If passing a file writable stream to the Console constructor in Node.js, is writing to it asynchronous?

Question

I've read the docs about the Console object and A note on process I/O, but can't figure out if the following would result in a synchronous or asynchronous operation:

const out = fs.createWriteStream('./out.log')
const logger = new Console(out)

logger.log('foo')

I'm curious about how this acts, especially on a *Nix system. But I wouldn't expect this to act differently on a Windows. The reason I am asking is because I had built a logger which leveraged the Console object, but I don't want the logger to be blocking when writing logs to files while in production.