Convective Outlook: Thu 01 Sep 2022
LOW
SLGT
MDT
HIGH
SVR
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Convective Outlook

VALID 06:00 UTC Thu 01 Sep 2022 - 05:59 UTC Fri 02 Sep 2022

ISSUED 06:18 UTC Thu 01 Sep 2022

ISSUED BY: Dan

An upper low will meander slowly eastwards across the Bay of Biscay on Thursday, eventually merging with a disrupting upper trough approaching from the Atlantic across Ireland. This will eventually cause the Biscay low to start to lift northwards, allowing a relatively high Theta-W airmass (14-16C 850hPa) to advect slowly from northern France across the English Channel towards southern England. Subtle forcing and gradual moistening the column on the northern flank of the Biscay low will likely result in sporadic elevated convection drifting west-northwestwards across southern England on Thursday daytime, expanding into the south Midlands and south Wales overnight. Forecast profiles also reveal potential for some surface-based convection in southern England during the afternoon/early evening. 

Slightly stronger forcing is anticipated to arrive towards Thursday evening and night, initially affecting the Channel Islands / Cherbourg peninsula and then drifting northwards towards southern England. This may be accompanied by deeper convection and the greater potential for a few thunderstorms which, according to some forecast profiles, may well also be surface-based over the English Channel given the seasonally high SSTs. Given the steering flow individual cells may struggle to move inland before weakening, and so much of the lightning activity may remain over the Channel with more generic showery rain eventually evolving over parts of southern England.