Nope, you have to use pastebin or a word document. Posting an unfinished story will result in it being deleted.

The best thing that you can do is to use a word processing program to write your story. This allows for all of the basic things you need like saving, spell check, and rich-text formatting.

Just keep in mind that when you are ready to post the story on the site you need to do so in source more or else your document formatting will carry over and mess up the page you are trying to make.