Convective Outlook: Thu 16 Apr 2020
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Thu 16 Apr 2020 - 05:59 UTC Fri 17 Apr 2020

ISSUED 07:12 UTC Thu 16 Apr 2020

ISSUED BY: Dan

An upper low centred west of Biscay, with an upper ridge retreating to central Europe, will create a broad southerly flow across western Europe during Thursday, bifurcating as it approaches the British Isles but advecting a (relatively) high Theta-W airmass towards southern Britain. Warming is most notable in the 850-950mb layer, which coupled with several impulses/shortwaves, rotating around the main parent upper low, helping to cool (and moisten) the mid/upper levels and generate some mid-level instability.

As such, occasional scattered showers will develop from this elevated instability through the day on Thursday, as the whole zone of interest (driven by a PVA strip) drifts slowly northwards with time. CAPE is a little meagre, but a few isolated lightning strikes could occur almost anywhere from these high-based showers - but most areas will likely remain void of lightning. Amounts of rain reaching the surface will also likely be fairly small.

On Thursday evening there is a signal for a few scattered high-based showers and/or thunderstorms to develop over the English Channel close to northern France, drifting northwards towards CS / SE England, but probably weakening on arrival. However, confidence of this (relatively minor) uptick in activity is not particularly high, but a low-end SLGT has been introduced to highlight this potential.

Stronger forced ascent will arrive towards the end of Thursday night as a more pronounced shortwave slides northwards across Biscay towards the Channel Islands. Increasing baroclinicity will likely result in the development of frontal rain, but some embedded elevated convection is possible which could produce some sporadic lightning, more especially on the eastern flank over France.