Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 28, 2022
Submitted:
December 28, 2022
Observer:
NWAC Forecaster - Andy Harrington
Zone or Region:
Snoqualmie Pass
Location:
Draft Dodger Ridge

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Isolated

Media/Attachments

A closer comparison of the Christmas Crust and how it changes with elevation.
A comparison of two pits in the Alpental Valley on 12/28 showing the differences in the Christmas Crust and the water content of snow below it.
A tilt test highlighting some a possible layer of concern just above the Christmas Crust at mid elevations. [4670']
The only wind-loaded pocket I could find today on a steep rollover and it cracked when I stomped on it.
Boot pen was around knee deep when stepping off a ski at mid elevations where the Christmas Crust wasn't as stout (~54cm in this spot)
The Snoqualmie River in the Alpental Valley had some sort of blow out during the storm, leaving wet debris along its river banks and even some broken tree pieces.

Advanced Information

Weather Summary

New/Recent Snowfall:
~1 foot of new snow (30-34cm)

Snowing all morning, at times moderate. The snow was wet and heavy at lower elevations, soaking us.

We noted numerous older small crowns from the recent cycle. Most were filled in. Visibility was poor, restricting our views of the upper peaks, but Source Lake did not have debris in it, so that bodes well. One D1.5ish sized slide was observed coming out of rocky terrain on the E side of Source Lake. There was debris coming out of Mushroom Couloir that looked somewhat fresh. The Snoqualmie River was full of wet debris on its banks down in the meadow near Mountaineer's Rock, indicating a blow-out of some kind.

Snowpack Observations

Traveled to Source Lake then up Big Trees to Draft Dodger Ridge today. The snow appeared to be generally well bonded to the underlying Christmas Crust in most locations, but on steeper slopes where the HN was shallow, I was able to push the new snow and scrape along on the crust. In a few locations, there was isolated collapsing into what I'm assuming were holes below. While giving a quick jolt of excitement, these collapses did not result in any actual hazard since they arrested quickly. We were generally sheltered from any wind effect, but I did find one wind-loaded test slope to stomp on. The wind affected snow as a bit stubborn but did crack and break into blocks after a bit of effort.

I dug two holes to take a look at the Christmas Crust and snowpack structure.
1. At Source Lake, the Christmas Crust was a 7 inch (18cm) thick block, technically comprised of two crusts and a little bit of softer snow between them. We'll just consider it to be one block for simplicity. This was formed by freezing rain and below it, the snow was still mostly dry. The crust was boot supportable. No exciting snowpack test results to report at this elevation.
2. Up on Draft Dodger Ridge, I found that the Christmas Crust still contained two separate crusts, but this time they were each less than an inch (~1cm each) thick with a bit of soft snow between them. All in all, about a 1.5 inch (4cm) "block". Below, the snow was moist and weak due to all the rain of the non-freezing category. When stepping out of my skis, I immediately sank anywhere from knee to thigh deep, punching right through the thinner Christmas Crust. A few snowpack tests highlighted a layer just above the crust to put in the back of your brain for further testing.

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