Convective Outlook: Sat 21 Sep 2019
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sat 21 Sep 2019 - 05:59 UTC Sun 22 Sep 2019

ISSUED 07:12 UTC Sat 21 Sep 2019

ISSUED BY: Dan

Atlantic upper trough will disrupt during Saturday, digging towards Biscay while becoming increasingly negatively-tilted. As a result, continued advection of a relatively high Theta-W airmass will occur from Biscay across SW England and Ireland, aided by isentropic upglide and a strong low-level jet. A corridor of elevated instability will exist, rooted from around 850mb, with 300-500 J/kg MLCAPE at times. This whole NNW - SSE oriented instability plume will shift gradually northeastwards through this forecast period, straddling a zone from SW Scotland to SE England by 06z Sunday.


Subtle forcing running northwestwards along this instability plume, ahead of the largescale upper trough, will encourage pulses of medium-level instability release at various times through Saturday and Saturday night. It is likely clusters of elevated showers will develop in a rather semi-random fashion, drifting to the N or NNW.

Consequently, sporadic lightning activity is likely in places within the instability plume, but trying to pick specific areas where this is more likely is rather difficult due to the crucial phasing of subtle forcing overlapping sufficient instability, which in itself is a little meagre. Given the uncertainty and marginality, a broad low-end SLGT has been issued for now, but confidence on much in the way of lightning is rather low and it is likely many areas within the SLGT will remain void of lightning.