Avalanche

Skyline Lake study plot

Josh Hirshberg, Matt PrimomoStevens Pass
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Observation photo 1Observation photo 2Observation photo 3Observation photo 4Observation photo 5Observation photo 6

Quick report

Cracking
isolated

We found wet snow surfaces that were variably supportive. Many areas did not support standing in boots, and steeper slopes seemed less supportive of skis. At 5,300ft, we found small glide cracks on a convexity above rock features (see photo).

Weather

Air Temp
32
Cloud Cover
obscured
Wind Loading
previous
Rain Elevation
~6,000ft
Recent Snowfall
0
Snow Avail For Transport
none

The weather was foggy, calm, and mild, with very light rain. Cloud levels were between 4,000-5,000ft. Evidence of significant recent rainfall.

Snowpack

Overall, the snowpack was surprisingly supportive to travel on skis for being moist to wet. We found some areas that were punchy and unsupportive. For being in the middle of a prolonged rain event and wet avalanche cycle, the snowpack has not necessarily taken on a lot of water. This is also reflected by the rain totals in the past week, which aren't huge compared to the number of days over which the area has received rain.

At our profile site, ENE, 5,320ft, we found HS 197cm and a mostly moist snowpack. There was wet snow near the surface and a drier layer in the middle of the snowpack. The midpack was notably dry, and grains were relatively un-transformed to melt forms, especially given that the layers above and below contained more meltwater. Water had made its way into the middle of the Solstice crust matrix, if not into early December melt forms @ 75cm. The Solstice crust weak layer was our primary concern, shown by multiple test results (DTM(SC), PST 43/117 END ↓117cm on 1.0mm MF/FCxr).

Avalanche

Size
D2
Type
WS
Aspect
NE
Trigger
N
Elevation
3300 ft

We were able to trigger shallow, loose wet surface snow on steep slopes. We observed numerous wet avalanches from the past 4 days, many are documented elsewhere: 1) More than one rock-shedding wet avalanches in the East Portal Highway 2 avalanche path up to D2. 2) Numerous avalanches in Tumwater Canyon between Hatchery Creek and Swift Water picnic area, up to size D2.5. 3) Debris on the SE face of Lichtenberg Mtn, below the large rock slab (couldn't see above the runout). 4) A skier triggered avalanche from 1/28 adjacent to the Double Diamond lift at Stevens Pass Mtn Resort