Avalanche Forecast

Archived

Jan 22nd, 2023–Jan 23rd, 2023

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Glacier.

Increasing winds will likely redistribute the new low-density snow, forming fresh wind slabs in the alpine, which will keep the hazard elevated for a few days.

High-quality skiing is still found throughout the Park, despite the below-average snowpack depth.

Confidence

Moderate

Avalanche Summary

MacDonald Gully 6 ran size 3.0 early on Sunday morning, likely initiating as a wind slab.

Frequent Flyer ran size 2.0 over the Connaught Valley skin track into the creek around noon on Saturday. The debris pile was ~1m deep and 10m wide.

A steady stream of size 1-1.5 skier-triggered avalanches have been reported over the last five days, likely failing on the Jan 3 surface hoar which is buried ~40cm.

Snowpack Summary

Fresh pockets of wind slab in the alpine exist in some locations. Early Jan surface hoar layers are present in the upper 40cm.

The mid-pack facets are slowly rounding and gaining strength, while the basal facets and Nov 17 facet/SH/crust weakness are still reactive when isolated in snowpack tests.

Weather Summary

A cold front moves through the region on Monday bringing 25-50km/hr Westerly winds, ~5cm of snow, and an alpine high of -10.

Small amounts of snow and continued wind on Tuesday. Temperatures gradually rise on Wednesday. No significant snowfall until the end of next week.

Terrain and Travel Advice

Be especially cautious as you transition into wind affected terrain.
Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
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.

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.

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.