I'm betting the stock is trending down today because insider info is out regarding the earnings release. It's unusual for a stock to go down like this the last trading day before earnings, especially when the overall market is up.
FWIW, I'm actually long ZUMZ and am continuing to hold that position. Even if the earnings aren't stellar this evening, ZUMZ still seems to have long-term potential. In addition, we're in a time of year that is generally favorable for retailers.