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Avalanche Forecast

Archived

Feb 1st, 2021–Feb 2nd, 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 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.

Regions

Cariboos.

Touchy storm slabs are sitting on a very weak layer of surface hoar which is very likely to be reactive to human triggers, even in low angle terrain. Avalanches may be larger than expected due to the presence of this weak layer.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system. Uncertainty is due to the limited number of field observations.

Weather Forecast

  

MONDAY NIGHT: Snow; 15-20 cm. / Strong, south ridgetop wind / alpine low temperature -7 / Freezing level valley bottom.

TUESDAY: Snow; 5-10 cm. / Moderate, southwest ridgetop wind / alpine high temperature -5 / Freezing level valley bottom.

WEDNESDAY: Mostly cloudy with sunny periods / Moderate, northwest ridgetop wind / alpine high temperature -10 / Freezing level valley bottom.

THURSDAY: Snow; 5-10 cm. / Strong, west ridgetop wind / alpine high temperature -9 / Freezing level valley bottom.

Avalanche Summary

Touchy storm slabs are sitting on a very weak layer of surface hoar which is very likely to be reactive to human triggers, even in low angle terrain. Avalanches may be larger than expected due to the presence of this weak layer.

A MIN report from just outside this region in Clemina Creek likely represents the surface hoar layer of concern that we suspect is present in much of the Cariboos. Report HERE.

Note: We currently have very few observations from this region. Please consider sharing what you see by submitting a MIN report.

Snowpack Summary

25-30 cm of new snow as of Monday afternoon brings recent snow totals up to 40 cm. Touchy storm slabs are sitting on a weak layer of surface hoar which has potential to surprise backcountry users by how easily these storm slabs may be triggered and how wide the slabs propagate across slopes.

A second weak of layer of surface hoar and crust from early January is 50-110 cm deep and tapers above 1700 m. This layer was last reactive almost 2 weeks ago (Jan 16) in the south of the region near Valemount. It is most suspect in sheltered, open slopes at and below treeline. Deeper in the snowpack, a couple of older persistent weak layers may still be identifiable from late and early December, consisting of surface hoar and a crust with faceted snow and buried anywhere from 70-150 cm deep. Deeper layers may wake up with heavy snow fall and warm temperatures.

Terrain and Travel

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Good day to make conservative terrain choices.
  • Be aware of the potential for human triggerable storm slabs at lower elevations, even on small features.
  • Avoid traveling through runout zones during stormy periods when large avalanches are likely.

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.