During Thursday evening, a sharpening upper trough and associated strong forcing will cause the warm front to buckle, developing a frontal wave and rapid cyclogenesis. A notable warm, moist low-level airmass will exist across England and Wales south of the warm front and ahead of the sharpening cold front - consequently, a few hundred J/kg CAPE will develop ahead of the cold front, and close to the triple point. Strong, largely unidirectional, deep layer shear will exist across the area, though the thermally-active cold front will be marked by a notable wind veer at the surface.

The environment, therefore, will be favourable for convective elements to develop during the evening and night hours as the frontal system crosses England and Wales to the North Sea. Embedded line convection / squalls are likely along the cold front, which may also exhibit some sporadic lightning - though difficult to say exactly how frequent this may be given rather saturated profiles and weak instability. An extension to the SLGT may be required across parts of the Midlands. Nonetheless, some damaging gusts of wind will be possible, and perhaps a tornado where any marked bow echoes can develop.

The best overlap of shear, instability and forcing appears to evolve over Wales initially during the first half of the evening, then into northern England before clearing to the North Sea quite quickly during the early hours. As a result, have issued a SLGT here where lightning seems more probable (with limited confidence given some uncertainty as to how far north the triple point may reach). Near this feature, forecast soundings yield curved hodographs, and given the pre-existing environment, this zone carries the greatest risk of a tornado.

Farther west, beneath the upper trough, a classic autumn/winter scenario will unfold with cold air aloft overspreading warm SSTs of the Atlantic to generate steep lapse rates and a few hundred J/kg CAPE - hence numerous showers and some sporadic lightning will be possible near the coasts of Ireland initially, and then W Scotland and Irish Sea coasts later in the night. Gusty winds will also be possible with this activity.