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A fresh cold outbreak is expected to move onto the South Island this morning.

MetService says the airmass behind the cold front is expected to become more unstable through the period with heavy, squally showers expected in a southwesterly flow.

“There is a moderate risk that a few of these may well be thundery from about day break.  Wind gusts to 90km/hr can be expected with many of the larger cells and snow is expected to low levels” says the crown forecaster.
 

The crown forecaster says the deep instability over the south of the South Island is expected to ease during this afternoon, but there is a lowering risk of the odd thunderstorm moving onto Southland and eastern Otago in early afternoon.

“Further north, the front mentioned earlier, will move up the Kaikoura Coast in the afternoon to reach the Cook Strait late afternoon/early evening, supporting a vigorous southerly change. There is a least a moderate risk of thunderstorms developing on this change as it moves up the Kaikoura Coast and through the Wellington area towards evening. This feature is expected to become very well organised and will support a brief period of heavy rain and very strong wind gusts. At this time, indications are that gusts may reach 110km/hr. North of Wellington, the activity on this front is expected to decrease quite quickly” says MetService’s Thunderstorm Outlook, funded by the NZ Govt.

There is lower risk of thunderstorms in a surrounding area from east Wairarapa to northeast Marlborough and down to include much of Canterbury. The Canterbury risk is really for the first part of the afternoon.
 

Maps courtesy of the NZ Govt