A cold south easterly wind flow is going to see temperature plummet in the South Island this weekend as reported by WeatherWatch.co.nz yesterday.

Today MetService has issued a Severe Weather Watch covering heavy rain in the west and north west of the South Island and about Bay of Plenty.

Heavy snow also in the forecast across the South Island.

See the detailed Severe Weather Watch below…

SEVERE WEATHER WATCH FOR RAIN IN WESTLAND AND BULLER NORTH OF FOX GLACIER, NORTHWEST NELSON, BAY OF PLENTY, CANTERBURY AND MARLBOROUGH, AND SNOW IN SOUTHLAND, OTAGO, CANTERBURY AND MARLBOROUGH ISSUED BY METSERVICE AT 1121hrs 06-Aug-2010 PERIOD OF HEAVY RAIN OVER NORTHERN AND CENTRAL NEW ZEALAND (INCLUDING CANTERBURY) OVER THE WEEKEND, ALSO SNOW FROM SOUTHLAND TO CANTERBURY AND MARLBOROUGH

A front in the Tasman Sea is forecast to move over much of the country on Friday night and Saturday bringing a period of northerly rain over northern and central New Zealand. The heaviest rainfalls are likely to be from Franz Josef Glacier to northwest Nelson from Friday night through to early Saturday afternoon and Bay of Plenty later on Saturday afternoon to early Sunday morning.

People are warned to be wary of rising streams and rivers.

A cold southeasterly airstream is forecast to strengthen over southern New Zealand during Saturday and rain is expected to turn to snow down to 300 to 400 metres by evening in Fiordland, Southland and much of Otago. Although there may not be enough snowfall to justify a warning, motorists especially should be prepared for winter driving conditions.

On Saturday night and Sunday strong south to southeast winds are expected to bring widespread heavy rain to Canterbury and Marlborough. This is likely to turn to snow as low as 300 to 500 metres during Sunday and last into Monday, with heavy falls inland including the plains near the foothills. The combination of strong or gale force winds, cold rain and snow is likely to make this a significant weather event.

People are advised to keep up to date with weather forecasts and plan accordingly. Farmers should be prepared to shelter vulnerable stock.