Avalanche Forecast

Issued: Mar 25th, 2017 4:01PM

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

cgarritty, Avalanche Canada

Sea To Sky.

Give storm slabs a chance to heal to the surface before stepping into bigger terrain. Steep, unsupported, and/or convex features will harbour instability for the longest.

Summary

Confidence

High -

Weather Forecast

Sunday: Cloudy with flurries bringing 5-10 cm of new snow. Moderate southeast winds. Freezing level to 1300 metres with alpine temperatures of -4.Monday: Cloudy with scattered flurries and a trace to 5 cm of new snow. Light southwest winds. Freezing level to 1400 metres with alpine temperatures of -4.Tuesday: Periods of snow bringing 15-20 cm of new snow. Moderate to strong southwest winds. Freezing level to 1400 metres with alpine temperatures of -3.

Avalanche Summary

Reports from Friday included numerous observations of storm slabs releasing generally from Size 1-1.5 with ski cutting and explosives control in the Whistler area. One natural Size 2 wind slab was reported as well as one remotely triggered Size 1.5 cornice. Crown fractures were typically 20-40 cm deep.Reports from Thursday showed explosives control in the Whistler area producing storm slab releases to Size 2. Crown fractures were generally 50-100 cm thick.Looking forward, storm slabs will likely remain reactive to human triggering on Sunday. At upper elevations, the deeper mid-February weak layer has been trending toward a low likelihood of triggering. However, with heavy storm slab and cornice triggers now widely available, it would be best to consider the potential for reactivity at this layer in your terrain selection.

Snowpack Summary

After another 25 cm of new snow fell over the region on Thursday night through Friday, roughly 50 cm of wind affected new snow now lies above a crust that formed over last week's storm snow. This crust exists at about 2000 metres and lower. Beneath the previous storm snow, an older rain crust that formed last week is now buried about 80-100 cm deep. The mid-February crust/facet layer can still be found at the upper end of treeline and into the alpine. This interface is now 125-165 cm deep and may be over 230 cm deep in wind loaded terrain. Although there is growing confidence in this layer becoming dormant, continued caution is warranted while our newly formed storm slabs remain triggerable. A big enough storm slab or cornice release in the right location may have the potential to coax this layer into reacting.

Problems

Storm Slabs

Expect our newly formed storm slabs to be especially thick and reactive at higher elevations and in the lee of terrain features that are exposed to the wind. Remember that the potential for human triggering persists as natural avalanching tapers off.

Be increasingly cautious as you transition into wind affected terrain.Dig down to find and test the storm snow interface before committing to bigger terrain.Be alert to conditions that change with aspect and elevation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Cornices

The warm, wet, and windy storm has seen cornices grow fat. While they are a hazard in themselves, the danger increases when they have the potential to act as a trigger to storm slabs sitting beneath them.

Even small cornice falls may trigger larger avalanches.Pay attention to overhead hazards like cornices.Extra caution needed around cornices with current conditions.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 26th, 2017 2:00PM