Avalanche Forecast

Issued: Apr 6th, 2013 9:33AM

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

Peter, Avalanche Canada

Sea To Sky.

Summary

Confidence

Fair - Track of incoming weather is uncertain on Sunday

Weather Forecast

Synopsis: A low pressure system is forecast to move through Washington on Sunday, most likely giving cloud and only light precipitation to the South Coast. If it tracks a little further north we could see greater accumulation. A ridge of high pressure should build in later on Sunday resulting in drier conditions and sunny breaks for Monday and Tuesday. Sunday: Mainly cloudy with a chance of flurries. The freezing level is around 1000-1200 m. Winds are easing to light from the northeast. Monday: Sunny breaks. The daytime freezing level rises to around 1500 m. Winds are light from the northwest. Tuesday: Increasing cloud and the possibility of snow late in the day. The freezing level is steady around 1500 m.

Avalanche Summary

Several small explosive controlled avalanches, 10-20 cm deep, were reported from lee alpine terrain on Friday morning.

Snowpack Summary

Recent snowfall amounts vary considerably with elevation due to fluctuating freezing levels. Some alpine areas may have accumulations over 50 cm. Dense new wind slabs are likely in exposed lee terrain at and above treeline. Most of the recent precipitation fell as rain below 1700-1800 m. The upper snowpack at lower elevations has become isothermal from recent warm temperatures and rain. Loose wet avalanches remain a concern below treeline. Cornices are very large and could pop off with continued mild temperatures or during periods of sun.

Problems

Wind Slabs

Dense wind slabs have formed in exposed lee terrain at higher elevations. Triggering is most likely in steep terrain below ridge crests or in cross-loaded gullies.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Cornices are large and weak and could pop off during sunny breaks or from daytime warming.

Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 6

Loose Wet

Loose wet avalanches are possible at lower elevations if the sun comes out or if the snow does not refreeze overnight.

Watch for wet loose or slab activity with forecast rain and/or warm temperatures.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Apr 7th, 2013 2:00PM