Due to the complex upper pattern, there is still at this stage marked variations in NWP guidance as to the exact track / shape / timing of a surface low and associated area of precipitation (occlusion) which will likely move northwards across England and Wales on Thursday morning. Strong upper forcing and marginal instability may result in a few isolated lightning strikes with this feature, though in general the risk is considered rather low.

The main focus for lightning activity will be within the post-frontal environment, as increasing insolation results in surface heating beneath increasingly dry air aloft. This will increase instability, generating 300-500 J/kg CAPE which combined with areas of frictional convergence will aid in the development of scattered showers and a few thunderstorms. 

Greatest risk of lightning is likely to be in a zone from SE Wales / SW Midlands northeastwards to NE / E England during the afternoon and early evening - a low-end SLGT has been issued here. A second area of interest could be inland parts of Ireland, though here a lack of shear suggests convection will be both slow moving and rather "pulse-type", with a risk of some localised water issues due to slow storm motion. Cloud cover is also some concern here given close proximity to some frontal rain at times - a low-end SLGT has been issued here.

In general, the best shear will exist across East Anglia / SE England, though here the potential for deep convection is somewhat restricted due to a shorter land track to the surface wind, and perhaps also slow cloud clearance depending on the timing of the earlier frontal rain. Nonetheless, decaying showers/storms from northern France may push into SE England later in the day, but probably with a weakening trend.

In any case, lightning activity is not expected to be as prolific as was the case on Wednesday, and any individual storm may only produce a few sporadic lightning strikes. Many places within the SLGT areas will likely remain void of any lightning. Quite a few reports of generally small hail are likely, perhaps locally up to 1.5cm in diameter. A couple of funnel clouds / weak tornadoes will be possible, primarily in Ireland with the best low-level convergence. Showers/storms will tend to decrease in intensity and coverage as daytime heating subsides.