Avalanche Forecast

Archived

Feb 26th, 2023–Feb 27th, 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.

Below Treeline

Natural avalanches unlikely.

Regions

North Rockies, Kakwa, McGregor, Pine Pass, Tumbler.

Make observations of recent wind transport to navigate around wind slabs produced by Saturday's storm. North through east aspects should be most problematic but older, more stubborn slabs from the previous wind event may still react to human or machine triggers on south aspects.

Confidence

Moderate

Avalanche Summary

Observations of new avalanche activity from Saturday and Sunday aren't in yet but we anticipate some degree of a natural avalanche cycle took place in areas like Pine Pass, where up to 30 cm of new snow fell and active human triggering conditions where accumulations were more limited.

Earlier in the week there was evidence of deep persistent slab activity that likely occurred during last weekend's storm with avalanches up to size 3.5. While we currently expect the deep weak layer to be dormant, riders should continue to avoid steep, thin, rocky slopes where triggering a deep persistent avalanche would be most likely, particularly near alpine ridgelines.

Looking forward, we anticipate that new wind slabs will form Saturday night which will be sensitive to human triggering on Sunday.

Snowpack Summary

Up to 30 cm of new snow fell in Pine Pass during Saturday's storm, with closer to 10-15 cm elsewhere in the region.

The snow overlies older wind slabs that formed between Tuesday and Friday as well as heavy wind effect from strong northeast wind during this period. This means a mix of stubborn old and reactive new wind slabs may now be found on all aspects.

The middle of the snowpack is generally strong.

A weak layer of large and weak facets is found near the base of the snowpack. The layer is currently dormant, except perhaps in very steep alpine terrain that is inherently shallow. Riders should continue to avoid thin, rocky terrain where the likelihood of triggering this layer is higher.

Weather Summary

Sunday night

Cloudy with scattered flurries bringing less than 5 cm of new snow. Light southwest winds.

Monday

Mainly cloudy with isolated flurries. Light south winds. Treeline high temperatures around -13 °C.

Tuesday

Mainly cloudy. Light east winds. Treeline high temperatures around -13 °C.

Wednesday

Increasing cloud and flurries with a trace of new snow by end of day, continuing overnight. Winds becoming strong southwest. Treeline high temperatures around -12.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Expect slab conditions to change drastically as you move into wind exposed terrain.
Recent wind has varied in direction so watch for wind slabs on all aspects.
Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.