Remnants of Hurricane Polo brought heavy rain and thunderstorms to Arizona on Tuesday, September 29, prompting flash flood warnings across parts of the state and disrupting conditions in and around Phoenix.
The National Weather Service issued a flash flood warning for Maricopa County after gauges recorded between 0.75in and 1.25in of rain, with a further 0.75in to 1.25in possible. Phoenix, New River, Cave Creek, Carefree, Anthem and Seven Springs were among the areas warned of life-threatening flooding.
Forecasters said the tropical moisture from Polo was interacting with an upper-level storm system moving across Arizona. The combination was expected to produce widespread showers and thunderstorms, particularly across central and south-eastern parts of the state.
In the Phoenix area, rain and thunderstorms were reported during the morning before conditions were expected to ease later in the day. The city was forecast to receive about half an inch of rain, with temperatures reaching 82F (28C).
Higher ground in northern and central Arizona faced the greatest rainfall threat, with totals of between 1in and 3in possible. The National Weather Service warned that heavy rain could quickly fill normally dry riverbeds and create dangerous flows through washes and low-water crossings.
Further warnings were issued in south-eastern Arizona, including Pima and Cochise counties, where radar indicated intense thunderstorms and additional rainfall of up to 2in. In parts of Pima and Pinal counties, officials reported that between 1in and 4in had already fallen, with more rain possible.
Residents were urged not to drive through flooded roads or attempt to cross moving water. The National Weather Service reiterated the warning to turn around rather than risk being swept away, as flash flooding remained possible into Tuesday evening.
