Thunderstorms Possible

There is a slight risk of thunderstorms today for much of Southern England with a Slight risk of Severe storms over France.


Valid: 18/06/2013 00z to 19/06/2013 06z

Upper low, which has cut off from the main belt of upper westerlies across the North Atlantic, will become slow moving across Iberia, the Bay of Biscay and SW France over the next days. A warm front, currently parallel to the south coast, will lift north across England and Wales during Tuesday, introducing warm and humid airmass from the near continent, while a cold front moves N and E across SW UK by 12z Tuesday.


Although surface/boundary layer will likely remain stable overnight, a warm/moist Elevated Mixed Layer (EML) characterised by steep lapse rates will advect north ahead of surface warm front and the resultant isentropic uplift of these warm moist layers above the cooler and drier boundary layer will continue to produce some elevated showers and isolated thunderstorms overnight and through Tuesday morning. These showers and storms perhaps drifting in across south Wales, The Midlands and E Anglia during Tuesday morning. Storms, though high-based, may bring high rainfall rates in a short space of time, bringing a risk of localised flooding and may perhaps be accompanied by hail and gusty winds.

Brighter skies with insolation following this area of mid-level activity heading north ahead of the surface warm front will allow temperatures to rise towards the mid 20s degrees celsius across SE England and E Anglia, which combined with increasing dew points, may allow sufficient CAPE to develop and thus potential for isolated to scattered surface-based thunderstorms to develop. 0-6km directional shear and upper speed shear will be fairly strong towards SE UK, so any storms could organise into bowing line segments with a small risk of large hail, strong wind gusts and localised flooding. However, given uncertainties over whether surface-based storms will initiate, will refrain from a categorical risk of severe weather.

Otherwise, there will be a continued risk of further isolated elevated storms moving north through later on Tuesday and overnight into Wednesday, bringing a threat of some localised flooding.

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