Diurnal heating will yield 300-600 J/kg CAPE by late morning, and more especially into the afternoon. The slack surface pattern will encourage areas of low-level convergence to form, and these (in conjunction with orographic forcing) will provide the primary focus for lift in order to develop a few scattered showers. CAM guidance suggests surface-based convection may initiate around 12-1pm, particularly across parts of Ireland and SW England, with additional development then likely through the afternoon and evening hours in other parts of Ireland / England and Wales.

Some sporadic lightning seems likely over parts of the Republic of Ireland into Northern Ireland (30-35% chance) during the afternoon and early evening where convection will be deepest (but dependent on sufficient cloud clearance), but is more questionable over England and Wales (20-25% chance) where instability will be somewhat lower and convection a little more restricted in depth - the risk over N Devon / Somerset considered just high enough to warrant a low-end SLGT (30%) if convection can fire early enough in the afternoon. In fact, forecast profiles suggest warming aloft may occur later in the day as a ridge axis develops and moves from southwest to northeast, reducing the window for lightning potential. We may consider extending the SLGT across parts of SE Wales / Gloucestershire / N Oxfordshire / S Warwickshire if confidence on lightning potential increases, given a pronounced convergence zone that may become established during the late afternoon / evening hours.