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December 30th Avalanche Cycle
On December 29th and 30th, a strong winter storm brought upwards of 2 feet of snow to the area, accompanied by strong westerly wind. An avalanche cycle ensured, likely in the afternoon or evening of December 30th. Visibility finally cleared today (12/31) which resulted in numerous reports of avalanches from this cycle. We have been unable to visit each avalanche up close and in person, so the pictures and information are the best that we have at this time. We will provide updated information as it is gathered.
Here is the observation from earlier in the day that the avalanches occurred: https://www.shastaavalanche.org/snowpack-observation/whumpfing-shooting-cracks-unstable-test-results. All slides occurred near and above treeline on S-SE-E facing aspects. We experienced a cold storm followed by a warm one with strong westerly wind. This warm-up likely caused the observed avalanches.
- Sun Bowl, start zone ~9,000 feet
- Powder Bowl, start zone ~9,000 feet
- Lower Casaval Ridge into Avalanche Gulch, start zone ~8,700 feet
- R2, D2.5 wind slab avalanche. Crown was along exposed rocks where the snowpack was shallower.
- Start zone was between 36-40°
- Occurred within the recent storm snow or on the Dec 23 ice crust.
- Avalanche ran ~1,100-feet with a 680-feet elevation loss.
- Upper Casaval Ridge, start zone ~12,000 feet
- St. Germain's Bowl, east Old Ski Bowl area, start zone ~8,300 feet
Weather data leading up to the avalanche cycle: