Convective Outlook: Mon 04 May 2020
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Mon 04 May 2020 - 05:59 UTC Tue 05 May 2020

ISSUED 07:03 UTC Mon 04 May 2020

ISSUED BY: null

Residual moisture from an old occlusion over eastern England on Monday morning will drift gradually inland and be subject to convective overturning through the day. Extensive cloud and light rain and drizzle is likely to break up, to then be replaced by a few isolated but locally heavy showers by the afternoon as diurnal heating yields 100-300 J/kg CAPE and low-level convergence aids in forced ascent. On Sunday, a few isolated lightning strikes occurred with ELTs around -16C, by Monday the subsidence inversion will have extended down to ~700mb, meaning convection will be even shallower with ELTs around -8C. This suggests that lightning is very unlikely, and considered a 5% chance in any one location. Once again, profiles will be highly-sheared above the cloud-bearing layer, but due to the shallow nature of convection this sheared environment cannot be utilised. Any showers will fade through the evening hours as diurnal heating subsides.

Elsewhere, thunderstorms are expected to erupt over northern Iberia / Bay of Biscay / western France on Monday afternoon, drifting northwards across the Brest peninsula mid/late evening and approaching the Channel Islands / Cornwall around/after midnight. However, the bifurcating steering flow combined with gradually reducing ThetaW suggests lightning activity will weaken as these elevated thunderstorms track northwards, with a transition from initially largely convective rain to more dynamic / frontal rain. A low-end SLGT (30% chance) has been introduced, but even this may be over-estimating the lightning potential.