Convective Outlook: Thu 09 Jul 2020
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Thu 09 Jul 2020 - 05:59 UTC Fri 10 Jul 2020

ISSUED 21:57 UTC Wed 08 Jul 2020

ISSUED BY: Dan

Broad westerly flow aloft over the British Isles on Thursday, but an upper trough will sharpen in the vicinity. Cooling aloft will lead to steepening mid-level lapse rates over Scotland during the afternoon hours, and increasing instability when combined with diurnal heating. The slack surface pattern will encourage areas of low-level convergence to develop, aided also by orographic forcing to generated heavy showers. Initially, convection may be somewhat stunted in height by a warm nose in the mid-levels, but this is likely to be eroded as cooling aloft occurs, resulting in deeper convection during the second half of the afternoon and into the evening hours.

Aside from a mid-level dry slot, much of the profile will be rather saturated which combined with limited CAPE (200-400 J/kg) suggests the risk of lightning is somewhat limited. Nonetheless, there does appear to be potential for a few isolated lightning strikes by the evening hours, most likely from Perth and Kinross / Sterling / Fife southwards to the Southern Uplands and Borders region - however, coverage is not thought to be significant enough to introduce a SLGT at this stage. Showers may merge into an area of showery rain that slowly drifts across SE Scotland into northern and eastern England on Thursday night, as divergence aloft on the forward side of the developing upper trough continues to encourage lift. This may also be reinforced by increasing low-level convergence along the east coast of England, which may aid in shower development late in the night. Either way, lightning activity during the night hours is questionable given rather saturated profiles and meagre CAPE.