Convective Outlook: Sat 22 Jul 2017
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sat 22 Jul 2017 - 05:59 UTC Sun 23 Jul 2017

ISSUED 21:04 UTC Fri 21 Jul 2017

ISSUED BY: Dan

... E ANGLIA / LINCS ...

Residual low/mid-level moisture along the remnant cold frontal boundary may provide the focus for a few heavy showers / isolated thunderstorms during the morning/midday hours, either surface-based or generated from medium-level instability. Confidence is not high enough to upgrade to SLGT for now, especially given marginal mid-level lapse rates.

... N ENGLAND / S SCOTLAND ...
Approaching upper vortex and associated cold pool drifting over remnant low-mid-level moisture close to the weak frontal boundary will likely allow scattered heavy showers and perhaps a few thunderstorms to develop during the afternoon and evening hours on Saturday, forced largely by low-level convergence. Some prolonged downpours could cause local surface water issues, along with perhaps some weak funnels or tornado given slack conditions.

... ELSEWHERE ...
Cut-off upper low over SW Britain and associated cold pool will lead to steeper mid-level lapse rates, and with diurnal heating and some low-level convergence, numerous showers are expected to develop during the day, lasting well into the evening/night. Some may become weakly-electrified given marginal instability - a low-end SLGT has been added to W / NW Wales where low-level wind convergence may aid some more substantial convective development. Some uncertainty about a messy mixture of dynamic and convective precipitation developing late afternoon into early evening in places, particularly Midlands and the Home Counties, which may inhibit true convective depth somewhat. Chance perhaps of a funnel or weak tornado.

... SE ENGLAND ...
Showers are likely to continue through the night given presence of upper low, but as mid-level lapse rates steeper slightly and the flow backs more, allowing deep convection over the English Channel to move farther inland, there will be some scope for an increase in lightning activity with this convection during Saturday night.