Convective Outlook: Thu 11 Jun 2020
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Thu 11 Jun 2020 - 05:59 UTC Fri 12 Jun 2020

ISSUED 07:04 UTC Thu 11 Jun 2020

ISSUED BY: Dan

Upper low will remain centred over the Bay of Biscay during Thursday, with various pulses of showery rain drifting east to west across central and southern Britain. One such feature, associated with a shortwave, will arrive over East Anglia early on Thursday morning, with some embedded elevated convection likely. This will drift westwards across the Midlands and southern England through the day, potentially fragmenting and in doing so allowing cloud breaks to increase insolation. If sufficient surface heating can occur (which is questionable given large amounts of cloud potentially), then 200-400 J/kg CAPE may become available. Low-level confluence along/ahead of the occlusion may then provide the focus for forced ascent to generate deep convection across portions of central southern England, and later southwest England. Cloud tops up to 26,000ft (-40C ELTs) are possible, with modest shear in the low-levels which may increase towards the evening hours.

As a result, some sporadic lightning will be possible, primarily within the SLGT area, during the afternoon and evening hours, but much will depend on the degree of surface heating and how much convergence/confluence can become established in an otherwise fairly brisk surface flow. Given the motion of the front to the west, the later the cloud cover may break the more restricted towards SW England the potential for lightning will be.
Scattered thunderstorms over NE France may also drift westwards offshore across the eastern English Channel - south of Kent and Sussex. However, given the surface-based nature these are likely to weaken fairly quickly on encountering colder SSTs.

Elsewhere, frontal rain over northern France will linger close to the Channel Islands for much of the day, but towards the evening hours some embedded elevated convection may evolve on the northern flank and a few isolated lightning strikes may be possible. Some pockets of weak elevated convection may also be present over E / NE England on Thursday night embedded within the main warm frontal rain.