Weather: Torrent of heavy rain to hammer South Island Saturday evening

The South Island is being warned to prepare for a bombardment of heavy rain as bad weather sweeps towards the eastern side.

"A low is expected to lie slow-moving east of central New Zealand today, directing a moist southeast flow and rain onto eastern parts of the South Island," MetService warns.

"Rain is expected to become heavy for parts of the eastern South Island this evening, and continuing into Sunday morning."

The areas that will see the heaviest rain are at risk for localised flooding and slips.

"Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous," MetService says.

North Otago has been upgraded to an orange warning for heavy rain from 9pm on Saturday. MetService says 40 to 60mm of rain is expected to fall in the following 12 hours with peak intensities of 5-10mm/hr.

Dunedin, the Canterbury high country and the plains near the foothills remain under a heavy rain watch with possible heavy falls during this time, especially in the north.

The colder air at higher altitudes will also see this heavy rain falling as heavy snow along the Southern Alps.

WeatherWatch says another one metre of snow is forecast for the mountain peaks over the weekend, increasing the avalanche risk as we head into next week.

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