Avalanche Forecast

Issued: Feb 18th, 2019 4:20PM

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

mconlan, Avalanche Canada

South Rockies.

Recent snowfall may continue to be reactive to riders. Use added caution at higher elevations where the wind has formed touchy deposits. Also use caution in any opening below treeline, where a buried weak layer may be touchy.

Summary

Confidence

High -

Weather Forecast

MONDAY NIGHT: Clear skies, light to moderate northwest wind, alpine temperature -15 C.TUESDAY: Increasing cloud with afternoon light snowfall, trace accumulation, moderate northwest wind, alpine temperature -13 C.WEDNESDAY: Cloudy with light snowfall, accumulation 5 cm, light to moderate northeast wind, alpine temperature -13 C.THURSDAY: Mostly cloudy with isolated snowfall, accumulation 1 to 5 cm, light to moderate northwest wind, alpine temperature -18 C.

Avalanche Summary

There was evidence of many small to large (size 1 to 2) wind slab avalanches in the region on Sunday and Monday. There was also evidence of 40 cm slabs scrubbing to ground in very shallow snowpack areas.

Snowpack Summary

Around 20 to 30 cm of snow fell within the past three days, with the highest amounts in the south of the region. The snow likely has slab properties where it fell with wind at higher elevations and could be loose in sheltered areas.The mid-January layer of surface hoar is buried around 50 to 80 cm. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m but has been found up to 2200 m. Snowpack test results suggest that this layer could be triggered by humans.The middle of the snowpack is generally consolidated. The bottom half of the snowpack is unconsolidated and composed of weak and sugary faceted grains. There is potential for shallower avalanches to step down to these deeper weak layers.

Problems

Wind Slabs

Around 20 to 30 cm of recent snow may be touchy. Use added caution in lee terrain features near ridges, as winds have formed deeper deposits. The wind was first from the west and more recently from the northeast, so all lee features are suspect.

Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered, wind slabs may step down to deeper layers resulting in large avalanches.Keep an eye out for reverse loading created by an upslope storm.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A weak layer of surface hoar is buried around 50 to 80 cm, which is best preserved in shaded and sheltered areas between 1600 m and 1900 m.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.Use added caution in open terrain features such as cutblocks, gullies, and cutbanks.Be aware of the potential for wide propagation.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Feb 19th, 2019 2:00PM