WARNING: Large hail and heavy rain forecast

UPDATE: Sunday, 4.08pm:

Severe thunderstorms are likely to produce large hailstones and heavy rainfall that may lead to flash flooding in the warning area over the next several hours. Locations which may be affected include Lismore, Grafton, Coffs Harbour, Byron Bay, Ballina, Casino, Kyogle, Yamba, Maclean, Woolgoolga, Nambucca Heads, Sawtell and Dorrigo.

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.

The next warning is due to be issued by 5:55 pm.
Warnings are also available through TV and Radio broadcasts, the Bureau's website at www.bom.gov.au or call 1300 659 218. The Bureau and State Emergency Service would appreciate warnings being broadcast regularly. 

UPDATE 5.50PM:

THE Bureau of Meteorology has issued a storm warning for heavy rainfall and possible flash flooding in parts of the Northern Rivers.

Severe thunderstorms are likely to produce heavy rainfall that may lead to flash flooding in the warning area over the next several hours.

Locations which may be affected include Lismore, Grafton, Coffs Harbour, Port Macquarie, Taree, Newcastle, Armidale, Orange, Tamworth, Moree, Dubbo and Parkes.

Lismore and Casino look to be most in the firing line, while Cawongla received 31mm in half an hour to 3.45pm.

Coonabarrabran AWS reported 35mm in one hour to 9am this morning. Narrabri AWS reported 59.6mm in one hour to 12:30pm. Cawongla in Northern Rivers reported 31mm in half an hour to 03:45pm.

The BOM is due to issue the next warning at 6.55pm.

Large parts of the Northern Rivers are expected to be affected.
Large parts of the Northern Rivers are expected to be affected.

ORIGINAL:

SEVERE thunderstorms, a three metre swell, and flash flooding are possible for large parts of the Northern Rivers this weekend. 

Weatherzone meteorologist Joel Pippard said severe weather patterns are expected to be caused by a low pressure system moving north from Sydney and the Central Coast.

Widespread and severe thunderstorms are also expected to hit the e

Showers are predicted to move north towards Lismore.
Showers are predicted to move north towards Lismore.

ntire Northern NSW region this weekend.

The heaviest rainfall is expected at Lismore.

"Thunderstorms are likely to form in Ballina, but not as likely as in Lismore," Mr Pippard said.

"Byron Bay will experience similar thunderstorms and showers to Ballina.

"Kyogle looks to be pretty severe.

"With a storm like this, lightening is a fairly high risk."

Up to 90 mms is expected to fall by Sunday.

"We're looking at pretty widespread rainfall, with up to at 30-40 mm likely over the weekend (in total)," Mr Pippard said.

"50 mm is definitely not out of reach.

"Places a bit West of Lismore, like Casino, and places like right on the coast like Byron Bay, it's possible that those areas will get 80 mm - 90 mm.

"With heavy rain there is always the risk of flash flooding."

Coastal Watch predictions for swell and winds for Byron Bay.
Coastal Watch predictions for swell and winds for Byron Bay.

Mr Pippard said with the movement of the low pressure system, particularly for Sunday, the swell should pick up on the North Coast.

"The peak is probably going to be on Monday, at about two to three metres on the beach, and a little bit higher just off shore," Mr Pippard said.

"That's going to be a southerly swell."

Sunday should again see a smallish easterly swell of two to three feet offering up fun peaks (with even better offshore winds).

A solid round of southerly swell is presently forecast to hit the Northern Rivers on Tuesday morning with some predictions waves reaching up to six feet.

The wind will be strong and southerly in a return to winter like conditions so the points at Lennox, Broken Head and Byron Bay will be the pick if you're trying to plan out your week.

Storms will also be severe on the Northern Tablelands, including Walgett, Lightening Ridge and north towards Moree, and the border.