NEW YORK (CNNMoney.com) -- JPMorgan Chase Wednesday reported earnings that blew past Wall Street forecasts, sparking a big rally in its stock, but executives warned that the second half may be tougher for the nation's No. 3 bank.

JPMorgan (up $2.06 to $42.77, Charts) stock, one of 30 in the Dow industrials, jumped about 5 percent on the news, helped by a broad stock market rally.

The New York-based bank said net income soared to $3.5 billion, or 99 cents a share, in the second quarter, from $1 billion, or 28 cents, a year earlier, which included a $1.2 billion charge for litigation.

Net revenue jumped 19 percent to $14.9 billion from a year earlier, though it was down about 1 percent from the prior quarter.

Excluding items, JPMorgan reported earnings of 92 cents, soundly beating Wall Street estimates of 87 cents, according to earnings tracker Thomson First Call.

Speaking on a call with reporters, JPMorgan's financial chief Michael Cavanagh said that while the company weathered the downturn in the stock market in the quarter, "I think its fair to say that conditions may be tougher in the second half."

JPMorgan CEO Jamie Dimon said the company also expects credit card losses to "go up several hundred million dollars next quarter."

Dimon said the company expects a $300 million increase in provisions for credit card losses in the third quarter and "maybe a little more in the fourth (quarter)." The company set aside $1.03 billion in loan loss provisions for the second quarter, down significantly from last year.

Cavanagh said the bank's pipeline of investment banking deals remains strong, but cautioned that much depends on how investors react to the downturn in the market.

If the market continues its downward spiral "it could have impact on how much of the pipeline comes to fruition in the third quarter," he added.

It's been a common theme among the commercial banks and brokers as they report second-quarter earnings.

While banks, including competitor Citigroup (Charts) which reported earnings Monday, and brokers, like Goldman Sachs (Charts) and Morgan Stanley (Charts), showed resilience in their quarterly results, the companies also raised concerns that prolonged stock market weaekenss could dry up equity offerings and hit trading results in the coming quarters.

"Like many of its rivals, JP Morgan Chase is beating the Street's second-quarter earnings estimates," said Louise Westerlind, analyst at independent research and consulting firm Celent LLC. But "the second half of this year looks a bit dusky due to the market conditions ahead of us."

That uncertainty pertains to the credit environment as well as market volatility.

Banks posted unusually strong performances in the first half due to the lingering effect of bankruptcy laws enacted in late 2005 that made it harder for individuals to file for bankruptcy. The law sparked a rush of bankruptcy filings last year, making this year's credit losses at banks lower by comparison.

"The whole company, wholesale and consumer, is performing very well," Dimon said on the call. "We're simply acknowledging that there will be another side to that mountain."

Dimon said the company's credit card operations will feel the effect as credit losses normalize and more loans are likely to go bad in the second half of the year because the banking industry increased the minimum payments that most cardholders must make each month.

While JPMorgan is not alone in forecasting a rise in credit losses in the second half, some of its competitors were less bearish.

Bank of America (up $1.30 to $49.74, Charts), which reported second-quarter earnings of $5.5 billion, or $1.19 a share Wednesday - beating Wall Street expectations by 9 cents - also indicated that there may be some slowdown in credit quality going forward, but said conditions for the credit card business remain fairly positive.

"We see signs of a consumer spending slowdown but they're modest," said financial chief Alvaro de Molina during the company's second-quarter earnings call. "They don't point to any kind of credit crash."

He declined to make any predictions on expectations for credit losses in the second half of the year.

In its report, JPMorgan cited strong investment banking despite the downturn in global markets, and ongoing low credit losses for the results.

Net income at its investment bank climbed 37 percent to $839 million while net income from credit card services rose 61 percent to $875 million.

The JPMorgan executives said said the company remains on track to achieve overall savings of $3 billion related to its $60 billion 2004 acquisition of Bank One, where Dimon originally served as CEO.

Dimon said the the company expects to reach $2.8 billion in savings by the end of the year.

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