A weekend of more rain and storms - possibly severe - is on the way for Sydney after Friday's lull in the gloomy weather.

A slow-moving high pressure system in the Tasman has been directing moist onshore flows into eastern NSW for more than a week. A rain-bearing front, meanwhile, is heading eastwards, raising the prospect of storms when they meet.

"There's quite a strong upper-level system coming through and it's very unstable," said Neale Fraser, a senior forecaster for the Bureau of Meteorology, adding he would be "extremely surprised" if warnings of severe weather were not issued on Saturday for parts of NSW.

Unstable atmospheric conditions that have brought more than a week of rain are tipped to turn even stormier this week. Credit:Nick Moir

For Sydney, the recent wet spell has been a sharp reversal of rainfall fortunes compared with the previous three months.