Avalanche Forecast

Issued: Apr 3rd, 2015 9:31AM

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

bcorrigan, Avalanche Canada

Sea To Sky.

Use caution when venturing into big terrain. Persistent weaknesses buried in the snowpack are still capable of producing large destructive avalanches.

Summary

Confidence

Good - Forecast snowfall amounts are uncertain

Weather Forecast

5-10 cm of snow overnight and into Saturday morning.Â This weather system should be out of the Sea to Sky region by Saturday afternoon, giving us clear skies and sunny conditions into next week. Daytime freezing levels are expected to be around 1500 m for the forecast period. Moderate southwesterly alpine winds are expected tonight, then light but gusty south-westerlies for the weekend.

Avalanche Summary

Two reports of large natural avalanches on NE and W aspects from yesterday, and explosive testing by one commercial operator produced a large, 2.5 hard slab avalanche.

Snowpack Summary

Up to 25 cm of low density storm snow is sitting on a thin breakable crust that caps 30-40 cm of recent moist snow on rain crust buried last Saturday. Reports suggest this 5 cm thick solid rain crust exists up to at least 2200m. Strong southwest winds have shifted these new accumulations into touchy wind slabs in exposed terrain. A facet/crust persistent weakness buried mid-March is down approximately 70-130 cm and is still producing hard but sudden results in snowpack tests. This remains the chief concern amongst avalanche professionals in the region due to it's potential for very large avalanches.

Problems

Persistent Slabs

Low probability, high consequence conditions exist these days. Hitting the "trigger" on a big slope could produce a very large destructive avalanche.

The new snow will require several days to settle and stabilize.>Be aware of the potential for large, deep avalanches due to the presence of a buried crust/facet layer.>Avoid convexities or areas with a thin or variable snowpack.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Storm Slabs

Redistribution of storm snow has turned storm slabs into wind slabs in lee terrain on all aspects at treeline and above

Be alert to conditions that change with elevation.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Apr 4th, 2015 2:00PM