Today was a trend day higher for the U.S. stock index futures after several days of very low volatility. After an initial push lower this morning the market found direction and ground higher with little opportunity to buy a pullback. Then at 10:51AM CT a large buy stop was triggered in the Nasdaq 100 futures and it ignited the rest of the market. This is what it looked like before the stop was triggered.
There was little opportunity for shorts to get out because the pullbacks were so shallow. These two screenshots of the volume imbalance footprint chart show very clearly the bias in the market and how sellers were absorbed (shown in image above).
This chart shows how ALL the volume was at the ask (offer) price until the order was finally filled to completion. It is typical for the market to be very skittish and volatile for the next few minutes after a large stop order gets triggered.