Santa rally stealing some of next year's cheer

As the Santa rally lifts stocks higher, Wall Street's expectations for 2015 gains have gotten slimmer.

A survey of the calls of 15 top Wall Street strategists shows they are mostly optimistic for the stock market in 2015, even with anticipated rate hikes by the Fed, falling oil prices and a soft global economy.

But with the S&P 500's 5.4 percent gain in the past six sessions, the average expectation of those strategists is that stocks will rise just 6.6 percent next year, and some are forecasting the market will will be flat by year end.

Strategists acknowledge next year's gains could be impacted by the strength of the December rally. Tobias Levkovich, chief U.S. equities strategist at Citigroup, said part of the market's recent surge is due to short covering. His target is 2,200 for 2015.

"We think some of the rally stuff we're getting is borrowing from next year," he said.

The S&P 500 closed at 2,070 Wednesday, very close to the Street's low forecast of 2100, from Goldman Sachs and Barclays. The high targets are RBC and Fundstrat at 2,325.

The S&P 500 is up about 12.6 percent for 2014 so far, and a number of strategists raised their views as the year progressed. The S&P 500 has gained more than 200 percent since its March 2009 low.

As the bull market heads into its sixth calendar year, Wall Street may be cheering on another year of gains but with more turbulence along the way, especially around Fed rate hikes.

Read MoreTraders say this could be the big short for 2015

2015 marks the start of a significant change in the investment environment where the Fed at some point will no longer be holding rates at zero, but other global central banks will continue to pump stimulus. That is expected to create turbulence, as the dollar rises and markets adjust to higher rates.

Read MoreTop business stories of 2014

Goldman analysts expect a "benign" reaction to the first Fed rate hike and they see stocks moving higher in the first half. But stocks could lose traction in the second half, as earnings contract as a result of Fed tightening, they wrote in their 2015 outlook.

"I think next year is going to be all about these moving parts. The cross currents for global liquidity are changing a lot of the relationships that have been in play for the last four years," said Gina Martin Adams, institutional equities strategist at Wells Fargo Securities. "Active asset managers will see some divergences develop. All boats will no longer be lifted by the rising tide."

Thomas Lee is among the forecasters with the highest targets. "I think stocks are going to do well in the end of this year, and I think people are going to start thinking about next year, and they're going to want to be positioned," said Lee, founder and strategist of Fundstrat Global Advisors. "They have various reasons to be optimistic about next year, everything from the gasoline dividend to QE taking place in Europe and Japan."