Custom validation with a requested response

I have participants in a survey doing a writing task. I'd like to give the participants a warning if they try to submit the page with less than the required number of words, but not force them to write the required amount. I'd also like to have a 5 minute timer where the page auto advances after 5 minutes.
I'm not having any trouble writing the validation itself, and I am able to rely on a Timer question for the time auto advance, but I am not sure what the right way to do the word count validation is. Right now I am considering something along the lines of:
Qualtrics.SurveyEngine.addOnPageSubmit(function()
{
    if( numOfWords < min_n_word-1 ){
       alert("Submit more words!")
    }
});
but this is flawed because it doesn't stop the page submission.

How can I add a warning message for page submission that allows participants to submit with less than the minimum number of words that also allows the timer to auto advance the page?

Also see:
https://www.qualtrics.com/community/discussion/10788/have-auto-advance-ignore-validation-rules