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Avalanche Forecast

Archived

Jan 5th, 2013–Jan 6th, 2013

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

Regions

Northwest Inland.

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Overnight and Sunday: Light snow overnight should accumulate another 2-3 cms by morning, and another 2-3 cms during the day on Sunday. Moderate Westerly winds overnight should become light Southwesterly during the day.Monday: Strong Southwest winds are forecast to build as the next pulse of moisture moves in from the coast. Expect 5-10 cms with temperatures down to about -5.0 in the alpine.Tuesday: Another pulse of moisture should bring 5-10 cms more during the day combined with moderate Southwest winds.

Avalanche Summary

Explosive control in the Ningunsaw area resulted in large avalanches failing on the facet layer near the ground.

Snowpack Summary

Thin layers of dry cold snow are accumulating each day. In some areas this new snow has been transported into wind slabs. The recent cold and dry weather has caused the surface snow to facet and become weakly bonded. This weak bonding has resulted in dry loose snow sluffing out of steep terrain. Forecast new snow on top of this weak unconsolidated surface should continue to sluff easily. The base layers of the shallow snowpack have also facetted and become weaker. The relatively strong mid-pack has formed a bridge above the deep facets. The forecast storm over the next few days may create a storm slab above the weak surface layers, and/or over-load the mid-pack bridge. This type of incremental loading requires frequent assessments of the amount of loading above the weak layers, and whether that load will react as a consolidated slab.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.