A yellow weather warning over wind has been put in place for western and northern areas of Scotland on Friday.
Chief Meteorologist Frank Saunders, said; "Strong winds at this time of year can increase the rate of leaf fall which can potentially block drains or culverts and, with the heavy rainfall expected over Friday and Saturday, could well heighten the potential for flooding".
The RSA said that with the risk of coastal flooding, motorists should not attempt to drive through flooded areas.
A zone of heavy rain associated with an intense weather system affecting western parts of the United Kingdom will become slow moving for a time, bringing prolonged rainfall and the potential for surface water flooding.
'We've got a wind warning which covers all the western side of the UK.More news: Trump says Chinese 'lived too well for too long'
She said the west coast was "not out of the woods" in terms of strong winds and there was still a danger to people on the roads.
Coasts on the south and west of the country are expected to be the worst affected by the storm, with risks of heavy flooding and structural damage.
Road and rail users have been warned to expect disruption and delays.
Pembrokeshire County Council is working with multi-agency partners to monitor the situation.
Train cancellations will affect those travelling the Shrewsbury to Aberyswyth line through Mid Wales all weekend.More news: Joseph's long TD return lifts Vikings past Eagles 23-21
NRW said its emergency response teams were checking flood defences, clearing gullies and ditches and installing temporary defences.
"This evening and tonight it will become very windy with strong to gale force southeast winds, associated with storm Callum", according to the national forecaster.
"Preparations are well underway to ensure we have engineers and equipment and customer care teams on hand to respond to faults should they come in".
There will be rain as well later in the night and combined with the stormy winds and high tides, coastal flooding is likely.
Temperatures will begin to plummet on Sunday, as rain clears to the east for a mostly clear but cool afternoon, with some areas even experiencing a 10 degree drop in temperatures.More news: India's debt lower than best, emerging market economies