Storm warnings extend over most of the country

Weather forecasters extended their severe weather warning last night to take in most parts of New Zealand.

The MetService forecast a stinker of a night and a bad day today with heavy gales, rain and snow.

The forecasters predicted heavy rain and strong winds for many places, the wind warning extended to the northern half of Northland and to Marlborough and North Canterbury, and said there would be heavy snow for South Canterbury.

Blamed for the bout of rough weather was a low deepening rapidly in the eastern Tasman Sea, which was expected to cross central New Zealand about midday today.

"Ahead of the low, gale north to northwest winds are bringing very heavy rain to the South Island west coast, and the headwaters of the Otago and Canterbury lakes and rivers," the forecasters said.

Severe northerly gales, with damaging gusts of 120km/h to 150km/h, were expected over all the North Island, accompanied by heavy rain in some areas.

Strong winds in the North Island, Marlborough and Canterbury could damage trees, power lines and lift roofs and make driving hazardous.

Wind gusts, possibly reaching 150km/h on the tops around Wellington, were forecast but they would probably ease slowly during the morning ahead of a southerly change.

The MetService also issued road snowfall warnings for the Milford Road and the Lindis, Arthurs and Porters Passes after torrential rain in the Grey district caused widespread flooding.

The downpour triggered a landslip that took out the main east-west rail-line inland from Greymouth, stranding the TranzAlpine tourist train.

Flooding closed a number of roads and a mini-tornado ripped a roof off a house in central Greymouth.

Greymouth was hit by 30mm of rain over three hours yesterday morning and the town got almost 50mm in a 12-hour period, MetService forecaster Peter Little said.

- NZPA