Convective Outlook: Sun 17 Apr 2022
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sun 17 Apr 2022 - 05:59 UTC Mon 18 Apr 2022

ISSUED 06:14 UTC Sun 17 Apr 2022

ISSUED BY: Dan

A frontal boundary straddling Ireland over the past 24 hours will finally begin to make progress northeastwards on Sunday as a sharp and increasingly negatively-tilted upper trough approaches from the Atlantic. The frontal rain may weaken slightly as it crosses Wales and SW England, but may reinvigorate for a time across the Midlands and northern England on Sunday evening as the aforementioned trough engages and then lifts/weakens during the overnight period. As the frontal rain clears western Ireland during the morning hours, cooling aloft will result in increasingly unstable profiles - especially in conjunction with some modest surface heating. Clusters/lines of showers are likely to develop and spread northeastwards into the afternoon and evening hours, with multiple waves possible as several PVA lobes on the forward side, then within the base, of the upper trough move across the area. 

A substantial PV anomaly and associated dry intrusion will overspread fairly moist low-levels, with forecast soundings suggesting deep convection possible with tops potentially as high as 20,000ft. Convection therefore will be largely restricted to below 500hPa, with some evidence of weak capping around ~800hPa - but this should be overcome given the warm/moist lower troposphere. Overall, how tall convection can grow is a little questionable given very dry air aloft, but cloud layer shear of 20-30kts should be sufficient to compensate to produce a few sporadic lightning strikes in places - and as such a few thunderstorms seem plausible. Hail, perhaps larger than 1cm in diameter, and gusty winds (40-50mph) may accompany some of the showers/storms. The tornado risk is rather limited due to mostly unidirectional winds, but the chance may be slightly higher early in the afternoon before the surface winds veer too much. As the upper trough relaxes north and the boundary layer cools during the evening hours, so the risk of lightning will broadly decrease overnight (but non-zero).