Issued 2018-06-15 21:43:16
Valid: 16/06/2018 0600 - 17/06/2018 0600
A fairly potent upper low will pass east across Scotland during Saturday embedded in broadscale strong westerly upper flow dominating the far north Atlantic and northern Europe. At the surface, an occluded front will traverse the UK in the morning and early afternoon, ahead of surface low moving east and filling as it approaches NW Scotand. An airmass unstable to surface heating will follow the occluded front.
... N. IRELAND, CENTRAL & SOUTHERN SCOTLAND, N and E ENGLAND ...
Upper trough crossing northern Britain will create steep lapse rates, surface heating in any sunny spells, following frontal cloud band with showery rain clearing east, will yield a few 100 j/kg CAPE, which will support development of scattered heavy showers and a few or more thunderstorms. 30-40 knots of deep layer shear could allow some organisation in multicell clusters which maybe capable of producing isolated strong wind gusts, hail and torrential rainfall leading to localised flooding. Backing of low-level winds with approach of surface trough from the west may induce enough low-level shear to perhaps support a few funnel clouds with stronger updrafts, a brief weak tornado can't be ruled out. The risk of thunderstorms will quickly fade after dark, as forcing for ascent clears east and surface heating wanes.
Issued by: Nick Finnis
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.