Deutsche Bank cut its global growth forecast on Friday and warned a summer tempest could await financial markets.
The German bank downgraded its estimate for U.S. growth this year by nearly a percentage point, down to 2.3 percent from 3.1 percent.
It now sees world growth at 3.3 percent in 2014, rather than the 3.5 percent predicted in March.
Deutsche said the "remarkable calm" that had settled over markets across the world in recent months would not last.
The widely followed VIX index, which tracks near-term volatility on the U.S. benchmark , has declined 15 percent since the start of the year.
"The calm cannot last indefinitely, and the question at hand is whether the clouds on the horizon portend merely a late-summer squall or a potentially far more damaging tempest," Deutsche economists wrote in a report published on Friday.
"Our baseline forecast assumes the former—a manageable storm."
Deutsche attributed its cut to U.S. outlook to "weather-driven disappointment" in the first three months of the year.
On Wednesday, the official estimate for first quarter GDP was cut to minus-2.9 percent annualized.
Goldman Sachs cut its U.S. growth forecast for the second quarter on Thursday, after data showed a smaller-than-expected 0.2 percent rise in consumer spending last month.
"Somewhat offsetting this downgrade to U.S. prospects is a substantial upgrade to growth prospects in Japan, where the economy has appeared more resilient to the consumption tax increase than we anticipated," Deutsche said in its report.
It forecast Japan's economy would grow by 1.2 percent this year.
Data out on Friday showed Japanese consumer prices rose 3.4 percent in May on the same period a year before. This was the fastest growth rate in over three decades and means prices have now gained for 12 straight months—a positive sign for Japanese policymakers as they battle to eliminate long-term deflationary pressures.
Despite the good news, the Japanese benchmark Nikkei fell below a one-week low on Friday, with the weak sentiment blamed on the strengthening .
—By CNBC's Katy Barnato