Charts storm coming. Nasdaq Low - High Logic measures the # of stocks hitting their 52 weeks low minus stocks hitting 52-week highs. As you can see rapid market selloffs always build months beforehand as stocks hit lower lows. S&P 50 / 200 day is rolling over, indicating less stocks are above the 200 moving average. NYSE breadth thrust appears to have formed a topping pattern, which means upward momentum should reverse soon.