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Avalanche Forecast

Archived

Mar 15th, 2023–Mar 16th, 2023

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 possible, human triggered probable.
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

Banff Yoho Kootenay, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Continued natural avalanches are expected on solar aspects over the next 24-48 hours, and cornice failures may continue to trigger the deep persistent layer on the lee aspects. Continue to avoid large avalanche terrain features and avoid climbing in gullies with any exposure to the sun.

Confidence

Moderate

Avalanche Summary

Observations of the recent avalanche cycle are starting to come in. On Wednesday, a large deep size 3 on Pilot Mountain and over the Sacre Blue ice climb on Mt. Rundle was reported. On Tuesday, a notable large, deep size 3 on Puzzle Peak crossed the standard up track (cornice triggered probably). The Lake Louise ski area reported whumphing and shooting cracks at and below treeline. Finally, a large natural avalanche in Kananaskis Country ran over some ice climbs on Mt. Kidd.

Snowpack Summary

3-day storm totals Sunshine 21 cm, Simpson, 13 cm, Stanley 12 cm, Bosworth 25 cm and Bow Summit 34 cm.

This new snow has fallen on a freshly buried (March 12) layer of surface hoar, facets and sun crust and will not bond well. Strong SW winds near the storm's end have created windslabs sitting above this weak layer. Expect this layer to fail with solar inputs. The midpack comprises various Jan crust layers that are now down 60-100 cm. The weak Nov. 16 basal facet layer is down 50-120 cm producing sudden results in snowpack tests.

Weather Summary

Sunny skies are forecasted for Thursday with afternoon cloudy periods. Light morning N-NW winds will ease to very light westerly. Freezing levels between 1300 to 1500 m with alpine temperatures ranging between -10 to -15C. Friday & Saturday, clear skies continue, daytime freezing levels climb to 1800 m with warmer alpine temperatures ranging between -5 and -10 C.

For a more detailed forecast click here.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.

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.