Portions of the interior western United States, including much of Arizona, will be at risk for localized flash flooding and isolated severe thunderstorms this week. That's the forecast for Thursday evening from AccuWeather.

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 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.

This pattern, which is a seasonal southerly breeze that brings higher humidity and tropical moisture northward from Mexico, helps to breathe life into the typically arid regions of the West. However, the thunderstorms generated during the pattern can sometimes be dangerous.

Through Thursday night, the swath that faces an elevated risk of thunderstorms with localized torrential rain and isolated strong wind gusts will extend from Arizona and New Mexico northward to Wyoming and portions of Idaho and Montana.

Parts of southeastern California and southern and eastern Nevada will share in the threat.

Individual storms have the potential to unload a half an inch of rain in a few minutes and more than an inch of rain during any downpour.

This is more than enough rain to cause flash flooding of countryside dry stream beds, called arroyos, and overwhelm storm drains in the large cities and small towns.

Even in urban areas such as Phoenix, Las Vegas, Salt Lake City and Denver, enough rain can pour down to cause urban flooding in some neighborhoods with little notice.

Hikers and motorists should keep an eye out for developing storms nearby.

Even if a particular area is directly missed by a thunderstorm, there is still a danger from a distance. Water can flow for miles downstream of the thunderstorm through canyons and across secondary roads.

"Lightning can strike areas well away from where it's raining," according to AccuWeather Meteorologist Courtney Travis.

If you can hear thunder, you are are at risk for being struck by lightning. Move indoors or seek shelter in a hard-top metal vehicle as storms approach.

"Lightning strikes in areas where little or no rain falls can also potentially spark a wildfire in grassy or wooded areas," Travis said.

Where rain has not fallen recently, strong wind gusts from distant thunderstorms can kick up a considerable amount of dust.

These dust storms, called haboobs, can travel for miles and bring a sudden drop in visibility, which poses a significant hazard for motorists traveling at highway speeds.

While the storms will take the edge off the heat in the region, humidity levels in most locations will be significantly higher when compared to this past weekend due to cloud cover and scattered downpours.

Late in the week and over the weekend, the overall size of the area of thunderstorms is forecast to shrink. However, there is still likely to be some thunderstorm activity centered over the Four Corners states.


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