WI can be E-filed. 

First go to the Federal Info Works, Part VIII - Electronic filing of Extensions & Amended Returns and check the box for State Extensions and the pull down choice for WI.

Then go to the WI Info Works, Part VI and fill in the date the return was originally Efiled and accepted by the state.

Go to the Electronic Filing of Amended Return and mark the box for The amended return will be filed electronically.