A strong south-shifted Atlantic jet stream will usher a series of low pressures toward the Great Britain, bringing outbreaks of heavy showers and potential thunderstorms in places.
An occluded front will sweep across many parts of UK over daytime, bringing heavy rain to many. Clearance behind the occluded front will allow shallow convection, with MUCAPE of 300-600 J/kg across Northern England. Due to the strongly saturated profile, these convection will be limited in activity, therefore only a few sporadic strikes are possible, mainly across northeastern England, hence a low thunderstorms risk has been issued for these areas.
Another surface low pressure will develop behind the milder southwesterly air-mass during the early night. A sector of relatively high Theta-E air-mass will be introduced by a warm front associated with the low pressure. Convective showers behind the warm front will develop due to an area of strong 0-3 km CAPE (>150 J/kg locally) and strong buoyancy. Surface-based thunderstorms will initialise across the Celtic Sea, advancing northeastward. Slightly less saturated profile across north of Cornwall / Bristol Channel might allow slightly more long-tracking thunderstorms to develop. Strong laspe rate could bring some hail, but strong low-level shear could limit it to marginally severe size (only). The combination of moderate shearing across the far SW England could also allow a waterspout / weak tornado but the risk is too low to issue a severe risk.
Highly saturated profile will limit the lightning activity, but some high-resolution models suggesting a slightly less saturated behind the band of thundery showers, allowing another area of thunderstorms to initialise across western parts of English Channel. Moving northeastward into Bournemouth/ Isle of Wight during 04-06z. Slightly strong deep level shear across the central and eastern parts of English Channel could also benefit this area of thunderstorms to be slightly more long-tracked compared to other across the Celtic sea.
There are some uncertainty on the timing but there is the opportunity of the surface based thunderstorms across Bournemouth/ Isle of Wight could develop into a weak elevated thunderstorms tracking into the far Southeast England during the early morning.
You can download the KML file of the convective outlook here:
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