Deep moisture over northern Arizona brought thunderstorms with heavy rain across the area. The sounding at Flagstaff (over 7000 feet) had a precipitable water content of over an inch.
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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 moisture over northern Arizona brought thunderstorms with heavy rain across the area. The sounding at Flagstaff (over 7000 feet) had a precipitable water content of over an inch. At least one thunderstorm produce strong winds.
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 Jul 21, 10:10 AM MST, 3 hours 22 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 1010 AM MST Fri Jul 21 2017 .SYNOPSIS...Expect very active monsoon conditions for the next several days. Local heavy rainfall capable of producing flash flooding remains possible from stronger storms. && .Discussion...The morning sounding showed a Pwat of 1.04" (very wet!) with light steering winds. Visible satellite loop showed two MCVs in the area--one over northern Navajo and Apache Counties and one southeast of Alpine this morning. These circulations will help trigger storms (already doing so at 1000 AM) today and will also influence the directions that storms will move. We expect another active day today with locally heavy rain. Some storms may also last through the evening and night. May have to adjust POPs up for the overnight hours. && .Prev DISCUSSION /307 PM MST/...Monsoon moisture will remain entrenched across all of northern Arizona today. The steering flow, albeit weak, will tend to guide storms south to southeastward. The primary forcing mechanism will be daytime heating with showers and storms tending to develop over the mountain areas first before moving into the valleys and lower elevation locations in the mid to late afternoon. Storms today will be slow moving with stronger/more organized storms capable of producing 1 to 3 inch downpours. Therefore, flooding will be the main threat from stronger storms today. For Saturday and Sunday...The forecast models are still insisting that a northeast to southwest flow sets up across Arizona in response to high pressure becoming centered over Nevada/Utah/Arizona. The described flow pattern will deliver a drier air mass to the northeast corner of Arizona with a decrease in shower and storm activity. From the Mogollon Rim and White Mountains southward and across central Arizona monsoon moisture will remain entrenched with a good chance of showers and storms each day. From Monday onward...Moisture will remain in place with the threat for daily showers and thunderstorms continuing. && .AVIATION...For the 18Z package...Expect scattered to numerous SHRA and TSRA developing into early evening, with isolated +TSRA. MVFR/IFR in the stronger storms. Shower and thunderstorm coverage gradually decreasing after 03Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Active monsoon conditions will continue with scattered to numerous showers and thunderstorms through Saturday. Heavy rain and gusty winds will remain the primary impact. Expect near average temperatures across the area. Sunday through Tuesday....Daily chances for showers and thunderstorms continue, favoring the Mogollon Rim southward Sunday, then all of northern Arizona Monday and Tuesday. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...MAS/McCollum AVIATION...DL/JJ For Northern Arizona weather information visit weather.gov/flagstaff
Hazardous Weather Outlook National Weather Service Flagstaff AZ 314 AM MST Fri Jul 21 2017 AZZ004>018-037>040-220345- Kaibab Plateau-Marble and Glen Canyons-Grand Canyon Country- Coconino Plateau-Yavapai County Mountains- Northeast Plateaus and Mesas Hwy 264 Northward-Chinle Valley- Chuska Mountains and Defiance Plateau- Little Colorado River Valley in Coconino County- Little Colorado River Valley in Navajo County- Little Colorado River Valley in Apache County- Western Mogollon Rim-Eastern Mogollon Rim-White Mountains- Northern Gila County-Yavapai County Valleys and Basins- Oak Creek and Sycamore Canyons-Black Mesa Area- Northeast Plateaus and Mesas South of Hwy 264- 314 AM MST Fri Jul 21 2017 This hazardous weather outlook is for Apache...Coconino... Northern Gila...Navajo...and Yavapai Counties in Northern Arizona. .DAY ONE...Today and Tonight Look for another round of scattered to numerous showers and thunderstorms. The steering flow aloft will be weak so storms today will be slow moving and capable of dropping 1 to 3 inch downpours. As a result, flash flooding will be possible with stonger storms. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Daily thunderstorms will continue into the middle of next week with the usual day-to-day variations of coverage and intensity. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
1010 AM MST FRI JUL 21 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0300 PM FLASH FLOOD 4 W FOREST LAKE 36.30N 110.38W
07/20/2017 NAVAJO AZ PUBLIC
AN ESTIMATED 2-3 FT. RISE IN THE DINNEBITO
WASH ALONG NAVAJO ROUTE 41. PICTURE FROM
SOCIAL MEDIA. TIME IS APPROXIMATE.
&&
TMThe Flagstaff radar (KFSX), 97 km away, was scanning. The volume nearest the first event began at 20:29 UTC.
2 flash flood, 2 heavy rain, 1 thunderstorm wind. Local standard time, as filed.
Heavy rain over the Goodwin Fire scar caused Big Bug Creek to flash flood in Meyer. The waster rose 2 to 2.5 feet (50 feet wide) at the Central Avenue Bridge.
Cedar Creek rose 8 feet at the Highway 73 Bridge after a thunderstorm dropped heavy rain over the Cedar Fire scar (June 2016).
A thunderstorm over Williams produce 1.37 inches of rain in 40 minutes, very gusty winds, and lots of lightning. Moderate street flooding was observed in the neighborhood southwest of Downtown.
Strong thunderstorm winds snapped a tree trunk greater than 12 inches in diameter in front of the Clemenceau Heritage Museum. The thunderstorm also produced penny sized hail and over an inch of rain in 30 minutes.
A thunderstorm began producing heavy rain in the Payson area by 419 PM MST. A spotter measured 1.10 inches of rain in 45 minutes. The street and neighbor's front yard flooded with no damage.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2017Every state in 2017This day in weather historyWarnings in Arizona, July 2017
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: 718711, 718712, 718715, 718714, 718716.