Convective Outlook: Fri 21 Apr 2023
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Fri 21 Apr 2023 - 05:59 UTC Sat 22 Apr 2023

ISSUED 07:44 UTC Fri 21 Apr 2023

ISSUED BY: Dan

An upper low will reside over the British Isles on Friday, with diurnal heating in the wake of morning rain across parts of England and Wales yielding an unstable environment in conjunction with the associated cold pool aloft. Outbreaks of rain will likely turn increasingly convective through the day, with additional showers developing elsewhere as low-level convergence zones develop in the relatively slack flow. A sample of forecast soundings reveals a rather variable thermodynamic profile from place to place, and this casts some uncertainty over favoured areas for lightning potential vs shallower convection. The deepest convection seems most likely across the Midlands and into Wales, which would also enable access to stronger flow aloft and therefore some reasonable cloud-layer shear. Therefore, these areas appear most favoured for some sporadic lightning, however a marked sea-breeze convergence may develop along the south coast which may provide sufficient forced ascent to generate some deeper convection here too. However, it should be stressed there is quite a lot of uncertainty over whether much lightning occurs.

While showers will largely weaken and decay through the evening hours, clusters of elevated showers/thunderstorms may drift northwestwards across the southern North Sea towards the East Anglia coast during the evening/overnight period (perhaps also develop further inland too, although this aspect is less clear). It is possible most lightning activity will remain offshore, but included a SLGT for coastal districts as a buffer.