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Avalanche Forecast

Archived

Apr 15th, 2017–Apr 18th, 2017

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

Regions

Waterton Lakes.

Sun will be the main driver of avalanche danger.  Be cautious of steep sunny slopes, or of exposure to cornices that may be sneakily catching sun from behind.

Weather Forecast

Sunday: Mainly Sunny. Westerlies easing to Calm. Freezing Level rising to 2000m. Treeline Low -6.5, High -1.Monday: Mainly cloudy. Light Westerlies/light flurries developing. Freezing Level 2200m. Treeline Low -1, High 0.5Tuesday: Cloudy, light flurries. Moderate Westerly winds. Freezing Level 2200m. Treeline Low -2, High 0.5.

Snowpack Summary

15cm of storm snow has trickled in over three days, creating storm slab pockets on slopes immediate lee to accompanying Strong SW winds. These sit on a widespread crust that formed after warm temperatures one week ago. Beneath is a well settled spring snowpack; however, facets still make up the bottom of the snowpack in some high Alpine areas.

Avalanche Summary

On Saturday, a recent cornice fall avalanche from an Alpine ridge was observed, which had triggered a small storm slab from a steep, unsupported lee slope. (This amounted to a Small avalanche - Size 1.5) On Friday, Numerous Small, Loose Wet avalanches occurred, as rain soaked fresh new snow that sat on a crust.

Confidence

Timing or intensity of solar radiation is uncertain on Monday

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.