Observation: Public
Observation Details
Name:
Robin PenderyObservation Date:
March 4, 2021Submitted:
March 4, 2021Zone or Region:
West SouthActivity:
Skiing/SnowboardingLocation:
Crystal - Valley of the CliffsObserved Avalanches
Did you observe any avalanches?
YesAvalanche Type:
Size:
Size 4: Could destroy a railway car, large truck, several buildings, or a substantial amount of forestElevation:
6800Aspect:
EComments:
Several large and one very large avalanche observed in the Sourdoughs and Burroughs, likely occurring between Friday Feb. 26 and Monday Mar. 1. The largest of these (near Mt. Fremont) ran the entire ridgeline, and sent debris up the opposite side of the bowl.Signs of Unstable Snow
Observations
We used the last day of clear weather to look for more large avalanches that may have failed on the mid January weak layer. We saw many throughout the subranges of Mt. Rainier. All avalanches shared an E component, although some occurred mid slope in rocky terrain and others appeared to start near ridgelines.
We also used the good weather to dig down to the mid January weak layer and check in. At 6,100 ft on an E aspect we found a total height of snow of around 347 cms. The upper 170 cms of the snowpack was generally right-side up. We could still identify the 2/11 weak layer, approximately 119 cms down from the surface. This layer was reactive to shovel shear tests but unreactive in more standardized tests.
The mid January layer is 173 cms from the surface. A thin layer of weak faceted snow caps a firm crust. Beneath this crust is an assortment of junky, rotten snow. Although the weak snow above the crust has been the culprit in recent very large avalanches in the area, we could not show reactivity in this layer at this time and in this location. We could get deep tap test results (DTH SC x2) within the rotten snow beneath the crust.
A strong southerly breeze at ridgetops kept upper elevations relatively insulated. We found a firm wind crust on west aspects, and a thin sun crust on all aspects that recieved direct sunlight. Shaded aspects generally remained cool and dry. At mid and lower elevations sheltered from the wind, the snow was soft, sun affected, and moist.
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