Avalanche Forecast

Issued: Apr 7th, 2013 9:23AM

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

Peter, Avalanche Canada

Sea To Sky.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday

Weather Forecast

Synopsis: A brief ridge of high pressure will result in drier conditions and sunny breaks on Monday. The next system arrives sometime on Tuesday bringing moderate precipitation through Wednesday. Monday: Cloudy with sunny breaks. The daytime freezing level rises to around 1500 m. Winds are light from the northwest. Tuesday: Increasing cloud with precipitation developing in the afternoon (~10-15 cm). The freezing level is around 1300-1500 m. Winds increase to moderate or strong from the southwest. Wednesday: Moderate precipitation continues. The freezing level is steady between 1300 and 1500 m.

Avalanche Summary

Numerous size 1-2 slab avalanches were released with explosive control on Saturday. Most of these avalanches occurred in the alpine and failed at the base of the recent storm snow on a melt-freeze crust. One event was reported to be a size 2.5 and may have released in wet snow below the crust.

Snowpack Summary

Recent snowfall amounts vary considerably with elevation due to fluctuating freezing levels. Some lee 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 or wet snow below 1700-1800 m. The upper snowpack at lower elevations has become isothermal from recent warm temperatures and rain.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

Possible - 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 in steep open terrain if the sun appears.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Apr 8th, 2013 2:00PM