Layers.

I will probably leave the jacket and wear a tech-tee/poly-pro/under armour/whatever shirt under my jersey and arm warmers in my back pocket just in case. When it's raining long enough, those jackets don't keep you dry, they keep you warm. I think I've said this before... I can deal with wet. Cold and wet is a whole different ballgame. I think it'll be warm enough to leave the jacket. It will surely be a last minute decision.