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Avalanche Forecast

Archived

Feb 14th, 2018–Feb 15th, 2018

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

Regions

South Coast.

New snow sits above a hard crust.  Be careful around terrain traps such as cliffs, trees, or gullies where a small avalanche could have severe consequences.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY: Increasing cloud with flurries starting in the evening, moderate west wind, alpine high temperatures around -4 C.FRIDAY: 5-10 cm of new snow by the morning then clearing throughout the day, moderate northwest wind, freezing level climbing to 1000 m with alpine high temperatures around -2 C.SATURDAY: Heavy snow starting Friday night with 20-40 cm possible by the end of the day, strong west wind, freezing level climbing to 900 m with alpine high temperatures around -2 C.

Avalanche Summary

The new snow was reactive above the crust on Wednesday, including a report of a small avalanche on a steep north-facing convex roll. See here for photo. On Saturday, a cornice collapse was the likely cause of a size 2 avalanche on a north facing slope near the West Lion. See here for images and more details. Looking ahead, the storm slabs may remain reactive, so be suspicious of the bond between the new snow and crust.

Snowpack Summary

15-25 cm of storm snow sits above a hard rain crust at most elevations and above firm wind affected snow in the high alpine. It will take time for the new snow to form a solid bond with these varied surfaces - especially the rain crust. The average snowpack depth at treeline is 300 cm of well settled snow with no significant layers of concern.

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.