Mystery surrounds the disappearance of a young Sydney man from a resort in the Blue Mountains, with the search becoming increasingly urgent ahead of possible snow showers forecast to hit the area this weekend.

Gary Tweddle, from Cremorne on Sydney's lower north shore, was attending a work conference at the Fairmont Resort in Leura this week when he vanished in the early hours of Tuesday morning after attending a function.

Missing: Gary Tweddle. Credit:Facebook

The 23-year-old, who worked as a sales representative at computer technology corporation Oracle, appeared to be in good spirits when talking on his mobile phone to a friend shortly after midnight, the last time he was heard from. He told his friend that he had been separated from a group and was lost in bushland near a main road.

Mr Tweddle's phone now has been either switched off or is out of battery.