A week of wind, snow and significant rain has drasticly changed the structure of the snowpack. Long story short, the new snow and rain have made the snowpack stronger and less likely to fail. Keep an eye out for signs of instability and act on them, if observed. Terrain features of concern, such as wind loaded areas, should still be identified and avoided.
Fresh wind slabs and wind loading are becoming more obvious than before this past storm. Yesterday, we were able to find wind slabs on a ridgeline that cracked from our skis. Large cornices are starting to form on ridgelines, which is a great indication that fresh wind slabs are present. The wind loaded slopes we encountered and observed were on NE-N-NW slopes.
(12/29/2022) Photo: J Thompson
A deep persistant weakness still sits dormant in the bottom 1/3 of the snowpack. Even though this layer isn't showing signs of waking up anytime soon, it's still a consideration and should be part of your thought process and decision making.
I don’t think I’ve ever seen such a drastic change to a snowpack as we just experiences over the past week. Things began to change on Christmas evening, with an air temperature of -14 and a very cold, dry and weak snowpack. As the storm cleared yesterday, we noted that the snowpack had received 5’’ of snow water equivalent (SWE), 12-24’’ of snow and experienced a 51-degree temperature swing! Usually, I’d expect big changes in the snowpack to cause an increased avalanche danger, but yesterday we found different results. It was a welcome surprise to see that the snowpack has settled and stiffened up quite a bit and become much more supportable (no more post holing!). Some additional characteristics of a strong snowpack were there as well, such as an equi-temperature gradient, right side up cake, which primarily means soft snow over firm snow, and the absence of persistent weak layers.
Yesterday, Micah and I started on snowmobiles out of Trestle Creek and then continued on skis to the ridge near Trestle Peak, which divides Trestle Creek, Lightning Creek and Quartz Creek. During our field day, we talked to numerous groups of snowmobiles. Based on their observations and route selections, they agreed with our findings. I was really surprised at the new gained strength of the snowpack but was still taking a conservative approach to the day. We watch multiple groups take their sleds into terrain we weren’t quite comfortable with yet, but watch as they highmarked and got stuck (multiple times) on a steep, open north facing bowl. Even though we weren’t willing to expose ourselves to the danger quite yet, it was good information gained to watch them push the limits. From our conversations with people, we assumed that their approach to the slope was a calculated decision based on snowpack observations.
Micah and I dug a data pit on a north facing ridge at 5850 ft, facing NW. We didn’t get any failures on 2 ECT tests or 2 CT’s. The snowpack was 210 cm deep. (see attached)
Be aware that improving avalanche conditions doesn’t mean a green light for everything. Natural avalanches are unlikely, but human triggered avalanches are possible. Don’t let your guard down! Keep an eye out for signs of instability and continue to manage terrain to minimize your exposure. We can learn so much from you! Please tell us what you see out there.
IPAC launched a new OBSERVATION PLATFORM last week. You should check it out. It’s much simpler than the previous version, plus it’s linked to the National Avalanche database so the information can be used on a much larger scale. Enjoy the pow and stay on the right side of the crack!
