Let's look at two charts.
In the weekly Japanese candlestick chart of QDEL, below, we can see that prices have formed what is called a bearish engulfing pattern. The bearish (red) bar of this week wraps around the bullish (white) bar of last week. This is a top reversal pattern. Normally we would wait for confirmation with Tuesday's price action but with prices so extended above the rising 40-week moving average line I will jump the gun a little bit.
In the lower panel is the 12-week price momentum indicator and if you look closely you can see a lower bar for this week's momentum suggesting the start of a correction.