Showers across SE England initially could produce a few lightning strikes, but these will likely ease for a time as warming aloft occurs during the late morning and into the afternoon. Scattered showers are likely to develop in many other parts of the UK and Ireland during Monday daytime, and as has been the case in previous days a few isolated lightning strikes are possible just about anywhere - but the risk overall is relatively low. 

During the afternoon a convective cluster over the Atlantic approaching the Celtic Sea will begin to become increasingly organised into a distinct comma feature as it approaches SW England and Wales, its precipitation shield expanding. As the upper trough sharpens and PVA increases, stronger forcing aloft coupled with increasing near-surface instability and convergence could result in strong, deep convection. This may be capable of producing quite a bit of lightning for a time to the west of SW England, this convective line then pushing into SW England and parts of S Wales during the late evening. Its northern edge (i.e. inland) may weaken, but could remain active where onshore flow from warm SSTs in the English Channel maintains its intensity towards Dorset/Somerset 11pm-midnight, and points east thereafter.

As a surface low deepens near Wales, the initially positively-tilted frontal boundary will become increasingly negatively-tilted (i.e. SW-NE to SE-NW) through the night as surface winds back (relative to the front angle), with an increasing tendency for an initially well-organised squall line/LEWP to become more broken with core-gap morphology. This suggests the initial threat will be largely locally damaging SLW, perhaps locally in excess of 60mph (especially near exposed coasts), but this may translate more to an isolated tornado threat through the night - albeit with a reducing lightning risk with eastward extent. It is worth stressing that most areas within the SVR will not experience severe conditions, but very locally some wind damage is possible.