Avalanche Forecast

Issued: Jan 14th, 2014 8:25AM

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

triley, Avalanche Canada

South Rockies.

New South Rockies Blog-post. View it here

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Overnight and Wednesday: Some very light precipitation with very strong Northwest winds overnight, becoming moderate Northwest during the day. Freezing level rising to about 1800 metres during the day with some sunny periods.Thursday: Light to moderate Northwest winds with thin high cloud and a chance of sunny periods. Freezing level near 2000 metres.Friday: Warm air trapped at higher elevations. Above freezing temperatures in the alpine with sunny periods.

Avalanche Summary

No new avalanches reported. Suspect extreme Westerly winds and warm temperatures have developed hard wind slabs. Areas with snow available for transport may have continued to experience natural wind slab avalanches. Forecast warm temperatures, limited precipitation, and continued very strong winds are expected to develop hard wind slabs and decrease natural avalanche activity. Avalanches that are triggered are expected to be large due to the amount of recent storm snow. Large storm snow avalanches may step down to buried persistent weak layers resulting in very large destructive avalanches.

Snowpack Summary

Intense snow transport was reported from the Flathead area on the weekend. Expect extensive wind transport and wind slab development in all areas of the region. Recent storm snow varies from 40-70 cm across the region and I suspect that in some alpine areas storm snow has been transported into slabs that are more than a metre thick. Persistent weak layers of buried crusts/facets/surface hoar continue to be a concern, and may have been the failure plane for recent large natural avalanches. Very warm and windy conditions are expected to continue for the next few days. In the long term the warm temperatures should help with some settling and bonding of the buried weak layers. In the short term I don't like the hard wind slabs above weak layers with a rapid change in temperature.

Problems

Wind Slabs

Very strong winds have created hard wind slabs in the alpine and at treeline. These hard wind slabs may be more than a metre thick.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>Watch for areas of hard wind slab in steep alpine features.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

Recent storm snow and hard wind slabs have been added to the load above buried weak layers. Deeply buried weak layers may become harder to trigger, but the consequences are very large destructive avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried facet/crust layer and depth hoar layer.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 15th, 2014 2:00PM