The warning was issued at around 9pm on January 9.

The warning covers, the Hunter parts of Mid-North Coast, Central Tablelands, North West Slopes and Plains, Central West Slopes and Plains, Upper Western and Northern Tablelands Forecast Districts.

Severe thunderstorms are likely to produce damaging winds and large hailstones in the warning area over the next several hours.

Locations which may be affected include Port Macquarie, Taree, Newcastle, Maitland, Tamworth and Gunnedah.

Severe thunderstorms are no longer occurring in the Metropolitan district and the warning for this district is cancelled.

The thunderstorm has already realised some severe weather conditions for parts of the state with 92km/h wind gusts at Condobolin at 2.40pm; 98km/h wind gust at Parkes at 3.59pm; 90 km/h wind gust at Forbes at 3.25pm and 122km/h wind gust at Nowra at 4.54pm.

Wee-Jasper recorded 4-5cm diametre hail while 38mm of rain fell in 30 minutes at Currarong.

The State Emergency Service advises that people should: 

* Move your car under cover or away from trees. 

* Secure or put away loose items around your house, yard and balcony. 

* Keep at least 8 metres away from fallen power lines or objects that may be energised, such as fences. 

* Report fallen power lines to either Ausgrid on 131 388, or Endeavour Energy on 131 003 or Essential Energy on 132 080, as shown on your power bill. 

* Unplug computers and appliances. 

* Avoid using the phone during the storm. 

* Stay indoors away from windows, and keep children and pets indoors as well. 

* For emergency help in floods and storms, ring the SES (NSW and ACT) on 132 500. 

The next warning is due to be issued by 11:55 pm.