Quick report
- Red Flags
- Heavy Snowfall, Wind Loading, Cracking, Collapsing, Poor Snowpack Structure
- Red Flags Comment
- <p>We noticed significant drifting at lower and mid elevations and did not get up to upper elevations due to the full-on weather and obviously dangerous avalanche conditions.... Collapsed a slope while showing the weak layer to Josh while digging a snow pit on an east facing slope at around 7500' in elevation. As he approached the pit from below we heard and felt the collapse and watched the obvious faceted weak layer just below the 1-8 rime-crust compressively fail in the upper face of my pit, before I had even isolated a column.</p>
Photos of localized cracking and evidence of today's extensive drifting at mid and lower elevations....
Video clip shows the weak snow structure we found on a shallow east facing slope at around 7500' in elevation just off the Tony Grove Road.
Snowpack
- Instability Comment
- <p>Widespread significant drifting formed wind slabs at all elevations and in some rather unexpected places... Many of these formed on lighter density powder from yesterday, and most of the cracking we triggered was caused by a failure of thicker fresh slabby layer on top of lighter snow; a density change at the interface of yesterday's and today's snow.... </p> <p>The extensive drifting was overloading slopes with buried persistent weak layers. Of greatest concern in the Tony Grove Area are ares where a rime-crust formed on the snow surface on January 8 and preserved very weak and well developed faceted snow. The sugary crystals just beneath the crust in many areas .are fairly large ( around 3 mm) and soft (fist harness). The final ingredient to this dangerous combination is the rapidly developing slab layer.. Large avalanches breaking into old snow are becoming increasingly likely, and you could trigger one from a distance or below in these conditions. In some areas, this poor snow structure is likely to persist for some time, a lingering and serious threat, even as other weaknesses gradually regain stability... </p>
Heavier snow today made the deep new snow from the last couple days inverted and hard to move through, especially in drifted areas. You needed fairly steep slopes to get moving fast enough to turn in in places, but dangerous conditions kept us away from sustained slopes with enough pitch. We stayed in the sheltered trees for perspective in near whiteout blizzard conditions, and there we found the best snow, since it was less drifted, shallower, and rime free....