Avalanche Forecast

Moderate - Intensity of incoming weather systems is uncertain

FRIDAY: Mostly cloudy with light snowfall, light southwesterly winds, freezing level near valley bottom.SATURDAY: Cloudy with light snowfall, accumulation 5-10 cm, light southerly winds, freezing level near valley bottom.SUNDAY: Cloudy with light snowfall, accumulation 2-5 cm, light southwesterly winds, freezing level near valley bottom.

A small slab avalanche was triggered by a skier below treeline on the December 15 surface hoar layer on a north aspect on Wednesday.  Numerous reports of whumphing were also noted in low elevation cutblocks and flat terrain.Numerous small loose avalanches were also noted on steep southerly slopes on Wednesday.Reactivity of the persistent slab is likely to increase with warmer temperatures below treeline as the snow forms slab properties.

A warming trend is creating a dangerous slab above buried weak layers in some areas.  Numerous persistent weak layers exist in the snowpack.  Dry snow overlies two layers composed of weak and feathery surface hoar, with the deeper layer (December 15) buried 50 to 70 cm.  This layer is found most often around and below treeline.  As the overlying dry snow becomes more cohesive and forms a slab, this layer has the potential to create easily-triggerable destructive slab avalanches.  Where and when this will occur is tricky to predict and even professionals are scratching their heads about it. It is a good time for conservative decision-making.The snow surface is variable, consisting of dry snow on shaded aspects, a sun crust on steep solar aspects, and wind effect in exposed alpine and treeline locations.Deeper in the snowpack at depths of about 90 to 150 cm, a rain crust from November is producing variable snowpack test results, from sudden fracture characters to no result.  This layer is considered dormant for now, but could be triggered where the snowpack is thin.If you have any recent observations, please share them through the Mountain Information Network.