Some elevated convection is possible on Friday morning over parts of northern England, associated with a narrow Theta-E tongue, with other pulses also likely to drift northwestwards towards NE Scotland and the Northern Isles, especially during the evening/night hours. There may be a few isolated lightning strikes over northern England during the morning hours, but given rather meagre CAPE and saturated profiles it is unlikely to be frequent or widespread enough to warrant a SLGT.

Otherwise, the main focus during Friday will be associated with a marked shortwave that will swing northwestwards from northern France across S / SW England, engaging with an occluded front lifting northwestwards at the same time. The easterly flow at 700mb will strengthen through the day, and this will encourage continued westward advection of a higher Theta-W airmass, with a narrow tongue forming immediately ahead of the main frontal boundary. Strong forcing for ascent is expected to develop around midday, as a marked PV lobe / shortwave overlaps and engages with the frontal boundary and instability plume as it arrives over Cen S / SW England.

A narrow band of elevated convection, primarily rooted around the 870mb level (bases of 4,000ft), is expected to erupt on the leading edge of the main frontal rain, and consequently some sporadic lightning may occur almost anywhere as this front continues to push northwestwards, while also extending eastwards across the Midlands, through the afternoon and evening hours. Uncertainty over how much lightning may occur exists given rather saturated profiles, which serves to inhibit buoyancy somewhat, although there should be some modest speed shear through the cloud-bearing layer. Given PWAT of 30-35mm, torrential downpours are likely but rain accumulations will be somewhat limited by the fact storms will be moving at 30-35mph and so are unlikely to last for any prolonged period in any one location. A general weakening trend is expected during the evening hours over Wales and the Celtic Sea as upper forcing overruns and relaxes to the west, while the narrow tongue of high Theta-W retreats northwards having been diluted somewhat by earlier convection.

It should be noted timing of the shortwave engaging with the instability plume is crucial in determining where and when elevated thunderstorms may develop - a later phasing will shift the focus further to the north and west of the SLGT. Other more scattered elevated thunderstorms may develop farther east into parts of SE England and East Anglia, but confidence here is lower - should confidence increase, the SLGT may be extended further east. It is also possible isolated surface-based showers may develop ahead of any elevated thunderstorms during the middle part of the day, if sufficient surface heating can lift temperatures into the 20-22C range (with dewpoints around 13-15C). However, such developments may be capped by the warm, dry mid-levels, with ELTs generally restricted below -20C and this limits the lightning potential significantly.

By Friday evening the Theta-W / instability plume will stretch from north Wales - north Midlands - East Anglia, while bending back towards BeNeLux. Subtle impulses running northwestwards in the stronger flow aloft could in theory generate random elevated showers/thunderstorms almost anywhere within this zone as it lifts slowly northwards through the night, but on a relatively localised level - which makes it very difficult to pinpoint specific areas that may require an upgrade to SLGT. A more substantial shortwave / PV lobe will likely exit the Low Countries and drift northwestwards across the North Sea, grazing parts of East Anglia and Yorkshire/Lincolnshire during the night hours. However, there is a lot of uncertainty at this early stage as to the exact track of this feature, and a relatively minor shift east-west of ~100 miles makes a significant difference as to whether this may bring an increased risk of elevated convection and at least some lightning to portions of N + E East Anglia into Yorks/Lincs, and perhaps as far north as Northumberland by 06z Saturday. The most likely scenario is that the bulk of lightning activity remains offshore, but developments during Friday will need monitoring to ascertain whether the risk to eastern parts of England needs increasing (or indeed decreasing).

There may also be a few scattered elevated showers that develop over the English Channel and drift into southern England on Friday night, capable of producing a few sporadic lightning strikes - more especially closer to southwest England where a more substantial shortwave approaches later in the night.