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Avalanche Forecast

Archived

Mar 1st, 2012–Mar 2nd, 2012

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

Kootenay Boundary.

Confidence

Fair - Intensity of incoming weather is uncertain for the entire period

Weather Forecast

Friday: Light flurries in the morning increasing throughout the day with 5-10cm possible by nightfall. Strong westerly winds and freezing levels as high as 1000m. Saturday: Another 15-25cm by the end of the day with continued strong westerly winds and freezing levels rising throughout the day to as high as 2000m. Sunday: Continued light flurries with freezing levels dropping throughout the day.

Avalanche Summary

Recent reports include several natural and human triggered soft wind slab and small dry loose snow avalanches in involving the new snow and a recent storm snow weakness. The slabs are generally in the 20-40cm range with avalanches in the Size 1-1.5 range. One report includes skiers on top of a ridge remotely triggering numerous storm slabs up to Size 2 on steep slopes below.

Snowpack Summary

10-30cm of new snow is sitting on surface hoar on shady aspects and a thin sun crust on south aspects. A weak storm snow interface of well-preserved stellars is down approximately 40-50cm and reactive to human triggers on steep shady (cold) slopes at and below treeline. However the main snowpack feature of concern continues to be the surface hoar buried mid-February, which is now down 60-120cm and still giving easy sudden snowpack test results. This persistent weakness is susceptible to remote triggering and has the ability to propagate in low angled terrain, and the overlying slab structure creates the potential for step-down avalanches. Although generally getting deeper and harder to trigger, avalanche professionals throughout the region continue to treat this weakness with extreme caution.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.

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.