Well, I got my degree (undergrad and grad) in meteorology, though not a forecaster per se. That's where a lot of my background synoptic and other related knowledge comes from. But beyond that, just reading in here (and other places), you learn the tendencies of how things work in this area. There are a lot of good posters on here, even if you have to filter out some of the BS posts. Pretty much any of the local "red tagger" mets in here have a plethora of great information and insight. But even those who are not technically "red tags", like @psuhoffman, @showmethesnow, @Bob Chill among others are great (though showme and Bob haven't been around here in some time, unfortunately). Really just reading a lot in this forum (and living here long enough) in a lot of ways helps. I learned an immense amount just by doing that, honestly.