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Archived

Avalanche Forecast

Apr 4th, 2013–Apr 5th, 2013
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Coast.

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. 

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.

Avalanche Problems

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

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