Discussion: A convergence zone will form across Midlands during the early afternoon drifting south towards SE England where intense cells are expected to form. Within this convergence zone lies a good amount of instability with around 400-600J/KG quite widely possibly exceeding 1000J/KG in places. Lightning will mostly remain sporadic particularly within the Area of interest where higher Cape values lie.
Technical Discussion: A southward moving area of convergence throughout the afternoon from the midlands down to the south should bring showers capable of sporadic lightning mainly focused in the SE. Potentially around 1,000 J/KG of MUCAPE could get fairly widespread but mainly due to the low-level lapse-rates increasing the lift in the surface-layer meaning that most energy is held close to the surface and storms may only reach up to 7-8km max and given the very weak DLS (mostly 0-20 knots from 0-4 miles) storms are unlikely to last long enough to reach 4-5km. There may be an increase on the south coast and into London-Oxford area (20-35 knots from 0-4 miles) combining with the energy available (there's 30+ knots further west in the low but with much weaker energy) for an increase in risk for a few storms to reach the 7-8km height. Into East Anglia, the risk is also an AOI with moisture pooling there better with the centre of convergence centred over roughly Cambridge area moving SSE, with most showers riding along it or further west where there's an energy pool. A few cells may form further east along the coast with more slightly increased moisture convergence, hence the AOI has been expanded into the whole of the SE and into the north sea. Clustering with increased forcing may allow for storms to stop being pulse-type and turn into a system moving SSW during the afternoon. But that depends on exactly how much forcing and also how many showers form. Low-level shear is fairly strong and that may allow for a funnel cloud andor an isolated tornado or two, especially given the low lCL's, just enough surface-bound vorticity and just enough 3CAPE at 50-100+ J/KG. But weak buoyancy at the cloud layer, as beyond the slight surface inversions it's very weak, limits both hail, funnel cloud and isolated tornadic potential. Weak updraft potential and fairly low post freezing energy and unless the updraft width strengthens from clustering, the hail looks limited to around half an inch maximum.