You can sync the same artboards from Sketch into both InVision and Overflow, so when you update a screen, both the prototype you've built in InVision and your user-flow diagram will update.

However, there's no way that I know of to automatically generate one from the other. Axure can do something closer to this, though.

I was searching for "create a user flow invision" and found your question and remembered that I had yet to try out an answer in Sketch using the User Flows plugin for Sketch.

I understand from InVision that there is no way to do this: invision fail