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Avalanche Forecast

Archived

Feb 13th, 2023–Feb 14th, 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.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

Old wind slabs formed last week will be harder to trigger but could still deliver an unexpected surprise. Cornices are large in some areas and could become active if it warms up in the afternoons. Deeper layers should still be on your mind in the Elkford and Flathead areas.

Confidence

Moderate

Avalanche Summary

A few small wind slab avalanches were observed over the weekend and one Cornice failure was observed on Saturday as described in this MIN.

On Friday, several skier-triggered wind slab avalanches were reported in the Fernie area. They were size 1 to 2, occurring in both alpine and open forested terrain, as illustrated in MIN reports here, here, and here.

Good quality riding was reported in sheltered, lower elevation terrain over the weekend.

Deep persistent slab avalanches should still be on your radar in the Elkford and Flathead areas.

Snowpack Summary

Up to 15 cm of new snow is possible Monday night and into Tuesday, which will fall above various layers, including sun crusts and hard wind-affected snow. Sheltered, shaded areas will likely have deeper soft snow from last week.

In the Lizard range specifically, the mid-pack is consolidated with a supportive 10 to 20 cm thick frozen crust buried 80 to 100 cm.

In the Elkford and Flathead areas, deeply buried weak layers are slowly gaining strength but are still a concern, especially in steep rocky terrain features where the snowpack is thin.

Weather Summary

Monday night

Mostly cloudy. 5-10 cm of new snow possible from flurries. Wind changing to north overnight at 10 km/h. Temperature -5˚C.

Tuesday

A mix of sun and cloud. Now new precipitation. Wind from the northeast at 10 km/h gusting 30 km/h. Temperature -8˚C to -5˚C.

Wednesday

Mostly sunny. Wind from the southwest at 15 km/h. Temperature -10˚C in the morning rising to -4˚C in the afternoon. Freezing level up to 700 m. Solar affect is likely.

Thursday

Mostly sunny. Wind from the southwest at 10 km/h. Temperature -12˚C in the morning rising to -5˚C in the afternoon. Freezing level up to 1100m. Solar affect is likely.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for areas of hard wind slab on alpine features.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.