Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 10, 2022
Submitted:
December 10, 2022
Observer:
NWAC Forecaster - Andy Harrington
Zone or Region:
Snoqualmie Pass
Location:
Alpental Valley

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Media/Attachments

A shovel shear test highlighting the 12/8 layer of concern. The arrows point toward a thing gray line that you may be able to find. This line can help you identify that this is the buried surface hoar layer we are tracking.

Advanced Information

Weather Summary

New/Recent Snowfall:
Approximately 2 feet of new storm snow over the 12/8

Snow showers in the morning, moderate at times, started to taper as the day went on. When we left the field at noon, the precipitation type was approaching snain at road level, but will still holding out as frozen precipitation.

No new avalanches were observed, but visibility was poor. A few older crowns were spotted and mostly filled in. I can't confirm their failure date.

Snowpack Observations

Went searching for the buried surface hoar (12/8 layer) that has been reported in multiple other zones throughout the NWAC forecast region. I dug at Source Lake and again at the top of Big Trees and found it in both locations. While this layer showed up with shovel shear tests, compression tests, and extended column tests (ECT); it did not propagate in any of the ECTs I performed (ECTN x3). I typically found the 12/8 layer 15-22 inches (40-55 cm) below the surface. A midstorm density break also showed up in my tests a little closer to the surface, but the slab lacked a lot of cohesion at this time.

The depth and softness of the new snow made travel difficult and falling over would have resulted in a somewhat monumental task to get back up. As we exited the field, the snow near the parking lot was a bit heavier than on the way in due to the warming temperatures.

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