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WED 27 MAY - THU 28 MAY 06Z - 2026: mesocast.uk/forecast/?date… UPDATE 27 MAY 2026 at 11:00am to expand slight risk polygon across Ireland and introduce a conditional lower confidence moderate for large parts of SW England, Wales and parts of the Midlands and South for later today and especially overnight tonight into the early hours of Thursday AM. Where models are firming up on plume destabilisation an active moderate is in place where strong/locally severe thunderstorms are possible, frequent to very frequent/prolific lightning (especially a cross the W Country into Soutern/Central Wales. A few active thunderstorms quite likely to break out across Southern and South West Wales through the rest of today could be locally surface based and an isolated LT supercell is possible. Main threats include large hail in stronger cells 2-3cm, locally damaging wind gusts to 55mph, torrential downpours and localised flash flooding and very frequent lightning. Thunderstorms will be predominiately elevated later this evening and overnight with storm coverage beginning to increase across Dorset/W Country/SW England migrating into Wales and with time expanding into the Midlands and Central Southern England through the early hours of Thursday AM. Close to issuing a conditional moderate for Wed., however confidence in consistency remains low. A few strong or even severe thunderstorms are possible again on Wednesday, perhaps less intense in coverage. An advancing short-wave should engage with a high theta-e plume advecting N from France through Wed. Timings of engagement are uncertain and therefore whether maximum convergence occurs during peak heating or later which dictates storm mode and coverage, however a few strong thunderstorms are likely. Main threats will be slow moving torrential downpours with the attendant risk of flash flooding, 1-2cm hail, possibly larger, gusty locally damaging winds upto 55mph, frequent lightning and the possibility of an isolated tornado. The situation will be monitored tomorrow morning with the possibility of an upgrade to a conditional moderate for favourable areas or an active moderate if confidence increases sufficiently.