ISSUED BY MetService AT 11.00 am 17-Jun-2015

A deepening low over the Tasman Sea should approach the South Island during Thursday and cross over the far south on Friday. This low and its associated fronts are expected to bring a period of stormy weather over parts of the South Island.

Initially, strong northwest winds are expected to affect eastern areas of the South Island, and the winds in Canterbury and Southland are likely to reach severe gale in some places this evening and during Thursday morning, with gusts of 130 km/h possible near the Canterbury Foothills.

Heavy rain is also expected to develop in Fiordland and Westland overnight Wednesday into Thursday and continue into Friday morning. During this time, 300 to 500mm of rain could fall about the ranges, although this will be heavy snow at the higher altitudes. About the Westland coast, 140 to 180mm of rain is possible.

Cold air moving onto the south of the South Island is expected to combine with the rain in southern Canterbury, Otago and Southland to bring significant amounts of heavy snow to low levels. Snow is likely to near sea-level in the south and about 300 metres in Canterbury from late Thursday morning until early Friday. Central areas of Otago are likely to be hardest hit, with accumulations reaching 15 to 25cm at 200 metres and a metre or more above about 700 metres.

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Later Friday, the threat of heavy rain moves northwards. There is high confidence rainfall accumulations will exceed warning amounts about northern Westland, Buller and northwest Nelson, with the confidence lowering to moderate for the Tararua Range, North Taranaki, Waitomo and the central high country. In addition, there is moderate confidence northwest gales will become severe about remaining parts of Canterbury, Marlborough, Wellington, Wairarapa and Hawkes Bay, with low confidence western areas from Waitomo and the central North Island high country to northern Westland will experience severe northwest gales.

On Saturday, there is moderate confidence that heavy rain will continue about North Taranaki, Waitomo and the central high country, with low confidence of a period of heavy rain affecting areas further north and also Bay of Plenty, Gisborne and Hawkes Bay. In addition, there is low confidence of severe northwest gales about Northland, Auckland, Waikato, Coromandel Peninsula, Bay of Plenty, Gisborne and Hawkes Bay.

A cold southerly lies over New Zealand on Sunday as the front moves away to the northeast and a ridge approaches from the west.