Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 14th, 2022–Dec 15th, 2022

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

Regions

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

Northerly winds have formed stiff wind slabs in unusual areas and at lower elevations than you might typically expect. These slabs are expected to bond poorly to the underlying crust.

Concern for buried weak layers continues to demand conservative terrain selection and good travel habits.

Confidence

Moderate

Avalanche Summary

During the storm last Friday, a natural avalanche cycle occurred, with natural storm slab avalanches up to size 2. Numerous skier-triggered storm slabs were reported in this time period as well. Notably, some explosive control produced persistent slab avalanches that failed on the mid-Nov crust down about 50cm and propagated around 50m wide.

Over the weekend, natural activity began to taper but human triggering remained likely! Many riders in the Squamish and Whistler area got surprised by size 1-2 slab avalanches. These slabs mainly occurred on wind-loaded slopes on north and west aspects in the alpine and treeline. Check out these MIN reports for examples (MIN1) (MIN2).

Looking forward to Thursday, northerly winds are expected to redistribute the surface snow into fresh wind slabs anywhere it remains loose and powdery. Keep in mind that small avalanches have the potential to 'step down' to deeply buried weak layers resulting in larger than expected avalanches.

Thank you for sharing your observations! Please keep posting to the MIN; it helps strengthen our information gathering.

Snowpack Summary

Surface: Large surface hoar growth has been observed in sheltered areas. A crust exists on solar aspects. Around 30 to 50 cm of recent snow, but also at or near the surface you can find wind-scoured, wind-pressed, and of course wind slabs.Upper-pack: The upper snowpack consists of 30-50 cm of settling snow. Below this, large surface hoar (up to 10 mm) has been observed mainly in shaded or sheltered areas. Mid-pack: 40-150 cm down is a late November crust, with soft facets above. This is likely the critical snowpack weakness. Professionals are concerned about the possibility of avalanches releasing at this deeper interface with the new snow load and warm temperatures.

Total snow depths remain low for early December with 90 to 140 cm at treeline and up to 200 cm in the alpine. Much of the below treeline elevation band is below the threshold for avalanches.

Weather Summary

Wednesday night

Clear with cloudy periods. Alpine temperatures drop to a low of -3 °C. Ridge wind 25 km/h gusting to 50 km/h from the northeast. Freezing level at valley bottom.

Thursday

Mainly sunny. Alpine temperatures reach a high of 1 °C. Ridge wind 25 km/h gusting to 55 km/h from the north. Freezing level rises to 1700 metres.

Friday

Sunny with an alpine temperature inversion. Alpine temperatures reach a high of 2 °C. Mostly light northerly ridge wind occasionally gusting to 45 km/h. Freezing level rises to 2500 metres.

Saturday

A mix of sun and cloud. Alpine temperatures reach a high of -4 °C. Ridge wind 20 km/h occasionally gusting to 45 km/h from the southwest. Freezing level at valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Be aware of the potential for surprisingly large avalanches due to deeply buried 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.