Severe weather warning for parts of North Island

Unusual weather pattern expected to his this weekend. Photo / Herald on Sunday

An unusual weather pattern could result in flooding and wind damage for localised areas around the top half of the North Island tomorrow, forecasters say.

A deep low was forming that could produce severe weather from the Far North to Taupo, WeatherWatch.co.nz head analyst Philip Duncan said.

Rain was likely to develop before dawn in Auckland with the chance of a heavy downpour, he said.

"As the morning goes on rain will cross the region with a mix of steady rain and some heavier and lighter falls - with a burst of heavy rain and isolated thunder possible towards the middle of the day as the end of the main rain bands moves through."

The afternoon looked drier as winds turned southerly, Mr Duncan said.

Some localised areas could be affected by some flash or surface flooding.

"With the low still deepening - and deepening further across the weekend - it makes it hard to pinpoint wind speeds and where any potential damage could be," Mr Duncan said.

"At this stage we think generally the winds won't be severe - but could be locally damaging within some of those torrential downpours or possible thunderstorms."

There was a moderate risk for thunder in Auckland tomorrow, he said.

The weather system was at the lower end of severity, but when a low was actively deepening when it crosses over our most populated regions there was a moderate potential for pockets of weather related issues, he said.