Wall Street seems to be getting more comfortable with the idea that the cold and snowy winter is to blame for the slowdown in homebuilding, retail sales, industrial production, job growth and other recent economic data, two market watchers told CNBC on Tuesday. That realization was one of the factors behind last week's rally, they said, which was the strongest so far this year.
But the full extent of the weather impact won't be known for a few months, JPMorgan's chief U.S. equity strategist, Tom Lee, said in a "Squawk Box" interview. "I just think that it's going to be for investors hard to figure out when we get clean data. I think, it's sort of, toward the spring."
(Read more: Home builders burned by the deep freeze)
Alongside Lee, Barry Knapp—head of U.S. equity portfolio strategy at Barclays—acknowledged the weather as a factor but was concerned about the downward revision in November retail sales. He said the narrative had been that the economy was improving in the fourth quarter. "You've revised a bunch of that away. So it's a little unclear how good a shape the consumer is actually in."
Knapp reiterated his position that stocks will struggle as the Federal Reserve normalizes monetary policy. "The history around this is pretty compelling."
"It's basically every business cycle since World War II. When the Fed ... start[s] normalizing policy, you get an 8.5 percent correction or pullback," he continued. "It lasts for two to three months. The market stuck in a range and then the uptrend resumes."
Last week, Knapp estimated the would finish 2014 at 1,900, which would be a 2.8 percent return for the year.
Lee, who's been bullish for four years, said Tuesday he remains so. "I think people should be putting money to work here."
(Read more: 'Probably too late'to buy US stocks: Marc Faber)
"I think the easiest way to follow what equities should do is look at high-yield spreads to Treasurys," he added—saying whenever those spreads are narrowing that means price-to-earnings ratios should be expanding.
As for a year-end target, Lee said last week that he sees the S&P at 2,075 by the end of 2014, which would be a more than 12 percent increase.
—By CNBC's Matthew J. Belvedere. Follow him on Twitter @Matt_SquawkCNBC.