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Avalanche Forecast

Archived

Nov 28th, 2018–Nov 29th, 2018

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

Regions

Sea To Sky.

We're working from very few observations right now, but it looks wet and soggy at lower elevations. The exception is in the alpine where storm slabs and cornices pose a serious threat. Please let us know what you're seeing on the MIN!

Confidence

Low - Due to the number of field observations

Weather Forecast

The storm has passed, and we are slowly transitioning towards a period of pronounced high pressure. The forecast period is marked by cooler temps, very little precipitation and the potential for clear skies by the weekend.WEDNESDAY NIGHT: Freezing level holding around 1000 m, light variable wind, trace of precipitation possible. THURSDAY: Scattered cloud cover, freezing level around 1000 m, light variable wind, no significant precipitation expected.FRIDAY: Broken cloud cover, freezing level around 1000 m, light southwest wind, no significant precipitation expected.SATURDAY: A few clouds, freezing level around 700 m, light east/northeast wind, no significant precipitation expected.

Avalanche Summary

Skies cleared Tuesday allowing some observation of avalanches that likely released at the height of the storm. A large (size 2.5) avalanche was reported on a northeast facing glacial feature between 2100 and 2200 m. The avalanche failed naturally with a crown up to 1 meter in depth. Another large natural avalanche (size 2) was reported from a north facing feature near 2000 m. Several natural loose wet avalanches to size 1.5 were also reported from treeline.Please submit any observations you have to the Mountain Information Network here,

Snowpack Summary

Monday and Tuesday's intense precipitation event rain-soaked the existing snowpack up to about 1800 m and left 20 to 30 cm of wet snow in place up to 2000 m. Above 2000 m the storm produced around 60 cm of new snow. The upper 20 cm of snow is reportedly dry in the alpine. Strong to extreme wind on Monday and Tuesday formed storm slabs, cornices, and wind damaged snow in high elevation alpine terrain. Above 2000 m, 50 to 150 cm of snow now sits on the early November crust/facet interface. Little is known about the reactivity of this interface in the alpine. This crust may be associated with weak faceted crystals in some places where it lies close to the ground. This is most likely to cause problems in glaciated terrain or on smoother, high elevation slopes where the summer snow did not melt out.

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.