I did a mid tempo ride to Oxford in the rain last winter. Was a bit cold at first due to stop-start getting out of west london, but wasn't concerned with staying dry. Was warm enough that by the time we made it out properly my back was steaming, which was also a pretty good indication of its breath ability.
Weather looks fine for it. Was going to suggest packing another shell layer in case of stops, but recon with the PT Softshell you should be fine. And no, doesn't get heavy really, as the moisture just breathes back out again
I did a mid tempo ride to Oxford in the rain last winter. Was a bit cold at first due to stop-start getting out of west london, but wasn't concerned with staying dry. Was warm enough that by the time we made it out properly my back was steaming, which was also a pretty good indication of its breath ability.
TL:DR Not waterproof but warm