Breach of the 50 day moving average combined with a bearish cross on the MACD. If it breaches the $17.58 support, I would look to $16.28 for the next significant support level. Breach of both is pretty slim IMO however.
Risk
Support and lower Bollinger line up, which can send it horizontal to build a stronger base. If $17.58 isn't breached on significant volume, look for another sign of confirmation. If it bounces of that line, look to the $18.49 as the resistance as a pivot to long.