Source: Bureau of Meteorology

For people in parts of the
Blue Mountains/Hawkesbury and
Sydney areas.

Issued at 3:57 pm Tuesday, 21 March 2017.

The Bureau of Meteorology warns that, at 3:55 pm, severe thunderstorms were detected on the weather radar near Wilberforce. These thunderstorms are moving towards the southeast. They are forecast to affect Cattai and Glenorie by 4:25 pm and Hornsby, Berowra, Dural and Terrey Hills by 4:55 pm.

Large hailstones and heavy rainfall that may lead to flash flooding are likely.

The State Emergency Service advises that people should:
* Move your car under cover.
* 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.