Convective Outlook: Sat 07 Aug 2021
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sat 07 Aug 2021 - 05:59 UTC Sun 08 Aug 2021

ISSUED 06:22 UTC Sat 07 Aug 2021

ISSUED BY: Dan

Quasi-stationary upper low continues to sit over the UK/Ireland on Saturday, providing the focus for another convective day across many areas. An occlusion, and associated rain, will swing eastwards across England and Wales during the day, but even this is likely to break up by the afternoon - albeit providing an eastwards-moving corridor of cloud and subdued surface temperatures. Ahead, a pre-frontal trough will spread showers or showery outbreaks of rain from the Channel Islands across Cen S England into SE England and East Anglia during the morning, and this feature may contain some sporadic lightning in places - although the extent/coverage is a little uncertain. Also, behind the occlusion increasing surface heating will aid numerous showers from Cen S England through the Midlands, northern England, southern and western Scotland and Northern Ireland, and these will likely migrate eastwards into east / southeast England later in the day. Republic of Ireland and into Wales is rather messy, with areas of cloud and outbreaks of rain generally reducing the coverage of heavy showers and casting some uncertainty as to how much lightning may actually occur. 

For the most part tall, skinny CAPE with rather weak shear at 5-10kts (locally higher), will likely result in a rather messy pulse-type mode. Some localised surface water flooding will be possible across Scotland and Northern Ireland in particular, where storm motion will be rather slow - regardless of whether there is much lightning or not. Storm motion may be a little faster across England and Wales, especially further south where some slightly better organisation may be possible with increased cell longevity.

Attempts have been made to highlight areas at greater risk of some sporadic lightning, however given the very messy setup it is certainly plausible that both (a) lightning could occur outside of the SLGT areas, and (b) large portions of the SLGTs could also remain void of lightning. Most lightning activity will fade through the evening, although another shortwave sliding eastwards through the English Channel could produce a few isolated lightning strikes near the Channel Islands during the night.