Convective Outlook: Wed 11 May 2016
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 11 May 2016 - 05:59 UTC Thu 12 May 2016

ISSUED 19:21 UTC Tue 10 May 2016

ISSUED BY: Dan

Large upper low west of Biscay will begin to flatten and expand W-E on Wednesday. At the surface, a slow-moving frontal boundary will tend to stall across northern England / north Wales. To the south of this boundary, slack flow (with local convergence zones) and developing insolation, in an environment with steepening lapse rates, will generate a few scattered slow-moving showers and thunderstorms. That said, lapse rates are marginally improved on Tuesdays, but still would prefer to see higher lapse rates for more frequent lightning potential.


DLS is weak and so any showers/storms that do develop will be poorly organised, limiting their severe potential significantly. However, given moist air mass (PWAT in upper 20s mm) and considering slow storm motion, then greatest risk will be from minor surface water flooding from prolonged downpours. Hail locally up to 1.5cm in diameter is possible from any stronger cores, and given low LCLs and some wind convergence, a couple of reports of funnels / weak tornadoes will be possible.

Attention is also given to showers/thunderstorms that may develop over the BeNeLux countries during Wednesday, as these may drift westwards to affect parts of East Anglia / SE England during the early hours of Thursday, albeit while probably weakening as they drift across the North Sea. Most NWP suggests an increase in elevated convection developing over the North Sea and drifting into North Yorkshire during Wednesday night.