Rain, strong westerly winds and plummeting temperatures are being predicted over the next 48 hours.
The Bureau of Meteorology issued warning on Wednesday afternoon to sheep graziers in the Northern Tablelands, with conditions posing a risk of losses of lambs and sheep.
Other areas likely to be affected include the Central Tablelands, Southern Tablelands, South West Slopes and Snowy Mountains.
The next warning will be issued by 11:00 pm EST Wednesday.
Visit www.bom.gov.au/nsw/warnings for updates.