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Avalanche Forecast

Archived

Nov 23rd, 2015–Nov 24th, 2015

Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Northwest Coastal.

Given the very limited information on hand for this bulletin, I would tread cautiously and take the time to gather snowpack information as I go. Submit any observations from your day to the MIN. Give info get info!

Weather Forecast

The first arctic outbreak of the season  remains stationary bringing outflow winds with a cooler air mass. This blocking high pressure system will likely keep things cold and dry, however, an above freezing layer may develop on Wednesday around the 1500 m level and could reach as far inland as Smithers.Tuesday: Ridgetop winds blowing Strong from the N-NE and temperatures at treeline elevations hovering around -12.0.Wednesday/ Thursday: Freezing levels will remain at valley bottom with average treeline temperatures near -5.0. Light winds will continue from the N-NE direction.

Avalanche Summary

No new avalanches have been reported ton Monday. In the north of the region on Saturday, explosives avalanche control produced several wind slab avalanches up to size 2.5 on north and east facing terrain above 1400m. At least one of the avalanches stepped down to a crust/facet interface 100cm below the surface. The newly formed storm slab may remain ripe for human triggering for the next few days, especially in areas where persistent weak layers exist.

Snowpack Summary

Reactive wind slabs have likely formed throughout the region in response to last weekends snowfall, warm temperatures and extreme westerly winds. At lower elevations, precipitation fell as rain and the surface now exists as a refrozen crust. The new wind slabs are likely most destructive in the north of the region where storm accumulations totaled around 30cm and ridgetop wind speeds peaked at 130 kmh. The reactivity of these new wind slabs will likely change with elevation and underlying snowpack structure. Due to limited observations, I have very little confidence in what that underlying structure may be, although faceting, crusts and surface hoar development have been reported from various parts of the region. The region is now seeing moderate outflow winds from the N-NE which may be redistributing some of the new snow onto opposite slopes. This makes thing tricky and you may find new wind slabs on unsuspecting slopes and terrain features.  I were traveling in the mountains, I'd maintain an investigative approach and dig down to test for weak layers before committing to a slope. If you've been in the mountains, please share your observations on our Mountain Information Network

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.