Avalanche Forecast

Issued: Feb 4th, 2015 8:47AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

triley, Avalanche Canada

Cariboos.

If more snow than forecast arrives during the day on Thursday, avalanche danger may reach HIGH.

Summary

Confidence

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

Weather Forecast

Snow starting overnight or early Thursday morning combined with strong Southwest winds and alpine temperatures near -10. Expect 10-15 cm of snow by early afternoon with continued strong Southerly winds and alpine temperatures around -5. Another 5-10 cm of new snow overnight, and snow continuing during the day on Friday. Strong Southerly winds are forecast to push warm moist air up over the arctic air that has been sitting to the North of the region. This may result in enhanced snowfall for some areas, and an above freezing layer between 1500-2000 metres in other parts of the region. Generally, I think it will be cooler with more snow in the North and East of the region, and warmer with a mix of snow and rain or freezing rain in the Southwest of the region. The storm should continue on Saturday with another pulse (10-15 cm) of warm and moist air pushed by moderate Southwest winds.

Avalanche Summary

There were a couple of natural cornice falls up to size 2.5 over the past few days, and several thin soft slab or loose snow avalanches up to size 1.0. The new storm starting on Thursday is expected to develop a thick storm slab that may release naturally and also may step down to the mid-January persistent weak layer.

Snowpack Summary

Recent snowfalls have developed a new storm slab that is 30-50 cm thick and sits on a variety of old surfaces including crusts, surface hoar, and old wind slabs. Ski penetration has been reported to be about 50 cm in the North of the region. A crust can be found below about 1900m in the north of the region and below 2200m in the south of the region. At higher elevations the new snow covers old wind slabs formed by moderate southwest winds. Several persistent week layers can be found deeper in the snowpack that may be capped by the overlying crust at lower elevations. The mid-January surface hoar is buried between 40 and 80cm down and remains a concern at treeline and above. The mid-December surface hoar layer is now 80 to 140cm below the surface and appears to be slowly gaining strength.

Problems

Storm Slabs

Forecast new snow and wind are expected to result in natural avalanches releasing within the storm slab, or on the buried crust. Incremental loading from several pulses of moisture may make it difficult to forecast the timing of natural avalanches.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>The new snow will requires several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

Buried persistent weak layers may be over-loaded by the forecast new storm snow resulting in human triggering, or storm slab avalanches in motion stepping down to the deeply buried weak layers.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Pay attention to overhead hazards like cornices.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Feb 5th, 2015 2:00PM