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Avalanche Forecast

Archived

Mar 12th, 2023–Mar 13th, 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 and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
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.

Regions

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

Warm temperatures, new snow and strong winds will create dangerous avalanche conditions on Monday.

Uncertainty is best managed by conservative terrain choices at this time. Avoid shallow areas where triggering the deep persistent weak layer is more likely.

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

Accumulating flurries on Monday will cover 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

Sunday Night

Cloudy with isolated flurries, 2-5 cm accumulation. Alpine temperatures reach a low of -5 °C. Ridge wind 25 to 40 km/h from the southwest. Freezing levels remain at 1400 meters.

Monday

Cloudy with mixed precipitation The Purcells will see 10-12 cm of new snow while the Rockies see 5- 8 cm. Alpine temperatures reach a high of -1 °C. Ridge wind 30 to 50 km/h from the southwest. Freezing levels rise to 1800 meters.

Overnight flurries continue bringing an additional 10 cm of new snow to the Purcells and 12-17 cm to the Rockies. Freezing levels remain around 1700 m overnight.

Tuesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -5 °C. Ridge wind 15 to 30 km/h from the southwest. Freezing levels 1300 meters.

Wednesday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -2 °C. Ridge wind 10 to 20 km/h from the west. Freezing levels rise to 1500 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for fresh storm slabs building throughout the day.
  • In times of uncertainty conservative terrain choices are our best defense.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.