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Avalanche Forecast

Archived

Feb 28th, 2014–Mar 1st, 2014

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Sea To Sky.

The February weak layer continues to be a concern for triggering a very large avalanche. See the Forecaster Blog for more information.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Overnight and Saturday: Cold and clear overnight with no precipitation and light Northwest winds. Cloud developing in the morning as the winds shift to the West. Light to moderate snowfall during the afternoon with freezing levels at or near sea level. Sunday: Southwest winds building to moderate, pushing moisture further inland against the arctic cold front. Expect 10-20 cm of snow near the coast and 5-10 cm further inland.Monday: Another 5-10 cm of snow combined with strong Southwest winds and freezing levels climbing up to about 1500 metres in the afternoon.

Avalanche Summary

There were a couple of more reports of slab avalanches released by natural loose wet activity on solar aspects on Thursday. No new reports of avalanche activity since the cold air moved into the region overnight. While natural activity has subsided on Northerly aspects in the region, human triggering with the possibility of long fracture propagations continues to be a concern.

Snowpack Summary

Cold arctic air has invaded the region creating a melt-freeze crust on all aspects at treeline and below, and on all but North aspects in the alpine. The recent very warm alpine temperatures and strong solar radiation caused a great deal of settlement in the old storm slab above the early February weak layer. The February weak layer of crusts and facets has been reported to be rounding and bonding in areas where the old storm slab is 150 cm or deeper. Shallow snow pack areas where the old storm slab is closer to a metre or less continue to give sudden planar shears in snow profile tests. North aspects in the alpine may have had enough warming to settle the storm snow into a cohesive slab, but not enough to improve the weak layer bond. Big un-supported alpine North aspects are the most likely place to find a well preserved deeply buried February weak layer that may continue to allow for long propagations resulting in very large avalanches.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.