Observation: Public
Observation Details
Name:
Matt PrimomoObservation Date:
December 23, 2020Submitted:
December 24, 2020Zone or Region:
East NorthActivity:
Skiing/SnowboardingLocation:
Near Varden CreekObserved Avalanches
Did you observe any avalanches?
YesAvalanche Type:
Hard SlabSize:
Size 3: Could bury and destroy a car, damage a truck, destroy a wood frame house, or break a few treesElevation:
3400ft up to 8,000ftAspect:
Comments:
Observed recent widespread avalanche cycle with activity on all elevations and aspects. Activity from upper elevation, defined avalanche paths appeared in the D3 size range, with a large percentage of the starting zone ripping out. The incredibly wide nature of some of these crowns points to faceted grains being the culprit.We spotted many lower elevation slopes that ran through treed zones as well. These likely ran on the tail end of the storm, or shortly after.
Photo:
Signs of Unstable Snow
Did you see shooting cracks?
NoDid you experience collapsing or whumpfing?
Yes, WidespreadObservations
Traveled between 3,200ft and 6,900ft generally on north to east facing terrain. Between 5,800ft and 6,200ft while skinning through the trees we experienced roughly 7 whumphs, with a couple of those propagating and initiating more whumphs. They collapsed roughly 30ft sections of snow, shaking the snow out of some trees. These are the types of instabilities that would be avalanches if the slope were steep enough to slide. Twice I was able to collapse the slope even after 3 to 5 people had skinned by, just by jumping up and down a few times. Collapsing was confined in nature given that it was only this relatively small elevation band, though widespread within that band.
Below is a summary of the layer of concern (Early December Crust and associated weak snow above and below) found through different elevations.
At 4,200ft NE aspect HS 143cm, Early December Crust found down 80cm as a thin, freezing rain crust. CTM (11) SC x2 on .5-1mm rounding facets below the crust. Much of the snow beneath this crust was moist, rounding facets.
At 5,100ft on an ENE aspect, found HS 135cm, and a thinner freezing rain crust was down 75cm.
At 5,800ft on NE aspect found HS 135cm. The layer of concern was down 75cm. CTM (11) SC on .5mm rounding facets above the Early December Crust PST 35/100(End) test was done on the small facets above the crust, but fractured through crust, and ran to the end on rounding facets below the crust.
At 6,200ft on NNE found HS 139cm, layer of concern down 70cm. CTH brk down 49cm on storm interface. CTH SC (within crust, down 1cm) down 69cm. PST 30/100 (End) on 1-1.5mm rounding facets within the crust.
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