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Avalanche Forecast

Archived

Mar 25th, 2023–Mar 26th, 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.

Small avalanches may be common in steep and/or leeward terrain.

Large human-triggered deep persistent slab avalanches remain possible.

Keep avoiding steep, rocky, wind-affected terrain and choose small, low-consequence features.

Confidence

Moderate

Avalanche Summary

Several dry loose avalanches (size 1) were naturally triggered within the new storm snow on steep northerly alpine features near St.Mary's.

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.

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, 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. Wind-affected surfaces are found 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

Unsettled weather will continue to bring scattered flurries until a ridge of high pressure invades the region early next week.

Saturday night

Cloudy. Isolated flurries. Low alpine temperatures of -8 °C. Light southwest ridge wind. Freezing level at valley bottom.

Sunday

Cloudy with sunny periods. Isolated flurries. High alpine temperatures of -3 °C. Light easterly ridge wind. Freezing level rises to 1400 metres.

Monday

Cloudy with sunny periods. Lingering flurries. High alpine temperatures of -5 °C. Light southwest ridge wind. Freezing level rises to 1400 metres.

Tuesday

A mix of sun and clouds. High alpine temperatures of -3 °C. Light easterly ridge wind. Freezing level rises to 1700 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.