The National Weather Service has issued a Flood Watch covering Scottsdale and Paradise Valley for Friday, Oct. 30, with scattered thunderstorms expected to bring locally heavy rain.

The NWS Phoenix office forecasts a 90% chance of rain for the Scottsdale and Paradise Valley zone on Friday. There is a chance of showers and thunderstorms in the morning, then showers and a chance of thunderstorms in the afternoon. Total rainfall of up to an inch is possible, with locally higher amounts in thunderstorms.

In the heaviest cells, rain could fall at rates of 1 to 2 inches per hour, according to Deep Arrival, which reported on the NWS watch. The NWS also noted a low-end chance that a few storms could become strong to severe, capable of damaging winds and large hail.

The Flood Watch for the Phoenix metro area runs from 6 a.m. to 6 p.m. MST on Friday, according to Deep Arrival. The NWS watch covers Scottsdale, Paradise Valley, Central and North Phoenix, Glendale, the East Valley, Fountain Hills, Buckeye, Avondale, Cave Creek, New River and Apache Junction, among other communities.

The NWS warned that runoff may flood rivers, creeks, streams and low-lying spots. Low-water crossings may also be flooded.

Highs on Friday will reach only 70 to 75 degrees, much cooler than recent days, with east winds of 5 to 10 mph.

Arizona's flooded-road law

Arizona's washes can go from dry to dangerous in minutes. Under the state's "Stupid Motorist Law," codified as Arizona Revised Statutes Section 28-910, drivers who go around barricades to enter a flooded roadway can be billed for the cost of their rescue, up to $2,000.

Six inches of water can cause a passenger car to lose control. Most passenger cars will float in 12 inches of water, and 24 inches can sweep away SUVs and trucks.

More rain expected Sunday

Saturday looks mostly dry, but the NWS Phoenix office expects another storm system to arrive Saturday night and last through much of Sunday, Nov. 1, according to Deep Arrival. The agency described moisture at record or near-record levels for this time of year, with an additional 1 to 2 inches possible around Phoenix and areas to its north and east.

Residents can check road closures and conditions at the state's AZ 511 site at az511.gov.