Convective Outlook: Fri 02 Sep 2022
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Fri 02 Sep 2022 - 05:59 UTC Sat 03 Sep 2022

ISSUED 07:03 UTC Fri 02 Sep 2022

ISSUED BY: Dan

A very messy pattern is anticipated on Friday, casting uncertainty over the forecast evolution. Diurnal heating across Wales and southern England will potentially yield several hundred J/kg CAPE, however the thermodynamic profile varies amongst model guidance with evidence of mid-level capping which may inhibit the depth of convection. At the very least scattered heavy showers may develop, especially across Wales and SW England, but the amount of lightning is questionable. Most convection will be tied to orographic forcing and low-level convergence, and will likely be heavily influenced by the extent of cloud cover/reduced surface heating. At the same time pockets of elevated convection are also possible, especially over the English Channel and environs. Any showers that do develop could give some locally high rainfall totals given prolonged, fairly slow-moving downpours.

During the evening and overnight hours a corridor of heavy rain is expected to develop from NW Wales across the Irish Sea / Isle of Man to Northern Ireland and SW Scotland. Forecast profiles appear rather saturated, suggesting the lightning potential is probably limited. Tentatively extended the (already marginal) SLGT to cover this area, but confidence on much lightning occurring is rather low. Also overnight substantial CAPE covers parts of East Anglia and SE England, but analysis of forecast profiles suggests this is largely driven by SSTs and is heavily capped. That said, steep mid-level lapse rates could potentially yield some rather active elevated thunderstorms, but in the absence of any larger scale forcing this is deemed rather unlikely (but non-zero).