Apple is said to be working on an incremental operating system update for Mac OS X 10.6 Snow Leopard that will let its users enjoy seamless integration with the iCloud service, which is scheduled to go live this Fall when iOS 5 debuts. MacRumors spotted the above notice in a developer’s .Mac preference pane in TIGER after he had upgraded his MobileMe account to iCloud:

You will no longer be able to sync with this machine because you’ve upgraded to iCloud. iCloud requires a computer running Mac OS X Snow Leopard v10.6.9 or later for Contacts, Calendars and Bookmarks.

This is actually the first mention of more detailed iCloud system requirements beyond a brief description on Apple’s iCloud page. OS X 10.6.9, of course, has yet to be released, but it’s nice seeing that Apple won’t be leaving out Snow Leopard users with its upcoming cloud service.

Apple last week released the ninth beta of iCloud for developers, in addition to beta versions of OS X Lion 10.7.2 Beta 3 and iPhoto Beta 3 which now supports photo streams between a 10.7.2 machine and iOS 5 devices. As part of the iCloud upgrade path, existing MobileMe users who convert their accounts to iCloud will lose the ability to sync Dashboard widget, Dock items, keychains, Mail signatures, Mail account rules, Mail smart boxes and Mail preferences, Apple warns.