Convective Outlook

VALID 06:00 UTC Thu 11 May 2017 - 05:59 UTC Fri 12 May 2017

ISSUED 20:00 UTC Wed 10 May 2017

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ISSUED BY: Dan

WAA regime will continue into Thursday as a surface warm front lifts north across England and Wales. As a result, showery outbreaks of rain from primarily medium/high cloud will continue to nudge northwards in a rather sporadic / erratic fashion, with some embedded elevated convection possible given destabilisation of higher WBPT plume as the Biscay upper trough approaches - some sporadic, localised lightning is possible, but unlikely to be too widespread given marginal instability.





Behind this front, increasing insolation over southern England during the afternoon hours may allow surface-based deep convection to occur late afternoon into Thursday evening, given heating of this higher WBPT airmass, surface convergence and the approach of the Biscay upper trough. Question marks remain over the extent of the cloud cover, which may act as an inhibitor - however, the vast majority of NWP guidance still develop some thunderstorms, if rather isolated in some cases. A SLGT has been issued to highlight the areas at risk (primarily Surrey/north Hampshire westwards to Somerset, then north and west from here across SW Midlands to mid-Wales), with perhaps some small hail from the most active cells and a risk of localised flash flooding. Additional thunderstorms may also be advected from France / develop in-situ over the Channel towards S/SE England in the evening (hence the SLGT here), but with lower confidence and perhaps weakening as they do so.