Informal Rush Process/COBs spring

Not really. Sororities are not likely to take new members too far into a semester because it's a better experience for those girls and the chapter to get new members at once and have them go through that experience together as a small class from bid to initiation. Bonding with each other and integrating into the chapter is important and wouldn't happen if intake were in dribs and drabs.

The fact is, there really isn't an 'informal process.' Continuous Open Bidding, COB, is just any sorority offering bids if they have spots open, and they can do it however they want without an announcement. If a chapter's membership is under whatever Chapter Total is for that semester, of if they don't take quota on bid day, they can offer bids up to that number. Panhellenic isn't really involved in COB, though they do take names of interested pnm's and/or make announcements for chapters as a courtesy, but they don't really organize or oversee any part of it.

Your best chance for a fall bid is making friends with members in the chapters and not getting fixated on certain letters.