After a 12-day rally in stocks, investors should stay in the market, Stephen Weiss of Short Hills Capital said Thursday.
"I think you continue to buy," he said, adding that "there are a lot of people that are still underinvested in the market."
Weiss said that at a recent two-day hedge fund conference, many newer money managers were cautious, while more experienced pros were seeing "a very up market."
On CNBC's "Fast Money," Weiss said that all signs were "go."
"So, I think you've got to get in. and I think the market looks extremely well," he said. "It's clear sailing now through the end of the year. I'm remaining very, very bullish."
Joe Terranova of Virtus Investment Partners said that he didn't chase stocks as they ran up following the Fed's announcement of unabated stimulus and one overbought exchange-traded fund was the .
"I sold short on the close the EEM," he said. "I think a lot of what went into yesterday's decision, although we'll never candidly admit it, relates to the EEM."
Terranova, who said that "nothing's fundamentally changed in the EEM," also pointed to a possible speedbump for the Federal Reserve: "Oil remains at $107. It's going to move uncomfortably high, and the Fed's going to have to respond to that."
(Read more: 'Investors were underweight risk': JPM's Tom Lee)
Josh Brown of Ritholtz Wealth Management took a skeptical perspective on the post-Fed run-up in stocks.
"I don't think that that's something that's going to be a continuing trend. I think it was just the market exhaling and coming back to some of the worst-performing groups that we've seen since what happened June."