"It was clear and you could see, but ... I suspect it would have been pretty icy in the morning. It had rained a lot beforehand, and so the snow would have been rained on and then frozen, making it quite icy."
The back part of the mountain where the men were skiing had steep gullies that lead into cliffs, Mr Thurlow - who has more than 20 years experience of climbing in New Zealand - said.
"So if you fall down one of those gullies, there's no hope of survival really, because it just runs out into cliffs out of the snow," he said.
There were dangerous spots on that part of the mountain, he said, but "in general, it's not dangerous".
"There are places where if the snow is hard and icy, particularly at this time of year in the morning the snow can be really hard and icy, so sliding is a particular hazard in the spring time early morning.
"People go out in the afternoon and it's all nice and soft and they think that's what the snow's going to be like first thing the next day. But early in the morning it can be really icy. So that combined with places that might not be too bad on their own but if you fall and slide down them they go steeper and steeper and off a cliff, then they kind of can sucker you in a bit."
If you fall into one of those, lose your ski, then you don't really have any way to stop.
"The two men would have had "quite a long way" to walk to access the back of the summit at this time of year, Mr Thurlow said, as the ski lifts were not running as the ski fields were closed.
But it would not have been difficult to access.
"You wouldn't have to be experienced to get there, it would be an easy ski tour," Mr Thurlow said.
"But even on an easy ski tour there are places where isolated hazards, I would call them, where if you do fall down then you could slide a long way."
Mr Thurlow said he did not know the details about what had happened the man.
"It can be anything from somebody trying to do something foolish to somebody being quite safe but you trip and fall into a place.
"That sort of [thing] could happen to anybody, so I don't really know what sort of situation that was."
Ski guide Mark Sedon said it was "not that common" to go to the back of the summit where the two men were skiing.
"They must have been very fit as it's a long way from the car park," he said in an email to NZME News Service.
Mr Sedon described the incident as "very sad", but said he did not want to comment further.
Mr Atkinson's skiing companion raised the alarm around 1.10pm on Monday, and it took rescue teams an hour to find him, indicating he had "fallen a fair way", Senior Sergeant Craig Dennison said yesterday.
An Alpine Cliff Rescue spokesman, who asked not to be named, confirmed Mr Atkinson slipped in icy conditions in an area behind the Treble Cone ski field.
"He was ski touring at the time. One [of the men] has taken a slip on some firm ice [and] he was unable to stop himself," the spokesman said.
"It's an unfortunate incident and the fault of no-one."
The death has been referred to the coroner.
- Additional reporting: Rhys Chamberlain of the Otago Daily Times
