A thunderstorm produce heavy rain over the Paria River drainage and caused flash flooding near Lees Ferry. Another thunderstorm caused flash flooding in Twin Arrows in the evening.
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The episode as NWS FGZ wrote it up.
A thunderstorm produce heavy rain over the Paria River drainage and caused flash flooding near Lees Ferry. Another thunderstorm caused flash flooding in Twin Arrows in the evening.
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 26, 8:40 PM MST, 2 hours 20 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 840 PM MST Mon Jul 26 2021 .SYNOPSIS...Scattered afternoon and evening showers and thunderstorms are expected through Tuesday with near average temperatures. Monsoonal moisture increases once again by Wednesday, extending into the weekend, resulting in widespread storm coverage across northern Arizona. && .UPDATE...Much of the activity across have diminished, aside from a few isolated showers mainly over far northern Arizona. Minor updates to the PoP grids this evening to incorporate radar trends and latest hi- res guidance. && .PREV DISCUSSION /310 PM MST/...Taking a look out the window this afternoon, mostly broken cloud cover is taking place with little to no wind. Current radar is showing some isolated to scattered thunderstorm activity popping up mainly west of I-17 into Yavapai County as well as for a few areas north of I-40. The later start to today's convection could be the result from the earlier cumulus development from this morning reducing daytime heating a bit. Expect storm chances to continue, tapering by sunset this evening. Global models, including the NBM, suggest much lesser shower and thunderstorm activity for Tuesday, however we are hesitant to "go all in" in this scenario. As the ridge of high pressure transitions and strengthens just north of the Rockies, the monsoonal flow pulls moisture a bit further west and north extending into the deserts of California and Nevada. Yes, this pattern reduces the moisture transport into Arizona with the majority of the GEFS and EPS members showing a decrease in PWAT values (1.1 to 0.6-0.7 inches by Tuesday afternoon), however low to mid-level, lingering moisture will remain present across much of the region during this time. This, coupled with enough daytime heating, should be sufficient enough for storm development to occur. No...not widespread, but some scattered coverage along the higher terrain, including the Mogollon Rim, White and Chuska Mountains, and the Kaibab Plateau. Hi-res guidance (HREF, HRRR, and SREF) support this forecast thinking. Moisture advection increases for Wednesday as the center of the ridge settles over the Rockies, resulting in a return to more widespread chances for thunderstorms across northern Arizona. PWAT values increase back to the 1.0-1.2 inch range by Thursday with higher confidence in flash flooding potential with 1-2 inch per hour rainfall rates likely. Similar thunderstorm activity, coverage, and impacts compared to last week is expected from Wednesday into the weekend. Average temperatures with generally light winds are also anticipated during this time. && .AVIATION...For the 06Z package...Mainly VFR condtions expected through the TAF period. Showers and thunderstorms possible after 18Z, mainly in the high terrain. Brief periods of MVFR conditions will be possible along with gusty and erratic winds in and around thunderstorms. Winds will otherwise be light. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Isolated to scattered afternoon and evening thunderstorms are expected through Tuesday. Moisture increases once again for Wednesday resulting in a return to widespread thunderstorms with the main threat being flash flooding, especially on burn scar areas. Daytime temperatures will warm to near-normal by mid-week with seasonal winds likely, outside of any gusty and erratic outflows from storms. Thursday through Saturday...Monsoonal moisture continues to increase into the weekend with widespread chances for thunderstorms across much of northern Arizona during this time. Some storms can be severe, however higher confidence exists in the main threat being flash flooding with rainfall rates of 1-2 inches per hour expected. Daytime temperatures will remain near- normal with generally light winds likely. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...Humphreys/LaGuardia AVIATION...Humphreys FIRE WEATHER...LaGuardia For Northern Arizona weather information visit weather.gov/flagstaff
The Cedar City radar (KICX), 138 km away, was scanning. The volume nearest the first event began at 05:58 UTC.
2 flash flood. Local standard time, as filed.
Heavy rain over the Paria River drainage (in Arizona and Utah) caused the river gauge at Lees Ferry to rise 2.5 feet.
Major portions of the Twin Arrows Casino were flooded. Flood debris went all over their roads.
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, July 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: 979574, 979576.