The Met Office has issued an amber weather warning for up to six inches of snow on Sunday.
The warning runs from 11pm tonight until 3am on Monday with significant amounts falling on ground over 500 feet throughout much of tomorrow, with a risk of up to 12 inches falling above 800 feet.
Strong winds may also produce snowdrifts and there's also a risk of overhead power lines icing up.
In lower areas, there's more likely to be rain and sleet, with sleet or snow in the west.
The Met Office says it will issue updates if the forecast changes.