“Down south it’s a bit of a different story. There is going to be rain for the West Coast and maybe a little bit of rain through Southland, Otago, and high cloud for the East Coast.”
Ashburton and Timaru were forecast to reach 21C today, about 8C above average for this time of year, while Christchurch tops out at 20C, around 7C warmer than usual.
But the warmth will be short-lived, with a low-pressure system moving over the South Island from tomorrow.
Bakker said the storm would be “quite significant”, with a “solid potential for disruption”.
“Don’t panic, pay attention,” he said.
Unlike a straightforward westerly flow, the rotating low could draw colder air from further south as it crossed the country, helping set the stage for heavy rain and snow.
Bakker said heavy rain would hammer the West Coast, while warning-level amounts of snow were possible from Central Otago and the Queenstown Lakes District north to the Mackenzie Basin.
“Instead of being a nice light dusting, it’ll … make it difficult to go places, [and] might be a threat to livestock.”
Snow is forecast to lower to about 700m late tomorrow and potentially 400m on Thursday.
NZTA has separately warned private forecasting suggests more than 30cm could affect SH8 and SH80, while up to 20cm could fall on SH73 above 700m.
“Accumulations at this level are likely to impede travel and NZTA may close sections of highway or introduce restrictions to keep people safe and avoid vehicles becoming trapped,” it said in a statement.
A 36-hour heavy rain watch is also in place for the ranges of Westland from noon tomorrow, which MetService expects to upgrade to a warning today.
Bakker said uncertainty remained around exactly where the low would track and which areas would receive the greatest rainfall.
While such a storm was “not super unusual” approaching spring, he said its impacts could nevertheless be substantial.