The event will be hosted by Welsh Secretary, David Jones and will feature young people sharing their own experiences of seeking employment.
Businesses including major Welsh employer, Airbus, will be asked to sign a pledge to raise awareness to help support young people into work.
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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.