At the surface, extensive low cloud and mist is expected once again, although forecast profiles reveal the low-level warm nose that was present on Friday will gradually erode, in theory allowing greater mixing to occur and prospects for some breaks in the cloud to allow surface heating. This will be crucial for developing deep convection, primarily focussed along low-level convergence zones - one likely close to the M4 corridor through London and then northeast into East Anglia, and another along the south coast. Temperatures into the low 20s will be required to trigger deep convection (in conjunction with convergence zones / topography), leading to very tall but very skinny CAPE profiles. 300-600 J/kg CAPE may build, primarily over East Anglia / SE Eng / Cen S Eng where cloud breaks are most likely (especially around London) and this could aid a few heavy showers or weak thunderstorms during the afternoon or early evening. Slow storm motion (5-10mph) and PWAT 35-40mm suggests the risk of local flash flooding where showers/storms do occur. A funnel cloud or weak tornado may be possible given low cloud bases and low-level vorticity that may be ingested into an updraft - especially SE England.

A low-end SLGT has been introduced where sufficient cloud breaks / surface heating is most likely, with concerns about cloud cover elsewhere. A SLGT has also been included for the Channel Islands where some sporadic lightning may be possible towards the end of Saturday night as thunderstorms approach from France, but uncertainty as to how active they will be by arrival.