In northern California, something that's cool is "koo" in tweets, while in southern California, it's "coo." In many cities, something is "sumthin," but tweets in New York City favor "suttin." While many of us might complain in tweets of being "very" tired, people in northern California tend to be "hella" tired, New Yorkers "deadass" tired and Angelenos are simply tired "af."
The "af" is an acronym that, like many others on Twitter, stands for a vulgarity. LOL is a commonly used acronym for "laughing out loud," but Twitterers in Washington, D.C., seem to have an affinity for the cruder LLS.