I think this might help you out, should have a bunch of information as well as webcams
https://wsdot.com/Travel/Real-time/Map/
Enjoy the trip down, and hopefully the roads aren't too bad!
Super late reply, but it's not a dumb question haha! Technically this dealership is in Vancouver, Washington (and I live here) so it's Washington Tax, but Portland is definetely the better known city...
If anyone is in the Portland, OR area I ended up picking up a 22' 3.0 Premium at McCords Vancouver Toyota (https://www.vancouvertoyota.com/). I threw down a deposit (1k, refundable) to get my name on the car in late October (10/2021) and drove out of the dealership a few days after Christmas...