There is an embryonic theory that there is quite a significant amount of localised cooling in the atmosphere after the passage of a total solar eclipse.
After we experienced some turbulence in the lee of the shadow of the last total solar eclipse (37,000 feet) that was not there prior to the shadow's passage (same location) there are some weather balloons being organised to fly before and after the next one in November.
Nothing to do with ISA though, but tangential to the discussion.
