Avalanche Forecast

Issued: Jan 26th, 2019 3:26PM

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

ghelgeson, Avalanche Canada

North Columbia.

Fresh wind slab formation is expected Sunday in the alpine, but our main concern is still the surface hoar down 20 to 35 cm which is most prevalent between 1400 and 1800 m, this interface continues to be sensitive to human triggering.

Summary

Confidence

Moderate -

Weather Forecast

Sunday marks the start of a pronounced ridge of high pressure that is expected to be with us through at least Tuesday. This period is marked by clearer skies, cooler temperatures and a lack of precipitation.SATURDAY NIGHT: Freezing level returning to valley bottom overnight, light southwest wind at most elevations with extreme northwest wind at ridgetop, 1 to 5 cm of snow possible.SUNDAY: Scattered cloud cover, freezing level at valley bottom, moderate to strong northwest wind, trace of snow possible.MONDAY: Mostly clear skies in the morning with cloud cover increasing throughout the day, freezing level at valley bottom, light northwest wind, no precipitation expected.TUESDAY: Clear skies, freezing level at valley bottom, light variable wind, no precipitation expected.

Avalanche Summary

Over the last four days storm and persistent slab avalanches up to size 2.5 were triggered by people on the recent weak layer buried approximately 30 cm below the surface. The majority of these avalanches occurred at treeline and below, however, there have been a few noted at higher elevations in the alpine. There were a few reports of remote triggering Friday on north, northwest and east facing slopes. One was triggered from a flat ridge 30 m away from the avalanche which ran on a moderately inclined north facing slope at 1900 m producing a size 2.5 avalanche. Wind slab avalanches have also been triggered remotely on east and northeast facing slopes.

Snowpack Summary

20 to 35 cm of snow sits above a layer of large surface hoar crystals and sun crust. In areas that have had wind effect the recent snow has been settling into a thin but reactive slab above this weak layer, with enhanced reactivity noted at elevations between 1400 and 1800 m. In sheltered areas the snow lacks cohesion above this layer and is only reactive as dry loose sluffing. The weekend temperature trend form warm to cold is expected to consolidate the upper snowpack but this layer of surface hoar will likely remain sensitive to human triggering.The middle and lower portions of the snowpack are generally well-settled and strong.

Problems

Persistent Slabs

20 to 35 cm of snow sits above a weak interface of surface hoar and sun crust. The recent warm to cold temperature transition may have allowed for a more cohesive slab to form above the surface hoar which is most prevalent between 1400 & 1800 m.

Take heed of obvious signs of instability such as whumpfing, shooting cracks and recent avalanches.Avoid convex rolls at and below treeline where buried surface hoar may be preserved.Use extra caution around steep open terrain features, such as cutblocks, gullies and cutbanks.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Wind Slabs

Northwest wind is expected to pick up Saturday night and should continue through the day Sunday. Watch for fresh wind slab formation which is expected to be most prevalent in the alpine.

Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.Recent wind has varied in direction so watch for wind slabs on all aspects.Carefully evaluate steep lines for wind slabs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Jan 27th, 2019 2:00PM