Convective Outlook UPDATED 2: High risk 12/05/2025 06:00 - 13/05/2025 05:59

UPDATE 2 (12/05/2025 08:50):

The moderate and high risk has been expanded due to increasing confidence that some deep-level shear will support organised thunderstorms across parts of the W Midlands and Wales. Strong gusts and hail are also more likely to reach severe criteria within any organised thunderstorms.

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UPDATE 1 (11/05/2025 09:05):

A moderate and high risk has been issued to highlight the area most likely to see multiple thunderstorms. Strong gusts have also been included as a severe hazard in the severe risk area.

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A warm and moist theta-e airmass, delivered by a frontal system on Sunday, will enhance instability during Monday daytime. MUCAPE values of 800–1300 J/kg indicate potential for numerous scattered thunderstorms in a moist environment with high low-level humidity. Cloud tops could exceed 36,000 ft, supporting frequent lightning.

Weak wind shear during the early afternoon will result in short-lived, pulse-type thunderstorms. However, a convergence zone within the Slight Risk area will provide sufficient triggers for scattered cell development. Outflow from these cells, combined with enhanced convergence, could lead to additional thunderstorms in the late afternoon, particularly in the Enhanced Risk area. While early storms will be short-lived, late-afternoon storms may persist longer due to outflow interactions, as well as small uptake in deep-level shear in the south. Small hail is possible due to steep lapse rates, especially where updrafts are strongest. PWAT of 30–40 mm suggests heavy rainfall, with a risk of localised flooding, particularly in areas experiencing multiple rounds of slow-moving or training storms.

Few scattered thunderstorms, perhaps producing frequent lightning, are also possible across southern parts of Scotland

Lightning activity will decrease during the late evening as diurnal heating weakens.

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