Convective Outlook: Sun 07 Jun 2020
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sun 07 Jun 2020 - 05:59 UTC Mon 08 Jun 2020

ISSUED 07:12 UTC Sun 07 Jun 2020

ISSUED BY: Dan

Positively-tilted upper trough over the North Sea will gradually retreat to the near Continent while weakening on Sunday. Cloud and outbreaks of rain will sink southwards across central and eastern England associated with a frontal zone, but this should start to clear southeastwards as the flow aloft veers more to the NW. Weak elevated instability on the western flank of this zone may allow some heavier bursts of convective rain to develop across the Midlands into East Anglia. Cloud will likely invade southwards across the Midlands and southern England associated with this front, but may thin and break at times to allow sufficient surface heating to occur and potentially yielding 200-400 J/kg CAPE in the best of any sunshine. Given a slacker surface pattern than recent days, a well-marked sea breeze convergence zone is expected to develop along southern coastal counties by midday onwards, and this may be briefly reinforced by a wind-shift line associated with a warm front sinking southwards, before eventually the whole zone is shunted offshore late afternoon / early evening by the increasingly northerly surface flow. A second convergence zone is also expected to develop from NW England through the West Midlands into E / SE Wales during the afternoon hours. Both of these areas will provide the focus for scattered showers developing, drifting southwards at 10-15mph (perhaps more to the SE across Kent / Sussex until the steering flow veers northerly during the evening).

Forecast profile suggest a warm nose will exist at 600mb, and more especially at 450mb, and these will serve to limit the overall depth of convection with cloud tops generally around 15,000 - 17,000ft (ELTs -15C to -20C). Deepest convection, at least potential, will be along southern coastal counties, but concerns exist over how much cloud cover may dilute surface heating and reduce available CAPE. Nonetheless, any showers that do develop and can grow tall enough may produce a few isolated lightning strikes, but the risk in any one location is not considered high enough to warrant a SLGT. Any showers in S / SE England will fade through the evening, but are likely to persist across Wales and perhaps SW England well into the night as a strip of PVA slides southwards, encouraging lift. However, by this stage much reduced CAPE suggests the risk of lightning is fairly low. Late in the night, shower activity may increase over the southern North Sea close to the coast of East Anglia and SE England as this same PVA strip engages with the remnants of the old frontal boundary.