MetService said a low was developing over the Tasman Sea and was set to affect New Zealand from Monday until Wednesday.
Persistent and cold easterlies were expected to develop over the southern South Island from tomorrow afternoon, bringing heavy rain that would turn to snow above 300 metres for areas including in Dunedin, North Otago and Clutha.
First to get the snow would be the Crown Range, linking Queenstown and Wānaka, where up to 15cm was expected to fall on the road above 700 metres from 6am on Monday. Further snow was expected during Tuesday to an even lower level.
The Lindis Pass (State Highway 8) in Central Otago may get up to 5cm of snow on the road about 700 metres on Monday and more was likely at a lower level the next day.
In Southland, between 3cm and 6cm of snow was forecast for the Milford Road (SH94), about the road above 800 metres east of the Homer Tunnel from 6am until 8pm on Monday.
A heavy snow watch is in place for inland areas of Otago and Southland, as well as eastern Fiordland, from 9am tomorrow until 6pm on Tuesday.
Periods of heavy snow above 800 metres would develop on Monday morning, where snowfall amounts may approach warning criteria, MetService advised.
"The snow level is expected to lower to 300 to 500 metres overnight Monday and during Tuesday morning with significant accumulations shifting towards eastern Otago."
A heavy snow watch was also in place for South Canterbury including the foothills for 24 hours from midnight on Monday.
Rain was expected to gradually turn to snow above 400 metres during Tuesday. Heavy snowfall is possible above 500 metres, where amounts may approach warning criteria.
Heavy rain, strong winds
Heavy rain is set to pelt North Otago, Dunedin and Clutha (southeast of Raes Junction), from 12pm tomorrow until 6pm on Tuesday; between 80mm to 120mm of rain has been forecast.
MetService said the rain was expected to turn to snow above 300 metres during Tuesday.
"Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions possible."
It advised people to clear their drains, avoid low-lying areas and drive cautiously.
Meanwhile, a strong wind watch is in place for Westland and The Fiords from 6pm on Monday until Wednesday.
Winds may approach severe gale in exposed places.
MetService warned that damage to trees, powerlines and unsecured structures were possible.
"Driving may be difficult, especially for high-sided vehicles and motorcycles. Drive cautiously."
MetService Road Snowfall Warnings
Lindis Pass (SH8)
Valid: 18 hours from 6am Monday July 29 to 12am Tuesday July 30
Forecast: Expect 5-10 cm of snow to accumulate on the road above 700 metres during Monday. Further snow is expected during Tuesday, to an even lower level.
Crown Range Road
Valid: 21 hours from 3am Monday July 29 to 12am Tuesday July 30
Forecast: Expect 12-18 cm of snow to accumulate on the road above 700 metres. Further snow is expected during Tuesday, to an even lower level.
Milford Road (SH94)
Valid: 17 hours from 3am Monday July 29 to 8pm Monday July 29
Forecast: Expect 3-6 cm of snow to accumulate about the road above 800 metres east of the Tunnel.
- ODT Online
