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Archived

Avalanche Forecast

Dec 5th, 2024–Dec 6th, 2024
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Little Yoho, Sunshine, West Side 93N.

One more day of clear skies and warm temperatures on Friday, with freezing levels up to 1900 m triggering loose wet avalanches into gullies. Ice climbers avoid south-facing terrain. Conditions change starting Friday night with extreme winds, then a storm day on Saturday with snow and rain throughout the day.

Confidence

Moderate

Avalanche Summary

Observations from across the park on Thursday of avalanches up to size 2 releasing on sunny exposures, both in the ski areas and backcountry. The common theme is moist snow releasing a small slab, then gouging down to facets and running further than expected. Lake Louise got one explosive-triggered avalanche in a steep N aspect, failing on the Nov 9 layer 40 cm above the ground.

Snowpack Summary

Two warm and clear days have left the snow surface a mix of wet snow, suncrust, wind crust and facets. This overlies a mostly faceted snowpack 40-90 cm deep with two weak layers near the base (Oct 20 and Nov 9 crusts). These crusts continue to produce isolated avalanches. No new snow is expected on Friday, but by Saturday expect new snow and wind to create easily triggered surface slabs, some may fail on the ground.

Weather Summary

Some active weather is coming our way as a warm Atmospheric River comes onto the coast of BC and spills over into Alberta starting Friday night and all day on Saturday. Expect extreme winds (>100 km/hr) on Friday night, rain and snow through Saturday and freezing levels to 1900 m, then clearing and cooling on Sunday as the system exits the region.

Terrain and Travel Advice

  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches.
  • Pay attention to the wind; once it starts to blow, sensitive wind slabs are likely to form.
  • Be mindful that deep instabilities are still present in the snowpack.

Avalanche Problems

Deep Persistent Slabs

The October and November crusts, on north and south aspects respectively, are still producing isolated slab avalanches down about 50-80 cm. Be mindful on steep, rocky alpine slopes where triggering is most likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1.5 - 2

Wind Slabs

Recent moderate to strong winds have formed wind slabs on lee slopes in the alpine. If triggered, these slabs could entrain facets, leading to longer-than-expected runouts.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 1.5