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

VALID 06:00 UTC Mon 12 Sep 2016 - 05:59 UTC Tue 13 Sep 2016

ISSUED 19:47 UTC Sun 11 Sep 2016

ISSUED BY: Dan

Sharpening Atlantic upper trough will continue to dig southwards to the west of Iberia, while pivoting to the NE. This will allow northward advection of high a ThetaW airmass on the forward side of the upper trough, ahead of a cold front. Strong, near-parallel flow along this frontal boundary will likely result with episodes of line convection along the cold front, capable of producing gusty winds and perhaps some isolated lightning - hence a fairly broad LOW threat level issued as the front migrates eastwards with time. Overall coverage of lightning is expected to be fairly small, if any. Given strong shear and low cloud bases, there may be scope for an isolated funnel/tornado.

Interestingly, ECMWF has been keen on developing some mid-level showers across parts of England during the day on Monday, but with little support from elsewhere so have tended to ignore this potential for now.

Overnight, as the upper trough begins to slowly disrupt, backing the upper flow, some destablisation may occur ahead of the cold front with hints of elevated convection advecting into and/or developing in-situ over parts of Devon/Cornwall late in the night, and perhaps also across the Channel Islands. Given notably steep mid-level lapse rates and strong DLS, there is scope for an upgrade to SLGT - but have refrained at this time due to a lack of cross-model agreement and also the close proximity to running into the next forecast period (for Tuesday).