Today is a big thunderstorm day for New South Wales. A volatile mix of moisture, heat, wind and instability aligning over the state today will trigger violent thunderstorms. The setup is so supportive of storms that they were already active over the North West and Central West Slopes and Plains and Northern Tablelands before sunrise. Lightning will strike over New South Wales through the day and continue long after the sun sets tonight. Inverell's first storm of the day arrived at around 2am and within a few hours, 50mm of rain had reached the gauge. There were reports of hail and frequent lightning amid heavy rain as a storm rolled over Dubbo around 8am. At midday today, a severe thunderstorm warning was in place along the slopes and plains from the Queensland border down to about Griffith. A number of storms have already developed in this region today. The most intense thunderstorms typically occur during the afternoon or early evening after the day's heat has been introduced into the mix. This means that despite the extent of storms already, the worst are yet to form. Storms are possible over most of the state's tablelands, slopes, ranges today and coastal areas this afternoon and tonight. Any storms that develop have the potential to generate heavy rain, damaging winds and large hail. Storms are possible in Sydney this afternoon and tonight and any that develop over the Basin could become severe. Some of today's storms are likely to become supercells, with the greatest risk being over the central and northern slopes this afternoon and early evening. Supercells are the most intense type of thunderstorms and increase the risk of destructive winds, giant hail and flooding. Unlike a typical thunderstorm day, this outbreak will last through tonight and continue on Tuesday. Tomorrow's storms will be over the central and northern districts in the morning, before shifting towards the northeast later the day. While Tuesday's storms will be less intense for many areas compared to today, a mix of large hail, damaging winds and heavy rain is likely.