A surge of moisture from the Gulf of California brought more thunderstorms to northern Arizona with hail and strong winds.
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.
A surge of moisture from the Gulf of California brought more thunderstorms to northern Arizona with hail and 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 Aug 21, 12:46 PM MST, 3 hours 48 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 1246 PM MST Fri Aug 21 2020 .SYNOPSIS...An Excessive Heat Warning continues for the lower elevations of the Grand Canyon and Glen Canyon through this evening. High temperatures start a decreasing trend this weekend and should be close to seasonal normal by Tuesday. Scattered afternoon and evening thunderstorms are expected along and south of the Mogollon Rim through the weekend with isolated storms elsewhere. A more typical monsoon pattern is forecast next week with daily thunderstorm chances. && .DISCUSSION...Hot temperatures continue today as upper level high pressure remains centered over Arizona. The hottest temperatures in our forecast area will be across the mostly sunny far north nearest the UT border. Excessive Heat Warnings continue for the lower Grand Canyon and Page areas through this evening. Temperatures look to gradually lower over the weekend, though will still remain much above normal. We are anticipating a similar day as compared to yesterday with scattered afternoon thunderstorms developing over the Mogollon Rim and Coconino Plateau and drifting southwest into Yavapai county this evening. Isolated storms are possible elsewhere. The caveat is northward moving cloud cover from a remnant circulation over southern Arizona. This may impede on afternoon instability. If the clouds give way, moderate instability is forecast to develop with daytime heating south of the rim over Yavapai county and a few strong to severe storms may develop. A similar pattern is forecast through the weekend. As moisture spreads northward across Arizona, storm chances will correspondingly spread north covering all of Arizona. We anticipate a more typical monsoon pattern to be in place next week featuring scattered afternoon thunderstorms each day and more typical August temperatures. && .AVIATION...For the 00Z package...Isolated to scattered showers and thunderstorms will diminish after 03Z. Storms will be most numerous along and south of a KCMR-KFLG-KSOW line. Wind gusts to around 40 kt and localized MVFR conditions near stronger storms. Otherwise, winds generally light less than 15 kts. Another similar round of storms on Saturday. Aviation discussion not updated for amendments. && .FIRE WEATHER...Look for scattered afternoon and evening thunderstorms on Saturday and Sunday with most activity extending from the Coconino plateau along the Mogollon Rim to the White Mountains, moving west to southwest into the evening. A bit cooler temperatures are in store from Saturday into Sunday. Monday through Wednesday...Daily chances for showers and thunderstorms will persist with the potential for a decent coverage of wetting rain by Tuesday and Wednesday. Daytime temperatures will return to near normal. && .FGZ WATCHES/WARNINGS/ADVISORIES...Excessive Heat Warning until 8 PM MST this evening FOR AZZ005-006. && PUBLIC...MCT AVIATION...McCollum FIRE WEATHER...McCollum For Northern Arizona weather information visit weather.gov/flagstaff
Special Weather Statement National Weather Service Flagstaff AZ 214 PM MST Fri Aug 21 2020 AZZ015-016-212145- Western Mogollon Rim-Eastern Mogollon Rim- 214 PM MST Fri Aug 21 2020 ...SIGNIFICANT WEATHER ADVISORY FOR NEAR MORMON LAKE IN COCONINO COUNTY UNTIL 245 PM MST... At 213 PM MST, Doppler radar was tracking a strong thunderstorm over Mormon Lake, or 20 miles east of Sedona, moving south at 5 mph. Half inch hail and wind gusts up to 50 mph will be possible with this storm. Locations impacted include... Mormon Lake, Dairy Springs Campground and Double Springs Campground. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3500 11148 3496 11133 3480 11138 3487 11159 TIME...MOT...LOC 2113Z 016DEG 6KT 3492 11144 MCT
Special Weather Statement National Weather Service Flagstaff AZ 246 PM MST Fri Aug 21 2020 AZZ017-018-212215- Northern Gila County-White Mountains- 246 PM MST Fri Aug 21 2020 ...SIGNIFICANT WEATHER ADVISORY FOR NEAR WHITERIVER IN GILA...APACHE AND NAVAJO COUNTIES UNTIL 315 PM MST... At 243 PM MST, Doppler radar was tracking a strong thunderstorm near Whiteriver, or 31 miles south of Show Low, moving southwest at 10 mph. Penny size hail and wind gusts up to 50 mph will be possible with this storm. Locations impacted include... Turkey Creek, Seven Mile, Fort Apache, Whiteriver and East Fork. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3391 10989 3384 10972 3367 10982 3377 11003 TIME...MOT...LOC 2143Z 027DEG 8KT 3382 10986 MCT
Special Weather Statement National Weather Service Flagstaff AZ 313 PM MST Fri Aug 21 2020 AZZ016-018-212245- Northern Gila County-Eastern Mogollon Rim- 313 PM MST Fri Aug 21 2020 ...SIGNIFICANT WEATHER ADVISORY FOR GILA AND COCONINO COUNTIES NEAR WHITERIVER UNTIL 345 PM MST... At 312 PM MST, Doppler radar was tracking a strong thunderstorm 7 miles northeast of Washington Park. This storm was moving west southwest. Penny size hail and winds in excess of 40 mph will be possible with this storm. Locations impacted include... Tonto Village, Washington Park, Whispering Pines, Mead Ranch, Clints Well, Knoll Lake Campground, Kehl Springs Campground, Water Wheel Burn At Houston Mesa Rd-N and Clints Well Campground. LAT...LON 3457 11110 3440 11104 3423 11123 3455 11137 TIME...MOT...LOC 2212Z 073DEG 4KT 3447 11116 ET
Special Weather Statement National Weather Service Flagstaff AZ 340 PM MST Fri Aug 21 2020 AZZ008-015-037-038-212315- Yavapai County Valleys and Basins-Western Mogollon Rim-Yavapai County Mountains-Oak Creek and Sycamore Canyons- 340 PM MST Fri Aug 21 2020 ...SIGNIFICANT WEATHER ADVISORY FOR SEDONA AND OAK CREEK YAVAPAI AND COCONINO COUNTIES UNTIL 415 PM MST... At 339 PM MST, Doppler radar was tracking a strong thunderstorm over Sedona, moving southwest at 25 mph. Penny size hail and wind gusts up to 50 mph will be possible with this storm. Locations impacted include... Sedona, Bridgeport, Village At Oak Creek, Garland's Oak Creek Lodge, Page Springs, Cornville, Slide Rock State Park, Cottonwood, Red Rock State Park, Dead Horse Ranch State Park, Manzanita Campground and Tuzigoot National Monument. LAT...LON 3503 11184 3481 11156 3462 11190 3482 11210 TIME...MOT...LOC 2239Z 048DEG 21KT 3485 11181 ET
Special Weather Statement National Weather Service Flagstaff AZ 353 PM MST Fri Aug 21 2020 AZZ008-037-212345- Yavapai County Valleys and Basins-Yavapai County Mountains- 353 PM MST Fri Aug 21 2020 ...SIGNIFICANT WEATHER ADVISORY FOR SELIGMAN IN YAVAPAI COUNTY UNTIL 445 PM MST... At 352 PM MST, Doppler radar was tracking a strong thunderstorm 12 miles west of Seligman, or 50 miles northeast of Wikieup. This storm was nearly stationary. Nickel size hail and wind gusts up to 50 mph will be possible with this storm. This storm will remain over mainly rural areas of Yavapai County. LAT...LON 3539 11306 3521 11292 3509 11317 3532 11333 TIME...MOT...LOC 2252Z 061DEG 4KT 3528 11309 ET
Special Weather Statement
National Weather Service Flagstaff AZ
406 PM MST Fri Aug 21 2020
AZZ016-018-212330-
Northern Gila County-Eastern Mogollon Rim-
406 PM MST Fri Aug 21 2020
...SIGNIFICANT WEATHER ADVISORY FOR GILA COUNTY NEAR PINE AND
COCONINO COUNTY UNTIL 430 PM MST...
At 405 PM MST, Doppler radar was tracking a strong thunderstorm over
Pine, or 11 miles northwest of Payson, moving west at 10 mph.
Penny size hail and wind gusts up to 50 mph will be possible with
this storm.
Locations impacted include...
Geronimo Estates, Freedom Acres, Flowing Springs, Pine, Strawberry,
Geronimo Boy Scout Camp, Water Wheel Burn At Houston Mesa Rd-
S, Tonto Natural Bridge State Park and Beaver Valley.
LAT...LON 3423 11155 3439 11158 3441 11156 3442 11153
3443 11148 3446 11140 3433 11127
TIME...MOT...LOC 2305Z 080DEG 10KT 3439 11142
ETThe Flagstaff radar (KFSX), 79 km away, was scanning. The volume nearest the first event began at 23:32 UTC.
1 thunderstorm wind. Local standard time, as filed.
A trained spotter reported strong winds, nickel sized (0.88 inch) hail, and heavy rain.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2020Every state in 2020This day in weather historyWarnings in Arizona, August 2020
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: 915245.