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Avalanche Forecast

Archived

Mar 22nd, 2014–Mar 23rd, 2014

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

Regions

South Rockies.

Check out the South Rockies Field Team's new blog. Sunny breaks on Sunday may reactivate weaknesses in the snowpack with the potential for very large avalanches.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Synopsis: The remnants of a very weak system pass over the region Saturday afternoon ahead of Sunday's strengthening ridge. A warm system approaches the coast Monday which should push high cloud into the region. There's potential for very high freezing levels on Tuesday, but its still too far out to say. There's a chance for significant precipitation on Wednesday.'Sunday: Freezing Level: 800m - 1200m; Precipitation: Nil; Treeline Wind: Very light, Variable | Ridgetop Wind: Moderate, NWMonday: Freezing Level: 1000m - 1200m; Precipitation: Nil; Treeline Wind: Light, NE | Ridgetop Wind: Moderate, WTuesday: Freezing Level: 1600m - 1900m; Precipitation: Nil; Treeline Wind: Moderate, W | Ridgetop Wind: Strong, W

Avalanche Summary

On Friday a few loose natural avalanches to size 2 were observed in steep alpine terrain. Explosive control work in the region produced size 2 avalanches that were only 10 - 30 cm in depth.On Wednesday a size 2 wind slab was accidentally triggered by a skier in the southeast corner of the region. The avalanche occurred on a northeast aspect at about 2600m.

Snowpack Summary

See this great video from our South Rockies field team that does an awesome job of summarizing the current state of the snowpack.60 - 100 cm of storm snow fell in the last week. Winds have been out of the SW through NW which has created fresh wind slabs in lee terrain. Around 70 cm of settling storm snow rests on a graupel layer that can be found in much of the region. This makes for around 90 cm on top of the mid march crust at this point. This crust exists on all aspects below 2000m and on solar aspects in the high alpine. North of Sparwood and in the Crowsnest Pass area, the buried crust seems more specific to previously sun-exposed slopes. The deep facet/crust persistent weakness buried at the beginning of February (now down up to 150cm) seems unlikely to trigger in areas where the hard, supportive exists. No matter where you are in the region, this weakness should stay on your radar as any activity at this interface would be large and destructive. Possible triggers include a large cornice fall, a large input in a thin snowpack area or solar warming.Cornices have also become large and unstable.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.