Avalanche Forecast

Archived

Apr 18th, 2023–Apr 19th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Regions

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

Storm amounts are uncertain. If you arrive at the parking lot and find more snow than expected, The hazard could easily increase to HIGH. Generally poor ski quality out there at the moment.

Confidence

Moderate

Avalanche Summary

A few small windslabs immediately below cornices were observed today on treeline, east aspects features in the Burstall pass area. Otherwise no other reports.

Snowpack Summary

10cm storm snow has fallen. This has been instantly removed by strong to extreme winds and most surfaces with exception to true North has been stripped back down to previous surfaces including suncrust and vintage windslabs.

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.

Weather Summary

Conflicting models are classic for this time of the year. Some models calling for 30cm other calling for only a few centimeters. What is consistent right now is the cooler temps and cloud cover. Day time highs of -5 with lows around -12.

Winds are swapping to more of a N-NE wind just over 20km/h

Freezing levels will remain around 1700m on Wednesday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
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.
Cornices become weak with daytime heating or solar exposure.

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.

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.