There are a few early spring CX races around, mostly pre-XC warm up's. There are however a lot of STXC (short track cross country) races that are basically fat tire versions of cross without the barriers. I have found that those are perfect for per-cross training.
Hear, hear! Portland has a great STXC series that runs seven weeks from late Jun through early August. When it's over, I take a couple of weeks off from intensity and then dive into 'cross clinics and practices in the weeks elading up to Cross Crusade. It's perfect, really. And it's FUN.
get in touch with larry grossman and ken getchell, both who are on these forums. larry did cult cross which had races in march/april in colorado, and ken did an august or july race two years ago but had to cancel last year (spectacross).
i'm a fan - and am trying to work with a local mtb promoter of having a cx category in his 8 hour mtb race. so many of the mtb races aren't that hard technically that you could have a cx category I think - that's one way to do it without another standalone event.