Avalanche Forecast

Issued: Jan 14th, 2018 5:06PM

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

cgarritty, Avalanche Canada

South Rockies.

The southeast corner of the province is just a step behind interior regions, which are experiencing a sharp increase in large avalanches due to solar input and warming. A Special Public Avalanche Warning is in effect in this region.

Summary

Confidence

Moderate -

Weather Forecast

Monday: A mix of sun and cloud with thicker valley cloud due to a building temperature inversion. Light south winds. Freezing level to around 2500 metres with alpine high temperatures of +2.Tuesday: A mix of sun and cloud. Strong southwest winds. Above freezing temperatures developing at all elevations with alpine temperatures dropping from about 0 to -2 over the day.Wednesday: A mix of sun and cloud. Moderate to strong southwest winds. Freezing level to about 1500 metres with alpine high temperatures to around -3.

Avalanche Summary

Recent report include observations of small loose dry and small thin wind slabs in the Size 1 to 1.5 range, and just maybe to Size 2.

Snowpack Summary

An unstable weak layer from mid-December (predominantly feathery surface hoar crystals and/or a sun crust) is found at treeline and below treeline elevations. Slabs can fail easily on this layer, either naturally or with the weight of a person or machine. Forecasted warm air temperatures could increase slab properties of the overlying snow and make this layer easier to trigger.The snowpack is variable across the region, but persistent slabs are generally a widespread problem. Wind slab and storm slab distribution will be more variable. New wind slabs can be found in parts of the region due to recent southwest winds. Windward alpine slopes may be scoured; and variable wind slabs are found at treeline and alpine elevations. New snow is likely to fail as storm slabs and/or loose avalanches.Deeper in the snowpack, an early-season rain crust and sugary facets exist. An avalanche in motion could step down to these deeper layers, creating a large and destructive avalanche. Overall snowpack depths are variable across the region. It is generally shallower in the east.

Problems

Persistent Slabs

Forecasted warm air temperatures could increase the likelihood of triggering buried weak layers. The trees may not be the safe haven you expect: adopt a cautious attitude to all avalanche terrain.

Avoid open slopes and convex rolls where buried weak layers may be preserved.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Minimize overhead exposure during periods of warming and/or direct sun on starting zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Recent variable winds have redistributed loose snow into wind slabs on a range of aspects at higher elevations. A big enough wind slab release in the wrong location may have the force needed to trigger a deeper persistent weak layer.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 15th, 2018 2:00PM