Convective Outlook: Wed 13 Sep 2017
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 13 Sep 2017 - 05:59 UTC Thu 14 Sep 2017

ISSUED 05:27 UTC Wed 13 Sep 2017

ISSUED BY: Dan

Positively-tilted upper trough will slide gradually southeastwards across the British Isles on Wednesday, the associated cold pool aloft providing an environment with notably steep mid-level lapse rates. Showers will develop widely, some weakly-electrified in western exposed areas, and across parts of Ireland where better instability will exist as the upper cold pool approaches during the afternoon hours. Areas southeast of a line from The Wash to Devon may experience some heavy showers, but profiles will be capped somewhat with limited depth and hence lightning seems unlikely here, despite strongly-sheared profiles.


However, through the evening and night hours the cold pool and upper trough will continue to track southeastwards, and hence the environment will become increasingly unstable in SW Britain with showers developing more widely, along with a few thunderstorms - especially near west-facing coasts.

Hail to 1.5cm in diameter and gusty winds will be possible with the strongest cells, rain accumulations limited somewhat by strong steering winds. Overnight a band of showery rain will drift south over the North Sea, grazing some NE and E coastal counties of England and perhaps bringing an elevated threat of lightning here too - though confidence is not high enough to upgrade to SLGT for now.