Avalanche Forecast

Archived

Jan 24th, 2020–Jan 25th, 2020

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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Inland.

Only light amounts of new snow are expected, but strong southwesterly winds are forming fresh wind slabs in exposed areas at upper elevations.

Confidence

Low - Uncertainty is due to difficult to forecast freezing levels. Uncertainty is due to the limited number of field observations.

Weather Forecast

Friday night: Around 5 cm new snow. Strong southwesterly winds. Alpine low -4 C. Freezing level around 1100 m.

Saturday: 5-10 cm new snow. Strong southwesterly winds. Alpine high -4 C. Freezing level around 1100 m.

Sunday: A trace of new snow. Moderate south to southwesterly winds. Alpine high -2 C. Freezing level around 500 m.

Monday: A trace of new snow. Moderate south to southwesterly winds. Alpine high -4 C. Freezing level around 500 m.

Avalanche Summary

Natural storm slabs size 1-2 were observed in steep north facing alpine terrain in the Bulkley area on Tuesday. Wind slab avalanches, skier triggered size 1.5 and natural size 2.5 were observed in the Howson ranges Monday.

Last weekend, a natural storm cycle was observed at treeline and below. Slabs were soft and thin but propagated widely resulting in avalanches up to size 2. They ran on the faceted interface buried January 17th.

There have been reports trickling in over the past month of natural persistent slab avalanches up to size 3 in the Bulkley Valley. These are thought to have been failing on the November crust/facet layer near the ground. The last reported activity at this interface was Monday January 13th.

Snowpack Summary

Southerly winds have formed fresh wind slabs from 15-30 cm (up to 50 cm in the Howson area) of recent snow in places that were previously scoured by northeasterly arctic outflows. In wind sheltered areas at treeline and below, the recent snow sits on a layer of touchy facets.

A layer of surface hoar now buried up to 1 m below the surface may also be found at treeline. A deep crust/facet layer lurks at the base of the snowpack. A couple of large avalanches are suspected to have run on this interface in the last few weeks. These larger avalanches have been specific to lee and cross-loaded features in the alpine.

Terrain and Travel

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Wind slabs are most reactive during their formation.
Be alert to conditions that change with elevation, aspect and exposure to wind.
The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.