A zone of weak elevated instability (100 J/kg CAPE) will linger across the East Midlands on Sunday morning, engaged by a shortwave to generate showery outbreaks of rain. This zone has a history of producing isolated lightning over the past few hours, but with each passing hour this morning instability will wane and so the risk of lightning - albeit already low (10-15%) - will continue to reduce with time.

As Arctic air continues to feed southwards atop relatively warm SSTs, scattered wintry showers will develop and affect the area. Despite 100-200 J/kg CAPE, the depth of convection will be notably shallow, and increasingly so as subsidence inversion continues to build, suggesting the risk of isolated lightning is very low (5-10%) and ever-reducing with each hour through Sunday daytime.

Firstly, weak elevated instability is present across the eastern half of the English Channel, and a subtle impulse running NE-wards from France continues to engage and develop some showery outbreaks of rain. This carries a low risk (10%) of isolated lightning on Sunday morning, perhaps increasing a little (15-20%) on Sunday afternoon as a second impulse drifts across the area from France.

Elsewhere, visible satellite imagery depicts areas of thick high cloud spilling northwards into southern England. However, should sufficient diurnal heating develop, lifting surface temperatures to 19-21C (and dewpoints 10-13C) then this may yield 100-300 J/kg CAPE (and up to 600 J/kg CAPE in Devon/Cornwall). There may be a window of opportunity for low-level convergence zones to become established in the slack flow ahead of the surface cold front, which combined with orographic forcing may provide forced ascent to generate a few isolated showers (particularly Essex-Surrey-Sussex, Dorset-Devon-Cornwall and Carmarthenshire-Pembrokeshire). However, the cold front will crash southwards with a surge of strong NNE-erly winds, and while this may provide a brief increase in forced ascent the cold undercut will ultimately scour away any remaining instability.

Conditions may be more favourable over SW Wales (20%) and perhaps more especially S Devon into Cornwall (25-30%) where the surface cold front arrives later in the day, allowing more sufficient sea breeze convergence to develop downwind from Dartmoor. This, combined with a subtle impulse arriving from the northwest serving to slightly cool the mid-levels, may offer a better environment for deeper convection and a few sporadic lightning strikes for a time. While confidence in much in the way of lightning is not high, have issued a low-end SLGT to better highlight area with the best potential.