Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3
About 3ft of recent storm snow rests over facets and a crust from mid-January. The resulting avalanches have already caused a number of burials and one fatality. They can propagate widely across terrain features and can result in surprising and deadly avalanches. Stay well out from under any large open slopes steeper than 30 degrees, as they can be triggered from a long distance away or from below. Most likely, you won't get a warning sign of whumphing collapses, or if you do, it is likely to turn into an avalanche. You can check for this weak structure with a pole handle or probe for weak snow above a crust as you travel. Snow pit tests can confirm this instability, but one pit is not enough to be sure of it's absence. Use recent avalanche information to identify terrain to avoid.
Recent activity has been focused near the crest of the East Central Zone, where more recent snow has piled up. The Salmon la Sac, Teanaway, Icicle, and other areas on the south and western edge of the zone have been favored for snowfall and now hold dangerous conditions. Northwest to Southeast aspects in terrain near or above treeline has been the most likely places to find these. The Wenatchee Mountains east of highway 97 hold less recent snow, so expect danger to be a notch lower there.
(2/9/2021) Persistent slab avalanches that may have run naturally on an east aspect at around 4900ft in the Knox Creek drainage above Cle Elum Lake. These are suspected to have run on the mid-January crust later in the storm cycle of Feb 5-9th.
