NZ has a winter snap coming tonight and across Wednesday and Thursday, a wind blast kicking off on Friday and through the weekend and next week things warm back up and may even feel spring-like. To make sense of it all WeatherWatch.co.nz has broken it down into bite size pieces.

TUESDAY PM:
Warmer than average over much of New Zealand, but the main cold front arrives in Southland and Otago and heads northwards up the South Island overnight.

WEDNESDAY:
Peak cold. The main southerly moves up the entire country and by the end of the day every part of the country, including northern NZ, will have experienced a temperature drop. About 50% of New Zealand will be cooler than average for the end of July, but the other half will either be back to normal or, if you’re on the West Coast, a degree or so above normal (thanks to the protective Southern Alps). Snow falls in the South Island to low levels (200 to 400m) and down over the ranges and Central Plateau of the North Island (down to 500m including SH1 the Desert Road) but as Wednesday wears on the snow showers dry up a lot over the South Island – flurries will be most frequent in Northern Southland and western and Central Otago.

THURSDAY:
The South Island springs back to normal temperatures, if not slightly warmer as the day goes on – this is due to the coldest air moving eastwards away from land. The North Island is colder than average in the south and east otherwise temperatures are also normal for winter, but still down on where they have been lately. The bulk of the cold shifts east of the North and South Island during Thursday to lie over the Chatham Islands.

FRIDAY:
A surge of gale force winds wallops parts of the South Island, shifting east of the South Island later in the day. Gales are likely in marine areas and through the mountains with severe gales possible too. Another surge of rain and snow (although snow levels won’t be as low as they will be on Wednesday). The North Island gets windier and showery but stays dry in eastern areas and won’t be as cold as Thursday.

WEEKEND:
Windy. Both Saturday and Sunday look windy in many places but perhaps Sunday is windier as another cold front moves through.

EARLY NEXT WEEK:
Westerly winds dominate. While Monday may kick off cooler with sou’westers, winds turn more westerly by Tuesday and high pressure brushes the very north of the country. This wind flow will be warmer and drier in the east for a time with a surge back into warmer than average daytime highs.

LATER NEXT WEEK:
Later next week winds look confusing around the country – some may have warmer northerlies with sub-tropical connections, others may get nor’westers out of the Tasman Sea (also warm), but some modelling shows a colder south to south west flow may move up the South Island thanks to a localised low pressure system. So we may see a split in temperatures across the two main islands if that occurs and we can’t yet lock in later next week.

RECAP:

• The main cold event is on Wednesday nationwide and will reset temperatures to “normal” for many regions, with 50% of the country dipping slightly below average. 
• A windy change kicks in on Friday over the South Island and leads into a windier weekend.
• Next week kicks of with westerly quarter winds, but unclear how the week will end at this stage.

– 9PM This Friday shows the secondary surge of wind, rain and snow (not as cold as Wednesday but Friday’s surge will be windier than Wednesday’s southerly change). ECMWF (European) modelling.

– WeatherWatch.co.nz