VIX vs. VX30
Tracks the VIX term structure: spot VIX against VX30, the 30-day VIX future.
Contango: spot VIX below VX30 (the calm, normal state)
Backwardation: spot VIX above VX30 (stress)
It matches today to past days at a similar VIX level where the gap was moving the same direction at a similar speed (both compressing toward backwardation, or both steepening back into contango), then shows what VIX did next. A fast compression while VIX is already elevated is the setup that has tended to precede spikes.