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Avalanche Forecast

Archived

Mar 12th, 2023–Mar 13th, 2023

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
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, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

Forecast snow and wind are expected to trigger large natural avalanches on Monday.

Travel in avalanche terrain is not recommended.

Confidence

High

Avalanche Summary

Several natural and rider triggered wind slabs up to size 1.5 on northerly aspects in the alpine were reported on Saturday.

Additionally, there was a size 2 cornice failure on a northeast aspect that did not trigger a slab on the slope below.

Forecast snow and wind are expected to form fresh storm slabs that are reactive to human triggers on Monday.

Snowpack Summary

Forecast snow and wind are expected to form fresh storm slabs that are reactive to human triggers.

The storm snow will add to the 10-20 cm of recent snow which overlies a variety of surfaces. These include surface hoar (3-10 mm) on shady slopes at all elevations, wind affected surfaces at treeline and above, and sun crust on sunny aspects.

The mid-snowpack is generally strong but the lower snowpack is a different story.

The November facets are still prominent at the base of the snowpack. They are showing signs of improving but this layer remains a significant concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.

Weather Summary

Sunday Night

Snow; 15-20 cm / Strong southwest ridgetop wind / Low temperature at treeline around -4 C / Freezing level valley bottom

Monday

Snow; 15-25 cm (rain below 1500 m); another 5-15 cm overnight / Strong southwest ridgetop wind / High temperature at treeline around 2 C / Freezing level rapidly rising to 1800 m

Tuesday

Mix of sun and cloud / Light southwest ridgetop wind / High temperature at treeline around -3 C / Freezing level 1200 m

Wednesday

Mix of sun and cloud / Light southwest ridgetop wind / High temperature at treeline around -2 C / Freezing level 1300 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Stick to non-avalanche terrain or small features with limited consequence.
  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.