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Avalanche Forecast

Archived

Feb 20th, 2020–Feb 21st, 2020

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

Regions

Cariboos.

Moderate southerly winds may create small wind slabs that are possible to trigger in steep, convex terrain below ridgetops.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

THURSDAY NIGHT: Few clouds, moderate south wind, alpine temperature -12 C, freezing level below valley bottom.

FRIDAY: Increasing cloudiness, moderate south wind, alpine temperature -6 C, freezing level 1100 m.

SATURDAY: 5-15 cm snow, moderate southwest wind, alpine temperature -8 C, freezing level 1000 m.

SUNDAY: Cloudy with possible flurries, light to moderate south wind, alpine temperature -10 C, freezing level 600 m.

Avalanche Summary

A cornice triggered size 3 deep persistent slab avalanche was reported on a steep convexity at treeline on Tuesday. This suggests large avalanches are still possible with large triggers in isolated locations. There has been limited avalanche activity reported over the long weekend, suggesting storm slabs have become less reactive. Old wind slabs below ridgetops are likely becoming increasingly stubborn to trigger.

Snowpack Summary

Last week it snowed 40-80 cm, with the greatest accumulations in the northern part of the region. This snow has shown signs of settling and gaining strength over the past few days, with the exception of some wind affected slopes. This recent snow sits above a few different interfaces (a hard rain crust below 1800 m, sun crusts on south-facing slopes, and potentially small surface hoar at treeline), but appears to be bonding well to these interfaces. Sunny weather this week could weaken cornices and surface snow on steep south-facing slopes. The mid and lower snowpack are generally well settled and strong.

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Cornice failure may trigger large avalanches.

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.