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Avalanche Forecast

Archived

Dec 28th, 2019–Dec 29th, 2019

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.

20-30 cm of new snow in the last 48 hours has created a storm slab problem to manage on Sunday. The recent snow is not expected to bond well with pre-existing snow surfaces, and thicker, more reactive slabs may form as temperatures increase.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Saturday night: Cloudy with scattered wet flurries accumulating 5-10 cm. Light southwest winds. Alpine temperatures near 0 C with freezing level rising to 1500 meters overnight.

Sunday: Mostly cloudy with scattered wet flurries with a trace of accumulation or possible light rain. Light southeast winds. Alpine high temperatures around 4 C with freezing level to 1900 meters.

Monday: Mostly cloudy, light southwest winds, alpine high temperatures around 3 C with freezing level dropping from 1800 meters.

Tuesday: Cloudy, 15-30 cm of snow, moderate southwest winds, alpine high temperatures near 2 C with freezing level around 1000 meters.

Avalanche Summary

No new avalanches have been reported in the region since the widespread natural avalanche cycle brought on by last weekend's storm.

The recent snow and warming temperatures present a storm slab problem to manage on Sunday, as warmer temperatures increase slab properties.

Snowpack Summary

20-25 cm of recent snow fell on a mix of crusts or old snow surfaces that are not likely to bond well. In areas where snow accumulations are deeper, this new layer may form a cohesive slab with the potential to slide.

Above 1200 meters, 50-100 cm of snow from last weekend comprises the upper snowpack. This storm snow is well settled with a strong bond to the previous surface. Below 1200 meters, the snowpack diminishes rapidly with elevation.

Terrain and Travel

  • Use small low consequence slopes to test the bond of the new snow.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.

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.

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.