A broad trough is expected to move eastwards across the country tonight (Friday) and Saturday. Preceding this trough, a very strong northwesterly flow is forecast to bring heavy rain to western parts of the South Island, and gales to many eastern areas from north Canterbury to Wairarapa.

Expect cold, unsettled, westerlies for Fiordland tonight and Saturday morning, with 20cm of snow forecast to accumulate above about 400 metres during this time. Heavy rain falling in the ranges of Westland should ease Saturday, however a further 60mm of rain is expected through to mid Saturday morning.

Northwesterly gales affecting inland parts of north Canterbury, Marlborough, Wellington and Wairarapa, with severe gale gusts of 120km/h, are expected to ease overnight tonight.

People in these areas are advised to look out for surface flooding and rapidly rising rivers and streams. In the east, strong gusty northwesterlies can make driving hazardous, especially for high-sided vehicles, and can damage trees, powerlines and any loose structures.

People are also urged to keep up to date with the latest forecasts and warnings, as snow is likely to affect higher roads in the lower South Island.

Note, the heavy rain warnings for Fiordland, and the Otago and Canterbury headwaters are now lifted. Severe gales for inland parts of Southland, Otago and South Canterbury have eased, and the warning for these places is now lifted.