Quick report
-Went up Cascadilla Creek for a close look at the previously reported very large (D3) avalanche on the east face of Nyack Mtn (photos). Continued up to the ridge crest dividing Cascadilla and Wahoo Creeks to a high point at 6700'. -Debris from this very large hard slab ran all the way down to at least 5000' elevation, possibly as low as 4600'. It was difficult to determine the exact terminus. This is a vertical fall of 2000-2500' and nearly a mile of lineal distance on the terrain. -Debris from this avalanche sympathetically triggered at least 5 additional slab avalanches, most D2 size. -Investigation of one of these smaller, debris-triggered crowns at 5100' on a NE aspect (photo) revealed the failure layer was facets right on top of the mid-Jan crust. -No obvious signs of instability on our route. No shooting cracks, collapses, or whumpfs. -Skied out on E-SE aspects and crossed underneath several old crowns from the Feb 20th/21st cycle. There was about a foot of softer snow on top of these old bed surfaces which was the mid-Jan crust.
Weather
- Cloud Cover
- broken
Overcast skies with occasional S-1 snowfall in the AM. Broken skies, no precip, and some occasional sunshine in the PM. Winds were generally calm or light from the west. Daytime highs reached the mid to high-teens at elevations above 5000'.