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Avalanche Forecast

Archived

Dec 26th, 2022–Dec 27th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
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

Sea To Sky, Brandywine, Garibaldi, Homathko, Powell River, Spearhead, Tantalus, Tetrahedron.

The next storm arrives Monday night and brings with it an additional 10 - 20 mm of precipitation and strong southerly winds. These conditions will continue to build thick storm slabs that are reactive to human triggering.

Confidence

Moderate

Avalanche Summary

On Sunday, explosives control triggered several storm slab avalanches up to size 2.5. Storm slabs were 30-50 cm deep. Explosive also triggered one size 2.5 persistent slab avalanche that is suspected to have run on the Dec 8 surface hoar.

Through Saturday, explosives and skier traffic produced multiple size 1-2 storm slabs in treeline terrain and higher, on average crowns were 30 cm deep. Later in the day skiers remotely triggered (size 1) a re-loaded slope at treeline. Loose wet avalanches were reported below 1700 m.

Please continue to post your observations and photos to the Mountain Information Network.

Snowpack Summary

By Tuesday morning 10 - 20 cm of additional snow brings storm snow totals to 40 - 50 cm. Extreme southerly winds have pressed surfaces and redistributed snow into thick slabs in alpine lees. A melt-freeze crust is found below 1800 m. The new snow covered a layer of weak and unconsolidated snow produced by the recent cold weather.

A number of layers persist deeper in the snowpack, consisting of facets, surface hoar, and crusts. Most recently, these layers have been unreactive and this heavy load of new snow should provide insight into any deeper instabilities. Total snow depths are roughly 90-140 cm at treeline and up to 200 cm in the alpine.

Weather Summary

Monday Night

A brief break between storms ends early evening as flurries start up again, 10-20 mm. Ridgeline low temperature -2 C. Southerly winds 25-40 km/hr. Freezing levels around 1100 m.

Tuesday

Moderate to heavy precip, 10-20 mm. Ridgetop high temperature 0 C. Southerly wind 30 - 50 km/h weakening in the afternoon. Freezing levels rise to 1800m during the day before falling to 1000 m overnight.

Wednesday

Cloudy with scattered flurries, trace accumulation. Ridgetop high temperature -4 C. Westerley winds 20 km/hr. Freezing levels 800-1000 m.

Thursday

Cloudy with scattered flurries, trace accumulation. Ridgeline high temperature -4 C. Southerly wind 40 - 60 km/h weakening in the afternoon. Freezing levels 500-1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be alert to conditions that change with aspect and elevation.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.