Convective Outlook: Wed 25 Apr 2018
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 25 Apr 2018 - 05:59 UTC Thu 26 Apr 2018

ISSUED 19:13 UTC Tue 24 Apr 2018

ISSUED BY: Dan

Cold pool associated with broad upper trough drifting eastwards across the British Isles on Wednesday will be accompanied by markedly steep mid-level lapse rates and some marginal instability. Numerous showers will move eastwards across many areas, some with small hail.


Best instability will exist in a zone from the Republic of Ireland - Wales - Midlands - East Anglia where lapse rates will be steepest, yielding up to 500 J/kg CAPE in response to diurnal heating. These regions will also benefit from 20-40kts DLS, which may compensate for the low levels of CAPE, especially across southern counties of England.

Theoretically lightning could occur almost anywhere given widespread deep convection (hence large LOW threat level), but given a reasonable overlap of CAPE and shear over these aforementioned regions, have introduced a low-end SLGT to suggest slightly better overall conditions for lightning activity. High-resolution models suggest convective gusts of 50mph may be possible.
One inhibiting factor across these areas could be true convective depth, with forecast profiles suggesting deep convection may be restricted to tops near 400/450mb (even shallower across southern England, while deeper over northern England but here CAPE will be much taller/skinnier with less DLS).