Convective Outlook: Wed 28 Jun 2017
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 28 Jun 2017 - 05:59 UTC Thu 29 Jun 2017

ISSUED 15:40 UTC Tue 27 Jun 2017

ISSUED BY: Dan

Upper vortex becomes increasingly elongated to the west of Ireland on Wednesday, digging across Biscay towards southern France. A surface low will only slowly drift NW from the southern North Sea across Norfolk towards The Wash by evening, its associated frontal precipitation envelope covering much of northern England / north Midlands / north Wales and across to northern Republic of Ireland. Some elements of medium-level instability release may be present at the beginning of the forecast period close to the Norfolk coast.


South of the surface low, potential heating of notably moist low-levels (dewpoints 13-16C) combined with some elements of wind convergence (sea breeze for example) will provide the focus for a few scattered showers, some perhaps weakly electrified. There remains quite a bit of uncertainty about cloud clearance, which will need to occur in order for sufficient heating to take place. This is also highly dependant over the exact position and shape of the surface low, and a slower clearance north would then place the areas of low-level wind convergence in different locations.

Nonetheless, two areas have been highlighted where some deep convection may occur, although with rather skinny CAPE profiles (and not overly-impressive mid-level lapse rates) combined with high moisture content in the low- to mid-levels, it is questionable as to how much lightning activity may occur, despite some very heavy downpours being possible. For now, this and the ongoing uncertainties over cloud preclude upgrading to a SLGT over S / SE England.