Flooding is no longer a forecast in the Phoenix valley — it is happening. The National Weather Service (NWS) office in Phoenix kept Flood Warnings in force on Sunday, November 1, for the Salt River and the Rio Verde and Fort McDowell area in Maricopa County and for Tonto Creek in Gila County, after dam releases upstream sent rivers over their low-water crossings. This site covered the atmospheric-river Flood Watch earlier in the week and the water rescues in Phoenix and Scottsdale on Friday; the warnings mark the next, more serious stage of the same storm system, with flooding now confirmed rather than merely possible.
Source: National Weather Service Phoenix, via Storm Recovery Hub
The Salt River warning, issued at 3:52 p.m. MST on Saturday, October 31, runs until 7:45 a.m. MST on Monday, November 2. The weather service said flooding is occurring along the river because of an upstream floodgate release, and that low-water crossings are inundated and may not be passable, including near Granite Reef Dam and Tempe Marketplace. The Salt River Project (SRP) was releasing 1,650 cubic feet of water per second below Granite Reef Dam on Saturday, flooding low-water crossings upstream of Tempe Town Lake, including McKellips Road.
A second Maricopa County warning, issued at 2:41 p.m. MST on Saturday, covers Rio Verde and Fort McDowell until 8:00 a.m. MST on Monday. The weather service said flooding is already occurring there as streams keep rising from releases upstream from Bartlett Dam, on the Verde River northeast of Phoenix. A separate warning for Indian Bend Wash in Scottsdale, where gauges rose above alarm stage on Friday, has since expired.
In Gila County, east of the Phoenix metro, the weather service issued a Flood Warning at 10:26 p.m. MST on Saturday for Tonto Creek near Tonto Basin, also running until 8:00 a.m. MST on Monday. Forecasters said flooding is ongoing, the creek is expected to keep slowly rising for 12 to 24 hours, and people should use the Tonto Creek Bridge because the Bar X Crossing and other low-water crossings will likely become impassable.
A weekend that began with water rescues
The warnings follow a dangerous Friday evening, October 30, when NWS Phoenix flash flood warnings for Maricopa County said local law enforcement reported multiple water rescues after 0.75 to 2.25 inches of rain fell in a short time. The warnings covered Scottsdale, Paradise Valley and Scottsdale Airport, including Loop 101 between mile markers 36 and 43, and separately Phoenix, Paradise Valley, Piestewa Peak Park, Camelback Mountain and the Arizona State Fairgrounds, each carrying a considerable, life-threatening flash flood threat. Stream gauges stayed above alarm stage around Cave Creek, Carefree, Desert Mountain, New River and Anthem into the night.
Source: National Weather Service Phoenix warnings, Oct 30-31
Northern Arizona is in the same system. Early on Sunday, NWS Flagstaff issued a Flash Flood Warning for Yavapai County after 0.5 to 1.5 inches of rain, with 1 to 2 more inches possible and a considerable, life-threatening threat. Granite Creek at Prescott stood at 10.61 feet at 1:30 a.m., just under its 11-foot flood stage. Flood Watches run until 5:00 a.m. MST on Monday for the Phoenix, Tucson and Flagstaff areas, and the Weather Prediction Center placed parts of the Four Corners region under a Moderate Risk of excessive rainfall for Sunday, November 1.
Source: WeatherBoy / National Weather Service
Never walk, swim or drive through floodwater. Federal safety guidance says just six inches of moving water can knock a person down, and one foot of moving water can sweep a vehicle away. Never drive around barricades at flooded crossings.
Why Arizona is flooding
The rain is riding an atmospheric river — a long plume of Pacific moisture, fed in part by moisture from Vance, according to the National Hurricane Center — into ground that was already soaked by storms earlier in the week. Forecasters expected an additional 1 to 3 inches of rain across much of northern and central Arizona, with 4 to more than 6 inches possible on slopes facing the incoming moisture. When desert washes, normally dry crossings and dam-managed rivers all rise at once, the danger is less the rain itself than the water moving across roads built over those washes.
For drivers, including the many Punjabi truckers who run Interstate 10 and Interstate 17 through the Phoenix metro, the practical risks this weekend are flooded low-water crossings, water over frontage and surface roads near the Salt River bed around Tempe and Mesa, and fast-rising washes on rural routes in Gila and Yavapai counties. Arizona's official road information service, AZ511, carries live closures, and the weather service stresses that flooding impacts continue after the rain stops, especially at night.
What happens next: the river warnings expire on Monday morning, November 2 — 7:45 a.m. for the Salt River and 8:00 a.m. for Rio Verde, Fort McDowell and Tonto Creek — but they can be extended if releases or river levels stay high, and Tonto Creek was still expected to be rising into Sunday. The wider Flood Watches run until 5:00 a.m. Monday. Anyone living near the Salt River bed, the Verde River below Bartlett Dam or Tonto Creek should follow NWS Phoenix updates and county emergency messages through Sunday night rather than relying on the morning's conditions.