By Eric Leister, AccuWeather meteorologist
July 17,2017, 10:33:14AM,EDT
A surge of warm and humid air into the United Kingdom will set the stage for dangerous thunderstorms from late Tuesday afternoon into Wednesday.
Very moist air from the Mediterranean will build across the U.K. on Tuesday, making it feel muggy and creating ideal conditions for heavy rain and thunderstorms.
The storms will originate over the English Channel Tuesday afternoon, moving into southern England during the evening commute.
These storms will take an uncommon northward track, spreading into Greater London, Wales and the Midlands Tuesday night, with the threat for flash flooding and damaging winds.
Rain and thunderstorms will be ongoing for the Wednesday morning commute from London and Cardiff northward to Manchester and Liverpool.
Rainfall will continue to advance northward on Wednesday, bringing downpours throughout northern England and reaching Edinburgh and Glasgow by the midday hours.
The heaviest downpours are expected from Northern Ireland into Scotland Wednesday afternoon and evening, while showers and thunderstorms become more isolated throughout Wales and England.
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Ample moisture will result in torrential rainfall at times, with rainfall rates in excess of 25 mm (1.00 inch) per hour and some locations seeing up to 75 mm (3 inches) of rain within a few hours.
Rainfall of this magnitude can result in dangerous flash flooding and significant travel delays.
While flash flooding and frequent lightning will be the most widespread threats, damaging winds will also be possible.
Wind gusts over 80 km/h (50 mph) can result in downed trees and power cuts.
The strongest storms will bring the threat for damaging hail, though this is expected to be isolated.
Improved weather is expected across much of the U.K. on Thursday, with a mixture of cloud and sunshine throughout England and Wales. A few showers will remain in the forecast for Northern Ireland and western Scotland.