Elevated showers are likely to be located over the Celtic Sea at the beginning of this forecast period, drifting northeastwards across Wales / Midlands / northern England through the morning and afternoon. Additional surface-based showers may develop in response to diurnal heating, but in either case weak instability, limited convective depth and fairly moist profiles suggests any lightning will be rather isolated.

Elsewhere, ahead of the front a tongue of relatively high Theta-W will be advected northwards. Shear will increase substantially along the front during the afternoon as a notable mid-level jet rounds the base of the upper low. Elements of line convection may develop on the rear-side of the main frontal rain, although depth of convection will generally be too shallow for much in the way of lightning - though this perhaps most likely across parts of Scotland late afternoon / evening hours.

Behind the front, upper cold pool will overspread NW Scotland through Wednesday night, steepening mid-level lapse rates and generating numerous showers - although any lightning activity will probably be quite isolated.