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Avalanche Forecast

Archived

Jan 28th, 2023–Jan 29th, 2023

Alpine
Natural avalanches possible, human triggered probable.
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

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

Expect wind loading around ridgelines as northeasterly winds continue to redistribute storm snow into unusual loading patterns.

Use extra caution around ridgelines and avoid rocky start zones. Low angle, wind sheltered slopes will hold the best conditions.

Confidence

Moderate

Avalanche Summary

Storm slab and loose dry avalanches were reported on Friday as snowfall accumulated.

Avalanche control work near Fernie this week produced wind slabs to size 1.5 from explosive and ski cut methods.

Although the deep persistent slab problem has not produced in they have not produced any avalanches for some time it could still pose a threat for now. Be wary of areas with thin or variable depth snowpack and shallow rocky start zones throughout the region.

Snowpack Summary

Up to 30 cm of storm snow can be found, wind affected by moderate north/east winds at higher elevations. New snow sits over wind affected surfaces at higher elevations and at lower, sheltered elevations - over a layer of surface hoar on sheltered areas or a melt freeze crust on south facing slopes.

A crust and facet layer from mid January, 2 to 15 cm thick at treeline sits 50 to 90 cm deep. Where it's thickest, it caps the settled and consolidated mid-snowpack.

The lower snowpack contains weak and facetted grains from November. Concern remains for heavy loads such as cornice falls, machine triggers or step down avalanches. Thin snowpack areas where weak layers sit closer to the surface should still be treated as suspect.

The total snowpack depth ranges between 90 and 250 cm.

Weather Summary

Saturday Night

Some cloud overnight. Moderate northeast winds. Freezing levels below valley bottom. Trace accumulations.

Sunday

Sunny with trace amounts of snow expected. Moderate northerly winds continue, alpine high temperatures of -16°C.

Monday

Sunny with increasing afternoon cloud. Winds switch to moderate (gusting strong) westerlies. Alpine high of -16°C.

Tuesday

A mix of sun and cloud. Moderate westerlies. Alpine high of -12°C.

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.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.