Thunderstorms tipped to last until Tuesday evening with up to 70mm of rain forecast to drench parts of the state.

A line of storms stretching from Broken Hill, Echuca and the Victorian town of Port Albert joined storms that moved along a low and upper-pressure trough across the eastern parts of southern Australia. 

When combined, the dynamic conditions were described as possibly triggering "some of the worst thunderstorms of the season" by Weatherzone Meteorologist Rob Sharpe.

"The worst storms spread across the North West and Central West Slopes and Plains districts in NSW," he said. 

On Monday, the Mid-Western region experienced moody skies, with lightning and thunder for most of the afternoon, before the rain and hail started just after 3pm around Gulgong.

Mudgee SES acting local controller, Tamara Robinson said that emergency services were "quite concerned" about the "supercell thunderstorms".

"As soon as we heard about the storm activity, we made sure that our trucks and equipment were good to go, we also put teams on standby," she said.

Mudgee town already experienced the ferocity of a ‘supercell’ this year, when a mini ‘tornado’ hit in January – ripping out trees and power poles. “The SES had 132 jobs out of the previous ‘tornado’ and looking at the damage that we sustained as a community, we were well prepared. It shows we are resilient,” Mrs Robinson said.

The wet weather is expected to continue across the region for the rest of the week. For SES assistance call 132 500 or for a life threatening emergency call 000.