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Avalanche Forecast

Archived

Feb 10th, 2023–Feb 11th, 2023

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

North Columbia, South Columbia, Esplanade, Jordan, North Selkirk, Shuswap, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

Light flurries and elevated winds should keep wind slabs fresh and reactive to skier triggering on Saturday. Seek out sheltered areas and remember that bigger wind slabs may step down to deeper snowpack weaknesses to create large, destructive avalanches.

Confidence

Moderate

Avalanche Summary

Reports from Thursday included more observations of the natural cycle described below, in addition to several size 1 (small) to size 2 (large) skier-triggered slabs. Size 1's were up to about 20 cm -deep wind slabs while the lone new size 2 north of Trout Lake failed on a 75 cm-deep freezing rain crust buried in early January.

With clearer weather on Wednesday, a widespread avalanche cycle from within the storm was observed across the region. Several persistent slab avalanches were reported between 2200 and 2400 meters on all aspects. Notable was a size 2 vehicle remote persistent slab avalanche, triggered from 70 m away on a northwest aspect. Several deep persistent slabs were reported to size 4 throughout the Selkirks and Purcells. Numerous wind slab and storm slab avalanches were reported to size 3 on all aspects at treeline and above.

On Tuesday, a few size 1 skier accidentals storm slab avalanches were reported 20-40 cm deep. Numerous natural avalanches were reported primarily on north and east aspects where storm snow and wind created deep pockets of slab. Explosive control produced numerous storm slab results to size 3.5.

Snowpack Summary

Southwest winds have been redistributing storm snow into 20-30 cm soft slabs in exposed alpine and treeline areas. 40-90 cm of storm snow from the week sits above wind-affected surfaces and a crust that extends up to 1800 m in the northern part of the region and up to 2000 m further south. Small facets may be found above the crust.

Deeper in the snowpack two layers of surface hoar which formed in early January are 60 to 120 cm deep. These weak layers are still on our radar, although snowpack tests are indicating they may be strengthening.

Large and weak facets from November are near the base of the snowpack, which continue to produce very large avalanches in the region.

Weather Summary

Friday night

Cloudy with isolated flurries and up to 5 cm of new snow. Light to moderate southwest winds, strong in the alpine.

Saturday

Cloudy with isolated flurries and and about 5 cm of new snow from the overnight period. Light to moderate southwest winds. Treeline high temperatures around -4 with freezing levels rising to 1300 metres.

Sunday

Increasing cloud and flurries bringing 5-10 cm of new snow by end of day, continuing overnight. Light to moderate southwest winds, becoming strong or even extreme in the alpine. Treeline high temperatures around -2 with freezing levels to 1300 metres again.

Monday

Cloudy with another 5-10 cm of new snow from the overnight period. Light southwest winds. Treeline high temperatures around -5.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.

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.

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.

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.