"The main areas are in the central inland parts of the North Island, from Hamilton down to Masterton almost across to Gisborne and pretty close to the Taranaki.
"In the South Island, it's concentrated in the northern portion of the inland area around south of Nelson down to about Arthurs Pass."
A low-pressure system sitting to the west of the country along with a ridge to the southeast is creating the stationary weather features.
Rince & repeat: Severe Thunderstorm Outlooks for Thurs & Fri. Watch issued for Severe Thunderstorms today. New for Friday: moderate Thunderstorm risk area over Auckland, risk of Severe Thunderstorms for upper S Island. Details https://t.co/GZIq9Jlbrwhttps://t.co/BZWb7ZPiRd ^RK pic.twitter.com/RZhrsRwaeZ
"Look at temperatures, sort of heading to the low 20s and on Saturday it's much of the same again, more showers off and on.
"Typical Auckland weather, lots of sunny spells but you could get wet."
Showers aren't expected to hamper the Capital on Saturday, meaning the Black Caps should be able to get underway against Sri Lanka in the first home test.
Wellington will be blanketed by cloud cover in the morning which will slowly degrade away to reveal blue sky as the day goes on.
Friday's forecast:
Whangarei: A few showers, especially after midday, possibly heavy and thundery. Northerly breezes. High 24C, Low 15C.
Auckland: A few showers, especially after midday, possibly heavy and thundery. Northerly breezes. 24C, 16C.