Avalanche Forecast

Issued: Jan 9th, 2017 4:48PM

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

rbuhler, Avalanche Canada

South Rockies.

Watch for signs of wind slabs on all aspects as wind direction is expected to reverse on Tuesday. Buried persistent weak layers also remain a concern and avalanches have the potential to step down to a deeper layer.

Summary

Confidence

Moderate - Wind speed and direction is uncertain

Weather Forecast

Mostly cloudy conditions are expected for Tuesday with lingering flurries in the morning. Treeline temperatures are expected to fall to around -20C and alpine winds are forecast to be moderate to strong from the north. Sunny conditions are expected for Wednesday and Thursday with treeline temperatures around -15C during the afternoon and -25C overnight. Alpine winds are forecast to be light from the northeast on Wednesday and moderate from the northwest on Thursday.

Avalanche Summary

No new avalanches were reported on Saturday or Sunday. On Tuesday, recently formed wind slabs are expected to remain reactive to human triggering. Ongoing wind loading is also expected on Tuesday with the forecast for moderate to strong northerly winds in the alpine. With the winds switching directions, wind slabs should be expected on a variety of aspects. Persistent slab avalanches also remain an ongoing concern. Buried weak layers are creating a low probably, high consequence problem for the region.

Snowpack Summary

10-20 cm of new snow on Monday with moderate winds will recharge our wind slab problem, feeding existing slabs with additional load and forming new slabs in the lee of exposed terrain features. Winds have been switching directions recently and wind slabs should be expected on all aspects. The mid snowpack is generally right side up, with the mid-December interface down 40-80cms, giving inconsistent results in snowpack tests. There is some faceting below this interface but resistances are good and showing signs of rounding and stabilizing. Travel conditions have been challenging (especially at lower elevations) and little change is expected until a significant warm up helps to settle the snowpack.

Problems

Wind Slabs

New snow with moderate wind on Monday is expected to have formed soft wind slabs in leeward features. Potentially strong outflow winds on Tuesday may cause reverse loading and form new slabs. Watch for signs of reactive wind slabs on all aspects.

Avoid freshly wind loaded features.Use ridges or ribs to avoid pockets of wind loaded snow.Wind direction has changed recently. Watch for slabs on all aspects.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Where denser snow overlies weak, sugary snow, there is the potential to trigger large, destructive avalanches. Remember that a small wind slab avalanche may provide enough of a trigger to step down to this deeper weakness.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Danger exists where denser snow overlies weak, sugary snow below.Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 10th, 2017 2:00PM