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Avalanche Forecast

Archived

Jan 22nd, 2015–Jan 23rd, 2015

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Sea To Sky.

Stormy weather will elevate avalanche danger for the weekend.

Confidence

Good

Weather Forecast

Moderate to heavy snowfall or rain is expected to continue throughout the forecast period with 20-40 mm of rain (or cm of snow) each day for Friday, Saturday, and Sunday. Strong southwesterly winds are expected to ease off on Saturday and remain light to moderate on Sunday. Freezing levels around 1500 m on Friday are also expected to drop below 1500 m on Saturday, but fluctuate on Sunday.

Avalanche Summary

Recent avalanche activity progressed from a limited avalanche cycle on Saturday and Sunday (mainly from wind loaded terrain), to several explosive and rider triggered avalanches up to size 2 on Monday and Tuesday. Conditions will start to change heading into the weekend. Warm temperatures and rain is expected to tip off another round of wet avalanche activity by Friday.

Snowpack Summary

Up to 50 cm of settled storm snow sits on a hard crust and/or surface hoar layer. Previous strong W-SW winds redistributed snow in exposed terrain creating deep and dense wind slabs in lee features. The new snow seems to be bonding well to the crust, which is most pronounced between about 1500 m and 2200 m. The distribution of the surface hoar seems spotty across the region, but some operators found it to be widespread in their tenure before it was buried. Deeper snowpack weaknesses have become unreactive, but a recent profile posted in Wayne Flann's avalanche blog highlights the stark hardness contrast between a deep persistent weakness and the surrounding snow. Scenarios like this with deeply buried soft snow surrounded by hard snow aren't confidence inspiring because it all hinges on the strength of the overlying slab, which is often volatile and susceptible to significant warming and loading. Especially with very heavy triggers (like a cornice fall) in the wrong spot (like a thin snowpack area).

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.