Chasing techniques#supercell

FFD — Forward-Flank Downdraft

Also: FFD

At a glance

The heavy rain and hail region out in front of a supercell's updraft. You want to approach from the south/south-east, never through the FFD.

Deep dive

The FFD is precipitation-driven outflow generated on the forward side of the mesocyclone by falling hydrometeors. It's the source of the 'precipitation shield' on radar. The boundary between FFD outflow and inflow to the storm is often a sharp baroclinic zone that contributes streamwise vorticity to the mesocyclone — small in scale, big in consequence.