Convective Outlook Issued: High risk 13/06/2025 12:00 - 14/06/2025 11:59

A surface low pressure across the Bay of Biscay will deliver a plume of warm and moist theta-e airmass as it moves northward during the evening, allowing 700 - 1000 J/kg of MUCAPE to develop across southern England during the early night.

Severe thunderstorms across France are expected to develop during the late afternoon, becoming increasingly organised due to the very strong deep-level shear (55-65 kt). As a result, an MCS with supercell characteristics are likely to develop and possibly move northward enough to affect parts of Kent. Very high cloud tops, as well as near-perfect background shearing, will allow a band of severe thunderstorms, embedded with very frequent lightning, to move northward into the parts of SE England and East Anglia along a shortwave. Strong gusts up to 60 mph, large hail ( around 2 cm max), as well as flooding (due to 40-50 mm PWAT) are all possible, mainly across the high-risk areas in parts of Kent.

Elsewhere, scattered showers and a few embedded thunderstorms are possible, although less likely to be severe. A particular area of interest is the Bristol Channel, Wales and parts of Northwest England, as the triple point of the low pressure could provide enough forcing and shear for another round of thunderstorms. Few scattered thunderstorms are likely to follow behind the frontal systems overnight, perhaps even turning frequent across N Wales and NW England if these cells can make use of the CAPE. These cells will struggle to develop initially, due to the saturated profile and rather low EL height, but as the front clears northward, few long living cells will be still possible during the early morning, although likelihood is low.

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