Grave concerns areheld for her safety following extensive rain and thunderstorms in the area where she is believed to be missing.
Const Mike Johnston said the weather forecast was such that it would be unlikely search parties could return to the national park before mid-day tomorrow.
"It is very inclement weather up there," he said.
Wanaka police released Ms Yun's name on Thursday in the hope she had left the Mt Aspiring National Park on Wednesday instead ofattempting to go to Dart Hut, as recorded in her intentions.
The police had notreceived any phonecalls from Ms Yun yesterday.
Ms Yun left the Mt Aspiring Hut at 7am on Wednesday and was last seen about halfway between the bush line and the Pylon (1835m), on the ascent to the Cascade Saddle.
The weather deteriorated rapidly on Wednesday, with thunderstorms, heavy rain and snow above1800m.
The Cascade Saddle Route is in difficult alpine terrain and has been the scene of several fatal accidents.
The weather cleared to allow aerial and land searches, without success, on Thursday.
Rain and thunderstorms closed in again yesterday.
Rivers at the headwaters of Lake Wanaka were rising yesterday and the Metservice issued a severe weather warning advising that up to 70mm of rain could spill into the headwaters by 6pm yesterday.
Police are asking for any person who has seen Ms Yun in the national park or who knows of her whereabouts to contact them.
Ms Yun is of medium build with long black hair and was last seen wearing a yellow Mountain Designs parka and a light pair of green tramping trousers.
She was carrying a walking pole and a small pack of unknown description.
