Severe thunderstorm warning cancelled

Severe thunderstorms are no longer occurring in NSW and the ACT.

Hail 5cm in diametre is expected today. Picture: Warwick Daily News

Severe thunderstorms are no longer occurring in NSW and the ACT.

UPDATE, 6.40pm: 

The immediate threat of severe thunderstorms has passed, but the situation will continue to be monitored and further warnings will be issued if necessary.

2-5 cm diameter hail was reported at Swan Creek around 2:30pm.

7cm diameter hail was reported near Grafton around 2:30pm.

EARLIER:

THE Bureau of Meteorology has issued a warning this afternoon for large hailstones, destructive winds and heavy rainfall.

In the next several hours severe thunderstorms are likely to produce giant hailstones 5cm in diameter, destructive winds, and heavy rainfall that may lead to flash flooding.

Lismore, Grafton, Coffs Harbour, Woolgoolga, Sawtell and Dorrigo may be affected.

BOM spokesperson Rob Taggart said the largest measurement of a hail stone today was a 7cm "giant" in Grafton at about 2pm.

Here's a look at those 'giant hailstones' falling in #Grafton. Thanks to @YvonneSum for sharing the photo. #Lismore, #Coffs Harbour, #Woolgoolga, #Sawtell and #Dorrigo could also be in the firing line. See the full @BOM_NSW warning here: https://t.co/O5n6RB6eBm. pic.twitter.com/3hdrNSpw3f

— ABC Emergency (@ABCemergency) December 9, 2017

"Based on current radar information there is no evidence that something like that is going to hit Lismore," Mr Taggart said.

"However this is a quickly evolving situation and residents in Lismore should be aware that there is a good chance they will get some hail.

"Large hail is the biggest risk with a severe thunderstorm, followed by damaging wind gusts, and there is an outside chance of heavy rainfall that could lead to flash flooding, but that is the least of our concerns."

Severe thunderstorms possible in the northeast, mainly in the afternoon over the Northern Rivers. Monitor warnings at https://t.co/xUE9U1Hn3Z #NSWweather pic.twitter.com/ygTnT4xJkx

— Bureau of Meteorology, New South Wales (@BOM_NSW) December 8, 2017

Mr Taggart said there are three factors contributing to storm activity today.

"Firstly, there is an upper level disturbance going across the Northern Rivers, about 5km above the surface.

"Secondly, there is unstable air.

"And the final ingredient is the fact that the winds over the Northern Rivers are generally southerly but about 5km  from the surface they are heading west."

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.
* 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.

The next warning is due to be issued by 4:10 pm.