Convective Outlook
VALID 06:00 UTC Fri 09 Jun 2023 - 05:59 UTC Sat 10 Jun 2023
ISSUED 07:48 UTC Fri 09 Jun 2023
ISSUED BY: Dan
A similar evolution is anticipated on Friday to that of Thursday, with a broad upper low residing to the southwest of the British Isles and slow advection of high Theta-W plume (>16C at 850hPa) progressively northeastwards. The main interest will be in the vicinity of an occlusion straddling NW France, western English Channel, SW England and into Ireland, where pulses of showery rain will continue to develop at various times through Friday and Friday night, with an ongoing chance of a few elevated thunderstorms - more especially from late afternoon and through the evening/night hours, although confidence on lightning coverage is rather low. Tentatively introduced a fairly broad SLGT risk although many areas may remain void of lightning.
Elsewhere, while substantial CAPE may build across central and southern Britain on Friday afternoon (this then advecting across the Irish/Celtic Sea to SE Ireland overnight atop the mixed layer), forecast soundings reveal very dry profiles with capping at several levels and therefore for the most part it is unlikely any substantial surface-based deep convection will occur. That said, additional orographic forcing over Exmoor and higher terrain in Wales may be sufficient to develop a few isolated heavy showers/thunderstorms, drifting offshore and towards SE Ireland where they could potentially grow upscale into a small cluster as vorticity associated with the remnant MCV over the Brest peninsular this morning arrives from the SE (this already not handled very well in CAM guidance this morning) - this aspect is rather uncertain, but a low-end SLGT has been introduced.
Also, there have been subtle hints on Friday night of odd elevated showers developing within the broader Theta-W plume across central/eastern England emanating from the Low Countries during the evening and migrating northwestwards with time. However, current thinking is the chance of lightning is too low to warrant any extensions/additions to existing highlighted areas.
