Convective Outlook: Mon 17 Dec 2018
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Mon 17 Dec 2018 - 05:59 UTC Tue 18 Dec 2018

ISSUED 14:14 UTC Sun 16 Dec 2018

ISSUED BY: Dan

On Monday morning, remnant instability will bring a few heavy showers close to Shetland, but even these should ease by the afternoon. Otherwise little to no lightning activity is expected through this period.

However, the cold front entering western Ireland on Monday evening will be strongly forced, with a consistent signal amongst NWP guidance for elements of line convection to develop as a tongue of relatively warm, moist low-level air gets drawn northwards ahead of the cold front, with both a marked temperature gradient and wind veer expected across the surface front. A narrow line of squally conditions (heavy rain and very strong, potentially damaging, gusts of wind), sandwiched in the middle of a broader precipitation envelope, is expected to migrate eastwards across Ireland during the evening and overnight hours, reaching the Hebrides during the early hours of Tuesday. Given the highly-sheared environment, such line segments can be capable of producing isolated tornadoes. However, very little (if any) lightning is expected given the shallow nature of such strongly-forced convection, and so no threat levels have been introduced.

Behind the cold front, deeper instability begins to approach western Ireland late in the night as cold air aloft moves across relatively warm SSTs, generating a few hundred J/kg CAPE. Showers are expected to affect western Connaught and Munster towards Tuesday morning, and hence the inclusion of a LOW threat level here.