THE Met Office has issued a yellow weather warning for rain on Saturday.
Both roads were closed, just days after they were reopened.
The latest warning from the Met Office is valid from 4am on Saturday until 7pm across Dorset.
A spokesperson said: “Outbreaks of rain will spread into parts of southwest England and south Wales overnight, persisting for much of Saturday daytime. Some heavy rainfall is likely in places.
“Given continued saturated ground conditions, the public should be aware of the likelihood of localised flooding.”
The chief forecaster added: “A complex set of frontal systems will move up into the southwest of Britain overnight and during Saturday morning and afternoon. The associated rainbands are likely to slow or stall for a few hours, before resuming their eastward progress later in the day.
“10 to 20 mm of rain could fall over a fairly wide area, while a few locations could see upwards of 30 mm resulting in some impacts.
“There remain some uncertainties as to where the rainbands will slow down, with the possibility of updates to details within this warning.”