Heavy rain, snow for parts of South Island

Heavy rain and snow is on the way for parts of the South Island. 

An active trough of low pressure moving eastwards across New Zealand this weekend will bring heavy rain and snow, MetService says. 

A heavy rain watch is in place for Fiordland, south of Doubtful Sound, from 9am until midnight today. 

Snow has been forecast for alpine roads on Monday and it was possible flakes could fall as low as sea level in Southland, the forecaster said. 

A heavy snow watch is in place for Central Otago south of Lake Wakatipu and Roxburgh, Clutha, Southland and Fiordland, south of George Sound from 2am until 3pm.

There would be frequent showers and strong southwesterlies, with snow to low levels. 

"Expect heavy snow at times above 400 metres, where snowfall may approach warning criteria in places."

Meanwhile, snow showers may affect the summit of the Crown Range, linking Queenstown and Wānaka, from 2am to 8am on Sunday.

A heavy snow watch was also in place for inland  parts of Canterbury, north of Waipara and Marlborough, south of State Highway 63 from 1pm until 10pm on Sunday. 

Rain turning to snow has been forecast for Canterbury alpine highways Porters, Arthur's and Lewis during Sunday morning before easing in the evening.

Alpine roads affected

Porters Pass (SH73)
From 8am until 8pm on Sunday: Expect 4cm to 6cm of snow to accumulate on the road above about 800 metres, with lesser amounts down to 500 metres.

Arthurs Pass (SH73)
From 7am to 8pm on Sunday: Expect 2cm to 5cm of snow to accumulate on the road above about 800 metres, with lesser amounts down to 500 metres.

Lewis Pass (SH7)
From 10am until 10pm on Sunday: Expect 8cm to 15cm of snow to accumulate on the road above about 800 metres, with lesser amounts down to 400 metres.