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Avalanche Forecast

Archived

Mar 27th, 2024–Mar 28th, 2024

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.

Complex snowpack this Spring.

Some light snow on the way will freshen things up. Take the time to evaluate snow conditions and terrain. Good skiing can be found on more moderate angled slopes.

Confidence

High

Avalanche Summary

One size 1.5 natural avalanche (wind slab) was observed in the Commonwealth area on a NE aspect. Also a report of a 0.5 wind slab that was remoted on a suncrust. It appears that both are wind slabs from the winds in the last 24hrs.

One skier triggered avalanche size 3 occurred in Tent Bowl on Sunday. The avalanche was triggered after the fourth turn and the skier was carried down with it and buried up to their neck, but without any injuries. The avalanche depth varied from thin to thick with evidence of the March 20 interface, the February 2 crust, the basal facets and the ground. Some of the blocks were the size of a Ferrari. Please see the MIN report at https://avalanche.ca/map?panel=mountain-information-network-submissions%2F3a547b44-ea29-11ee-97c1-0a58a9feac02

Snowpack Summary

Quite a complex snowpack for this time of year. Let's break it down starting from the top of the snowpack and working our way down:

  • In general, there is about 10-20cm of settled overlying the March 20 temperature crust. Generally this snow is well bonded to the crust except on steeper terrain where you could still sluff it while skiing. Any terrain that is tipped slightly to the sun has a sun crust on it in the morning and will soften when the sun comes out. The forecasted 5cm of snow will freshen things up.

  • The March 20 temperature crust (down about 20cm) is anywhere from 1-10cm thick and can be mostly found below 2400m on North aspects and to mountain top on solar aspects. Some areas do not have this crust and is not providing any bridging.

  • The February 2 crust is down about 60-80cm and has started to break down with facets on top and below it. This layer is not to be trusted anymore in terms of bridging any deeper instabilities

  • The basal facets make up more than half of the snowpack and are clearly visible when you dig a snow pit. Any avalanche that is triggered in the upper snowpack could easily step down to this layer. If this happens, one is looking at a full depth avalanche to ground.

The depth of the snowpack is quite variable with thin to thick areas of snow. The Tent Bowl size 3 avalanche that was skier triggered a few days ago is a classic photo of thin to thick areas. In this instance, the avalanche appears to have been triggered from a thin area that went full depth and is right beside a thick wind loaded feature. With everything going on in the snowpack, a more conservative approach seems reasonable. The bigger ski lines and larger features are best left alone in these conditions.

Weather Summary

Thursday will be mostly cloudy with light flurries and 2-4cm. Winds are expected to be around 40km/h from the SW at ridgetop. Freezing level will be 2200m with a high of -3c in the alpine.

Be aware that when the sun does come out it packs a punch at this time of year and snow stability will quickly deteriorate on the solar aspects. Thin cloud can also lead to a "Greenhouse Effect" that can make the upper snowpack moist and unstable. Lots going on in Spring!

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Conditions may have improved, but be mindful that deep instabilities are still present.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.

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.