Greetings
This is a very important point,
ONLY WET WINDSHEAR IS DETECTED , to extend a little bit the subject, weather radar detects
WATER IN LIQUID FORM 
Ice cristals are poor reflectors, in fact water in liquid form has the particularity to change it spatial orientation when radiated by microwave, when in cristal form the molecules as interlocked and cannot move, thus cannot present a front on which the wave will be reflected
