Flood watches have been issued for all of Arizona, including metro Phoenix and Tucson, effective from late Tuesday morning until late Wednesday evening.
Increasing tropical moisture will produce showers and thunderstorms capable of producing heavy rainfall, with the threat increasing Tuesday afternoon and continuing into Wednesday, the National Weather Service said.
Forecasters said locally heavy rainfall of up to 2 inches (5 centimeters) per hour combined with saturated ground will likely result in flash flooding in normally dry washes, small streams and poor drainage areas.
Low-water crossings are particularly vulnerable to flooding while burn scars from past wildfires are a particular concern because they’re prone to flash flooding and debris flow, the weather service said.
The Arizona Department of Transportation said particular areas of concern were southern Arizona, the Tonto Basin in hill country east of metro Phoenix and along U.S. 60 near Globe.
