Convective Outlook: Sat 16 Sep 2017

LOW SLGT MDT HIGH SVR

What do these risk levels mean?

Convective Outlook

VALID 06:00 UTC Sat 16 Sep 2017 - 05:59 UTC Sun 17 Sep 2017

ISSUED 18:52 UTC Fri 15 Sep 2017

ISSUED BY: Dan

Longwave trough over western Europe and associated cool airmass / steep mid-level lapse rates will result in yet another showery day across the British Isles. Instability of just a few hundred Jkg^-1 CAPE is marginal, and profiles exhibit tall but skinny CAPE, suggesting lightning activity is unlikely to be too widespread nor frequent. However, areas of low-level convergence can aid in forced ascent and may become the focus for lightning activity - this seems most likely along southern coastal counties where elements of sea breeze convergence may allow a line of heavy showers or weakly-electrified thunderstorms to develop, though the exact placement is a little uncertain with perhaps the showers peaking in intensity (and hence lightning probability) as they move offshore to the English Channel during the second half of the afternoon. For now, no SLGT has been issued but one may be required if confidence improves. The English Channel then providing the main focus for any lightning potential on Saturday night. Hail to 1.5cm and a few funnel clouds will be possible.