Jirginsama, you haven't got it quite right. Aircraft weather radar works by detecting solid and liquid water in the atmosphere in the form of ice and rain. What it can't normally detect is water vapour which is an invisible gas. It could be detected if we had any way of measuring humidity in flight, but of course we don't. The actual returns will of course depend on the type of radar fitted in an individual aircraft. Drizzle and fog will normally only be detected by very short wavelength (1cm) Ka band radars, which you'd be unlikely to find in a normal commercial airctraft weather radar.
Phonewind thanks for the update. I m still learning how to fly, and that was what i learnt. At least, i have learnt more today.
