Observation: NWAC Forecaster

All Observations

Basic Information

Observation Date:

January 24, 2023

Submitted:

January 24, 2023

Observer:

NWAC Forecaster - Dallas Glass

Zone or Region:

Snoqualmie Pass

Location:

Snow Lake Divide Area, Snoqualmie Mt, Thunder Creek, Avalanche Col (All Aspects Near and Below Treeling)

Recent Avalanches?

None Observed

Cracking?

None Experienced

Collapsing?

None Experienced

Snowprofile in the near treeline band on a shaded aspect.

The 1/21 interface failed repeatedly in snowpack test. Fortunately, its very shallow and currently doesn't have much of a slab over it.

Large stellars were found at the 1/21 interface on Northerly aspects.

Crust layers in the upper snowpack on southerly (SE-SW) aspects at Snoqualmie Pass.

The surface sun crust is about 1in thick but very breakable in most spots.

A few large cornices hang along the ridgelines. Some of them are in some unusual places from prolonged periods of S and E winds earlier this month.

Visual clues of possibly wind loaded slopes.

Advanced Information

Cloud Cover:

Obscured

Temperature:

32°F

Wind:

Light , W

New/Recent Snowfall:

Trace

Kind of drippy and damp. Very light snowfall and mist began around 10am. While it didn't really accumulate, I ended up soaked. Winds were only really noticeable along ridgelines where they manages to lightly drift snow.

Avalanche Observation Comments:

No new avalanches were seen.

We found the snowpack to be remarkably similar on slopes that receive direct sunshine and those that don't. The only real difference was the presence/absence of sun crust at recent storm interfaces. (See photos).

Snowpack tests consistently highlighted the 1/21 interface on non-sunny aspects, but it was only 6in (15cm) below the surface and didn't demonstrate the ability to propagate a failure.

There was plenty of sign that the winds had built slabs on the lee sides of ridges and features. We found rime, drifts, cornices, blowing snow, and deeper slabs. However, test slopes did not produce any cracking nor failures. Even still, we actively avoided one obviously wind loaded slope with rocks and trees in its runout.

On southerly aspects a thin (1in/2-3cm) sun crust formed Monday 1/23. It was breakable and didn't impede travel.

Problem	Location	Distribution	Sensitivity	Size	Comments
Wind Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5

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