I didn't see this news posted elsewhere on the site and thought it was worth a diary.
Blog for America has a banner at the top of the page announcing the coming announcement. (It says 1:00 PM; I assume they mean Eastern Time.)
I assume Dean is timing his speech to coincide with this month's DNC Meetups and hope he will call on his supporters to attend (usually 7PM, you can get info on yours at Meetup.com.)
(more below)
FWIW, I'll be at the "Goose Island" Meetup in Chicago, which is run by a former Clark supporter. I'll be interested to learn his take on the Chairmanship race.
I hope all Deaniacs in good standing will attend their local DNC meetups tonight and show their support for the next Chairman of our Party.