Steamboat & Flat Tops
AvalancheMax Strotbeck · Dec 18, 2024 · Steamboat & Flat Tops
Weather
Temperatures were in the low-teens in the morning and rose to the mid-twenties by mid-afternoon. Skies started broken but then became scattered clouds by afternoon. Light to moderate south winds. No new snow.
Snowpack
I primarily observed the snow above 10,000 feet on west through northwest through north aspects. I found ski penetration to be deeper in sheltered terrain (15-25cm) where the wind did not create a supportable layer higher in the snowpack. In both sheltered and wind-effected terrain, I sank to near the bottom of the snowpack when I stepped out of my skis. There was about 8cm of new snow from the storm the prior day. In a snow pit dug on a west-northwest facing slope in sheltered terrain, I found the height of snow to be 72cm. The entire snowpack was very low or low hardness (fist or four-finger) on the hand hardness scale. The 12/9 weak layer was buried 16cm down, and hastily looking at this layer the grains appeared to be small rounding facets and small rounding surface hoar crystals. While I saw failures initiate in an extended column test on the 12/9 layer and the basal facets, there was no propagation. Digging on a north-facing that was more exposed and previously wind-loaded, I found the height of snow to be 124cm and varied more in hardness than the WNW facing snow pit. The 12/9 weak layer was buried 35cm down, and in an extended column test I saw propagation on this layer with moderate taps (ECTP14). The column slid on 4-8mm surface hoar grains.
Avalanche
As I was traversing the low-angle saddle of Hahns Peak, I remotely triggered a soft-slab avalanche that was small relative to path but large enough to injure a person. This appeared to break on the weak snow that formed during the early December drought (SS-ASr-R2-D1.5-O). I dug a profile above the crown, and found that the snowpack was quite shallow (53cm) and consisted of 22cm of decomposing fragments above faceted grains and depth hoar. This occurred on a north-facing slope near the tree line of Hahns Peak.