Avalanche Forecast

Issued: Mar 12th, 2018 3:59PM

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

mconlan, Avalanche Canada

South Rockies.

Freezing levels above the mountain tops and sunny skies are warming the snowpack, particularly around midday. Best to avoid sunny slopes and overhead avalanche terrain. Read our blog on the impact of warming.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TUESDAY: Sunny, light southwesterly winds, alpine temperature 3 C, freezing level 3100 m.WEDNESDAY: Mix of sun and cloud, light southwesterly winds, alpine temperature 3 C, freezing level 2500 m.THURSDAY:Â Mostly cloudy with light snowfall, accumulation 2 to 5 cm, light westerly winds, alpine temperature -2 C, freezing level 1500 m.

Avalanche Summary

Loose wet avalanches were noted on solar aspects to size 1.5 on Sunday.Â Some of these triggered small slabs, about 10 cm deep.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 around 1400 m.Â On shady aspects at higher elevations, expect to find wind slabs in lee features and loose dry in sheltered features.Cornices are large and prone to failure with warm air temperatures and sunny skies.The upper/mid-pack is generally well-settled and strong.Â The lower snowpack is weak with a combination of crusts and facets near the bottom of the snowpack that are widespread. The primary concern is the potential of these deeper persistent weak layers becoming active by rapid warming of the snowpack through rising freezing levels and intense solar radiation. This is most likely to occur on south-facing slopes.

Problems

Deep Persistent Slabs

Deeply buried weak layers linger near the base of the snowpack. These layers are most likely to be triggered from thin snowpack areas. Avoid lingering below corniced ridges, as a cornice fall could trigger deeper layers.

Pay attention to overhead hazards like cornices which could trigger deep persistent slabs.Avoid steep, rocky, and shallow snowpack areas where triggering deeper layers is more likely.Steep, south facing slopes are the most likely areas to trigger deeper layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

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.

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

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

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