The unfortunate truth is that the best way to avoid jail time is to get a decent lawyer in the area of the court and go deal with the situation directly. If your only violation is failure to appear and register, your making things worse the longer you delay them.
Even if you live somewhere outside the geographical limitations of the warrant, you are setting yourself up for more future time. For instance, if you lived in Illinois and were pulled over for speeding, the officer would serve the warrant. If you can post the bond, you get a court date in Washington and have to get yourself there. If you don't go, another warrant issues, this time with a higher bond.
When you are picked up on a warrant you cannot post on you sit in the local county jail until the state of Washington formally decides not to come get you.
Get this taken care of now, and save yourself the headache later.