Direct seeding will work fine for your fall tomatoes. I don't know if I'd plant them at the same time I transplant the spring crop into the ground. Because the seeds sown and the plants that sprout from them, will be grown in increasingly favorable weather conditions, I think they'd grow too fast and almost catch up with your spring transplants. (Trust me, I've seen this happen with volunteer plants I found sprouting in my garden about the same time that I was transplanting home-grown transplants into the ground. The same thing happens every year with volunteer ornamental pepper seedlings.)

If I was going to direct sow in your part of the state, I'd sow the seed 4 or 5 weeks earlier than the OSU-recommended dates to put fall tomato transplants in the ground. Those dates are, I believe, July 1-15th.

Dawn

I've grown fall tomatoes but you really need to figure out the days to maturity.

figure your time from sprouting to time to transplant, then days to maturity. then the time you think it may frost.

it can be done but pick a variety that will mature before frost or danger of frost.

I like to grow long-keepers in the fall because then we'll have them to eat deeply into winter.

I only plant a fall garden in rainy years. In drought summers, fighting the drought and wildfires all summer long suck all the life out of me and just kill my desire to plant a fall garden because, well, who wants to go on fighting drought for a few more months? Not I.