 2 km wide crown was reported on an east facing aspect which started in the storm snow and then stepped down to the March 27th crust/facet combo. These shouldn't be forgotten yet; especially this weekend.

Snowpack Summary

Recent snow accumulations range from 20-40 cm over the past few days. 40-80 cm of snow from the past week is sitting on a reactive weak layer over a crust. This weak layer was buried March 27th in the Interior. We've received recent reports from the field of large, destructive avalanches occurring on this layer. Remote triggering (from afar) has also been reported. This indicates the likelihood and potential sensitivity of this layer. Slopes below 1000 m continue to experience little or no overnight refreeze (recovery). The deeper early February surface hoar layers seem to have been unreactive in the short term but still remain a concern with very heavy triggers such as a cornice fall, or step down avalanches.

Problems

Storm Slabs

Recent storm snow may become reactive under sunny skies. Smaller storm slab avalanches may trigger a deeper instability relating to a crust 40 to 80 cm deep; especially on south facing slopes. Watch the sun and afternoon warming.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Cornices

Large, looming cornices exist and may become weak with daytime warming and solar radiation. They could trigger deeper instabilities on slopes below. Wind slabs are touchy to rider triggers on lee slopes, behind terrain features, and gullies.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 7

Loose Wet

Warming temperatures, sunny skies with intense solar radiation are likely to trigger avalanches on sun exposed slopes. Pinwheels, snowballing and point release slides from rocky outcrops are initial indicators of the snowpack deteriorating.

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Valid until: Apr 7th, 2012 9:00AM