|Convective Outlook: Sun 13 Dec 2020|
|What do these risk levels mean?|
VALID 06:00 UTC Sun 13 Dec 2020 - 05:59 UTC Mon 14 Dec 2020
ISSUED 08:30 UTC Sun 13 Dec 2020br> br>
ISSUED BY: Dan
Outbreaks of rain will spread erratically northeastwards across the British Isles as a frontal system arrives from the Atlantic. Behind, cold air aloft with reasonably-steep mid-level lapse rates will overspread relatively warm SSTs to generate a few hundred J/kg CAPE over open waters and coastal districts in the west. Therefore, scattered showers become increasingly likely, initially over Ireland during Sunday afternoon before the risk expands eastwards across Britain through the evening and night, and these will become organised into discrete bands as one or more shortwave troughs swing through the in the broad southwesterly flow aloft. Given the strongly-sheared environment, some line segments will be possible at times with perhaps a low-topped supercell, capable of producing squally winds and the risk of an isolated tornado. The risk of sporadic lightning is greatest near western coasts, and so particular attention is given to the Irish Sea into parts of Wales, NW England and SW Scotland - however the coverage of lightning is not expected to be significant enough to warrant a SLGT.