On Saturday night, as a longwave trough over the Atlantic approaches, the backing flow will tend to push the frontal boundary over southern Britain gradually farther north, encouraging warm advection over NE France and towards SE England. This is likely to result in scattered elevated showers during the early hours of Sunday over NE France, which may pass close to SE England, posing the threat for a few lightning strikes. However, most (if not all) activity is likely to remain away from SE England, and so no threat levels have been introduced at this stage.