Severe Weather Outlook Get File

Severe Weather Outlook

Issued : 2:31pm Saturday 17 Mar 2018, Valid from Monday 19 March 2018 to Thursday 22 March 2018

A strong northerly flow develops over the South Island on Monday ahead of an approaching front that should become slow moving over Fiordland on Tuesday. The front should then move northwards across New Zealand on Wednesday delivering a change to cooler southwesterlies through Thursday.

In southern Westland and Fiordland, there is moderate confidence of rainfall amounts reaching warning criteria on Monday and Tuesday, then low confidence on Wednesday as the front moves north.

Northerly gales are also possible about exposed parts of the lower South Island during Monday and Tuesday, but the strongest winds are expected to remain offshore to the west.

On Wednesday, the change to cooler southerlies behind the front is expected to deliver a period of heavy rain into Southland and Otago. There is low confidence of rainfall accumulations reaching lower threshold criteria in Southland and eastern Otago as indicated on the chart. At this stage, snow is not expected to fall below about 1300 metres.

The front should continue to move northwards during Wednesday and to move north of the country overnight Wednesday, bringing about a noticeable cooler change in temperatures. However, severe weather is not expected with this feature at this stage.

On Thursday, a ridge builds over the lower South Island, while southerlies persist over the remainder of New Zealand.

Probability/Confidance Map

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

Image Valid Till 1:00pm Monday 19 Mar 2018
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