Notice that the “b” in “doubt” is silent, which is good news. Notice the glottal stop for the “t” in “it”. I’ve talked about this a lot before. If you look at the bottom of the list of phrases, you’ll find one or two with explanations if you want. Remember, though, that your tongue should be relaxed, and not touching the top of your mouth.
The phrase means “I don’t think so”. It could be a reply to the question “Do you think it’ll snow?”.