Snow for some this week but details still elude forecasters
Sunday, 28 July 2019
Snow is coming this week - but just how low it settles and where the worst will fall is still bamboozling forecasters.
The arrival of the cold air on Tuesday night ushers in what are likely to be some of the coldest days of the winter.
As well as heavy and low-level snow in eastern parts of the South Island and the central North Island on Wednesday, a second pulse of frigid sub-Antarctic air may be lining up the South Island in its sights on Friday and Saturday.
The bitter snap will be a reminder of what season it really is and will kickstart August with a vengeance after a mild and mostly settled July.
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On Monday, rain is expected in Westland and Fiordland, with heavy falls south of Hokitika, while Northland could have some heavy showers with possible thunderstorms. MetService is forecasting cloud for much of the rest of the country, with showers at times in some places.
Auckland is expected to be mostly cloudy, with northeasterlies and the odd shower north of Whangaparaoa, spreading elsewhere from afternoon. It's possible falls could be heavy by evening.
Wellington is forecast to have a mainly fine day with some evening cloud and northerlies. Christchurch is expected to have a fine Monday with high cloud and northeasterlies dying out at night.
MetService said it should have more details of Wednesday's blast by mid-morning Monday.
On Sunday afternoon meteorologist Tom Adams told Stuff there was still a lot of uncertainty about where the snowy conditions would hit hardest mid-week, due to the development of small spinning centres within a larger area of low pressure and below an upper-level trough.
Several computer models on which forecasters made their predictions were indicating slightly different positions for these centres on Wednesday and, as a result, possibly different outcomes.
Canterbury was probably more in the firing line generally than other regions but it was tricky to say how low the freezing level would be, which determined how far down the snow would fall before melting into rain.
'The key will be how close the centre of low pressure is to the east coast.'
The possible snowfall later in the week would be borne on a more straightforward icy southwesterly from the southern ocean rather than the complex Wednesday pattern, Adams said.
In its latest severe weather outlook, issued on Sunday afternoon, MetService said there was low confidence on Wednesday of 'a period of heavy snow above 500 metres in southern and eastern parts of the South Island from southern Fiordland and Southland through to eastern Marlborough, with snow possible to lower levels as well in some places during this time'.
On Twitter and Facebook, Adams said the forecasts for snow could easily change to warn of it at lower levels once the models showed more agreement.
'Although this is not unusual for the time of year, motorists and high-country farmers should be prepared for the colder conditions.'