A small low drifting off the south east coast of Australia overnight tonight will rapidly expand on Friday to engulf much of the Tasman Sea by the end of the working week.

The incredibly fast development of this low means a rough weekend for some parts of New Zealand.

While a large low often means the rain clouds get fractured and broken up (which means you end up with large sunny/dry areas too) the low has enough energy to bring localised flash flooding to some areas.

The centre of the low – which may spawn a secondary centre – is likely to cross through the central part of the country on Saturday morning.

By Sunday the main low will lie east of the South Island with yet again another large clockwise airflow engulfing the entire country.  This setup means very wet easterlies move into Otago and parts of Canterbury – and in the North Island, wet west to north west winds.  The flip side means the west of the South Island may be mostly dry on Sunday but heavy rain could still form over the dry eastern North Island as a colder southerly sweeps in.

Rain may also become heavy in Dunedin and coastal Otago this weekend – with set-in rain lasting a day or so, those concerned with flooding may want to keep a close eye on the movements of this low.

Next week – May ends and June kicks off with a cold southerly flow and then an incoming high for the first week of Winter.

9pm Thursday 

9pm Friday

9am Saturday

– Maps by Weathermap.co.nz

– WeatherWatch.co.nz