Avalanche Forecast

Issued: Mar 12th, 2018 4:06PM

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

mconlan, Avalanche Canada

Lizard-Flathead.

Freezing levels well above the mountain tops and sunny skies are intensely warming the snowpack, particularly around midday. Best to avoid areas with sun exposure, wind effect, and overhead avalanche terrain. Read our blog on the impact of warming.

Summary

Confidence

High -

Weather Forecast

TUESDAY: Sunny, light southwesterly winds, alpine temperature 4 C, freezing level 3000 m.WEDNESDAY: Mix of sun and cloud, light southwesterly winds, alpine temperature 3 C, freezing level 2500 m.THURSDAY: Mostly cloudy with light snowfall, accumulation 5 cm, light westerly winds, alpine temperature 0 C, freezing level 1500 m.

Avalanche Summary

Numerous wind and wet slabs to size 2 were reported in the region on Sunday, being triggered naturally and by large triggers. The wet slabs were on southerly aspects in the alpine and the wind slabs were on a northwesterly aspect. Small loose avalanches to size 1.5 were observed on solar aspects. Two natural cornice falls were also noted on alpine ridges.The forecast warming and sunshine may wake up a deeper weak layer on steep south facing slopes resulting in large and destructive avalanches.

Snowpack Summary

Warm air temperatures and daytime sun have produced moist snow on solar aspects into the alpine and moist snow on all aspects up to 1400 m. On shady aspects at higher elevations, expect to find wind slabs in lee features and loose dry in sheltered features. These snow surfaces are sitting on patchy surface hoar in parts of the region.Cornices are large and prone to failure with warm air temperatures and sunny skies.In the upper to mid snowpack, a surface hoar or facet layer buried mid-February is 80 to 110 cm below the surface on sheltered northerly aspects.Deeper in the snowpack, the widespread mid-December and late November weak layers are composed of a combination of crusts and sugary facets which are down 200-300 cm. These layers have been dormant but may be awoken by the warm and sunny weather throughout the weekend or by a large trigger, such as a falling cornice.

Problems

Cornices

Daytime heating and solar radiation will weaken cornices making them more prone to failure. Natural cornice falls have been observed with this warming trend. Falling cornices may trigger large avalanches on deeply buried weak layers.

Limit your exposure to overhead cornices.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Wind Slabs

Wind slabs exist in the region and may still be reactive to human triggers. Use caution when entering into lee features.

Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.Approach lee and cross-loaded slopes with caution.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

High freezing levels and sunny skies are causing intense warming of the snowpack on solar aspects. Peak danger will likely be during afternoon hours. Pay close attention to the effects of the sun on avalanche terrain and avoid overhead exposure.

Avoid terrain traps such as gullies and cliffs where small avalanches can have high consequence.Watch for signs that the snow is heating up such as pin-wheeling and point-releases below cliffs.Start early to stay off south facing slopes during the heat of the day.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 13th, 2018 2:00PM