Convective Outlook: Fri 16 Mar 2018
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Fri 16 Mar 2018 - 05:59 UTC Sat 17 Mar 2018

ISSUED 11:53 UTC Fri 16 Mar 2018


UPDATE 11:53 UTC As mentioned in forecast below issued 12 hours ago, contemplated upgrading parts of the W Country / SW Midlands / S Wales to a SLGT. 00z soundings still look rather dry with a warm nose, particularly 600-650mb, resulting in quite skinny CAPE. Overall conditions look more conducive to producing lightning compared with yesterday, but confidence still not quite high enough to upgrade for now

Upper low to the southwest of the British Isles on Friday, with cold air aloft and steep mid-level lapse rates. Diurnal heating will generate 300-500 J/kg CAPE with a few scattered showers and isolated thunderstorms possible, enhanced by areas of low-level convergence. Given rather dry forecast profiles it is once again questionable as to how much lightning activity may occur, and for now have refrained from issuing a SLGT - though it is plausible parts of Somerset / Gloucestershire / S Wales may need to be upgraded.

While the main focus will be on surface-based convection over England, Wales and the Republic of Ireland, it is possible later in the afternoon and first part of the evening for some showers/thunderstorms over N France to approach S/SW England, though probably weakening by mid-evening. Main threats are localised surface water issues given a combination of heavy showers and already saturated ground, and perhaps some hail 1.0-1.5cm in diameter.