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Severe Weather Outlook

Issued at 2:19pm Thursday 19 Apr 2018
Valid from Saturday 21 April 2018 to Tuesday 24 April 2018

A trough sweeps across the country during Saturday from the west, preceded by a strong northwest flow and followed by disturbed west to southwesterlies.

On Saturday, there is moderate confidence of west to northwesterly winds becoming severe about exposed parts of Marlborough, the Canterbury High Country, Otago and Southland. There is also moderate confidence of severe gale northwesterlies ahead of the trough for Wellington and Wairarapa, then following the trough there is moderate confidence of westerlies becoming severe in exposed parts of northern Wairarapa and Central Hawkes Bay.

Late Saturday, the trough weakens as it moves northeast across the North Island and eventually away to the north. On Sunday, the southwest flow across New Zealand eases as a ridge of high pressure spreads over the country from the west.

Late Monday, another trough moves onto the far south of the South Island from the west, weakening during Tuesday as it moves onto central New Zealand. There is moderate confidence of westerlies becoming severe about exposed parts of Southland and Clutha during Monday, and also low confidence of rainfall accumulations reaching warning criteria for Fiordland and southern Westland late Monday and early Tuesday.


Low confidence:
A 20% likelihood (or 1 chance in 5) that the event will actually happen.

Moderate confidence:
A 40% likelihood (or 2 chances in 5) that the event will actually happen.

High confidence:
A 60% likelihood (or 3 chances in 5) that the event will actually happen.

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