Heavy rain warning issued

The lower South Island is likely to be hit by heavy rain tomorrow and Monday.

The MetService said today a cold front should move onto the area Sunday morning, preceded by a strong moist northwest airstream.

It looked likely to stall over Fiordland for a time, but there was some uncertainty as to exactly where and for how long.

"At this stage it looks as if up to 250mm will fall in parts of Fiordland between 3am Sunday and 3am Monday," said forecaster Mark Pascoe.

"Further heavy rain is likely after that, but the rain should ease sometime Monday."

He said rainfall could end up accumulating to as much as 350mm, which was a significant amount, even for Fiordland, and people in the area should keep a look out for rapidly rising river levels.

In Southland, significant amounts of rain could start falling from the early hours of Sunday as a weak southeast flow developed. However, it was uncertain at present whether amounts would reach warning criteria of 50mm in 12 hours.

"There is also uncertainty as to exactly where the front will stall and for how long," Mr Pascoe said.

"Heavy rain is likely to develop in the Westland ranges, also the headwaters of the Otago lakes and rivers, at some stage. This could be as early as Sunday morning, but is more likely to be delayed until Monday morning."

Some heavy falls could also develop in the Canterbury headwaters on Monday.

- NZPA