Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3
We've now made it through three days with no reported avalanches. Snowpack data is still coming in daily pointing out that the instability is still there. Now we are at the most challenging part of this avalanche cycle. Collapses and whumpfing have become less common and snowpit test results are more variable or harder to trigger. It is not uncommon for a persistent slab avalanche to occur after days of no avalanches, such as a day like today. If a slope is going to avalanche, it's going to go big.
The Dec 1 persistent weak layer remains weakest on NW-N-NE aspects above about 8,000'. It is buried 1.5 to 4 feet deep near the bottom of the snowpack. Avalanches that have occurred on this weak layer have had a minimum size of D2 and wide propagation. Expect the same for any avalanches that are triggered today.
If you choose to enter avalanche terrain today it is a high consequence environment. Large, wide propagating avalanches are difficult to survive. Anticipate that any avalanches triggered will be bigger, wider, and run longer downslope than expected. Previous tracks on a slope are not an indication of stability for this type of avalanche problem. I won't be surprised to hear about an avalanche that takes out previous tracks. Luck and skill may have similar outcomes in the backcountry, but they are not the same thing.
(12/7/2022)
One of two wide propagating natural avalanches on this slope. Likely occurred on Dec 3 or 4. N aspect terrain around 7,700'. Deer Creek drainage near Mt. Watson, CA.
