Convective Outlook: Mon 18 Jul 2022
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Mon 18 Jul 2022 - 05:59 UTC Tue 19 Jul 2022

ISSUED 09:05 UTC Mon 18 Jul 2022

ISSUED BY: Dan

An exceptionally hot, dry airmass covers many parts of the British Isles on Monday beneath a substantial upper ridge. The deep, mixed layer produces very steep mid-level lapse rates, however the lack of any substantial forcing precludes any significant convection, however subtle moistening of the mid/upper troposphere will be sufficient for pockets of incredibly high-based (15,000ft) elevated convection almost anywhere during this forecast period. As such, random isolated showers will be possible, but virtually all rain may not reach the ground, and the depth of convection may not be sufficient for much in the way of lightning - but the risk is non-zero.  Perhaps the greatest risk (albeit still very low) is across Wales, the Midlands into northern England during the afternoon and evening hours.

On Monday night, the upper low and associated longwave trough near Portugal will swing northeastwards across Biscay, with increasing PVA on the forward side encouraging larger scale ascent while cooling aloft atop EML increases instability in an environment with strong shear. As such, very high-based elevated thunderstorms (13,000ft) are possible late in the night approaching south Cornwall and the Isles of Scilly - timing is a little uncertain, and it may be that most activity is beyond the end of this forecast period. There is also the possibility of additional lightning in parts of western Ireland into the Outer Hebrides during the overnight period, but confidence on placement/extent precludes a SLGT at this stage.