"The biggest (thing) to me is going to be the jobs report, and the biggest thing there is going to be the wages number. I think we're just one higher wage number away from a completely different reaction from Wall Street," Paulsen said.
Whether the labor market has healed enough has been a point of debate within the Fed, making it a hot topic for markets. Some Fed officials have argued that the slack in labor market and the lack of wage inflation makes it important for the Fed to keep rates low for longer, but some of the hawkish members say labor is already strong enough and it's time to consider returning to a more normal environment.
The market is anticipating another strong jobs report next Friday, with nonfarm payrolls above 200,000.
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Paulsen expects the economy to become so strong that inflation could pick up, and that could force the Fed to move faster to hike rates, a potential shock for stocks.
In Europe, meanwhile, the ECB is expected to sound dovish in the week ahead. While there's speculation it could slightly tweak its policy, it is not expected to announce quantitative easing—or a sovereign bond buying program—any time soon, if at all.
"There's a lot of pressure on the ECB to do something," Chandler said.
Since ECB President Mario Draghi spoke in Jackson Hole earlier this month, suggesting further policy moves, traders have been anticipating the ECB would take action Thursday.
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Investors have been barreling into European bonds, driving bund rates to record lows and shorter duration sovereigns from multiple countries to negative yields. U.S. yields have fallen with them, as Treasurys look relatively more attractive and traders play an interest rate differential.
The ECB program designed to encourage bank lending begins in mid-September, and there is speculation the ECB could entice banks to participate by making the terms more appealing with lower rates. There is also speculation the ECB could announce a plan to buy asset-backed securities.
"The odds of the ECB doing something are reasonable. The odds of them doing something big and new in the month of September are relatively low," McDonald said.
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"I would argue over the next month, the economic numbers will be a bigger story because I think what we're going to get from the ECB and the Fed will be incremental," he said.
McDonald expects the Fed to raise rates in the second half of next year. "I think the Fed has given us a very clear path. Their moves are going to be very small. It will be dependent on the labor data we get between now and then as to whether they get any shift."
McDonald said after watching U.S. data, he focuses on China and expects the Chinese PMI data at the end of September to be important after this month's disappointing numbers. "If the U.S. and China can do well, that would offset Europe," he said.
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Besides the employment report in the week ahead, there is the ISM manufacturing survey Tuesday; Fed beige book and auto sales Wednesday and ADP employment, trade, productivity and costs, and ISM nonmanufacturing data Thursday.
Looking around the world, Chandler said there are other risks for markets lurking in September. Scotland votes on a referendum to leave the U.K. on Sept. 18. "Most people think Scotland will be staying with the U.K., but if they don't it would be very impactful," Chandler said.
Traders are also watching politics closer to home. By the end of September, Congress must act to reauthorize the Export-Import Bank, which lends and provides loan guarantees to foreign buyers of American products. Republicans oppose the authorization and Democrats are lining up behind the president. "If the Export-Import banks does not get renewed, it will show the tensions in Congress, policy paralysis and the U.S. withdrawal from the world," Chandler said.
That would take markets to the November mid-term election and focus on that should pick up after September.
"I think we've got to turn our attention to the FOMC meeting before we turn our attention to the U.S. election," he said.