VALID 06:00 UTC Thu 11 May 2023 - 05:59 UTC Fri 12 May 2023

ISSUED 07:07 UTC Thu 11 May 2023

ISSUED BY: Dan

Broad, disrupting upper trough lingers over the British Isles on Thursday, resulting in a fairly slack flow at the surface. Areas of low cloud and patchy fog should thin and break through the morning, with increasing insolation aiding surface heating and yielding 300-700 J/kg MLCAPE (locally >1,000 J/kg SBCAPE). Forecast profiles reveal tall, skinny CAPE with cloud tops to potentially 30,000ft. Widespread little showers are likely to develop fairly quickly, from late morning and through the afternoon. Under the upper trough, speed shear will be weak and so most showers will be of the pulse variety with a few odd isolated lightning strikes from time to time. Showers will tend to become a little better organised where both stronger low-level forcing and better moisture pooling exists, such as over mountains or in particular along convergence zones. Vorticity stretching along CZs beneath developing showers may also allow a number of funnel clouds to develop. The direction of movement of showers will vary depending on location, rotating around the broader upper low, although sea breeze induced CZs will tend to migrate farther inland through the afternoon. Outflow/cold pools from individual cells will ultimately dictate as and when daughter cells develop nearby, leading to a rather complex and messy evolution through the afternoon and early evening.