Search co-ordinator Sergeant Aaron Nicholson said the group had been frustrated by poor weather in the mountains all weekend and had taken advantage of a "small window" of improvement to fly into the search area.
However, the weather is expected to close in again and remain unsettled in the mountains until Friday.
Grave concerns are held in Wanaka for Ms Yun, who has been missing since December 31, but NZPA reported yesterday Ms Yun's former partner, Oleg Amiton, was holding out hope.
Mr Amiton and a friend of Ms Yun were due to arrive separately in Wanaka yesterday to help with the search but the Otago Daily Times has not been able to contact them.
Mr Amiton is the father of Ms Yun's 4-year-old daughter, Liann.
NZPA yesterday reported Ms Yun, who lived in Uzbekistan before moving to New Zealand several years ago, had some climbing experience.
Mr Amiton told the Sunday Star Times: "She used to be a mountaineer in Kazakhstan.
''We feel that she is alive and very frightened.
''I hope she has just got lost and doesn't have any injuries."
Sgt Nicholson said given the weather, if Ms Yun had been injured or become ill, her chances of survival would be low.
But searchers remained hopeful she would be found, he said.
Ms Yun is a yoga instructor and a keen snowboarder and photographer, with a passion for the outdoors.
However, it is believed she is relatively inexperienced with the alpine conditions in the Wanaka area and she is understood to have been lightly equipped for her intended tramp between Mt Aspiring Hut and the Dart Hut.
She was advised by a Department of Conservation hut warden not to attempt the 8- to 10-hour tramp to Cascade Hut on New Year's Eve because of the conditions.
Police received confirmation yesterday she was carrying a cooker.
When last seen about 9.30am on Wednesday, she was wearing a yellow parka and green tramping trousers.
Four areas on the Cascade Saddle Route were pinpointed for searching yesterday, but one area - the bluffs near the Pylon where other trampers have died in falls - could not be checked yesterday because the conditions made it unsafe, Sgt Nicholson said.
Climbers needed to use ropes to search those areas.
Sgt Nicholson said he would pull the searchers out if conditions proved too bad to continue but the search would not be cancelled, despite poor mountain forecasts until Friday.
