Severe thunderstorms have dumped more than a month's worth of rain in under an hour in parts of southern New South Wales and there are more severe storms to come. Young, in the South West Slopes, was drenched by a massive 74mm in an hour, 16mm more than its monthly average and its highest daily rainfall in seven years. The high moisture levels and slow-moving nature of the storms have led to these large downpours. The low pressure trough responsible is also slow-moving and will generate further intense storms during the following few hours and few days. The main areas of NSW to be affected are likely to be the west and south between now and Thursday. The the trough will move a little faster and trigger more widespread storms across western, southern and central parts of the state on Friday and further northeast on the weekend. Flash flooding is the most likely feature but damaging wind and large hail are also possible.