Convective Outlook: Tue 12 Apr 2016
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Tue 12 Apr 2016 - 05:59 UTC Wed 13 Apr 2016

ISSUED 20:28 UTC Mon 11 Apr 2016

ISSUED BY: Dan

Omega Block over NW Atlantic maintains a broad upper low west of Biscay, extending towards the British Isles through Tuesday. The associated cold mid-levels combined with diurnal heating will generate 300-500Jkg-1 CAPE. Forecast profiles are quite dry, and convective initiation will be heavily reliant on low-level wind convergence (from sea breeze and topographical effects), hence even within the broad SLGT there will be a good deal of dry weather still in many places with showers generally well-scattered and focussed over small areas.


Scattered showers and a few thunderstorms will develop, particularly from late morning and moreso through the afternoon and into the evening, capable of producing hail locally bigger than 1.0cm in diameter in any stronger cells. DLS is rather weak and hence showers/storms will be rather lacking in organisation, but slow storm motion will likely produce 10-15mm rain accumulations in just 1-2 hours, with elements of shower training also - and hence there is a risk of some local surface water flooding issues.

It is hard to ascertain any particular areas where showers/storms are most likely to occur, hence the broad SLGT, although most NWP are in agreement for north Cornwall/Devon eastwards along M4 corridor to Thames Estuary as being on area of focus, along with S + E Wales into the W Midlands perhaps. Coverage (albeit still fairly well-scattered) may continue to expand in the SLGT well into the evening hours, before eventual decay takes over later in the evening due to nocturnal cooling. A few funnel clouds or a weak tornado are possible close to convergence zones.

Some question marks remain over how quick frontal rain clears East Anglia/Lincolnshire during the morning, which may inhibit convection here until quite late in the day. There is also a suggestion that frontal rain may turn more convective in nature across parts of northern England perhaps.