Detailed Observation

Date2019-04-14
LocationEastern Alaska Range
ObserverKeane Richards
AvalancheN

General Observations

Snow pit / general condition report from Castner Glacier up to 4.5 miles in (Rum Doodle approach). 

04-13: Skijored in to Rum Doodle approach, nice fluffy new snow (about 5 inches), very warm and sunny after evening prior of wind near Black Rapids. Some small avalanches on N aspects of steeper slopes, seemed to reach only to recent snow depth. Those avalanches stopped when they reached moderate slopes.

1st pit at ~5:00PM: NW aspect at base of Rum Doodle. About 12cm new snow, 5cm ice crust layer, then wet, sugary snow till the bottom of the pit at ~1 meter. At bottom of pit, could easily ball up facets into a snow ball (very wet). On shovel shear, new snow was sliding on the top, but only if you forced it. Crust layer would slide also if you forced it with the shovel, but it was pretty well bonded to the layer below. CT 20 (column test failed after 10 hits from wrist and 10 hits from elbow), at 70cm below the surface, relatively planar, on small facets. Wet slab above stayed intact after sliding, was pretty consolidated. ECT-X (extended column did not fail in any way after 30 hits); could not get the slab to fail across. We dug a second pit in the same area to get a second perspective, just did the ECT, with same results. Eventually on the 2nd pit ECT test, got the area below the shovel to slide after smacking it hard enough, but it still did not propagate across the rest of the column. (See the pictures; note that shovel was just placed on the snow on the left side, we actually smacked on the snow on the right side where the snow is missing.) Snow below the failure layer seemed drier (?), I think there might have been an ice layer there and there is a wet slab above and then a relatively drier layer of facets below that layer because water didn't percolate down as well (did not investigate it well enough to confirm this, but there seemed to be a density difference between the snow below the failure and the slab below  – above seemed heavier). 

Also noticed some localized settling on the shallower snowpack near the rocks on same aspect (when stomping on it to get a place to set skis etc.). Not major, but noticeable. (I think this was just the crust layer settling.)

This morning after a hard frost (it was pretty cold last night), CT-N (no failure), ECT-X (no failure), snow was very much consolidated, snow on top was nice and powdery. Couldn't get CT block to fail on that layer even with the shovel; eventually just sheared off on facets toward the very bottom.

My interpretation is that possibly the snow is getting a lot of meltwater percolating through and that is forming wet slabs, which may ride on top of weaker layers lubricated by the water. A cold frost seemed to reduce the risk. Climbing and skiing during the morning / during colder temps seems to be a wise idea. 

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