An active cold front will push erratically northeastwards through this forecast period. Forecast cross sections over Ireland and southwest Scotland reveal a substantial PV anomaly with stratospheric air descending down to the surface by mid to late afternoon, substantial lift likely in the vicinity of the rearward-sloping frontal boundary. A tongue of relatively high Theta-W (12-14C at 850hPa) will exist ahead of the cold front, this warm, moist air subject to forced ascent to create deep convection. As surface convergence increases along the frontal boundary during the afternoon, a narrow cold-frontal rainband may develop producing a short spell of torrential rain. CAPE is rather meagre, however the fast upward motion from forced ascent may be sufficient to compensate to produce a few sporadic lightning strikes - this perhaps most likely during the evening hours across SW Scotland to the central Highlands in the vicinity of an (elongated) surface low that may develop. If the broad precipitation shield can be somewhat eroded to leave the NCFRB then this will increase the chances of lightning occurring. Confidence is too low at this stage, but a SLGT may be considered later. Squally wind gusts of 50-60mph may be possible in sections that exhibit bowing, while the strong low-level shear environment may also be conducive to a couple of brief QLCS-type tornadoes.

Despite strong surface heating with TMax near 26C, profiles remain largely capped to surface-based convection. However as the cold front approaches from the west during the late afternoon and more especially evening hours, subtle forcing may be sufficient for a few elevated showers/thunderstorms to develop within the relatively high Theta-W plume. Profiles are not as unstable as was the case over the weekend, and so lightning activity is unlikely to be as widespread or long-lasting as a result. Multi-model guidance suggests the highest risk of a few thunderstorms developing will be portions of the English Channel east of a line from Cherbourg to Bognor Regis, and perhaps moving inland into parts of SE England. However, it is certainly possible odd showers/weak thunderstorms could develop as far west as a line from Weymouth-Humber, and points east from there. Confidence is not overly high, but a low-end SLGT has been introduced where there is better CAM support. Such activity will generally clear to the North Sea by or soon after midnight.

Behind the cold front, increasing amounts of sunshine in western and central areas may yield a few hundred J/kg CAPE. This is heavily dependent on how slow cloud/rain clears northeastwards, but there may be scope for a few showers/weak thunderstorms to develop in the afternoon/evening hours. Meanwhile, around mid-evening onwards an arc of heavy showers/showery rain along an occlusion will arrive into Munster and spread northeastwards during the evening and overnight, reaching SW Scotland during the early hours of Wednesday. This may produce a few lightning strikes sporadically, perhaps especially close to the west coast/offshore. Confidence on much in the way of lightning is not particularly high, but a low-end SLGT has been introduced.