Agnes Witton was with family in the city centre when she wandered off at about 2.30pm.
She suffers from dDementia and officers say she may be disorientated.
She is described as being a white female, 70-80 years old, of a tiny build, with white hair and is wearing a black and white chequered coat (which appears more grey from CCTV), carrying an umbrella and white tote style bag.
Anyone with information should contact police on 101 quoting LC-20161121-0728.