Source: Bureau of Meteorology

For people in Gosford/Wyong and parts of Maitland/Cessnock, Greater Newcastle and Sydney areas.

Issued at 9:36 am Friday, 17 January 2020.

The Bureau of Meteorology warns that, at 9:30 am, severe thunderstorms were detected on the weather radar near Calga, Brooklyn and Dooralong. They are forecast to affect Lower Mangrove, Spencer, Dural and Mangrove Mountain by 10:00 am and Upper Mangrove and Glenorie by 10:30 am.

Heavy rainfall that may lead to flash flooding is possible.

The State Emergency Service advises that people should:
* Keep clear of creeks and storm drains.
* Don't walk, ride your bike or drive through flood water.
* If you are trapped by flash flooding, seek refuge in the highest available place and ring 000 if you need rescue.
* 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.