Quick report
Deep, yet shallow...
Guy and I checked out conditions in the avalanche terrain adjacent to Whitefish Mountain Resort (video summary).
- Knee- to thigh-deep snow above 6000 feet
- Head-high alder above the floor of the canyon, thanks to the shallow snowpack this season.
- While the recent snow has stiffened, we did not observe any cracking or collapsing and weren't able to release any slabs or sluffs with our slope cuts.
- There was a natural avalanche cycle during the storm. The crowns we saw and investigated were shallow yet with wide propagation (Avalanche tabs, pics)
- The natural avalanches we saw were on sunny slopes and the debris indicated soft slab avalanches. There may have been more slides we didn't find on shady slopes.
- The most concerning layer in the snowpack was a layer of rounding facets below a thin, friable rime crust (video in snowpack tab). This propagated or collapsed in tests, and while the rime crust is widepspread below 6700 feet, it's not clear yet if there's more than an isolated persistent slab avalanache problem.
- LOTS and LOTS of snow is available for wind transport. And there are powerful winds coming.
Weather
- Air Temp
- 12
- Cloud Cover
- obscured
- Wind Loading
- light
- Recent Snowfall
- 2
- Snow Avail For Transport
- large amounts
Overcast, with clouds dropping below ridgeline early afternoon. Calm except for a few gusts and light winds at the summit. S1 snow showers in the early afternoon, though visibility on the front side of the mountain was good.
Snowpack
The most concerning layer is thin (3 cm) soft layer of rounding facets below a thin, friable (1 F) rime crust that's buried about 40-60 cm below the surface. You can feel the rime crust with pole plants. We found this layer on both sunny and shady aspects. WMR patrol reported a crust like this on 12/31.
Profile near adjacent to the crown of a large natural avalanche at 6150 feet:
- HS 112 cm
- 30-60 cm of new/ recent snow above this rime crust> It's progressively harder with depth (right side up ), going from Fist to $ finger hard right above the rime crust.
- The rounding facets sit on a stout melt-freeze crust (12/23) that is pencil+ hard and 5+ cm thick.
- The bottom 40-50 cm of the snowpack is refrozen melt-freeze grains that are pencil to knife hard.
- CTM 13 progressive compresion/ ECTN 14 down ~25 cm on mid storm density change (likely failure layer for natural avalanche). Wes suspected surface hoar but could not find it.
- CTH 21 sudden collapse and ECTP 20 on rounding facets below rime crust
Avalanche
- Size
- D1.5 R2
- Type
- SS
- Count
- 2
- Aspect
- SW
- Trigger
- N
- Elevation
- 5900 ft
Saw crowns from several natural soft slab avalanches that appear to have released during the storm 1/6-7. One higher, to skier's left on Skook Face, we didn't get a close enough eye on to include here.