"With that main rain band going through, that cloud will break up so you'll start to see some patches of blue appearing in the afternoon.
And then you'll start to see some showers turning up, with the heaviest ones at first, really.
"You'll probably start seeing some patches of blue turning up across the region, then into showers but you'll still get patches of blue in between instead of a solid grey sky."
The thunderstorm watch would stay in place for the afternoon, Mr Kerr said.
Heavy showers would be possible tomorrow but clear in the afternoon, with a fine forecast for the weekend, he said.
WeatherWatch's lighting tracker detected 27 lightning flashes between 8am and 9am, mostly off the coast between Taranaki and Northland.
There was a chance of minor localised flooding in the heaviest downpours, WeatherWatch head analyst Philip Duncan said.
"The main rain band [is] now clearing Auckland but could still be followed by an isolated torrential downpour before sunny spells develop later this afternoon," he said.
Auckland should expect a high of 15C today with briefly thundery rain easing to showers and a high of 14C tomorrow.