Avalanche Forecast

Issued: Apr 4th, 2013 9:28AM

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

Avalanche Canada pmarshall, Avalanche Canada

We're expecting a return to winter conditions heading into the weekend. Choose conservative routes until the weather improves and the snow has a chance to stabilize. 

Summary

Confidence

Fair

Weather Forecast

Synopsis: A series of frontal systems will affect the South Coast over the next few days bringing steady precipitation and gradual cooling to near seasonal temperatures. Tonight and Friday: Moderate to locally heavy precipitation – 10-15 cm overnight and another 15-20 cm during the day. The snow line should drop from to around 1400 m by the morning. Winds are moderate from the southwest. Saturday: Expect another 5-10 cm, mainly in the morning. The freezing level continues to drop to around 1200 m and winds remain moderate from the southwest.  Sunday: Most likely a drier day but we should still see mainly cloudy skies and flurries. The daytime freezing level hovers around 1200-1400 m.

Avalanche Summary

Observations were limited on Tuesday and Wednesday. Previous reports were primarily loose wet sluffs up to size 2 on solar aspects and isolated cornice failures.

Snowpack Summary

New snow may not initially bond well to the previous snow surface, which potentially includes a melt-freeze crust, moist or wet snow, or pockets of surface hoar. Also, expect pockets of wind slab to form in exposed lee terrain in the alpine as winds pick up on Thursday night. The upper snowpack at lower elevations has become isothermal from recent warm temperatures. Adding rain to this on Friday could trigger loose wet sluffs or wet slabs in steep terrain. Cornices are very large and could pop off with continued mild temperatures. A layer of surface hoar (buried on March 11; now down about 60 cm) is still being observed in some locations. Triggering this layer has become unlikely, and would most likely require a large trigger or from a thin snowpack zone. Mid and lower snowpack layers are well bonded.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slabs will form in response to forecast snow and wind. Triggering is most likely in exposed north through east aspects at or above treeline. Greater snowfall amounts in the south could lead to locally higher avalanche danger.
Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Cornices

An icon showing Cornices
Cornices are large and weak. Thick cloud could make it difficult to determine where overhangs begin, so give cornices a little extra space.
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

Valid until: Apr 5th, 2013 2:00PM

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