Snow predicted in expected cold snap

LATEST: It's down to the wire as to whether August turns out to be a record-breakingly dull and miserable month in Christchurch, as a cold southerly and the arrival of spring collide.

The forecast cold blast is one of the few of its kind over the past few months and could bring snow to low levels in Canterbury, Otago and Southland on Thursday night and Friday.

It comes as the polar vortex – the westerly wind belt around the Antarctic – weakens in line with predictions, breaking the barrier keeping in the coldest air and allowing it to escape further north.

Two weeks ago, forecasters said the strength of the vortex had been at record highs but pointed to computer models showing it was expected to dwindle over the next few weeks.

MetService spokesman Bob McDavitt said that had now happened. "This increases the chances of a polar outbreak somewhere ... and indeed there seems to be one near the Horn [the southern tip of South America] this weekend, but none, so far, anywhere else."

While the brief cold change this week would bring a burst of wintry showers and biting winds, it was unlikely to be a full-scale polar outbreak, he said.

Conditions would quickly clear on Friday night, he said, with a disturbed southwesterly flow bringing a mostly fine weekend.

It's down to the wire as to whether August turns out to be a record-breakingly dull and miserable month in Christchurch.

The darkest hours? 
 
Any more than seven hours of sunshine today and our attempt to break the 80-year record will fail.

 The sun is shining brightly over Christchurch at present despite a forecast of rain and drizzle.

August 1930 is the dullest August on record, with only 85.8 hours of sun at the Botanic Gardens.

By sunset yesterday there had been a measly 78.7 hours of sun in the city this month, so 7.2 hours today would be enough to consign August to the merely gloomy stakes rather than put it up on a pedestal as a new record.

The next few hours, and a bank of cloud to the east, will be the deciding factor.

- © Fairfax NZ News

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