Avalanche Forecast

Issued: Apr 23rd, 2014 9:16AM

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

triley, Avalanche Canada

Sea To Sky.

Forecast new snow and wind are expected to increase the avalanche danger. Check out this Blog Post for more information on spring ratings.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Thursday

Weather Forecast

Overnight and Thursday: Freezing levels falling down to 1000 metres overnight and rising to 1700 metres during the day. Precipitation starting overnight, bringing 5-10 cm of snow by morning combined with strong Southwest winds. Expect another 3-8 cm during the day.Friday: Winds becoming light Southerly overnight. Freezing level dropping to 1000 metres and then rising to 1700 metres. Chance of some broken skies with periods of strong solar radiation.Saturday: Mix of cloud and broken skies with some light precipitation, and light Northwest winds.

Avalanche Summary

Size 1 soft slab avalanches continued to result from ski-cutting and explosives control on Tuesday in the Whistler area. Some ridge tops had stiffer slabs up to 60 cm deep in isolated areas.

Snowpack Summary

A highly variable spring snowpack exists across the region and conditions can change rapidly throughout the day. At lower elevations below-treeline, the snowpack is isothermal and melting rapidly. At mid elevations, between roughly 1500 and 2000m (and higher on sunny slopes), the snowpack is undergoing daily melt-freeze cycles. In the mornings, a refrozen surface generally means good stability. In the afternoon when the surface melts, the stability can deteriorate quickly, especially on sunny slopes. The recent storm has produced dry snow in the alpine resulting in the formation of storm slabs and wind slabs which sit on an old crust. The stability of these slabs has generally been improving but on the first really sunny day, stability is expected to deteriorate rapidly and natural avalanche activity is likely, especially on sunny slopes. Large cornices remain a concern and are expected to become reactive during periods of solar warming. The early-Feb facet/crust layer (down ~2m) and a weak basal layer are both dormant but remain a concern during periods of intense warming, especially in thinner snowpack areas, when large spring avalanches may step down to these layers.

Problems

Wind Slabs

Forecast new snow and wind may result in new wind slabs developing in the alpine and at treeline. Wind slabs may not be well bonded to recent melt-freeze crusts.

Use caution in lee areas in the alpine. Recent wind loading have created wind slabs.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Wet

During day time warming snow may become moist or wet and slide easily at lower elevations and on solar exposed aspects.

Be cautious of sluffing in steep terrain.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Cornices

Cornices may become weak from loading from new snow and wind, or from day time warming.

Cornices become weak with daytime heating, so travel early on exposed slopes.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Valid until: Apr 24th, 2014 2:00PM