An active front, preceded by strengthening northwesterlies, moves north across the South Island during Monday and the North Island on Tuesday. Another front should move over the South Island from the Tasman Sea on Tuesday. The front should then move over the North Island during Wednesday and weaken.

There is high confidence of rain reaching warning amounts for Fiordland and Westland south of Hokitika on Monday and a warning is in force for these areas. The confidence for heavy rain then decreases to moderate for these areas on Tuesday. There is high confidence that a rain warning will be needed for Westland north of Hokitika, Buller and the ranges of northwest Nelson during Monday and Tuesday. Also, there is moderate confidence for warnable amounts of spillover rain into the headwaters of the Canterbury and Otago Lakes and Rivers on Monday, and a watch is in force for the headwaters of Otago at this stage.

For the North Island, there is high confidence that rainfall warnings will be needed for the Tararua Range during Monday and Tuesday, and for Mount Taranaki, Tongariro National Park and Taumarunui on Tuesday and Wednesday. There is also low confidence of warning amounts of rain about the ranges of eastern Bay of Plenty on Tuesday and Wednesday.

In addition, gale northwesterlies are expected in central and eastern areas from Gisborne down to Southland until late Tuesday. For exposed parts of Fiordland, Southland and Otago, there is moderate confidence that the winds will reach severe gale on Monday and a watch is in force. In Canterbury, the confidence is high for severe gale northwesterlies in exposed places on Monday and a warning is in force. For Marlborough, Wellington and Wairarapa there is high confidence that northwesterlies will reach severe gale in exposed places on Monday and Tuesday and a watch is in force for these areas. Meanwhile, there is moderate confidence of severe gale northwesterlies in southern Taranaki, Taihape, Whanganui, Manawatu, Horowhenua Kapiti Coast, Hawkes Bay and Gisborne on Monday and Tuesday.