Convective Outlook: Tue 11 Jun 2019
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Tue 11 Jun 2019 - 05:59 UTC Wed 12 Jun 2019

ISSUED 08:21 UTC Tue 11 Jun 2019


UPDATE 08:21 UTC SLGT over southern England shifted south in light of latest radar trends and guidance - not overly convinced there will be much lightning given limited cloud depth and weak instability

Broad upper troughing will persist across the British Isles on Tuesday, the main upper low located over northern France with a smaller (filling) upper low east of Shetland. Between these two features, heights will tend to rise which will tend to weaken the frontal boundary straddling Wales / northern England, leaving a zone of cloud and increasingly light, patchy rain.
South of this front, sufficient low-level moisture will exist (dewpoints of 11-13C) which combined with surface heating could yield a couple hundred J/kg CAPE. Low-level convergence zone will likely provide the trigger for a few scattered heavy showers, particularly from midday and through the afternoon hours in a line from SW England northeastwards towards London and/or East Anglia. The environment will be reasonably well-sheared, allowing cells to become somewhat organised and capable of producing sporadic lightning and small hail. Given saturated ground from recent rain events, there will be a risk of some localised surface water flooding.

Main concern is somewhat limited convective depth, which may serve to inhibit much in the way of lightning. In fact, it is primarily the UKMO suite that consistently signals deep convection and heavy showers/thunderstorms, whereas most other model guidance appears rather lacking in any particularly noteworthy convection. For now have issued a low-end SLGT.

Any showers/storms that do develop will tend to weaken during the evening hours as daytime heating subsides, though some weak elevated convection may develop in a rather random fashion during the night hours over the English Channel and adjacent southern coastal counties, including the Channel Islands.