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Avalanche Forecast

Archived

Feb 15th, 2022–Feb 16th, 2022

Alpine
Natural avalanches unlikely, human triggered possible.
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, 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

Cariboos.

New snow will bond poorly to the underlying crust. Small but reactive pockets of wind slab may form in lee areas in the alpine and treeline. 

Manage open slopes at treeline carefully where triggering a persistent slab avalanche is most likely.

Confidence

High -

Weather Forecast

A passing frontal system will bring light snowfall, with greater amounts forecast for Thursday.

Tuesday Overnight: Mainly cloudy, light snowfall 5 cm. Freezing level dropping to valley bottom. Light to moderate northwesterly winds. 

Wednesday: Partially cloudy with light flurries. Freezing level rising to 1000 m. Moderate northwesterly winds. 

Thursday: Mainly cloudy and snowing with 5-10 cm forecast. Freezing level rising to 1500 m in the afternoon. Moderate to strong northwesterly winds. 

Friday: Snowing, heavy at times 10-20 cm. Freezing level rising to 1500m. Strong to extreme westerly winds. 

Avalanche Summary

If you see more than 10 cm of fresh snow expect to see some isolated pockets of reactive wind slab on leeward slopes and terrain features on Wednesday.

On Monday, a natural cornice fall size 1.5 was reported and did not pull a slab from the slope below. The aspect and elevation are unknown. 

Last Friday, sledders near Blue River remote triggered several large slab avalanches on shaded aspects at treeline. The failure plane of these avalanches is uncertain, but large remote triggered avalanches would make us suspect it failed on the late January buried surface hoar. Photos from this incident can be seen here.

As a result of the rain event last Wednesday (a week ago), operators in the north of the region observed a large natural avalanche that initiated as a storm slab in the alpine and gouged to ground lower down in the track in wet, uncohesive snow.

Snowpack Summary

A light amount of snow is expected to bond poorly to the old surface. This surface is comprised of near-surface faceting and in some areas, surface hoar growth overlying a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline. 

Several weak layers exist in the upper snowpack including buried crusts, facets, and a prominent weak layer of surface hoar. This surface hoar is the dominating feature. It was buried in late January and exists 40 to 100 cm deep in the snowpack. Reports suggest that the surface hoar is most prominent in sheltered openings at and below treeline. Terrain features to be suspect of includes the lee side of protected ridges, openings in the trees, cut blocks, and burns. 

The lower snowpack is generally strong and well-bonded.

Terrain and Travel

  • Wind slabs may be poorly bonded to the underlying crust.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.

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.