Avalanche Forecast

Archived

Apr 20th, 2023–Apr 21st, 2023

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Kananaskis, Bow Valley, Highwood Pass, North 40, Spray - KLakes.

Good skiing can be found on polar aspects and sheltered areas. Deeper instabilities still linger. Best to start early and finish early as the sun has a lot of power this time of year.

Confidence

Moderate

Avalanche Summary

No new avalanches have been observed or reported. Check out the min report for more details. https://avalanche.ca/map

Snowpack Summary

15-20cm of recent snow overlies a variety of surfaces such as wind slabs and melt/freeze crusts. Sheltered areas and polar aspectds will provide the best skiing with little wind effect. Be aware of sluffing on solar aspects if the sun comes out. Forecasters continue to track persistent weaknesses down anywhere from 40 to 100cm on polar aspects. These weaknesses are highly variable in nature and travelers should take the time to dig down and evaluate the snowpack frequently. Also, the lingering deep persistent slab problem is still alive and well.

If the sun comes out stability will deteriorate quickly so pay attention to the incoming radiation on aspects you are travelling on or under. Early starts and finishes are a great way to deal with some of these issues.

Weather Summary

Friday is expected to be mostly cloudy with some flurries and light NE winds. Temperatures are expected to be between -7c and -1c. It is Spring time, so even though 5cm is forecast for snow, anything is possible, even sunshine. At this time of year, the weather can change several times a day from intense sunshine to intense snow; if you don't like the weather, wait 5min...If the skies remain cloudy and some heat remains, then the re-freeze might not be as good as a clear night. Same goes for solar radiation during the day as it can quickly increase avalanche hazard.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.