Strong temperature inversions all day w valley fog in the AM. High, thin clouds built in the PM. The effects of both short and longwave radiation were evident in the variety of surface conditions that we found.
Jan 12, 2022
Rainy Pass, Point 6937
|D2.5||HS-Hard Slab||8ft||NC-Cornice Fall||Report|
Jan 12, 2022
Hairpin Valley, Hwy 20
Widespread loose wet avalanches on E-S-W aspects generally to size D2 with a few larger slides or deeper piles that resulted from overlapping avalanches. Most were older and I didn't see any that appeared to have occurred within the past 3 days. It seems the bulk of the activity was with the Jan 12th rain event, tho I saw many examples of more recent wet avalanches. Notable slides including 2 older, deeper slab avalanches, may have involved cornice fall.
We focused on the range of surface conditions. E-S-W slopes that are exposed through the sun have widespread, and sometimes stout crusts. Sunny slopes near Rainy Pass softened during the day above 4,600ft, though it appeared that areas in deep drainages and at lower elevations stayed cold and frozen with temperature inversions.
Under the tree canopy, surfaces were a bone-jarring, "coral-reef" textured melt-freeze crust that stayed frozen solid all day. Near Rainy Pass from 4,600-6,300ft we saw no change with aspect in tight trees. However, the snow in open trees was consistently softer with only a light crust on the surface.
We found surface hoar of different varieties (see photos) along the highway, in valley bottoms, and near lakes and drainages. Some intricately feathered grains exceeded 5cm. Little to none was observed in other terrain or on slopes steep enough to slide.
Shaded, wind-sheltered slopes near and west of Washington Pass are still holding dry snow that initially fell on Jan 20th. At 6,300ft on a NE aspect near Heather Pass, we found 10cm of soft, dry wind rippled snow over a crust. Up to 20cm may exist on similar slopes. These areas, along with many slopes holding just thin crusts, are also building near-surface facets.
No avalanche problems. Travel hazards- slip and fall, challenging snow, etc outweigh avalanche hazards. That said, we made sure not to linger under overhead cornices.