Storm Cooper-Ryan, 17, has been missing for three days

The police are appealing for help finding missing teenager Storm Cooper-Ryan, who has been missing since Tuesday.

The 17-year-old girl was last seen at Heddon Greta, west of Newcastle, at about 4pm on Tuesday.

Officers attached to Port Stephens-Hunter Police District were notified on Thursday after she could not be located or contacted.

'Police and family hold serious concerns for her welfare,' the police said on Friday.

Storm is described as having a fair complexion with a slim build and blonde hair.

She is about 155cm tall.

She is known to frequent Metford, Maitland and Sydney.

Storm Cooper-Ryan has been missing since Tuesday. Picture: NSW Police