Convective Outlook: Wed 23 Aug 2017
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 23 Aug 2017 - 05:59 UTC Thu 24 Aug 2017

ISSUED 19:23 UTC Tue 22 Aug 2017

ISSUED BY: Dan

Upper trough will continue to destabilise the Theta-E plume on Wednesday as a cold front moves gradually eastwards across the British Isles. Thunderstorms will likely be ongoing at the beginning of the forecast period, embedded within general areas of rain across Scotland (rapidly weakening through the morning) while more scattered farther south towards the Midlands. Most models are in reasonable agreement for a cluster or line of (primarily elevated) thunderstorms along the Theta-E ridge to drift eastwards across northern England during the morning hours, exiting to the North Sea by early afternoon - though perhaps lingering over or close to Aberdeenshire into the afternoon. Forcing reduces farther south, and so thunderstorm potential becomes much lower - but an isolated thunderstorm could not be ruled out as far south as London, though in reality most activity will be generally north of The Wash. Main risk will be localised flooding from torrential downpours.


A few showers (or isolated thunderstorms) could form behind the main front over Scotland during the afternoon, but in general profiles in the post-frontal environment will be fairly capped, away from Ireland where an approaching trough axis will introduce cooler air aloft and increasingly steep lapse rates. Scattered heavy showers are likely, perhaps weakly-electrified though for much of the day rather stunted in vertical development somewhat. Deeper instability then arrives overnight here, fringing into western Scotland by dawn Friday, though too late for the diurnal cycle and so by this stage much more reliant on SSTs to generate deep convection.