SIGNIFICANTLY HEAVY RAIN FOR WESTLAND, NORTHERN FIORDLAND, THE HEADWATERS OF THE CANTERBURY AND OTAGO LAKES AND RIVERS, ALSO THE RANGES OF BULLER AND NORTHWEST NELSON.
SEVERE NORTHWEST GALES FOR THE CANTERBURY HIGH COUNTRY.
An active trough is expected to move onto the South Island on Wednesday and is preceded by a strong, moist northwest flow.
Rain is expected to become heavy in the southwest of the South Island this evening, with the heaviest falls likely about the Westland Ranges and Alps, where around 400mm could accumulate in a 24 hour period about some higher slopes.
About remaining parts of Westland, northern Fiordland, including the Otago and Canterbury Headwaters and the Buller and northwest Nelson ranges around 150mm is expected during the same time.
Although the rain is expected to ease in the far south later Wednesday, the flow is likely to remain northwest and further periods of heavy rain are possible later in the week.
This is a significant amount of rain for these areas.
People are advised that streams and rivers will rise rapidly, affecting areas further downstream, especially in Canterbury and Otago.
Surface flooding and slips are possible.
In addition, severe northwest gales are expected about the Canterbury High Country during Wednesday, gusting 130km/h.Winds of this strength are likely to bring down trees, powerlines and making driving conditions hazardous for high-sided vehicles.