VALID 06:00 UTC Thu 06 Jun 2019 - 05:59 UTC Fri 07 Jun 2019
ISSUED 06:17 UTC Thu 06 Jun 2019
ISSUED BY: Dan
Upper low west of the British Isles will elongate and sharpen, with cold mid-levels creating steep mid-level lapse rates. Early very active elevated thunderstorms over the central North Sea will tend to weaken somewhat as they continue to nudge north towards or to the east of Shetland.
Elsewhere, diurnal heating will yield 300-500 J/kg MLCAPE with scattered showers developing, particularly aided by areas of low-level convergence. By the afternoon, dewpoints of 6-8C seem likely (GFS typically too moist).
A few thunderstorms will be possible - instability will be greater over Ireland (due to proximity to upper cold pool) but with weaker shear, so more "pulse-type" convection seems likely here, whereas over Britain instability will be less but with stronger shear on the forward-side of the upper trough, lending to slightly better cell organisation. As such, have issued a couple of low-end SLGTs to better highlight areas with reasonable multi-model agreement for a few sporadic lightning strikes.
Some uncertainty exists over Northern Ireland, depending on how much cloud may linger courtesy of the nearby wrap-around occlusion. However, the slack regime would support the development for scattered showers and/or a few thunderstorms should cloud breaks be sufficient for reasonable surface heating to occur - this area will need monitoring for a potential upgrade.
On Thursday night, a rapidly deepening area of low pressure will approach from Biscay, pushing frontal rain northwards across the English Channel into S / SW England. There may be some pockets of embedded elevation convection, but any lightning will probably fairly isolated.