Ubuntu :: Execute A Delayed One-time Hibernation?

way to hibernate at a specific time or after a some minutes (like 40 minutes to an hour, guess the exact time doesnt matter anyway). normally i shutdown my comp at night with

Code:
sudo shutdown - P HH:MM

which works just fine, but sometimes i have like 4 workspaces of stuff open that i'm working on so i'd rather just hibernate. shutdown -H does this halt thing that is really not my cup of tea so from the aformentioned googling i found out about at and sleep and crontab etc. but at and sleep cant recieve my sudo password beforehand so its useless and crontab is for repetitive scheduling, which i'd like to avoid cause i would hate to be working and suddenly have my forgotten crontab script hibernate me.

so is there any way to do a delayed hibernation? or at least some way to provide the sudo password to an at or sleep prefixed command, beforehand?

i'm only interested in doing it straight up through the terminal, not through other 3rd party software cause i tried a few of those before i found out about shutdown and they didnt work very well.