Convective Outlook: Thu 06 Apr 2023

LOW SLGT MDT HIGH SVR

What do these risk levels mean?

Convective Outlook

VALID 06:00 UTC Thu 06 Apr 2023 - 05:59 UTC Fri 07 Apr 2023

ISSUED 07:21 UTC Thu 06 Apr 2023

ISSUED BY: Dan

A disrupting upper trough will drift across the British Isles on Thursday, the cold pool aloft creating an unstable environment in conjunction with modest surface heating. This is especially true across south and southeast Britain where a residual moist low-level airmass in the wake of earlier frontal rain could yield several hundred J/kg CAPE as near-surface temperatures reach 11-14C. Assuming cloud cover thins/breaks sufficiently to allow some reasonable insolation, scattered showers may develop into Thursday afternoon, before slowly decaying through the evening hours. Forecast profiles suggest convection in southern England could reach 25,000ft with reasonably dry air in the mid-level, albeit rather weak wind shear under the upper trough axis. Nonetheless, a few sporadic lightning strikes will be possible, especially as cells mature as they drift gradually southeastwards, and therefore southern and eastern coastal counties perhaps most favoured for some lightning activity. An enhanced convergence zone may evolve by the afternoon as the land-sea thermal differential increases, however the background wind may be too strong to allow this sea breeze to advance inland, and so instead it could linger close to the coast or even offshore, perhaps providing an extra boost for forced ascent to any cells that drift offshore to the English Channel later in the day, before weakening later in the evening. For the most part convection will tend to be rather outflow-dominant, with cold pools tending to help showers propagate southeastwards while enabling daughter cells to develop nearby. Sub-severe hail and gusty winds will accompany the most intense cells.