A potent low over the Tasman Sea will continue to strengthen is it moves east toward New Zealand tonight and tomorrow.

WeatherWatch.co.nz Weather Analyst Howard Joseph feels the western regions of the South Island will see the rain first, starting overnight tonight.  By the time sunrise rolls around, Mr Joseph says heavy rain may already be showing up about the ranges of northwestern Nelson.

Heavy rain will be possible about the West Coast as well, main after sunrise.  The threat will continue throughout the day for both regions.  The likelihood of the rainfall amounts reaching warning criteria is not particularly high, but it’s worth watching.  Government forecaster MetService says they are moderately confident that warnings will be needed for heavy rain for these regions.  The threat for heavy rain will extend into Tuesday as well.

Mr Joseph adds that heavy rain will also be possible about Taranaki, Waikato, Bay of Plenty and the Coromandel Peninsula.  The chances for heavy rain in these areas are pretty small.  Anything that does develop wouldn’t start until mid to late afternoon.

Snow is also a threat from this incoming system.  At this time, the greatest threat is for Canterbury and Otago.  Snow is likely to stay above 600 metres.  MetService has Road Snow Warnings up for Porters Pass where heavy snow is forecast.  10 to 15cm of snow is expected to accumulate on the road tomorrow morning before turning to rain tomorrow afternoon.

A Road Snow Warning is also in effect for Lindis Pass where 2 to 4cm of snow is expected to accumulate tomorrow morning.

WeatherWatch.co.nz