Avalanche Forecast

Archived

Jan 19th, 2023–Jan 20th, 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.

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.

Keep an eye open for wind slabs forming in unusual places as northwest winds pick up tomorrow, particularly in the alpine and exposed treeline.Surface conditions aside, the weak basal snowpack continues to demand conservative terrain selection. Keep up the safe group management decisions and avoiding shallow rocky start zones like the plague.

Confidence

Moderate

Avalanche Summary

On Tuesday and Wednesday, human-triggered wind slabs up to size 1 were reported at treeline and above.

Ski cutting in the Fernie area on Monday yielded small (size 1) wind slab releases after the area received 15 cm of new snow. Natural dry loose releases from steep alpine terrain reached size 1.5.

Snowpack Summary

Roughly 10 cm of recent snow has been getting moved into small wind slabs in exposed areas and otherwise settling on older wind-affected surfaces above 1800-2000 m and on a crust below this elevation.

A crust/facet layer (2-15 cm thick at TL elevation) is down 50-90 cm. Where it's thickest, it caps the settled and consolidated mid-snowpack.

Another crust/facet layer is down 70-150 cm. Below this crust, the basal snowpack is weak and faceted.

Weather Summary

Thursday night

Cloudy with isolated flurries. Light to moderate southwest winds, increasing into the morning.

Friday

Mainly cloudy. Light southwest or northwest winds, more northerly with elevation and potentially strong in the alpine. Treeline high temperatures around -5.

Saturday

Increasing cloud with scattered flurries bringing less than 5 cm of new snow in the afternoon. Finishing quickly in the evening. Light to moderate southwest winds, increasing over the day. Treeline high temperatures around -5.

Sunday

Mainly sunny. Light to moderate northwest winds. Treeline high temperatures around -6.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.