During Saturday an intense front is expected to move east across the South Island, preceded by a strong northerly flow and a period of heavy rain for the west coast and Alps.

A Warning has already been issued for heavy rain in Fiordland north of Milford Sound, Westland south of Otira and the headwaters of the Canterbury lakes and rivers.

This Watch is for a period of heavy rain in Fiordland about and south of Milford Sound and the headwaters of the Otago lakes and rivers during Saturday morning and afternoon. After this time, heavy showers and possible thunderstorms are expected through to late Saturday. Rainfall in these areas may approach warning amounts, and rivers and streams could rise rapidly.

In addition, northerly winds ahead of the front may rise to severe gale in Wellington Saturday evening, easing overnight Saturday.

People in these areas are advised to keep up to date with the latest forecasts, in case this Watch is upgraded to a full Warning.