I took a 2500 mile trip from Boise, Idaho, to Chicago in October the other year and rode in all kinds of weather including snow and was caught by a hurricane blowing itself out across the country. That winter I rode the dirt bike around the city through the whole winter... just to do it.
The right layers is key. Synthetic/wool base layer to get moisture away from the skin that also helps with insulation (meaning not the thinnest). A thin secondary layer that stops wind and insulates. Lastly a jacket with a liner that is water resistant and windproof while the outer cordura type layer to take the punishment.
Packing an emergency rain jacket may be a good idea for extra help in breaking the wind in the most extreme conditions (high speed and high winds).
Try experimenting before the next race to know what works best for you.