A decision is due today on where to site a planned incinerator for south Wales.
There are two companies in the running. Veolia have a bid in for the Llanwern steel site and Viridor are bidding to build a facility in the Splott area of Cardiff.
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The heaviest bursts are expected in the south and east, with some western areas either remaining dry or becoming dry by dawn.
Many places will start dry, but rain in the southeast will spread to most for a time overnight.
The family of Isaac Nash who went missing after being swept out to sea last summer have presented a cheque for £10,000 to the RNLI.