Flooding is possible from the evening of Thursday 17 December through to the morning of Saturday 19 December.
Heavy rain will spread in from the west overnight on Thursday. Showers and drizzle are forecast for Friday morning. This will turn into heavy and intense rainfall during Friday afternoon, evening and into the early hours of Saturday.
Totals of up to 60mm are forecast to fall in a 12 hour period from Friday afternoon, with up to 75mm in 24 hours.
Areas of higher ground may see totals of up to 100mm in 24 hours.
Rivers are expected to respond quickly to this rainfall. Flooding of low-lying land and roads close to rivers is possible. Surface water may be deep, especially where leaves have blocked the drains. Further heavy rainfall is also forecast for Sunday and Monday.