Convective Outlook: Sun 18 Aug 2019
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sun 18 Aug 2019 - 05:59 UTC Mon 19 Aug 2019

ISSUED 21:02 UTC Sat 17 Aug 2019

ISSUED BY: Dan

Broad upper trough covers the British Isles through Sunday, the main upper low centre drifting slowly northeastwards across northern Scotland. The associated cold pool will create an unstable environment with steep mid-level lapse rates and pockets of 300-500 J/kg CAPE.  As such, scattered showers will affect many areas at various times through this forecast period, and hence it is difficult to pinpoint specific areas for when/where lightning may occur.


In general, the best potential for lightning will be associated with the passage of a couple of shortwave troughs, where CAPE becomes maximised coupled with stronger forcing aloft. One will affect the Bristol Channel and environs first thing on Sunday morning, swinging northeastwards across the Midlands then out to the North Sea around midday. Another will drift eastwards across Ireland late morning / early afternoon, while the main upper low will reside close to Scotland maintaining a lightning threat here.

A few low-end SLGTs have been introduced for corridors where lightning potential may be somewhat greater, but it is likely some isolated lightning will occur elsewhere within the LOW threat area. The most intense cells may produce hail up to 1.5cm in diameter and gusty winds - the main area of interest for any semi-organised convection will be Sunday morning from SW England / S Wales and across the Midlands.

Showers will continue to affect many western areas (particularly W Wales / NW England / Bristol Channel) overnight as shortwaves slide eastwards, atop warm SSTs.