Avalanche Forecast

Archived

Feb 27th, 2023–Feb 28th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Regions

Jasper, Brazeau, Churchill, Cirrus-Wilson, Fryatt, Icefields, Maligne, Marmot, Miette Lake, Pyramid.

Wind transport continues to build wind slab at tree line and in the alpine. Minimize your overhead hazard and avoid wind-loaded terrain. If triggered, wind slabs may step down to the deep persistent problem resulting in large avalanches.

Confidence

Moderate

Avalanche Summary

Size 2 and 2.5 deep persistent slab observed S end of Medicine lake - one starting low in north facing alpine start zone with a 1m deep crown.

Last week we experienced a widespread avalanche cycle on all aspects in the alpine. Many of these avalanches started as wind slabs and stepped down to the deep persistent facet layer. Most were size 2-3 but one size 4 was observed. Most notably the main Buck Lake slide path and the Churchill South slide path ran into the ski lines.

Don't forget to post avalanche observations to the MIN.

Snowpack Summary

Recent strong winds from the north and southwest have redistributed surface snow increasing the wind slab hazard at and above treeline. Ridgetop has been scoured in most locations with wind effect visible throughout the alpine.

The upper snowpack consists of 20-50 cm of settled snow or wind slab sitting on top of a generally weak mid and lower snowpack. Facets and depth hoar linger at the base of the snowpack with the height of snow varying from 60 to 160cm.

Weather Summary

Tuesday

Cloudy with sunny periods and isolated flurries.

Precipitation: Trace.

Alpine temperature: High -10 °C.

Ridge wind east: 10 km/h.

Freezing level at valley bottom.

Wednesday

Cloudy with sunny periods and isolated flurries.

Precipitation: Trace.

Alpine temperature: Low -20 °C, High -11 °C.

Ridge wind west: 15 km/h gusting to 45 km/h.

Freezing level at valley bottom.

Thursday

Cloudy with sunny periods and isolated flurries.

Precipitation: Trace.

Alpine temperature: Low -20 °C, High -12 °C.

Ridge wind southwest: 20-40 km/h.

Freezing level at valley bottom.

Detailed weather forecasts from Avalanche Canada: https://avalanche.ca/weather/forecast

Terrain and Travel Advice

Expect slab conditions to change drastically as you move into wind exposed terrain.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.