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Avalanche Forecast

Archived

Mar 24th, 2023–Mar 25th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Rockies, St. Mary, Bull, Elkford East, Elkford West.

New snow is expected to bond poorly to the underlying surface, small but reactive storm slab or dry loose avalanches may be common in steeper terrain.

Large human-triggered deep persistent slab avalanches remain possible. Stay diligent in your terrain selection by avoiding steep, rocky, wind-affected terrain and choosing small, low-consequence features.

Confidence

Moderate

Avalanche Summary

On Wednesday, a very large natural deep persistent was observed north of Elkford. This avalanche occurred on a southwest aspect in the alpine, likely as a result of strong solar radiation. It ran to valley bottom and took out the Smith Basin trail. Full MIN report here.

On Monday, a natural cornice failure resulted in a size 1 avalanche in the St Mary's area east of Kaslo. The cornice dropped onto a steep slope and gouged down to the weak facets at the base of the snowpack.

While activity may have started to taper off on the deeper layers in this region, nearby avalanches are a reminder that the layers are likely still reactive in some locations in the region, especially thin, rocky areas in the alpine.

If you have any observations from this data sparse region, let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

At upper elevations, up to 15 cm of new snow overlies a crust on solar aspects, faceted snow and surface hoar up in shaded and wind-sheltered areas, and wind-affected surfaces in exposed areas. At lower elevations, a crust exists on or near the surface.

In the middle of the snowpack, there are at least a couple of lingering persistent weak layers, including surface hoar in wind-sheltered terrain and a sun crust on south aspects. These layers appear to have generally gone dormant but could still be reactive in isolated areas and should be on your radar in the Purcells part of the region.

The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. This weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.

Weather Summary

Friday night

Clear periods. Alpine temperatures drop to a low of -8 °C. Ridge wind 10 to 35 km/h from the southwest. Freezing level at valley bottom.

Saturday

Cloudy with sunny periods. Alpine temperatures reach a high of -5 °C. Ridge wind light from the southwest. Freezing level rises to 1500 metres.

Sunday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -3 °C. Ridge wind light from the east. Freezing level rises to 1600 metres.

Monday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -5 °C. Ridge wind light from the southwest. Freezing level rises to 1400 metres.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • It's critical to stay disciplined and choose only well supported, low consequence lines.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
  • Minimize your exposure time below cornices.

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.