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Avalanche Forecast

Archived

Dec 30th, 2021–Dec 31st, 2021

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Northwest Coastal.

The calm before the storm ! Wind slabs will remain reactive to riders, especially at treeline where they are overlying a weak interface.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

An arctic ridge of high pressure will briefly build, leading to another clear and cold day heading into Friday. The next round of snow is expected late Friday, with heavy rates of precipitations to invade the northern ranges for the weekend.

THURSDAY NIGHT: Clear / Moderate north winds in the alpine / Low of -18 

FRIDAY: Cloudy / Snow beginning in the evening / Light southwest winds in the alpine / High of -15 / Possible temperature inversion with -8 at 1500 m. 

SATURDAY: Snow 30-50 cm / Strong to extreme southwest winds in the alpine / High of -10

SUNDAY: Snow 20-40 cm / Strong southerly winds in the alpine / High of -10

Avalanche Summary

No human-triggered or natural avalanches were reported in the last 24h. 

If you go out in the mountains, please consider filling out a Mountain Information Network report.

Snowpack Summary

The region received 10-20 cm of new snow Wednesday night, along with strong to extreme northerly winds. Fresh and reactive widespread wind slabs can now be found at treeline and alpine on all southerly slopes. This new snow is likely to poorly bond to the old surfaces, especially in the alpine where the surface is hard wind slabs or scoured surfaces.

Two layers of surface hoar exist within the upper snowpack in protected areas near treeline; one is down 20-40 cm (Dec 21) and the other is down 55 cm (Dec 18) with larger grains up to 12mm. It will likely become a concern in isolated locations in the treeline where a wind slab has formed above it.

Snowpack depths vary greatly across the region, expect to find anywhere from 140-300 cm of snow around treeline.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Be aware of the potential for large avalanches due to the presence of 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.