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Avalanche Forecast

Archived

Mar 12th, 2018–Mar 13th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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.

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:  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.  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.  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.  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

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.