Deep monsoon moisture brought another round of thunderstorms across northern Arizona.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS FGZ wrote it up.
Deep monsoon moisture brought another round of thunderstorms across northern Arizona.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Flagstaff, AZ wrote its last area forecast discussion before the first event at Aug 25, 10:41 AM MST, 1 hour 19 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 1041 AM MST Sat Aug 25 2018 .SYNOPSIS...Deep monsoon moisture will bring another round of numerous showers and thunderstorms today, with scattered storms continuing Sunday. Drier air moving into the region will lead to a significant downturn in shower and thunderstorm activity through much of next week with most areas remaining dry. && .UPDATE...A mesoscale circulation centered east of Payson this morning is bringing an area of rain and thunderstorms to northern Gila, SE Coconino and southern Navajo counties this morning. Copious moisture is leading to some localized pockets of heavy rainfall, with a spotter report of 1.00" of rain in 15 minutes at Forest Lakes. The circulation is moving slowly toward the northwest. Elsewhere, instability is increasing with daytime heating. Storms are already developing near the San Francisco Peaks, just east of Prescott, and over the northeast AZ mountains. This morning's sounding at Bellemont showed little change in the air mass over the area, with perhaps a bit more instability due to cooler mid levels - in other words, look for another active day of storms. Main threat will be locally heavy rainfall and flash flooding, though gusty wind and hail are also likely with the stronger storms. Forecasts updated to increase storm chances today. Also raised Sunday afternoon's rain chances after getting a look at new model runs this morning. Updates sent. && .PREV DISCUSSION /452 AM MST/...A meso-scale circulation over east central Arizona is triggering showers and thunderstorms over southern Apache, southern Navajo, and northern Gila Counties this morning. Meso scale model shows this area of storms continuing and expanding northwestward through the day. Expect an active day across much of northern Arizona today. A trough of low pressure moving into the Pacific Northwest has gradually pushed monsoon moisture over the southern Great Basin eastward over the last two days. The boundary of 0.5 inch PW air has now moved into far southeastern Nevada this morning. This drier air will continue to push southeastward over the next several days and will result in a significant downturn in shower and thunderstorm activity Sunday through much of next week. Some isolated storms are possible in the White Mountains with dry conditions expected elsewhere through at least Thursday. A cut off low may form off the southern coast of California while a high center develops over the Southeastern States late next week. this would bring a return of deep moisture over Arizona. However, confidence is low that this pattern would develop. && .AVIATION...For the 18Z package...An area of steady shra/+shra and embedded tsra from KPAN-KSOW will persist through 18Z-19Z and will then slowly dissipate. Localized MVFR conditions exist in this region. Otherwise, expect sct-nmrs shra/tsra and isold +tsra to develop aft 18Z-19Z in other areas, but especially along and SW of a line from KFLG-KINW-KRQE. Brief MVFR/IFR in the heavier showers, Winds generally light. Conditions becmg VFR aft 01Z-02Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Monsoon moisture will remain in place today, with scattered to numerous thunderstorms developing. Greatest coverage is expected along over Yavapai county, northern Gila county, southern Coconino county and southern Navajo and Apache counties. Drier air moving into the region will slowly reduce thunderstorm chances on Sunday. Monday through Wednesday...A drier airmass will bring mostly sunny skies to the district, with afternoon fair weather cumulus, mainly over higher terrain. Temperatures will be near normal for late August. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...JJ/MAS AVIATION...Peterson FIRE WEATHER...Peterson For Northern Arizona weather information visit weather.gov/flagstaff
The Flagstaff radar (KFSX), 97 km away, was scanning. The volume nearest the first event began at 19:00 UTC.
8 flash flood, 1 heavy rain. Local standard time, as filed.
Big Bug Creek rose 2.1 feet in 70 minutes due to heavy rainfall near and over the Goodwin Fire scar upstream from the town of Mayer. Big Bug Creek flowing through Cordes Lakes rose by 3 feet in 45 minutes (415 PM).
Heavy rainfall caused Granite Creek in Prescott to rise 2.65 feet in 30 minutes.
Sycamore Creek near Dugas rose 2.71 feet in 70 minutes starting at 120 PM MST.
Pictures on social media showed 6 to 8 inches of water running over urban roadways and other land surrounding structures near Steamboat and State Route 264.
The Arizona Department of Transportation reported that State Route 264 was impassible in both directions at milepost 439 due to flash flooding caused by heavy rain.
Ten inches of water and debris were flowing across a roadway north of the town of Grease wood.
Swift water rescue was conducted around 350 PM to rescue a driver in 2.5 to 3 feet of water on Interstate 40 due to flooding of Black Creek near Houck. The I-40 frontage road (dirt) on the north side was impassible due to flooding through at least 630 PM.
The Agua Fria gauge (up stream from Big Bug Creek/Goodwin Fire scar) rose 3.6 feet in 70 minutes.
Arizona State Route 71 southbound was closed at milepost 95 west of US 93 due to a wash flowing over the roadway.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2018Every state in 2018This day in weather historyWarnings in Arizona, August 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 786355, 786354, 786398, 786357, 786358, 786359, 786399, 786407, 786400.