The last 10 minutes of trading could make or break the stock market’s performance for the whole day. At least that’s what could happen this week as low trading volume and a lack of material catalysts until Friday morning — when Fed Chair Jerome Powell speaks in Wyoming — will likely prompt professional traders to focus on placing market orders at the end of the day, according to JPMorgan’s trading desk. “A slow grind higher on light volume and then (presumably) systematic flows push markets materially higher into the bell to take advantage of market-on-close liquidity?” the Wall Street firm asked in a note. Traders usually place a market-on-close order at or after the day’s close in anticipation of the market’s movement the next day. On Monday, about a third of the gains in both the S & P 500 and Nasdaq-100 indexes came during the final 10 minutes or so of trading, JPMorgan noted. Even with the low liquidity, the S & P 500 climbed about 1% Monday, sitting just 1.1% below its all-time high, while the equal-weighted S & P 500 set a record high during the session. The bullish bias led JPMorgan to believe this is a “broad-based rally.” All eyes are on the Fed’s Powell, who is scheduled to speak at the central bank’s annual economic policy symposium in Jackson Hole. The speech takes place just three weeks after a July Fed meeting strengthened investor confidence that a September rate cut is “on the table.”