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Avalanche Forecast

Archived

Nov 23rd, 2013–Nov 24th, 2013

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

Regions

South Rockies.

Please note this bulletin is based on limited information. If you have been out and have observations, please send them to [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis: The ridge of high pressure continues to strengthen, driving an inversion pattern across the region that should persist through the forecast period. Sunday: Cloudy with sunny periods. Precipitation: Nil. Alpine temperature: High 1 Light ridge wind. Freezing level: 2400m Monday: Sunny with cloudy periods. Precipitation: Nil. Alpine temperatures: Low -4 High -3 Light ridge wind. Freezing level: 1500 m. Tuesday: Cloudy with sunny periods. Precipitation: Nil. Alpine temperatures: Low 0 High 0  Ridge wind southwest 20 gusting to 65 km/h. Freezing level: 2300 m.

Avalanche Summary

Avalanche activity was reported in pockets of deeper snow from Monday (18th) and Tuesday (19th) in both western and eastern areas of the region. Activity appears to have tapered off. Recent slope tests have produced results only in isolated pockets of wind slab on steep convex rolls.

Snowpack Summary

Treeline snowpack depths in sheltered areas vary between approximately 40-80 cm. In the alpine, coverage is highly variable due to recent high winds. A crust or significant density change may exist around 40 cm below the surface. This has been reported to have weak faceted crystals above and below, and produces sudden "pop" results in compression tests. Below this near the base of the snowpack, an earlier crust buried in October lies close to the ground. This layer may still be of concern on isolated smooth terrain features that have not seen avalanche activity.

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.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.