Upper trough extends south towards the NW of Britain on Monday, with a jet / belt of moderately strong SWly winds across central UK, marked at the surface by a slow-moving cold front separating cooler polar air to the north and warmer/moister Tm air to the south. Heavy showers and thunderstorms are likely in the more unstable polar airmass across Scotland and N. Ireland today.
... SCOTLAND & N. IRELAND ...
Steep lapse rates generated by colder air aloft across N/NW UK in association with upper trough towards the NW will yield around 200-500 j/kg CAPE by peak heating this afternoon across the above areas. This will support increasing coverage of scattered heavy showers and thunderstorms through the day, which will be accompanied by hail and gusty winds. Locally, showers/storm may form lines/bands that could bring prolonged rainfall leading to localised flooding.
... N ENGLAND, N MIDS, LINCS ...
As morning showery rain fragments along slow-moving SW-NE aligned cold front lying across Wales up to NE England - cloud breaks may allow enough insolation to yield sufficient instability, combined with surface wind convergence / lift from front, to support strong enough convection to produce some heavy showers that may produce isolated lightning.
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.