We had "explosion" at our house, too. From virtually no words to hundreds of words, and from no two-word phrases to complete sentences.
If our experience is any guide, a kid who tends to move by explosion has that tendency across a variety of areas. So DD went from "can't read a single word" to "can read first-grade books independently" in a week or so. And she never crawled or cruised - one day she just stood up and walked, with enough control that she didn't ever fall down.
It can be extremely frustrating to wonder "she can do all the precursors to X, so why can she not do X even a little tiny bit?" particularly when kids who don't have all the precursors down are attempting X with some level of competence. And then one day the switch flips, and she's mastered X with little or no apparent effort.
