Avalanche Forecast

Archived

Dec 16th, 2023–Dec 17th, 2023

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

Weak layers in the mid and lower snowpack are likely still reactive to human triggering. Stick to conservative terrain.

Confidence

Moderate

Avalanche Summary

Persistent slab avalanche activity seems to have tapered in the past few days. That being said, explosive control has consistently produced small to large (size 1.5 to 2.5) slab avalanches across the region over the past week. These avalanches all occurred above 2200 m and have failed on both surface hoar and facet layers.

There were reports few size of a size 1 wind slab avalanches on Friday.

Snowpack Summary

A dusting of new snow buried a recently formed surface hoar layer, sun crust, and wind-affected snow. A prominent rain crust is found 30 to 50 cm deep and has been reported to extend as high as 2300 m around Invermere and 2000 m around Golden. A layer of surface hoar is also found at this depth and is a particular concern in areas without a thick crust. The bottom of the snowpack contains large weak snow grains and in some places a hard crust near the ground. Typical snowpack depths at treeline are 60 to 110 cm, and taper rapidly below treeline.

Weather Summary

Saturday Night

Mainly cloudy with clear periods with, alpine wind southwest 15-30 km/h, treeline temperature -8 °C.

Sunday

Cloudy with sunny breaks, alpine wind west 20-40 km/h, treeline temperature -6 °C.

Monday

Mix of sun and cloud, alpine wind southwest 10-20 km/h, treeline temperature -5 °C.

Tuesday

Cloudy with flurries, alpine wind southwest 15-30 km/h, treeline temperature -6 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Use conservative route selection and resist venturing out into complex terrain.
Surface hoar distribution is highly variable. Avoid generalizing your observations.
Be especially cautious as you transition into wind affected terrain.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.