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 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.

15-30cm of snow is expected Monday depending on location. Watch locally for snow amounts and slab development. We are also waiting to see how this new snow impacts the deeper weak layers as they are hard to predict. Rain is possible in lower elevation locations such as Kootenay Park.

Confidence

Moderate

Avalanche Summary

No new avalanches have been reported or observed in the past 24 hours. There have been plenty of recent avalanches over the past few weeks, with many stepping to the ground. However, activity has tapered off in recent days with few weather inputs.

Snowpack Summary

A sun crust is present on steep solar slopes at treeline and below while 10-30 cm of soft snow can be found on northerly aspects. The various Jan PWL interfaces (sun crusts, facets, and surface hoar) are now down 40-80 cm. The weaker Nov. 16 basal facet layer is down 50-120 cm producing variable results in snowpack tests.

Weather Summary

10-30cm is expected Monday and Tuesday.

Monday: 5-10cm on West facing slopes, and 2-4 cm further East. Freezing levels, in general, will be 1500-1700m with potential rain below treeline. Winds will be S/SW 50-60 km/h and temperatures 0 to -5C at ridgetop. Snow continues Monday night with 5-10cm and potentially higher amounts in Kootenay with 20cm possible.

Tuesday: Tapering residual snow and winds through the day with the passage of a cold front.

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.