3:21pm Thursday 21st March 2013
Surface water has been causing problems on the A31 eastbound between Ringwood and the M27 as a band of heavy rain sets in.
And after drivers were forced to avoid surface water on one lane the Highways Agency has decided to do an overnight check to find out the cause.
Spokesman James Wright said they will check if any culverts are blocked.
"We are going out when traffic flows are lowest tonight and put in a lane closure to try and check why it has happened," he said
The weather warning in place for today and tomorrow has been extended until midnight on Friday, with forecasters warning rain will be even heavier than initially expected.
The warning, updated on Thursday lunchtime, says: "Persistent rain will spread into south west England during Thursday, turning heavy at times and extending further north and east on Thursday night and into Friday.
"Brighter, showery conditions will return from the southwest later on Friday. The public should be aware that some minor flooding impacts from rivers and surface water are expected.
"An active frontal system, struggling to bring milder air into the south of the country, is expected to bring 20-30 mm of rainfall quite widely, and possibly as much as 50-60 mm in a few locations on high ground exposed to the strong southeasterly winds.
"These accumulations are expected to result in some river or surface water flooding."
An amber warning is being issued for southern parts of Devon and Cornwall which are likely to be the worst affected areas.
The heavy rain is forecast to last most of the day tomorrow, with a temporary break at lunchtime. 20.4mm of rain is forecast to fall today across the county and another 11.3mm tomorrow. Winds look set to reach 43 mph.
Traffic monitoring sites, including Trafficlink, which provides the Echo's traffic feed, are reporting the A31 is down to a single lane, but an Echo photographer has been to have a look as says the road is open, but very wet.
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