Over the next few days, light to moderate rain will fall across the Sonoran and Chihuahuan Deserts of the American Southwest, bringing some relief to the ongoing drought in those areas. Across the higher terrain of Northern Arizona and New Mexico, the precipitation will fall as snow.
The benefactors for this scenario are a deep atmospheric trough across the Western U.S. and a "cutoff low" (i.e. not associated with a front) off the coast of Northwest Mexico. This low, spinning counterclockwise over the Pacific will sweep in moisture from both the ocean and the Gulf of California. Farther east, the southern edge of the trough will angle to the northeast, igniting showers and thunderstorms across Texas and the Gulf Coast States.
Meanwhile, high pressure over the Great Basin, interacting with the cutoff low, will send strong Santa Ana winds through the canyons of Southern California, increasing the risk for wildfires. In effect, the same atmospheric conditions may produce beneficial and destructive results in two adjacent geographic areas.
