Hurricane Hilary: Could Arizona feel the effects from the powerful storm?

PHOENIX - As Hurricane Hilary continues to make its way north towards the U.S. from waters off the Pacific coast of Mexico, Arizonans are preparing for the possibility that the state could feel the impacts from the storm.

The hurricane is set to hit parts of Mexico and California this weekend. It's expected to downgrade to a tropical storm when it reaches southern California, but it's the first time in history that the West Coast has been under a Tropical Storm Watch or a Tropical Storm Warning. 

"Potentially four to six inches or higher," said Sean Benedict, the Lead Meteorologist with the National Weather Service in Phoenix, in reference to the potential for rain in parts of California. "In that three-day time span, that amount of rainfall would be equivalent to one or two years' worth of that normal annual rainfall for those areas."

While there is a chance for rain in Phoenix, southwestern Arizona, including Yuma, could feel the excess effects of the hurricane.

"You don’t often see a land-falling tropical cyclone in the U.S. on the West Coast," said Benedict.

Arizona could start to see some showers on Saturday, but some of the worst tropical impacts may be felt Sunday and Monday.

"Its potential is there for considerable flooding - and even localized catastrophic flooding," Benedict said.

Tony Badilla, the Yuma County Emergency Management Director, asks for residents to be alert and prepared.

"The National Weather Service just issued a High Wind Advisory for us. We’ll have winds up to 65 mph. Obviously, we’re gonna have up to an inch and a quarter of rain. I don’t know if that includes today or what. So we’re expecting the worst and preparing for that, so we’ll see how this plays out tomorrow. They did put a slight warning out for possible tornadoes along the Colorado River area, which is our area," he said.

They’re asking everyone to stay inside once the storm hits.

"With high winds, we want to anchor everything down that we can. Put everything away. Furniture, anything that could become a flying object," he said.

Experts say ocean water that is at least 79 degrees is a key ingredient for tropical storms and hurricanes. On the East Coast, warm water travels up from the south, causing these storms frequently. 

On the West Coast, however, ocean water travels from north to south, typically too cold for these storm conditions, which is what makes this weekend so rare. 

NWS Phoenix says Arizona will likely see the side effects with around 1–2 inches of rain throughout the weekend into early next week.

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Arizona weather forecast: How will Hurricane Hilary impact the state?

The best rain chances across the state will arrive this weekend. The pattern combines a typical monsoon setup, a high pressure "heat dome" to the east and a small area of low pressure to the west, with a tropical system: Hilary.

Flash flooding in Arizona may be possible, and emergency response teams from across the state are preparing for an influx of calls.

While good for the megadrought in the Southwest, Arizona's soil could have trouble soaking all of it up, so road conditions could become treacherous.

"You never know what the condition of the roadway underneath that water is," said Shawn Gilleland with the Rural-Metro Fire Department. "No matter how deep the water looks, it could be deeper than you anticipate. It could be moving faster than you anticipate. It really doesn’t take much. Maybe a foot or so of water to actually start to move a vehicle off the roadway."

The rain, no matter how severe, could even impact the Phoenix area.

"We also want to remind folks that are in the area or near burn scars - for instance, the Diamond Fire in North Scottsdale and Rio Verde - it’s going to change the flood patterns coming off the McDowell Mountains there, so there’s a potential for places to flood that haven’t previously flooded," said Gilleland.