All the right ingredients for severe thunderstorms are coming together across New South Wales today, with a busy afternoon and evening likely for the state's east and north. Thunderstorms typically need three key components to form: heat, moisture and a trigger. The trigger, a low pressure trough which moved into the state's west last night bringing little in the way of rain is interacting with moisture-laden northeasterly winds sourced off the Tasman Sea today. Combining with plentiful amounts of warmth being dragged from the nation's interior, conditions are prime for thunderstorm development. However, the formation of severe thunderstorms generally require an extra ingredient or two at the very least. One of these elements is stronger mid-level and upper-level winds (also known as wind shear) which aids in updraft strength and allows thunderstorms to sustain themselves for longer periods of time and hence become stronger. Another is cold upper level air which when combined with warm air at the surface leads to steep lapse rates i.e. the rate at which atmospheric temperature decreases with height. Steeper lapse rates are generally associated with more rapid and intense convection. When also combined with dry air in the upper atmosphere, cold upper level temperatures also greatly increase the risk of large hail. These ingredients are present in the thunderstorm setup today, meaning thunderstorms bring the risk of damaging wind gusts, large hail and heavy rainfall this afternoon and evening. The focus of the thunderstorm activity will be over the state's east and north, including Sydney. In the state's northeast, there is also potential for rainfall totals of 20-30mm (most likely on the ranges) which will aid in easing severe rainfall deficits across the region. Severe thunderstorms are not atypical in November, which is one of the stormiest months on average across the state. On Thursday, the trough will move over northeastern NSW bringing further risk of severe thunderstorms before generally clearing the state on Friday.