It is likely that some elements of elevated deep convection will be present at the beginning of the forecast period over portions of Wales, SW Midlands + CS England. This will continue to migrate NE-wards during the morning hours, but with large uncertainty over coverage of lightning, and probably tending to fragment with time - hence some sections of the SLGT may remain lightning-free.

Early elevated convection may gradually become rooted in the boundary layer and / or new surface-based thunderstorms may develop as the trough axis continues to move NE through the day - this most likely to occur over northern and eastern England assuming there is sufficient preceding heating during Saturday morning. Large CAPE and sufficient shear would suggest the risk of large hail greater than 2.0cm in diameter, frequent lightning and strong, gusty winds will be possible with these storms, hence the inclusion of a SVR. However, it is worth noting not every location will necessarily be affected by a thunderstorm, but those that do occur have the potential to be severe. Given backed surface winds, some scope for a tornado will exist - but perhaps mitigated by relatively high cloud bases in general.

Behind the trough axis, profiles become very dry aloft but with high dewpoint air remaining near the surface until the shallow cold front moves through later in the day. Provided some upper support and a return to strong insolation in the afternoon, a new round of surface-based thunderstorms will be possible - some perhaps severe. The exact location will be dependent on the eventual shape of the surface low over Northern Ireland, but general trends would suggest this potential new round of thunderstorms is most likely over northern England, perhaps moving into S Scotland by evening - a MDT has therefore been issued for this activity. Farther south, very dry profiles and weaker upper forcing may limit the potential for any afternoon/evening thunderstorms.