In its Q3 financial earnings press release today, Apple, has announced that OS X Mountain Lion will be available tomorrow. The release will come exclusively through the digital Mac App Store, and the new Mac OS will not be sold on optical discs or on a USB stick.

“We’re thrilled with record sales of 17 million iPads in the June quarter,” said Tim Cook, Apple’s CEO. “We’ve also just updated the entire MacBook line, will release Mountain Lion tomorrow and will be launching iOS 6 this Fall. We are also really looking forward to the amazing new products we’ve got in the pipeline.”

OS X Mountain Lion will cost $19.99, a $10 drop from OS X Lion’s $29.99 pricing. A user can download Mac OS 10.8 via the Mac App Store on one machine, and they will have the ability to install it via the purchased apps feature on up to five total Macs. The system software update will be available to Snow Leopard users in addition to Lion users.

We first speculated that Apple would release OS X Mountain Lion tomorrow, July 25th, when Apple announced that its earnings call would be today, July 24th. Over a week ago, we confirmed this with our retail sources who said Apple would be holding product-indicative overnights tonight. Apple Stores will be ready to show off the new Mac OS tomorrow morning.

OS X Mountain Lion includes over 200 new features, according to Apple, including Notification Center, Game Center, AirPlay Mirroring, enhanced iCloud integration, Notes and Reminders apps, an improved Safari and Mail, Twitter and Facebook integration, and voice dictation.