Convective Outlook: Tue 27 Jun 2017
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Tue 27 Jun 2017 - 05:59 UTC Wed 28 Jun 2017

ISSUED 15:53 UTC Tue 27 Jun 2017

ISSUED BY: Dan

UPDATE 15:53 UTC In hindsight, activity over East Anglia today would have warranted a SLGT (borderline MDT) - but confidence was not high enough to upgrade at time of forecast issuance. Broad theme for instability here to weaken through the afternoon (earlier update) remains, with a marked decrease in lightning activity recently. The attention herein probably turns to any thunderstorms that may develop over NE France and BeNeLux this evening, which could then be advected towards the East Anglia coast overnight - though becoming increasingly elevated and likely weakening with time.

UPDATE 10:55 UTC No notable changes to the forecast, subtle forcing is promoting mid-level instability release with showery precipitation with embedded lightning drifting NNE-wards across SE England and East Anglia at present. In general terms, guidance continues to suggest instability reducing through the afternoon hours as profiles become more saturated and broad areas of showery rain develop more widely

Atlantic upper trough will dig south towards Iberia on Tuesday, strong northwesterly jet on its western flank but rather weak return southerly flow on its forward side. Broad upper flow is anticyclonic across the British Isles for much of the day, but higher WBPT airmass will begin to advect northwards from France as the flow backs. Falling heights will promote some destabilisation of this airmass, but in a rather messy fashion with pulses of showery precipitation drifting north from France into southern Britain - majority of NWP guidance suggest these pulses will be largely dynamic (vs convective). Forecast profiles also exhibit saturated mid-levels with only marginal instability at best. That said, some embedded lightning cannot be ruled out, but point probabilities remain very low.
The bulk of any noteworthy instability will likely remain over the nearby Continent, with perhaps a slightly better chance of some lightning close to coasts of Kent/Sussex and East Anglia late Tuesday afternoon into the evening/night, but confidence is not particularly high - no SLGT issued for now. 

Elsewhere, behind the main frontal rain some insolation combined with cool air aloft will generate some instability across Northern Ireland, with scope for a few heavy showers or thunderstorms here. In general conditions remain too marginal to upgrade to SLGT for now. Some surface-based convection will also be possible over SW England for a time in the afternoon too.