First Cross...ing

SPY weekly chart is showing a 3/10 "First Cross" sell signal. The slow line is beginning to dip into negative territory while the fast line corrects into it (merely pointing out a first lower high in price trajectory). The trigger would be to see a larger (more negative) reading in the histogram's (fast line) current reading (whether it be this bar or the next few).
These tend to me more powerful moves when you have the fast line correct into the slow line as it is crosses into negative territory. Interesting how desperately price is holding on to the Lehman gap level.