If I'm currently on probation for DWI, can I ask to serve the jail time instead?

Usually when a judge sentences someone on a DUI he orders the following: fines; incarceration; and classes.  However, he may stay the jail sentence and place you on probation.  Judges usually order community service and successful completion of the sentence while you are on probation.

That said, you could file a motion to terminate probation.  Usually, this is done after you have completed the terms and conditions of probation.  For instance, if you have paid all the fines, done all the community service, and done all the ordered classes, you can petition the court to terminate your probation early.  I would recommend getting a stipulation from the prosecutor prior to filing the motion.

Note, if you request jail instead of probation you are subjecting yourself for the total jail term.  So, the judge could place you in jail for the entire term, usually, at least a year.  Most people would rather be on probation then serve the entire probationary period in jail.

Hope this helps.