Avalanche Forecast

Archived

Feb 22nd, 2023–Feb 23rd, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

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

Low angle, sheltered slopes at treeline are your best bet for good skiing. Limit exposure to overhead avalanche terrain, even in valley bottoms. Cold, dry snow can run far in an avalanche

Confidence

Moderate

Avalanche Summary

Control today had results, but not what we were expecting. Out of 6 shots, we had three sz1.5 slab avalanches. They were all windward aspects which contributed to their relatively small size.

Snowpack Summary

This latest storm has left us with 40-50cm of snow. This is rapidly settling out for two reasons: the facets underneath are being crushed, and the new snow is settling within itself. Both of these are good things. So far we haven't seen a widespread cycle, and we probably won't. But, keep in mind, while those depth hoar and facet layers are being crushed, they are very sensitive to triggering. The other thing worth chatting about is the unusual wind pattern with this weather system. While cold isn't a stranger with arctic highs, sustained moderate winds are. Expect wind loading on all aspects. Slabs are out there, and they are still in the human triggering phase of their life. And finally, who could write a snowpack and not talk about the deep facets and depth hoar? Those layers are still there and probably not liking the new snow load. Don't assume anything has gotten better because it looks like winter.

Weather Summary

The cold will continue for a few days yet. Tonight's low will be about -31 with a piddly 5 degree warm up tomorrow. The winds will be the real kicker. With moderate (42km at treeline) east winds expect wind chills of minus a million. Well, maybe not a million, but you get the idea. The good news? Skies will be clear and no snow in the near future.

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.
Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
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.

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.