A late-summer cold front will sweep across the central United States on Friday, trimming daytime highs by about 10–12 °F in Colorado and the Upper Midwest, according to National Weather Service offices in Boulder, the Twin Cities and Chicago. Denver is expected to fall from recent 90 °F readings to the low 80s on Friday and the upper 70s by Sunday, while Minneapolis–St. Paul should reach only the low 70s on Saturday after scattered thundershowers move through today. The cooler air mass will tap additional Gulf and monsoonal moisture, generating hit-or-miss thunderstorms from northern Arizona to Illinois. Forecasters warn that slow-moving storms could trigger flash flooding in Arizona’s high country, and a few stronger cells may flare along Colorado’s northeastern plains before a quieter, seasonably cool stretch settles in over the weekend. Across the Atlantic, the UK Met Office expects largely bright and temperate conditions for England, Wales and Northern Ireland during the Summer Bank Holiday weekend, with the sunniest spells in the south-west and only isolated light showers in northern England. Scotland, which does not share the holiday, will see skies clear after Friday cloud. France is also headed for calmer weather. Météo-France projects weekend highs of 21–25 °C north of the Loire and up to 33 °C along the Mediterranean, offering a respite from the exceptional heat and violent storms that dominated earlier in August.