Your weather: Antarctic storm battering Australia has New Zealand in its sights

An Antarctic storm lashing southeast Australia with rain and snow will make its presence felt here tomorrow.

From early Friday morning the deepening low, currently over the Tasman Sea, will move on to the lower South Island, MetService meteorologist Andrew James says.

Rain will spread over western parts of the South Island first, while the storm's associated front will bring rain to the west of the North Island, reaching Auckland in the afternoon/evening.

An early blast of winter later this week. Cold, blustery winds with possible snow along parts of the southern/central ranges on Friday. Check your forecasts at https://t.co/REl2VBlGnA (and dig out your winter coats - this is the daytime temp map for Friday!) #NSWWeather pic.twitter.com/tqXk6pLQZb

— Bureau of Meteorology, New South Wales (@BOM_NSW) May 8, 2018

Over Saturday the rain will spread over the whole country.

"We are in for a wet weekend," James said.

An unsettled weekend beckons as the first of two lows is set to cross NZ tomorrow. The second, larger, area of low pressure moves in from the west on Sunday, though Mothers in the lower South Island are forecast to see a dry morning. For more details: https://t.co/hnwmGxU1gR ^AC pic.twitter.com/LMzgHF4lj2

— MetService (@MetService) May 10, 2018

MetService has issued heavy rain warnings for parts of Westland from 8am to 11pm tomorrow with up to 100mm forecast in the ranges.

Heavy rain is also expected about northwest Nelson and northern Fiordland, and Taranaki and Tongariro National Park in the North Island.

A low is set to cross the South Island tomorrow bringing heavy rain to the West Coast & strong winds to Canterbury High Country. A front associated with this low also pushes onto the North Island bringing a bout of rain to most regions. More details at https://t.co/qHyE5zhh6X ^AC pic.twitter.com/VnHD0jeFuy

— MetService (@MetService) May 9, 2018

On Saturday and Sunday another low over the western Tasman Sea is expected to maintain the moist north to northeast flow over New Zealand.

WeatherWatch analyst Philip Duncan said the North Island could be in for some very heavy rain.

"The main threat for New Zealand is this weekend in the upper half of the North Island as very heavy bands of rain slowly track eastwards."

Converging sub-tropical winds - northwesterlies from the Tasman low and northeasterlies from the departing high - would create a very heavy, potentially torrential, narrow slow moving band of rain, he said.

"[It] will cross over the northern half of the North Island from Saturday afternoon to Monday morning at this stage."

MetService said there was potential for further heavy rain from Fiordland to northwest Nelson.

Rain could be heavy about western areas in the North Island on Saturday and Sunday, and Bay of Plenty and the Gisborne ranges on Sunday and Monday.

Temperatures are forecast to stay fairly mild in the North Island, with Auckland forecast to hover around 20C through to mid next week.

Trend of ensemble mean rainfall forecast from ECMWF over past 4 days for upcoming event, valid midday Monday. Note subtle shift northeast & narrowing of where heaviest rain MAY fall (warm colours).

Message: confidence continues to grow for significant NI wknd rain.

~Chris pic.twitter.com/btpomyUNIo

— NIWA Weather (@NiwaWeather) May 9, 2018

The South Island however is in for a cool southerly change on Saturday, with Christchurch dropping to a maximum of 14C, and just 12C on Sunday.

Temperatures are forecast to remain in the low teens across the South Island through next week.

Today, a ridge of high pressure is keeping the weather relatively settled throughout the country.

This morning's fog in Auckland is forecast to clear late morning for a fine day, with a high of 19C.

#Auckland is not the only place affected by fog - Taupo, Rotorua & a few other cites north of the central plateau won't see the sun until later this morning too. Lights winds, moist air near the ground & clear skies last night provided perfect conditions for fog formation ^AC pic.twitter.com/bYR9GFDnKj

— MetService (@MetService) May 9, 2018

Similar conditions are forecast across the North Island today and tomorrow until late afternoon.

In the South Island there might be some isolated showers in the afternoon, before the low arrives from the Tasman.

Today's weather

• Whangarei

Becoming cloudy, could also be some morning fog. Northeast breeze. 20C high, 14C overnight.

• Auckland

Fine with high cloud, but areas of morning low cloud or fog. Northeast breezes. 19C high, 15C overnight.

• Hamilton

Morning low cloud or fog, otherwise fine with high cloud. Light winds. 20C high, 11C overnight.

• Tauranga

Fine with high cloud, but areas of morning low cloud or fog. Northeast breezes. 19C high, 14C overnight.

• New Plymouth

Fine with high cloud. Northerly breezes. 18C high, 14C overnight.

• Napier

Fine, high cloud. Light winds. 20C high, 11C overnight.

• Wellington​

Cloudy at times. Northerlies. 17C high, 13C overnight.

• Nelson​

Becoming cloudy, few showers from afternoon. Northerlies. 17C high, 13C overnight.

• Christchurch​

Fine with high cloud. Northerlies developing. 17C high, 9C overnight.

• Dunedin​

High cloud. Possible light rain around midday. Northerly. 18C high, 10C overnight.