Portions of the interior western United States will be at risk for localized flash flooding and isolated severe thunderstorms this week. Just about every state west of the Great Plains and east of the Pacific coast will be at risk for thunderstorms in the pattern. However, some of the most dangerous storms may target the desert areas. As July ends and August begins, a surge of humid air from Mexico is forecast to bring a significant uptick in the amount of shower and thunderstorm activity over the deserts and mountains. The weather pattern is no stranger to the region during the summer and is considered to be routine during the North American monsoon season that extends from June to September.