Issued 2019-03-12 11:19:14 Valid: 12/03/2019 0600 to 13/03/2019 0600
CONVECTIVE / THUNDERSTORM OUTLOOK - TUES 12 MARCH 2019
Deep low pressure Storm Gareth will track SE across northern Scotland tonight embedded in a deep upper trough shifting east across the UK behind an active cold front which will bring squally rain with emdedded line convection SE across England and Wales today, followed by heavy and squally showers with hail and thunder across NW Britain.
UK and IRELAND
An active cold front will continue to push SE across England late morning and into the afternoon, strong winds aloft parallel with strong SWly winds at the surface will bring line convection on the leading edge of the band of squally rain along cold front moving SE, convection will be shallow, with weak instability and profiles too saturated to support lightning, though the odd strike can't be ruled out. Convectively enhanced damaging wind gusts of 50-60mph and brief intense rainfall leading to localised flooding are possible with the line squall. A few brief tornadic spin ups can't be ruled out along the front.
Post cold front polar airmass will see increasingly cold mid-levels spreading aloft of moist surface airmass, as upper trough moves east. This will create sufficiently steep lapse rated to support frequent heavy showers with hail and thunder across the northwest - with a few of these passing southeast elsewhere. Convectively enhanced very strong wind gusts are possible in association with these heavy showers, with damaging gusts of 60-70mph.
Issued by the Netweather forecast team whenever there is a risk of storms or severe convective weather, these discussion based and in depth forecasts will highlight the areas at risk and give an in depth description of the risk and the factors surrounding it.
Thunderstorms - Severe thunderstorms unlikely to occur, slight risk of hail, gusting winds and localised flooding.
Slight Risk - A slight risk of severe convective weather exists. Hail >2.0cm diameter, wind gusts exceeding 50mph or 5-10% risk of a tornado within 50 miles of a point, or > 30% risk of localised flooding.
Moderate Risk - A moderate risk of severe convective weather exists. Hail 4-5cm in diameter, or wind gusts of 60-70mph, or a 10-15% chance of a tornado within 50 miles of a point, or >50% risk of localised flooding.
High Risk - A high risk of severe convective weather exists. Rarely, if ever used on the UK. Hail >5cm, or wind gusts in excess of 80mph, or >20% risk of a tornado within 50 miles of a point, or >70% risk of localised flooding.