Wales weather: Forecasters' strong winds and rain warning
Heavy rainfall and high tides may cause localised flooding across Wales, Environment Agency Wales has warned.
Gusts reaching 60mph (96kmh) are also forecast in most Welsh counties on Thursday evening and Friday.
Warnings strong winds may cause coastal surges, large waves and sea spray on the south Wales coast have been made.
Four flood alerts have been issued for the Wye estuary, the Usk estuary, Swansea Bay and the coast from Aberthaw to the Severn Bridge.
Environment Agency Wales (EAW) warned that as river levels rise, further flood alerts may be issued as well as some localised flood warnings.
Strong winds may also damage trees and cause debris to block drains which could lead to localised flooding.
Agency officers were checking flood defences and clearing blockages that may pose a flood risk, it said.
The Met Office has issued a severe weather warning for south-west England from early Thursday afternoon, and said this would extend to south Wales by Friday.
Forecasters said it was the type of storm more usually seen in the during autumn or winter.
MeteoGroup said gales would spread north east to affect north Wales, with gusts reaching 60mph (96kmh).
"The public should be careful when they are outside, and there is a danger of damage to trees," it warned.
Forecaster Mark Seltzer said: "Strong winds, possibly up to gale force, are expected from the afternoon onwards in south-west England particularly Devon and Cornwall.
End Quote Brendan Jones MeteoGroup senior forecaster
This sort of Atlantic storm is more normally seen in the autumn and winter months”
"On Friday the warning is extended to include south Wales and many parts of southern England as well as the south-west, again with a risk of gales.
"Winds should gradually ease from the south west during the day."
Brendan Jones, the senior forecaster with MeteoGroup, the weather division of the Press Association, predicted "potentially disruptive winds".
"This sort of Atlantic storm is more normally seen in the autumn and winter months," said Mr Jones.
"There will also be a lot of rain in the next 48 hours," he added.
BBC Wales weather presenter Behnaz Akhgar said 100mm (3.9 in) of rain was expected to fall in the west of Wales on Friday, but the severe weather was expected to lift by Saturday.