One of Wall Street's most accurate forecasters has abandoned his bearish stance on stocks following Donald Trump's victory and the Republican sweep of Congress.

The breathtaking rally that briefly carried blue-chip stocks to a new record high—and helped them set their best week in five years—still has some room to run despite Friday's retracement.

"We think it (markets) can go a bit higher from here," JPMorgan global head of derivatives and quantitative strategies Marko Kolanovic told CNBC's "Fast Money" this week.

Kolanovic predicts that the president-elect's policies, which would include "the promise of a massive stimulus package," would be great for stocks —at least in the short-term. "This would be reflationary in nature," he said.

His firm, which has a 2100 year-end price target for the S&P 500 Index, says the index could surge to 2300 in early 2017, a figure that would support a nearly ten percent rally.

Kolanovic, who's often hailed as a Wall Street voice who moves the markets, predicted a Trump win could be a reality on CNBC as early as last March. He also did not agree with the consensus view that Trump would spell disaster for the markets, and cause volatility to spike.

However, he acknowledged a Trump presidency, no matter how friendly it is to business, generates longer-term downside risks to the market. It comes amid speculation his policies, like opposing free trade and threatening to slap tariffs on major U.S. trading partner China, could spark a trade war.

"There are still uncertainties," said Kolanovic.

"We do think that should keep realized volatility over the market a bit elevated. There are going to be things the market is going to be surprised about," he said. "I wouldn't necessarily shun all safe-haven assets."