KEY POINTS:
A storm building over the Tasman Sea is set to strike New Zealand for much of the rest of the week.
MetService this morning put out a severe weather warning for Westland and predicted heavy rain for northern and western areas of both islands.
Forecasters said the front would move quickly eastwards over the country on Tuesday preceded by strong northerly winds. Bands of heavy showers and thunderstorms would follow through to Wednesday morning.
Philip Duncan, head weather analyst for the Radio Network, said a band of cloud now stretches from as far as Darwin in northern Australia to New Zealand.
Duncan said wind speeds have reached 120km/h on Wellington's hilltops this morning with gusts to near 80km/h in the city.
Further north, winds have reached 60km/h in Auckland and 80km/h on the Hauraki Gulf.
He said: "In the past 24 hours the low has doubled in size and over the next two to three days it's going to lash New Zealand with heavy rain, severe gales, thunderstorms, hail and snow to low levels."
Near the ranges of Westland and the Paparoa Range 90 to 120mm of rain is expected over about 24 hours from around 4am this morning with the heaviest falls from Franz Josef Glacier to Otira, MetService said.
Today's rain warning added: "There is likely to be useful spillover into the headwaters of the main hydro lakes and rivers of Canterbury and Otago but probably not enough to justify a warning there.
"Although the amounts of rain are not expected to be unusual for these areas, people should be prepared for streams and rivers to rise quickly."
A wintry southerly blast will be felt in southern and eastern areas through to Friday.
Duncan said the storm has the potential to "be destructive to lives and property".
"There'll be damaging gales in central and eastern areas, heavy hail and thunderstorms along the North Island's west coast, the risk of mini tornadoes along the entire west coast and snow to low levels in the South Island.".
He said Auckland would be hit by strong westerlies tonight and on Thursday snow is possible on the Desert Road.
"Winter temperatures will cover all of New Zealand by Friday and while skies will clear in the north west, temperatures will be much lower. Auckland's high on Friday and Saturday may only be around 11 degrees with the wind chill making it feel more like 6 or 7,". Duncan said.
- NZ HERALD STAFF
