Sun Bowl / Powder Bowl

After writing the forecast without real-time weather station data this morning, I headed out to see what last night's storm brought to the Southside of Mount Shasta. I arrived to heavy snowfall and three inches of new snow at the Bunny Flat Trailhead. With light to moderate northwest wind and snowfall rates up to an inch per hour, visibility was poor. Near and above the treeline, snowfall intensified and the northwest wind was steadily blowing 15 to 25 mph, ideal wind speeds for building wind slabs. Snow depths between 8,000 and 9,200 feet ranged from 18 to 25 centimeters, with up to 60 centimeters in drifts and on leeward aspects (east and southeast). On inconsequential test slopes, I initiated three small (D1) wind slab avalanches ranging from 18 to 30 centimeters deep and broke up to 30 feet wide. These occurred on east and southeast aspects with slope angles of 30 to 40°.

Although the snowfall should end this evening, moderate northwest winds will persist. This means that wind slabs will continue to grow deeper and/or denser. Tomorrow, when the sun comes out, be sure to assess steep leeward aspects carefully for wind slabs; look for cracking, pillowy, or lens-like snow surfaces, and areas where wind-blown snow is accumulating.

Triggered three small D1 wind slab avalanches on test slopes. Depths ranged from 18 to 30 centimeters. All approximately 30 feet wide running until the slope angle was under 30°.