A southwesterly airflow lies over the country today and it is set to become colder as a front moves in from the Tasman Sea, moving over the South Island from afternoon then the North Island overnight.

MetService has issued a Road Snowfall Warning for the Desert Road - State Highway 1. This warning is valid until 11am today.

A period of snow is likely above 900 metres from Friday tonight into Saturday morning, and 3 to 5 cm may settle on the Desert Road.

"Note, another period of snow is likely overnight Saturday and another warning may be issued closer to the time," says a MetService spokesperson.

Periods of heavy snow are also likely for the southern South Island.

"A cold southwest flow spreads onto the southern South Island Friday, then persists through to Monday morning.

"There are several troughs embedded in this flow, which are forecast to bring snow to low levels over the southern South Island."

Heavy Snow Warnings are now in force for southern parts of Otago,Southland including Stewart Island and southern Fiordland, while a Heavy Snow Watch remains in place for northern Fiordland.

Snow falling to low-levels is likely to be impactful, even where accumulations do not meet warning criteria. Strong Wind Watch is now in force for Southland, Clutha and Dunedin.

A Heavy Snow Warning has been issued for:

Area: Fiordland about and south of Doubtful Sound
Valid: 40 hours from 12:00pm Sat 1 Jul to 4:00am Mon 3 Jul
Forecast: Expect 30 to 40 cm of snow above 300m, with lesser amounts down to near sea level.

Area: Otago south of line from Queenstown to Alexandra and Mosgiel, also Southland and Stewart Island
Valid: 41 hours from 4:00pm Sat 1 Jul to 9:00am Mon 3 Jul
Forecast: Expect periods of heavy snow above about 300 metres, with some falls down to near sea level.

The heaviest snow in Fiordland and Otago is expected from Saturday evening through to Sunday evening, where 20 to 35 cm of snow is expected above about 300m, with lesser amounts down to near sea level.

Heavy snow may disrupt travel in affected areas and could damage trees and powerlines. Cold conditions may cause stress for livestock.

Severe gales forecast

Possible severe gales are forecast for parts of the North Island and the lower South Island.

"Meanwhile, over the North Island, an active front crosses the upper North Island Friday night, followed by a strong west to southwest flow.

"Strong Wind Watches are now in force for Northland and also for central Hawke's Bay and the Tararua District."

Northland, Auckland, Waikato & Bay Of Plenty
Partly cloudy with occasional showers, especially in the west. Showers becoming a bit heavier overnight. Blustery westerly winds.
Highs: 13 – 16

Western North Island (including Central North Island)
Showers, heavy now and then, easing late afternoon then picking up again later in the evening. Snow to 800m. Blustery westerlies.
Highs: 6 – 14

Eastern North Island
A mix of sun and cloud, chance of a spit or shower, more so for Wairarapa. Blustery westerlies.
Highs: 12 – 15

Wellington
Morning showers clear then expect sunny spells, showers again later in the evening as blustery westerlies tend northwest.
Highs: 12 – 13

Marlborough & Nelson
A mix of sun and cloud, a few showers especially for Nelson in the morning then again in the evening. Westerly winds.
Highs: 12 – 13

Canterbury
Early showers clear then expect sunny spells. Southwesterlies freshen later in the evening with further showers for a time.
Highs: 6 – 11

West Coast
Morning rain eases to the odd shower, rain picks up again during the afternoon spreading northwards with southwesterlies freshening. Snow to 600m, 300m for Fiordland.
Highs: 7 – 12

Southland & Otago
Early rain eases to showers, drying out in the afternoon for Otago. Rain picks up again in the evening spreading northwards. Snow to 300m in the morning, 200m in the evening. Southwest winds.
Highs: 6 – 8