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Avalanche Forecast

Archived

Dec 27th, 2019–Dec 28th, 2019

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

Regions

South Coast.

The recent 15-20 cm of new snow is not expected to bond well to previous snow surfaces, and it may form slabs that are possible to trigger in deeper areas at higher elevations or where the snow has been drifted by wind.

Confidence

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

Weather Forecast

Friday night: Mostly cloudy, light to moderate northwest winds, temperatures around -3 C.

Saturday: Mostly cloudy with scattered wet flurries and 1-3 cm of accumulation overnight. Moderate to strong southwest winds. Alpine high temperatures near 0 C with freezing levels to 1000 meters, rising to 1200 meters overnight.

Sunday: Decreasing cloud with scattered wet flurries and a trace to 3 cm of accumulation. Light southeast winds. Alpine high temperatures around 2 C with freezing levels to 1500 meters.

Monday: Increasing cloud, light to moderate west winds, alpine high temperatures around 2 C with freezing levels rising to 2000 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 presents a new storm slab problem to manage on Saturday. Thicker, more reactive slabs should be expected at higher, more wind-exposed elevations.

Snowpack Summary

15-20 cm of new snow from the last 24 hours 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.

Below the new storm snow, 50-100 cm of snow from last weekend comprises the upper snowpack above 1200 meters. 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

  • Be alert to conditions that change with elevation.
  • Carefully monitor the bond between the new snow and old surface.
  • 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.

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.