Information on update: Warning area expanded to cover more of western and northern Scotland. Warning start time brought forward. Areas of heavy rain with isolated thunderstorms are expected to arrive from the south during Saturday afternoon, becoming persistent in places and leading to some large totals building up, particularly on southeast facing areas of high ground. Many places are likely to see 20-30 mm, but some locations could see 50-75 mm in just a few hours. For further details see https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-warnings