I've got a Joomla 2.5.28 site that I want to upgrade to Joomla 3.3.x. 

All available docs say all I need to do is set my update server to short term, and the 3.x series upgrade option will appear. Well, it doesn't! I've cleared my caches, logged out and back in, etc. and the control panel shows the nag that Joomla 2.5 will be desupported soon-- but the Joomla Update view just says

> 
> You already have the latest Joomla! version, 2.5.28.
> 
> 
> 

I don't see any option to begin the migration. 

Any ideas?