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Avalanche Forecast

Archived

Jan 2nd, 2021–Jan 3rd, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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

South Rockies.

Avalanche danger will rise as a storm crosses the region over Saturday night through Sunday. There's uncertainty in the forecast, so gather info as you travel and step back from avalanche terrain altogether if new snow accumulations in your area reach 20 cm or more.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

SATURDAY NIGHT: Cloudy with snowfall bringing 5 to 15 cm of new snow. Moderate southwest wind, becoming strong at ridgetop.

SUNDAY: Cloudy with continuing flurries bringing another 5-15 cm of new snow, easing by evening. Moderate southwest winds, strongest in the morning. Alpine high temperatures around -4, cooling over the day. Freezing levels beginning near 1700 metres and falling over the day.

MONDAY: Mainly cloudy with isolated flurries and a trace of new snow, increasing a bit overnight. Moderate southwest winds. Alpine high temperatures around -4 with freezing levels rising to about 1500 metres.

TUESDAY: Cloud and flurries diminishing over the day with 5-10 cm new snow, including overnight accumulations. Light southwest winds. Alpine high temperatures around -5 with freezing levels around 1500 metres.

Avalanche Summary

No recent avalanches have been reported in the region. Avalanche activity is expected to increase on Sunday. Riders could trigger storm or wind slabs and the possibility of triggering larger, more destructive avalanches involving deeper weak layers will be increased.

Snowpack Summary

Another 10 to 30 cm of snow is forecast to accumulate by Sunday afternoon with associated strong southwest wind. New storm slabs are expected to form in sheltered terrain and wind slabs in exposed terrain features.

Weak layers of feather surface hoar and/or sugary faceted grains may be found above a hard melt-freeze crust around 50 to 100 cm deep. The most recent avalanche activity on these layers were reported on December 23 and 25.

The base of the snowpack consists of faceted grains and a hard melt-freeze crust from early-November. The most recent activity on this layer was on December 23. The likelihood of avalanche activity at these deeper layers will be heightened during and immediately after the storm.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid slopes that sound hollow or drum-like.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.