Day 1 Convective Outlook: Sun 19 May 2019
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Day 1 Convective Outlook

VALID 06:00 UTC Sun 19 May 2019 - 05:59 UTC Mon 20 May 2019

ISSUED 06:57 UTC Sun 19 May 2019


Broad upper trough covers the British Isles on Sunday, with a rather slack pressure pattern. Early in the forecast period some remnant elevated instability will pass close to Orkney and Shetland. Thereafter, provided there are sufficient cloud breaks, diurnal heating of the moist low-level airmass will yield 300-500 J/kg CAPE, with scattered showers likely to develop forced by low-level convergence and orographic forcing. As was the case on Saturday, weak steering flow (and hence weak shear) will lead to very slow movement of showers, bringing the risk of some local surface water flooding. 

Forecast profiles are slightly cooler aloft compared with Saturday (when a warm nose at 600-700mb limited convective depth) and so it seems plausible there is a greater chance of a few sporadic lightning strikes on Sunday - main focus will be central southern England where sufficient moisture pooling will likely occur late afternoon as sea breeze convergence meets inland convergence zone. A low-end SLGT has been introduced to better highlight the area of interest. However, lack of any notable shear and rather saturated profiles will tend to result in pulse-type convection with restricted buoyancy of air parcels - which may serve to reduce lightning potential. A couple of funnel clouds will be possible given low cloud bases and areas of low-level convergence.