Download and install iReboot 2.0 in Windows.
Run a program immediately on startup in Windows (add to autostart) that will check the time and if it's between 1300 and 0000 it will call iReboot from the commandline and tell it to boot into Ubuntu.
(iReboot is an application that can boot your PC into a pre-determine OS)
btw - from your username I take it your from the Windy City, too? GO BLACKHAWKS!