Gary Tweddle still missing in Blue Mountains as search hits critical point The family of a young Sydney man missing in the Blue Mountains after vanishing from a work conference in the middle of the night say Saturday will be a critical day for searching before cold weather sets in. 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 disappeared in the early hours of Tuesday morning after a function. The 23-year-old, 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. Police and officers from the Rural Fire Service and the State Emergency Service have been searching bushland near the resort since Tuesday. About 200 people were part of the search for Mr Tweddle on Saturday morning, a NSW Police spokeswoman said. Mr Tweddle's family continue to appeal for help online. His father David flew from the UK to Australia this week and has joined the search, as well as posting missing person notices in nearby residential streets. "Today is the big one, the weather turns tonight ... and tonight is 6 nights out so its big," Mr Tweddle said on Facebook. May I ask you to put all your best wishes and thoughts in to willing him to stay strong. The Bureau of Meteorology said the temperature in nearby Katoomba ranged from 12 to 15 degrees during the week. But on Saturday morning it was eight degrees, with an apparent temperature of 0.1. Senior forecaster, Peter Zmijewski, said it was unlikely to snow. "It's going to be cold, but we probably won't get any precipitation," he said. Gary Tweddle grew up in the UK before moving to the Gold Coast as a teenager, and then to Sydney several years ago.