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Avalanche Forecast

Archived

Mar 2nd, 2012–Mar 3rd, 2012

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

Regions

Purcells.

Confidence

Good

Weather Forecast

An "almost pineapple" weather pattern is setup across the province, and while the neighboring regions to the north & west receive the full brunt of the firehouse the Purcells will likely see a more modest garden house amount. The latest model run show the Purcells receiving a bit more moisture than originally expected with slightly lower Freezing Levels (FZLVL). SAT: FZLVL will be on the rise, climbing to 1700 m by 4:00 pm. 11.7 SWE forecast, expect around 15 cm of snow above 1700m, rain below. 2km wind: West, Mod increasing to upper end of Mod throughout the day. SAT NIGHT: FZLVL drops to 1000m overnight. SUN: FZLVL near 1800m most of the day. 14.3mm SWE expected. MON: FRLVL slowly lowers throughout the day. 3.1mm SWE forecast. Winds initially Mod SW Tapering to Light W late in the day.

Avalanche Summary

Natural size 2.5, failing on mid Feb. SH in the north of the region. A few different remote triggered avalanches to size 1.5 on steep south facing slopes in the south of the region.

Snowpack Summary

A cohesive slab continues to settle over the mid-February surface hoar, which is generally down in the 40-55cm range. Recent reports include whumpfing and cracking, and moderate but sudden compression 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. Basal facets have only been reactive on steep, shallow, and rocky slopes, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are the most suspect locations.

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.

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.

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.