Parts of Arizona had a lot of rain from hurricane remnants earlier in the month. That much rain in mountain/desert country can be very bad news.
They are used to the monsoons, but they rarely get these amounts of water at this time of year.
In the Phoenix Valley a week ago Monday, on the 8th, we all got blasted. It was the biggest single storm event for Phoenix on record. The whole valley got record amounts.
Cars thought they could get through 10” of water but passing trucks flooded them out and then the water went to 3’ deep on some of the interstates as vehicles were backed up waiting and unable to get off.
The ground, while desert dry, does not absorb like ground elsewhere where vegetation keeps top soil in place. Run-off is fast. Likewise there are drainage canals that flow into retention basin areas but in this storm the basins got so full the canals backed up and flooded whole subdivisions five hours after the storm was at its peak.
The tropical depression remnant is going to go more to the east of the valley and Tucson will get hit worse than Phoenix today and tomorrow. Arizona and New Mexico will get a lot of rainfall that they need as the Phoenix Valley by getting that last huge rain is still a half inch below annual average.
Ground water aquifers are 100 to 300 feet lower than they were sixty years ago.