I have also been thinking about the rapidly changing avalanche and weather conditions that occurred over the weekend. When comparing the Patrol Race to the accidents, it is critical to differentiate between overall conditions each day, avalanche problems and danger ratings, terrain exposure, and weather patterns. My assessment is from experience on race day, publicly available information, and my professional training.
Avalanche Problems: Both avalanches are reported to have run on facets or on the new/old snow interface that was buried on 2/23 (not the 2/13 persistent slab problem in the forecast). Photos from Cottonwood Lake seem to show a tapering crown, which are often associated with a Wind Slab problem—this was the primary forecasted avalanche problem for Sunday. This wind slab was much more dangerous on Sunday than Saturday due to heavy snowfall Saturday night accompanied with snow-transporting wind speeds. Neither preliminary accident report mentions a step-down avalanche into the lurking Deep Persistent Slab (2/13 facets).
It is also important to mention that there was an Avalanche Warning issued for Sunday, due to the increasing hazard, that was not given on Saturday. The avalanche danger was rated as "high" on Sunday which is says that "human-triggered avalanches are very likely" by the North American Public Avalanche Danger Scale.
Terrain: The Patrol Race largely avoids avalanche terrain for its length. It does cross some small paths and a couple of larger paths (e.g. Silver, Tinkham). It never crosses through the start zone of larger paths. Overall exposure time is limited in this terrain, since the Silver paths are crossed on what is essentially a traverse (300m wide) and the Tinkham/Mirror path is a downhill ski leg along the lower margin of the path'trim line.
The accidents on February 25 both occurred in near treeline avalanche terrain with large, steep, open slopes that are more affected by wind and sun than the mostly below treeline, low-angle slopes of the race course.
Weather: Telemetry at the Pass shows between 7-10" of storm snow accumulating Saturday night after the race ended. This rapid loading, accompanied by moderate (snow-transporting) winds, ratcheted up the hazard quickly in the evening and early morning hours of February 25. Wind slab (and storm slab) avalanche danger rapidly rose with these conditions. Low density snow caused by colder than normal temperatures likely contributed to greater redistribution of storm snow, allowing wind slabs to form more readily with lighter wind speeds.
In summary, I feel like the race organizers did a good job evaluating avalanche hazard and weather conditions. The mountains are dynamic and our risk treatment must adapt to these changes. What is appropriate one day is often not appropriate the next. Limiting (or eliminating) exposure to avalanche terrain is always the primary way to reduce risk, especially when there are higher levels of uncertainty caused by strong storms and rapidly changing avalanche problems.
