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Avalanche Forecast

Archived

Mar 13th, 2023–Mar 14th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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

Storm snow blankets the region and has created reactive storm slabs. If triggered storm slab avalanches could step down to weak layers deep in the snowpack creating large destructive avalanches. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential for a safe day out in the mountains.

Confidence

Moderate

Avalanche Summary

On Saturday, a few cornice failures were observed in the alpine during a brief period of direct sun. Observed failures did not trigger the slope beneath them. Check out the MIN report for more details.

If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

By Tuesday morning 20-40 cm of storm snow overlies a variety of surfaces including small pockets of wind slab on exposed south and west slopes, hard wind-affected surfaces in open areas, a sun crust on steep solar aspects, and facetted snow in sheltered areas.

In the Purcells, several weak layers from Jan and Feb can be found down 50 to 120 cm however they are showing signs of strengthening. The mid-snowpack is generally well-settled.

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

Monday Night

Cloudy with mixed precipitation, 10-16 cm new snow at higher elevations. Alpine temperatures reach a low of -5 °C. Ridge wind 20 km/h gusting to 50 km/h from the southwest. Freezing levels lower slowly from 1800 m to 1000 m.

Tuesday

Mainly cloudy with isolated flurries, trace accumulation. Alpine temperatures reach a high of -7 °C. Ridge wind 15 to 30 km/h from the southwest. Freezing levels 1100 meters.

Wednesday

A mix of sun and cloud with isolated flurries, trace accumulation. Alpine temperatures reach a high of -5 °C. Ridge wind 15 km/h gusting to 30 km/h from the northwest. Freezing levels rise to 1200 meters.

Thursday

Mainly sunny. Alpine temperatures reach a high of -2 °C. Ridge wind southwest 20 km/h. Freezing levels rise to 1500 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.

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.