Convective Outlook: Wed 29 Mar 2023
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 29 Mar 2023 - 05:59 UTC Thu 30 Mar 2023

ISSUED 06:12 UTC Wed 29 Mar 2023

ISSUED BY: Dan

A series of waving frontal boundaries will migrate erratically northeastwards across the British Isles on Wednesday, tending to contain a messy mixture of convective and dynamic precipitation. Particular interest is given to the post-frontal environment over Ireland during the afternoon and early evening hours, as increasing insolation will allow heating of a moist low-level airmass (T 13-15C / Td 10-12C) coinciding with cooling aloft to yield 500-800 J/kg MLCAPE. Numerous showers and a few thunderstorms are likely to develop across central portions of Ireland, migrating northeastwards into Northern Ireland. Cloud tops could well push up to 30,000ft potentially. Strong flow aloft and slight backing of the low-level winds will create substantial cloud-layer wind shear, typically 30-40kts, although this will tend to reduce towards the evening as flow aloft weakens somewhat. Nonetheless, this will be sufficient to aid organisation/longevity of any semi-discrete cells, and there is scope for some cells to exhibit low/mid-level rotation. If a cell can become organised and remain relatively discrete then this may pose the risk of marginally-severe hail and perhaps a tornado, but the fairly uni-directional wind profile suggests convection may tend to form lines/clusters which may limit the risk of severe weather to some extent. 

Elsewhere, waves of showery rain will drift northeastwards across portions of England and Wales at times, and coupled with some weak elevated instability could produce a few lightning strikes locally. Perhaps particularly so from late afternoon and into the evening hours across the English Channel and southern parts of England in the vicinity of an approaching PV anomaly/dry intrusion. However, given mass ascent it is unclear how much lightning activity may occur, with convection tending to morph into areas of heavy rain. Tentatively introduced a low-end SLGT over parts of Devon and Cornwall. That said, some torrential bursts of rain will be possible for a time, especially across SW England and Wales. Any potent convection that can remain sustained for a period of time may also produce some rather strong gusts of wind.