More chilly nights ahead

May 1, 2017

A burst of polar air which flowed northwards over New Zealand yesterday meant a very cold start to this week for many inland places, with frosts reported this morning, and Queenstown recording an overnight low of -1C, Alexandra -2C and Mount Cook -3C.

MetService Meteorologist Andy Best said, “Even though the cold southerly winds have now started to ease, the building ridge of high pressure over the country today and overnight tonight will result in clear skies and light winds. This is the perfect recipe for radiational cooling to take place, meaning there’s another crisp, clear autumnal night ahead and frosts expected in many inland places Tuesday morning.”

Looking ahead to Wednesday, a new front makes its way onto the South Island in the morning, preceded by a burst of heavy northwesterly rain about and west of the Alps. A period of rain is also expected overnight Wednesday into Thursday over central New Zealand, with possible heavy falls in the west of the North Island. The front is also expected to bring northwest gales, possibly severe for a time over western parts of Southland, Otago and Canterbury as well as Stewart Island. The front is expected to clear the North Island on Thursday evening.

Behind the front, we are forecasting another strong, cold southwest airstream to impact the country on Thursday, with gales possible about the east coast of the South Island extending northwards to Cook Strait. These southwest gales are then expected to affect the east coast of the North Island during Friday.

Also during Friday and Saturday, a new ridge of high pressure is forecast to move over the country from the Tasman Sea, easing the winds and leaving us in a similar scenario to the start of the week: clearing skies, good cooling and a good chance of frosts starting in the South Island Friday morning, and over most of New Zealand Saturday morning.

Forecast position of the front at midnight Thursday

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MetService issues Warnings, Watches and Outlooks for severe weather over New Zealand.

Warnings are about taking action when severe weather is imminent or is occurring. They are issued only when required.
Recommendation: ACT 

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