Deep moisture over northern Arizona lead to scattered thunderstorms with heavy rain that caused flash flooding.
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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 lead to scattered thunderstorms with heavy rain that caused flash flooding.
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 1, 2:23 PM MST, 1 hour 41 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 223 PM MST Sun Aug 1 2021 .SYNOPSIS...Scattered thunderstorms will continue through this evening before diminishing overnight. Expect decreasing thunderstorm chances Monday with a drying and warming trend in store Tuesday through Thursday as high pressure strengthens over the area. && .DISCUSSION...Scattered thunderstorms have developed this afternoon. The most pronounced activity has been across eastern Coconino, Navajo and Apache Counties with lesser activity to the west. A few of the stronger storms have been producing heavy rainfall and gusty outflow winds. Locally heavy rain and training storms leading to flash flooding will again be the main concern today. Scattered storms will continue over Navajo and Apache counties this evening before ending overnight. A downturn in thunderstorms is still expected to begin on Monday as strong high pressure over the Rocky Mountains builds westward and over the southwestern states. This will lead to a drier northwest flow over Arizona Monday, causing thunderstorm chances to retreat to the east. We'll still see isolated to scattered activity, but much less than the past several days. Lightning, gusty winds and locally heavy rain will be the main storm threats. Thunderstorm chances will continue the downward trend through the middle of the week with only isolated activity expected Tuesday through Thursday. In addition, the building high pressure and much more daytime sun will allow temperatures to rise above average. The lower elevations of the Grand Canyon will near heat warning criteria of 110F by Wednesday/Thursday. The high pressure ridge axis is forecast to slide east of Arizona on Friday opening the door again to a northward push of monsoon moisture. Operational and ensemble models are in agreement with the return of moisture and thunderstorm chances Friday through next weekend. && .AVIATION...For the 00Z package...Mainly VFR conditions will prevail. Scattered storms will continue through this evening, mainly along and north of a KFLG-KSOW line. Periods of MVFR/IFR conditions and gusty, erratic winds will occur in and around thunderstorms. Storm activity will gradually diminish after 03Z. Another round of isolated to scattered storms will develop after 18Z Mon. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Scattered thunderstorms with locally heavy rain will continue this evening. Look for decreasing thunderstorm chances Monday and Tuesday with a drying and warming trend. Wednesday through Friday...Warm and mainly dry conditions continue through midweek with light winds. Moisture and storm chances return Friday. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...MCT AVIATION...MCT FIRE WEATHER...MCT For Northern Arizona weather information visit weather.gov/flagstaff
Special Weather Statement National Weather Service Flagstaff AZ 303 PM MDT Sun Aug 1 2021 AZZ012-013-012130- Little Colorado River Valley in Coconino County-Little Colorado River Valley in Navajo County- 303 PM MDT Sun Aug 1 2021 ...A STRONG THUNDERSTORM WILL CONTINUE TO AFFECT THE WINSLOW AREA UNTIL 230 PM ARIZONA TIME... At 202 PM Arizona time, Doppler radar was tracking a strong thunderstorm near Winslow, moving north at 15 mph. Half inch hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Winslow. I-40 near Winslow. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3492 11074 3498 11091 3522 11087 3519 11061 TIME...MOT...LOC 2102Z 197DEG 11KT 3504 11079 TM
Special Weather Statement National Weather Service Flagstaff AZ 326 PM MDT Sun Aug 1 2021 AZZ012-013-012200- Little Colorado River Valley in Coconino County-Little Colorado River Valley in Navajo County- 326 PM MDT Sun Aug 1 2021 ...A STRONG THUNDERSTORM WILL CONTINUE TO MOVE NORTH OF WINSLOW THROUGH 300 PM ARIZONA TIME... At 224 PM Arizona time, Doppler radar was tracking a strong thunderstorm near Winslow, moving north at 10 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. This storm will remain over mainly rural areas north of Winslow and I-40. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3504 11071 3506 11088 3527 11088 3524 11059 TIME...MOT...LOC 2124Z 190DEG 10KT 3509 11078 TM
Special Weather Statement National Weather Service Flagstaff AZ 355 PM MDT Sun Aug 1 2021 AZZ009-039-012230- Black Mesa Area-Northeast Plateaus and Mesas Hwy 264 Northward- 355 PM MDT Sun Aug 1 2021 ...A STRONG THUNDERSTORM WILL CONTINUE TO DEVELOP NEAR KAIBITO THROUGH 430 PM NAVAJO NATION TIME... At 353 PM MDT, Doppler radar was tracking a strong thunderstorm east of Kaibito, or 36 miles northeast of Tuba City, moving northeast at 10 mph. Half inch hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Inscription House Landing Strip, Shonto, and Kaibito. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3637 11092 3641 11111 3680 11114 3665 11049 TIME...MOT...LOC 2153Z 211DEG 8KT 3657 11090 TM
Special Weather Statement National Weather Service Flagstaff AZ 312 PM MST Sun Aug 1 2021 AZZ012-016-012245- Little Colorado River Valley in Coconino County-Eastern Mogollon Rim- 312 PM MST Sun Aug 1 2021 ...A STRONG THUNDERSTORM WILL CONTINUE TO DEVELOP NEAR STARLIGHT PINES UNTIL 345 PM MST... At 311 PM MST, Doppler radar was tracking a strong thunderstorm near Starlight Pines, or 26 miles northwest of Forest Lakes, moving north at 15 mph. Half inch hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Starlight Pines, Blue Ridge Campground, Rock Crossing Campground and Chavez Mountain. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3445 11098 3452 11123 3492 11115 3487 11083 TIME...MOT...LOC 2211Z 192DEG 12KT 3466 11105 TM
Special Weather Statement National Weather Service Flagstaff AZ 315 PM MST Sun Aug 1 2021 AZZ013-016-012245- Little Colorado River Valley in Navajo County-Eastern Mogollon Rim- 315 PM MST Sun Aug 1 2021 ...A STRONG THUNDERSTORM WILL REMAIN NEAR CLAY SPRINGS UNTIL 345 PM MST... At 314 PM MST, Doppler radar was tracking a strong thunderstorm over Clay Springs, or 15 miles northwest of Show Low. This storm was nearly stationary. Half inch hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Clay Springs and Pinedale. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with this storm, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3430 11040 3448 11043 3447 11015 3428 11010 TIME...MOT...LOC 2214Z 273DEG 3KT 3435 11028 TM
Special Weather Statement National Weather Service Flagstaff AZ 321 PM MST Sun Aug 1 2021 AZZ012-015-012245- Little Colorado River Valley in Coconino County-Western Mogollon Rim- 321 PM MST Sun Aug 1 2021 ...A LINE OF THUNDERSTORMS WILL GRADUALLY MOVE SOUTHEAST ALONG I-40 BETWEEN TWIN ARROWS AND TWO GUNS UNTIL 345 PM ARIZONA TIME... At 319 PM Arizona time, Doppler radar was tracking a line of strong thunderstorms moving east of Twin Arrows along I-40. Pea size hail and winds in excess of 30 mph will be possible with these storms. Locations impacted include... Two Guns, Rimmy Jims, Twin Arrows, and Meteor Crater. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring with these storms, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 3529 11105 3492 11095 3498 11125 3531 11131 TIME...MOT...LOC 2219Z 307DEG 6KT 3525 11126 3501 11121 TM
The Flagstaff radar (KFSX), 143 km away, was scanning. The volume nearest the first event began at 23:06 UTC.
5 flash flood. Local standard time, as filed.
Substantial flooding was reported within Vernon. County Roads 3131, 3137, and 3187 were impassable.
Water and debris were flowing over the roadways in Polacca/Second Mesa.
A photo on social media showed a dirt road that was partially washed out north of Greasewood Springs Chapter House. A video on social media also showed a significant rise on wash.
A creek in Payson rose 19 inches. Water was flowing across one lane of Highway 87.
A video showed a significant rise of water flowing through the wash.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2021Every state in 2021This day in weather historyWarnings in Arizona, August 2021
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: 981905, 981995, 982012, 982000, 982003.