Antarctic air arriving Saturday night may bring sea level snow for south

Friday, 2 August 2019

Sea ice on the ocean surrounding Antarctica. Air arriving over New Zealand on Saturday night has come from as far as 72 degrees South. (File photo)

The freezer door is about to open.

If you think it has been cold over the past few days, just wait for what is about to be unleashed across the country.

An extremely deep low pressure system south of New Zealand is churning proper Antarctic air towards the country (light whitish-blue in this map), the coldest air mass to affect New Zealand so far this winter. This European model weather map for Sunday evening is from the Windy.com website.

A swirling mass of sub-zero air from Antarctica is on its way and should arrive in the far south on Saturday evening.

The parts of the South Island most exposed to the southwesterly – the west and south – will be battered by bitter gales at times on Sunday and into Monday next week. Snow to sea level, or close to it, is also highly likely.

A bitter blast of air from Antarctica is about to bring freezing conditions to parts of the country from Sunday. (File photo)

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Eastern and northern parts of both islands should escape the worst weather but not the bitter temperatures.

MetService meteorologist Stephen Glassey told Stuff severe weather watches or warnings for very low snow for Sunday and early Monday would probably be issued on Saturday.

An active cold front will move on to the south of the South Island on Saturday evening, ushering in the freezing air mass.

It reaches Christchurch in the early hours of Sunday and Wellington by mid-morning, blowing up the North Island into Auckland by mid- to late-afternoon.

The air is truly Antarctic, originating from about 72 degrees South, and will arrive in New Zealand courtesy of a deep low-pressure system spinning vigorously to the south of the country.

The lowest snow is forecast for parts of Fiordland and Southland on Sunday and Monday morning.

But later on Sunday afternoon there is also a complicating factor, in the form of a small trough of low pressure, which could bring very low snow to parts of the top half of the South Island too.

Glassey said the coldest of the cold air would probably be on Sunday night and Monday morning.

'This is the coldest we have had this winter. We haven't seen any snow to anywhere near sea level yet and this will be the first time it gets close to that.'