Avalanche Forecast

Archived

Feb 14th, 2023–Feb 15th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells, Dogtooth, East Purcell, St. Mary, West Purcell.

The best way to manage a complex snowpack like the one in this region is to stick to smaller, low consequence terrain. Don't let your guard down as large persistent and deep persistent slab avalanches are still being reported every two or three days.

Confidence

Moderate

Avalanche Summary

A number of new natural wind slab and storm slab avalanches up to size 2 were reported from the Purcells in the last 48hrs.

Also of note from last weekend.

On Saturday, skiers at Quartz Creek remotely-triggered a size 3 avalanche on a northwest-facing alpine slope at 2300 m. It failed on a 40 to 80 cm deep weak layer.
On Friday, skiers near Invermere remotely-triggered a size 2 on a north aspect at 2400 m. The avalanche started on a 30 cm deep surface hoar layer and stepped down to the deep persistent weak layer.

Snowpack Summary

15-40 cm of of recent storm snow has been variably distributed by winds and is settling above a layer of surface hoar, facets, and/or crust. This layer has become reactive in the southern and western parts of the Purcells, where it is more deeply buried.

The lower snowpack contains a widespread layer of large, weak facets that is typically 80 to 150 cm deep. Snowpack depths at treeline range between 80 and 200 cm, with the shallowest depths found on the eastern edge of the Purcells.

Weather Summary

Tuesday night

Mostly clear. Winds from the west and southwest 10 km/h. Temperature -12˚C in the alpine.

Wednesday

A mix of sun and clouds. No precipitation. Winds from the southwest 20 km/h. Temperature -12˚C to -5˚C.

Thursday

A mix of sun and clouds. Possible flurries in the afternoon. Winds from the southwest 10 km/h. Temperature -14˚C in the morning rising to -7˚C in the afternoon.

Friday

Cloudy. Flurries delivering up to 7 cm of new snow. Winds from the southwest 10 km/h. Temperature -8˚C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Use careful route-finding and stick to moderate slope angles with low consequences.
Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
Avoid steep convex slopes.
Be especially cautious as you transition into wind affected terrain.

Problems

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.

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.