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Avalanche Forecast

Archived

Nov 26th, 2013–Nov 27th, 2013

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

Regions

Northwest Coastal.

Early season forecasts are based on limited observations. Expect a great deal of variability across the region. If you have any observations, please email us at [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Overnight and Wednesday: Light precipitation overnight and continuing on Wednesday combined with moderate winds from the South that should increase towards the evening. Freezing levels are expected to stay around 1500 metres.Thursday: Moderate to heavy precipitation is expected to start during the morning, with 20-30 mm expected near the coastal areas of the region. Winds are expected to increase to strong or very strong from the Southwest.Friday: Precipitation should taper off to light values and the wind should slow a bit, but remain strong from the Southwest.

Avalanche Summary

Numerous natural avalanches up to size 1.5 were observed from steep un-skiable terrain along the Skeena corridor on Monday. Older large natural avalanches in the Shames area appear to have run on a deeply buried crust that developed during clear warm weather in October. Recent soft slab avalanches released at the base of the November 23rd storm snow. Ski cuts resulted in wind loaded pockets releasing up to size 1.0 in the alpine.

Snowpack Summary

Reports of extensive wind transport since the end of the November 23rd storm. There is a little more than a metre of snow at 1000 metres elevation, and the snowpack has been described as "generally moist" below this elevation. Snowpack tests resulted in moderate planar results down about 20 cm, and hard planar results on the early season crust down about 90 cm. These layers of concern may persist or become more reactive with the forecast snow load in the next few days.

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.