Convective Outlook: Wed 13 Jul 2016
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 13 Jul 2016 - 05:59 UTC Thu 14 Jul 2016

ISSUED 08:29 UTC Wed 13 Jul 2016

ISSUED BY: Dan

UPDATE 08:29 UTC SLGT extended across Midlands / N Wales (see previous comments in forecast below) for any late afternoon/evening activity

Broad upper trough continues to sit over the British Isles, albeit beginning to clear eastwards with a northwesterly jet aloft on its rear flank. A pocket of cold mid-levels will drift slowly SE-wards across Scotland/Northern Ireland during the day into northern England/north Midlands, responsible for scattered showers and perhaps a few weakly-electrified thunderstorms. This particular zone contains the steepest lapse rates, and with better upper support may be where lightning is more likely. DLS is more conducive to some organisation of cells across Northern Ireland / Ireland, with a risk of hail to 1.0cm in diameter and gusty winds possible here.

Farther south, forecast profiles are drier than on Tuesday, resulting with showers being more well-scattered, with many areas staying dry. Overall convective depth is probably too shallow for lightning in most areas, however far southern England will likely have just sufficient depth for lightning potential during the afternoon from the strongest cells. There may also be a short window during the evening where parts of Wales / Midlands have a marginally-better environment for a few isolated occurrences of lightning.

It is difficult to ascertain specific areas most likely at risk of lightning given a broad relatively low threat - for now have issued a couple of low-end SLGTs, but these areas may be tweaked to better fit latest guidance.