Convective Outlook: Wed 05 May 2021
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 05 May 2021 - 05:59 UTC Thu 06 May 2021

ISSUED 07:42 UTC Wed 05 May 2021


A notably cold airmass covers much of Europe on Wednesday, within a broad upper trough. Cold air aloft combined with diurnal heating will yield 300-500 J/kg CAPE through the day in an environment with steep mid-level lapse rates. A strip of shear vorticity from Northern Ireland - Wales - SE England, on the northern/eastern edge of the mid-level jet, will migrate gradually eastwards through the day. An area of PVA is likely to swing into Wales mid-morning, move across the Midlands early afternoon and reach East Anglia by the evening - and this will likely be the focus for a more organised area of widespread heavy showers/weak thunderstorms. However, numerous showers and weak thunderstorms will also develop elsewhere across parts of Scotland, northern England, Northern Ireland and eastern Ireland. Low-level winds will be weaker compared with Tuesday, and this will aid in a slightly better sheared environment as flow remains strong aloft - aiding with venting. Overall, parameters are generally more favourable for some sporadic lightning in many different parts of Britain in particular (compared with Tuesday), but the risk is generally considered 15-20% in any one location which falls below SLGT criteria. Model guidance suggests a relative minima in shower activity from Lancs through the south Pennines to north Midlands. Hail is likely in many of the showers, carpeting roads and producing difficult driving conditions, with the potential for wind gusts of 40-50mph around some of the most intense cells. Guidance suggests substantial cold pooling occurring over the south Midlands and later towards SE England.