A low pressure trough and an associated cold front will cross NSW today and Saturday morning, causing widespread and intense thunderstorm activity.
The trough has already triggered a few thunderstorms over inland parts of the state yesterday evening and overnight, with 3000 cloud to ground lightning strikes since Thursday afternoon. These thunderstorms were generally not severe, but brought winds up to 65km/h at Walgett and Coonabarabran, and up to 17mm of rain at Mt Kaputar near Narrabri.
Thunderstorm activity will become much more widespread today, as warm air over NSW converges with cold air from the south. During the afternoon, some of these thunderstorms are likely to be severe, with large hail, damaging winds and heavy rainfall all likely. The most intense thunderstorms are most likely over the Central Tablelands, Hunter, Mid North Coast and Northwest Slopes and Plains. Large hail is especially likely in the Upper Hunter and North West Slopes and Plains.
Once it is evening, thunderstorms are likely to turn into rain areas. In some parts, particularly the Hunter and Lower Mid North Coast, very heavy rainfall is a possibility, with falls of up to 60-80mm expected. This has prompted the Bureau of Meteorology to issue a flood watch for possible future flooding for these regions.
Thunderstorms remain a possibility on Saturday morning, although the risk decreases significantly throughout the day as the trough moves offshore.
For the rest of the weekend, cooler and drier conditions are expected across the state's inland in the wake of the front, with a few showers along the coast.
© Weatherzone 2013
07:24 EST A severe weather warning has been issued for Sydney and parts of New South Wales, raising the prospect of damaging winds and heavy rainfall.