best guess Misumena vatia on Vinca major
Apocynaceae
Despite being considerably south from where I live, I have really liked UC Irvine's Natural History of Orange County for their pictorial representations, but I have some doubts their spider IDs are entirely correct. I've linked to BugGuide twice in the common name and the scientific name above, and even they're not all that accurate. I'm not criticizing them, it's just the nature of the beast, so to speak. There are so many insects and spiders out there, it's a challenge for everyone. I suspect the people who really know, don't spend their time posting pictures online. I found this list of Spiders of California helpful to check what actually occurs around here.
A fellow nature blogger and I were e-mailing about how we don't want to add to the prolific online misinformation. Yet, I want to learn more. For people who find my blog through searches (apparently, google and bing are now my best "customers"), they may not be aware that this blog is my learning tool and I'm totally okay making mistakes. I've said it once and I'll say it again, I am NOT an expert. All I can guarantee are that my pictures are taken on the date of the blog post and at the location indicated in the labels.
At the end of the day, my final thought on the above pictures is, "Oooh, look at the cool white spider on the pretty purple flower."