An active front lying over Fiordland and Otago Sunday night should cross the rest of New Zealand during Monday. This front is preceded by a very strong northwest flow and followed by a brief period of strong southerlies.

Heavy rain warnings have already been issued for Fiordland, Westland, Buller and the headwaters of the Canterbury rivers. Watches for possible heavy rain have also been issued for northwest Nelson, Southland, Otago and the rest of Canterbury.

The main focus of heavy rain on Monday is northwest Nelson, Buller and Westland including the coastal lowlands, and the Canterbury Alps. Some particularly intense falls are possible in north Westland and Buller. Following the front a cold southeast flow will bring widespread rain to eastern areas of the South Island. Substantial rainfalls are also expected over most of Otago and Canterbury away from the Alps, and a moderate risk of heavy falls is indicated there.

A very strong northwest flow should cover central New Zealand on Monday.

Severe gales are likely from Napier to Wairarapa, for Wellington and the Marlborough Sounds. A lower risk of severe gales is also shown for the rest of Marlborough and the southern half of the North Island.

By the end of Monday the severe gales and heavy rain should all be over.

A ridge of high pressure should cross New Zealand on Tuesday.

Another fast moving front should bring rain to western areas of both islands on Wednesday. There is a low risk of heavy falls western areas of the South Island.

A strong west to southwest flow should cover New Zealand on Thursday.