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Avalanche Forecast

Archived

Dec 30th, 2020–Dec 31st, 2020

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

Regions

South Coast.

Recent heavy snowfall means that storm slabs will be widespread and are still likely to be triggered by people, especially in wind loaded areas. Continue to choose low-angle terrain.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

WEDNESDAY NIGHT - Snow, mixed with rain at times, 15-20 cm / southwest wind, 40-60 km/h / alpine low temperature near -1 / freezing level 1000 m 

THURSDAY -Mainly cloudy / light northwest wind / alpine high temperature near 0 / freezing level 1200 m 

FRIDAY - Snow, mixed with rain, 50 cm or 50 mm of rain / southwest wind, 60-80 km/h / alpine high temperature near 1 / freezing level 1600 m

SATURDAY - Snow, mixed with rain, 75 cm or 75 mm of rain / southwest wind, 70-90 / alpine high temperature near 1 / freezing level 1500 m 

Avalanche Summary

Recent fresh snow with strong winds will mean that the likelihood of avalanches remains elevated on Thursday, in spite of the drier weather. 

There were numerous avalanches up to size 1.5 reported in the North Shore mountains during the storm on Wednesday. It is likely that a widespread natural avalanche cycle occurred throughout the region on Wednesday as well, especially at higher elevations.

Many thanks for all of the great MIN report submissions on Wednesday!

Snowpack Summary

The South Coast received up to 60 cm of new snow with moderate to strong winds between Tuesday evening and Thursday morning. This new snow sits on a crust in many areas, and may also sit on surface hoar in some places. The new snow may take longer than usual to gain strength if these weak layers are present.

Around 100-150 cm of snow now overlies a hard melt-freeze crust up to around 1500 m. The depth of this layer varies greatly due to the wind transport of snow as it fell over the last two storms. It seems to be bonding well with the surrounding snow.

The remainder of the snowpack is well-settled.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid freshly wind loaded terrain features.
  • Be aware of highly variable recent wind loading patterns.

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.