This will be Shirleen and her husband Jesse's third child.
They are already parents to daughters Shayla and Gigi.
"We need a little brightness," Shirleen said as she made the reveal with an Eyewitness News AccuWeather Forecast graphic.
Sam Champion couldn't believe she kept it a secret.
"I'm so excited," he said. "I know we have to move on, which is why they just took the tight shot, but I want to talk about this for hours...How am I supposed to go on after that?"
Fellow morning team members Anchor Ken Rosato and Heather O'Rourke also shared their congratulations - along with GMA's Robin Roberts.
Robin Roberts congratulates Shirleen Allicot on her pregnancy
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Artist's polar bear snow sculptures represent climate change
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