Modern airborne weather radars fitted to modern passenger aircraft have powers of no more than about 200W, and many are much lower than that.
So; imagine a 200W lightbulb* fitted into a reflector dish and pointing away from you, scanning left and right.
How much light are you going to see when sitting behind the reflector? (none).
Now imagine that reflector fitted on the other side of a substantial aluminium bulkhead.
How much light are you going to see from the bulb now? (less than none).
Radar is the same sort of "radiation" as light - it won't go through the metal - and at these powers, there will be no adverse effect on the human bodies seated in the cockpit.
Any reflections from targets will be 1000's of times lower power than the transmitted output. The radio frequency emissions from your mobile phone into your body will be much much greater than anything received from behind your weather radar and the forward bulkhead.
In a previous life I worked with microwave transmitters - the same sort of thing as a radar. One day I went up a tower to derig a transmitter but forgot to turn it off first. I was standing in front of the dish, making sure I was securely tied to the tower, and for about a minute the transmitter was firing right into my b*lls before I realised my mistake. I have since "helped" produce a very healthy lad who is now 6' 2" and at University.
*in other words, like two 100W domestic lightbulbs