Avalanche forecast

Cariboos

Jan 29 – 30, 2012Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–6
    Wind slabs continue to build behind ridges and terrain breaks. Areas that avalanched earlier this week may re-load as the storm continues. Dropping cornices can add to the problem.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–6
    Large cornices are looming over many slopes. A falling chunk could trigger an avalanche on the slope below.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    4–7
    The Jan 20 and Jan 13 layers are starting to blend. Doesnèt matter - theyère pretty similar it seems. Large planar slopes at 1500m and below.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–5
    Storm slabs continue to build above buried weak layers. Warming and snowfall this weekend will increase the storm slab problem.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

After the storm clears a westerly zonal flow pattern with short lived disturbances is expected for Monday & Tuesday. That means westerly (upslope) regions should see the bulk of the precipitation (around 10 - 20 cm daily in favoured areas), moderate SW winds, and freezing levels around 1000 m on Monday and a little higher (warmer) on Tuesday. Wednesday the pattern is set to change as a ridge builds and dries out the area with warming temperatures. Thursday freezing level is expected to be around treeline (2000mis possible).

Avalanche Summary

Few avalanches reported Saturday; limited visibility restricted observations. Professionals working in the area expect today (Sunday) to have a widespread natural avalanche cycle including large full-path avalanches running from alpine to valley bottom, large windslabs at treeline and alpine elevations (to around size 2.5), widespread storm snow avalanches (independent of wind-loading) at all elevations, and possibly even deep releases at treeline and below treeline elevations on the deeply buried facet & crust combination. Looking forward to Monday I expect natural activity will taper off but will not have fully stopped and conditions will remain primed for human-triggered slides, which could be large. I would continue to remain very suspicous of cornices and the possibility of cornice triggered slides.

Snowpack Summary

Around 40 to 60 cm of new snow in the past 24 hours and storm snow totals of 150 cm or more are reported. Mod southerly or southwesterly winds have created windslabs and large fragile cornices. Warm temperatures are promoting storm slabs in the short term (upside down storm snow layers) and settling (strengthening) in the slightly longer term. All this new snow increases the load (stress) on deeper layers created during the mid-January cold snap; namely facets (sugar) and a crust at lower elevations (say 1500m and lower). This layer is now deeply buried (around 200 cm or more in many places) but snowpack test results on this layer range from no result to easy (variable strength) but the shear pops (if triggered it wants to propagate).

Regions covered