[Nw Radar - Snow/sleet/rain?]

Probably completely the wrong place to be posting this (couldn't find anywhere more logical though) - apologies.

A question primarily for the NW team I guess, but will take any answers I can get. I was just wondering how the distinction between rain/sleet/snow was made on the radar display. Is this using data from the radar, or model temperature data, or something else? Be quite technical if you can as I know quite a lot about radar meteorology.

Cheers

[May Photo Competition]

Here is my entry, taken from my back garden in Herts.

the back end of a cumulonimbus cloud.

p.s. if anyone can explain what is causing this phenomenon then that would be appreciated.