Observation: NWAC Observer

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Weather Summary

Upon arriving at SPMR base area at ~10:45am, the wind was calm, no precipitation was falling, and there was some blue sky visible between clouds (BKN). By the time we were nearing the top of the Skyline lift, the sky became obscured and snowfall increased to S1. As we made our way up a ridgeline out of the resort, winds increased to light gusting moderate, with shifting directions. Snow transport was evident during gusts. Snow held steady at S1-S1+ and the sky remained obscured until the end of our tour.

Avalanche Observations

#	Date	Location	Size	Type	Bed Sfc	Depth	Trigger	Photos	Details
5	Mar 13, 2023 ()	Lichtenberg SE Slopes SE 4800ft	D1.5	WL-Wet Loose			N-Natural		Report
5	Mar 13, 2023 ()	Berne S 5800ft	D1.5	WL-Wet Loose			N-Natural		Report
1	Mar 13, 2023 ()	Tumwater Canyon between Cabin and Fall Crks E 5500ft	D3	U-Unknown			N-Natural		Report

Snowpack Observations

Skinning up towards a ridgeline to avoid steep slopes in the SPMR backcountry, away from the resort, we found 10-15cm HST. Heavier, moist snow made for a slight upside down feeling below about 4,500ft. We were unable to produce results on hand shear & skin track tests, indicating a lack of storm slab formation, and a decent bond of the new snow to the old snow surface. Dense, heavy, and large tree bombs were a common occurrence, especially at lower elevations, but even into the upper reaches of the elevations we travelled today. As we increased in elevation, HST increased, and we found the snowpack to be less affected by temperatures, creating a drier right side up top layer on the snowpack. Some wind effect was noticeable in the NTL, and a very thin sun crust had already formed on southerlies.

We dug a pit at 5400' on a NE aspect, finding HS to be 390cm. The snowpack was generally right side up, trending from F to 4F to 1F to P approaching the Valentine's Crust. The Valentine's Crust was 150cm down and 1-2cm thick where we dug, and P in firmness. Worthy to note, there is a layer of .5mm-1mm of rounded facets below the crust. While we did not get any fracturing results on 2 separate deep tap tests, on an informal test with more force applied we got a sudden collapse on this layer. This indicates that while the Valentine's is deep and the weaker snow beneath it is stubborn to trigger, there is still a possibility for very large avalanches to slide if triggered in the right spot.

As we descended down the ridgeline back towards the resort, there was starting to be some cohesion in the top layer of snow, and some fracturing could be seen in our ski tracks at lower elevations (see photo).

Driving both up and back down Highway 2 to Leavenworth, we spotted multiple D1.5-D2 wet loose slides on mostly southerlies and some easterly aspects at all elevations. In Tumwater Canyon, we were able to spot a D3 slide on a NE aspect, but had limited visibility above to see if was a loose wet or a slab.

Avalanche Problems

Problem	Location	Distribution	Sensitivity	Size	Comments
Wet Loose	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Comments: Multiple recent natural wet loose slides were spotted along the Hwy 2 corridor at all elevations, including in the SPMR backcountry. While the likelihood for these decrease as gain elevation increases, we still observed some at the upper reaches of the NTL.
Storm 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	Comments: While were were not seeing much slab formation in the top layer of snow at the beginning of the day, at lower elevations there was starting to be some cohesion leading into the afternoon, leaving the potential to trigger a near surface slab on steeper, unsupported rollovers and convexities.