Observation: Public
Observation Details
Name:
Andy GoodwinObservation Date:
January 29, 2021Submitted:
January 29, 2021Zone or Region:
West SouthActivity:
XC Skiing/SnowshoeingLocation:
Mt St Helens, Worm Flows Climbing RouteTriggered Avalanches
Did you trigger any avalanches?
YesWas it intentional?
NoAvalanche Type:
Hard SlabSize:
Size 1: Relatively harmless to peopleElevation:
5500'Aspect:
SComments:
Southern aspect of a broad ridge. A 35 degree slope untraveled since recent storms. I was stopping at this small protected 35 degree slope to examine the snow condition. As I approached the test slope it spontaneously failed taking the entire patch of 35 degree slope with it (see picture). In this spot, the sensitive layer (it looked like hoar) was 5-15 cm below the surface.Photo:
Signs of Unstable Snow
Did you see shooting cracks?
Yes, WidespreadDid you experience collapsing or whumpfing?
NoObservations
The weak layer that failed at 5500' was present from 3500-5500+'. At altitudes below 5,000' the snow layer above the weak layer was much more firm. The weak layer became less reactive at lower altitudes but it seemed to be present everywhere and on all aspects. It looked like hoar frost. This was the first 35 degree slope above 5,000 feet on the climbing route. The area that failed is my usual safe, isolated test slope. It failed spontaneously as I approached it. Other much larger 35 degree slopes are not avoidable on the climbing route, so I turned around and went home (thus, I have no observations at higher altitudes). Temperatures were in the teens and west winds of 25 mph above 5,000 feet were still moving a lot of snow around. I suspect that the depth of snow over the weak layer continued to increase with altitude, especially on lee south and east slopes.
Snow in this week's storms accumulated 2-3" at Marble Mountain deepening to 2 feet by 4,000' and perhaps more by 5,000'. Clouds were protecting slopes below 5,000' from the sun today but some large rollers and small loose wet avalanches from yesterday were apparent below 4500'. Above 5,000' teh sun was out a lot but temps were in the mid teens with winds up to 25 mph.
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