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Avalanche Forecast

Archived

Mar 11th, 2023–Mar 12th, 2023

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

Regions

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

Easterly winds formed wind slabs on lee aspects in the alpine.

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Confidence

High

Avalanche Summary

A couple cornice failures that did not trigger slabs on the slopes below and small (size 1) rider triggered wind slab avalanches in the alpine were reported on Friday.

A cornice triggered size 3 deep persistent slab avalanche was reported on the northeast face of Mt. Mackenzie on Thursday. See MIN.

Snowpack Summary

Easterly wind has formed small wind slabs on lee aspects at treeline and above. Sun crust on sunny slopes and surface hoar (3-10 mm) on shady slopes at all elevations. Previous wind effect in open areas at treeline and above.

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 rounding but there is still a considerable step in resistance between them and the overlying snow. These facets are most pronounced in shallow rocky areas.

Weather Summary

Saturday Night

Cloudy with isolated flurries; 5-10 cm / Light southwest ridgetop wind / Low temperature at treeline around -10 C / Freezing level valley bottom.

Sunday

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

Monday

Snow; 15-25 cm; + 10-20 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 / Moderate west ridgetop wind / High temperature at treeline around -3 C / Freezing level 1200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.

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.