Uncertainty will be a certainty this fall, according to experts at fund giant Pimco.

A government shut down and another debt ceiling standoff is possible, say Pimco Executive Vice President Libby Cantrill and Managing Director and Portfolio Manager Josh Thimons.

Congress will probably reach a short-term deal to avert a shutdown and agree on a debt ceiling increase — but not until the last minute, they write in an article on Pimco's website.

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"We think a shutdown will be avoided largely because it would not benefit anyone politically," they contend.

But don't expect any grand bargain given the deep differences between parties, the Pimco executives advise. Instead, expect more of the same: demagoguery and brinkmanship followed by an 11th-hour "kick the can" deal.

"Political rhetoric that threatens to shut down the government or default on government debt is inherently destabilizing," they argue. "However, in what perhaps is a sad commentary on the state of affairs, the markets now expect very little out of Washington and have become accustomed to politicians taking us to the brink of fiscal catastrophe."

The debate over selecting a new Federal Reserve chairman will also cause uncertainty and market volatility this year, the duo predicts. The press has framed the debate as a choice between Fed Vice Chair Janet Yellen and former Treasury Secretary Larry Summers.

Yellen is seen as dovish and willing to experiment. Summers is also viewed as dovish, although not as much as Yellen. Due to a lack of direct monetary policy experience, he is much less known to markets.

"Regardless of who the ultimate nominee is," the executives say, "we expect the debate will increasingly lead to greater uncertainty and greater market volatility. Added to the potential volatility from the government spending and debt ceiling debates, investors should brace for a bumpy road ahead this fall."

House Speaker John Boehner, R-Ohio, said the Republican-controlled House wouldn't raise the debt ceiling without cuts to Social Security, Medicare, Medicaid and other government programs.

"We’re going to have a whale of a fight," he said at a fundraiser in Boise, according to the Idaho Statesman.

"I wish I could tell you it was going to be pretty and polite, and it would all be finished a month before we’d ever get to the debt ceiling. Sorry, it just doesn’t work that way," he said.

"If this were easy to do, somebody over the last 20 or 30 years would have gotten it done. We’re going to do it this fall."

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