Situation for all New Zealand issued at 2:15pm Friday 16 Nov 2012
 
A narrow ridge across the country moves away to the east today. A complex trough over the Tasman Sea should move onto the South Island tonight and then the North Island tomorrow afternoon.


Summary:  Issued by MetService 1:21pm Friday 16 Nov 2012
 
Sunday
North Island, showers spreading to most places, some heavy in the south and east, but clearing north of the Bombay Hills. South Island, showers, some heavy in the north, becoming less frequent and fine spells increasing.

Monday
Mainly fine, but a few showers near Foveaux Strait, and isolated afternoon and evening showers for inland areas.

Chatham IslandsRain easing to showers on Sunday, and strong northerlies turning westerly. Occasional showers and westerly winds on Monday and Tuesday.


Short forecast for all New Zealand to Midnight Saturday 17 Nov 2012
Issued by MetService 7:59pm Friday 16 Nov 2012

Northland to Manawatu and across to Bay of Plenty and the central high country
Cloud increasing. Rain spreading eastwards tomorrow with some heavy falls about the ranges, easing to showers from afternoon, clearing north of Taupo at night.

Gisborne to Wairarapa
Remaining showers clearing tonight. High cloud tomorrow, with scattered rain developing in the morning, clearing afternoon.

Kapiti, Wellington
Cloud increasing. Rain tomorrow morning, easing to isolated showers in the afternoon.

Marlborough, Nelson
High cloud thickening. Occasional rain developing in the morning, some heavy falls in the afternoon, easing in the evening.

Buller, Westland, Fiordland
Rain with heavy falls spreading north overnight, possibly thundery in Westland and Buller tomorrow, easing in Fiordland and South Westland later.

Canterbury, Otago, Southland
High cloud, with a few spots of rain in Southland and Otago tonight. Becoming showery tomorrow, some heavy and possibly thundery in the afternoon, easing from the south at night.

Chatham Islands
Cloudy periods. Rain tomorrow evening.
 
Updated at or before:
6:00am, 12:30pm, 4:15pm, 10:00pm daily.  Updates/amendments may be issued at any time.
http://www.metservice.com/national/index

Tomorrow is looking good for thunderstorms to form in some parts of the South Island. A low pressure system will form just east of the South Island tomorrow afternoon with cold air higher up in the atmosphere moving in from the west. Behind the low a cool south to southwest change will develop triggering some thunderstorms.
 
WeatherWatch.co.nz says the most likely places to see storms are south of North Canterbury on the east coast. The West Coast may also see a few storms during the day at first in the morning for Fiordland then further north towards evening in Buller.
 
Hail may form in any storms that do develop tomorrow with a potential for hail of a large size of 15 to 20mm plus falling in an area south of Banks Peninsula through into South Canterbury.
 
To get into slightly more detail for the east coast of the South Island, the thunderstorm risk begins early afternoon for parts of inland Southland and then for most of Otago with a tendency for storms to form more in the eastern part of the district. The chance of storms happening is fairly good here.
 
Mid to late afternoon the risk moves into South and Mid Canterbury particularly in inland areas however storms may spread towards the coast. Finally early evening a chance of storms develops in North Canterbury as the southerly change mentioned above moves in. The risks of storms happening is fairly good in Canterbury with perhaps a slightly lower risk as unstable conditions move into North Canterbury however only slightly lower.
 
Weather analyst Aaron Wilkinson from WeatherWatch.co.nz also notes that with the wind profiles through the atmosphere tomorrow there is also the outside chance of a funnel cloud or small tornado forming somewhere in Canterbury, “The atmosphere is looking a little more conducive to them happening then other storm set ups I’ve seen”. The chance of this actually happening Aaron says is fairly low however and if it does happen it may go un noticed anyway.
 
Further north into Marlborough thunderstorm chances look lower due to surface northwesterly winds keeping moisture levels low, and thunderstorms need relatively good surface moisture to grow.
 

WeatherWatch.co.nz
http://www.weatherwatch.co.nz/...outh-island-tomorrow