Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
January 19, 2023
Submitted:
January 19, 2023
Observer:
NWAC Forecaster - Andy Harrington
Zone or Region:
Snoqualmie Pass
Location:
Snow Lake Divide

Signs of Unstable Snow

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

Media/Attachments

Rollerballs and other wet loose activity coming out of steep rocky terrain as the sun started to come out on 1/19.
A shovel tilt test highlighting a layer of interest at the base of the recent storm snow and a few inches above the MLK crust. [N 4500']
Up to 1.5 feet of snow now sits over the MLK crust at mid elevations. In this location, the crust was 3" thick with softer melt forms below it.
Weak snow grains observed at the 1/18 interface, a few inches above the MLK crust [N 4500']

Advanced Information

Weather Summary

New/Recent Snowfall:
~1 foot HST (30cm)

Popcorn clouds and haze of varying heights with periods of sunshine. Calm to no wind experienced. Kinda warm out there.

No new avalanches were observed. Some rollerballing and other wet loose activity were observed as I exited the field around noon, but nothing I would yet call an avalanche.

Snowpack Observations

The quick-hitting storm this week dropped about a foot of new snow at the Pass proper. The depth of snow over the MLK crust increased with elevation from about 15" to closer to 20". I topped out at the Divide today, so depths could be different in the true ATL. While the recent snow did have a few interstorm layers that were highlighted in small column and tilt tests, I did not find any of them overly concerning at the time. Of further interest was a layer ~13cm above the MLK crust at the base of the HST. I dug in two locations - Snow Lake Divide (N 4500') and Source Lake (SW 3700'). This layer failed in both locations CT+1 and consistently showed up mostly planar in tilt tests. At Snow Lake Divide, I found needle-like grains at this interface but I didn't notice anything too significant grain-wise at Source Lake. The thickness and rigidity of the crust varied slightly between locations, with a firmer ice lens on the top of it at the divide

While plenty of wind sculpting was evident on and near the Divide, I did not find any actual Wind Slabs in this location. On the drive home, it looked like there was some blowing snow off the top of McClellan Butte, and there were rollerballs and pinwheels starting to form on sunny slopes along the Alpental Road and i90.

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