Freezing Rain and Drizzle
 

Freezing Rain or Rain Ice (as opposed to Freezing Rain . . .!) Rain Ice is super cooled water droplets which when they hit the airframe of the aircraft freeze AND spread back along the `whatever they hit` then the entire droplet freezes, this covers the airframe with a polished sheen of ice, almost invisible and if at all visible will appear like a polished surface. The main problem with this ice is that it is insiduos, or, it creeps up on you, and, ice falleth upon ice, so the build up, hetherto unnoticed, will just keep polishing your airframe with coating after perfect coating and it is the weight of the stuff which is the problem and it sticks tight. Not the aerodynamics or airflow, as in rime ice which breaks off in chunks at the leading edge disturbing flow or forms mini mountains where it should not, disturbing airflow, this rain ice - invariably from Drizzle will weigh you down, quickly, uniformly and you may not even see it - best cure = don`t go in it, get out of it by descending to warmer air below if MSA or OCL allow it or turn 180 - avoid flying along a warm front as you will get more of the same - it is invariably a warm Front thing. Read all about it. . .

Freezing Rain Example
 

http://i462.photobucket.com/albums/q...evereIcing.jpg

Theres not a de-icing system in existence that can deal with this phenomenon.
It always amazes me when someone asks about flying in freezing rain.
FZ implies supercooled liquid hence severe icing conditions. The decision to go-no go is the easiest one you should ever have to make.