It’s a beautiful end to the week in many regions but the weekend is about to go downhill as a polar blast gets ready to pounce.

FRIDAY:
Friday is mostly sunny and calm across New Zealand with daytime maximum temperatures getting up around 10C in the South Island and 13 to 15C in the North Island. It’s all ahead of a cold change on Sunday which will get even colder on Monday and into Tuesday for many regions.

OVERNIGHT:
Tonight radiation cooling (warm air by day escapes into the atmosphere at night) will occur, so minimum temperatures will be near 0C or below in the South Island meaning more frosts will be possible. Some may also affect sheltered inland parts of the North Island.

SATURDAY:
As an area of low pressure approaches the South Island on Saturday clouds will gradually cover both islands spreading from the west. Rain will start to fall in the Tasman Sea side of the South Island on Saturday afternoon and snow is expected over the mountains.

Showers will also be possible in the North Island on Saturday, mainly in the west from Taranaki to Northland with plenty of dry spells.

SUNDAY:
Winds will get even stronger from the west to north west (generally) on Sunday. It will be rain in most areas on Sunday – or by Sunday night. Rain will fall as snow in higher elevations. Snow accumulation will locally reach 50-100cm Saturday afternoon until Sunday night. The Southern Alps may be covered with snow.

Cold westerly winds may also reach 20-40 km/h, especially in coastal areas, and will be above 40 km/h in the Cook Strait with gales possible by the end of the day and through the mountains further south.

MONDAY & TUESDAY:
The peak of stormy Antarctic weather will be Sunday afternoon until Monday morning with a surge of cold air pushing into the North Island on Tuesday too.

POSITIVES:
Fairly calm and sunny weather is expected around Christchurch this weekend due to the rain shadow effect of the Southern Alps. This should also make for sunnier and drier weather in the east of the North Island too.

NEGATIVES:
Some travel plans may be affected, such as Alpine Highways affected by snow, the West Coast affected by any localised flooding or slips and gales in Cook Strait may impact ferry crossings or some flights on Sunday or Monday.

– WeatherWatch.co.nz