An upper-level trough stretched from Utah southward into Arizona and a cold front near the Utah-Arizona border gradually moved southward triggering strong thunderstorms over far 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.
An upper-level trough stretched from Utah southward into Arizona and a cold front near the Utah-Arizona border gradually moved southward triggering strong thunderstorms over far 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 Sep 28, 2:40 PM MST, 3 hours 20 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 240 PM MST Tue Sep 28 2021 .SYNOPSIS... Breezy southwest winds will continue today with showers and thunderstorms in the east. Scattered showers and thunderstorms will continue across northern Arizona each day through Thursday. Drier and warmer conditions are forecast for the weekend with a return to more seasonable fall weather. && .DISCUSSION...A weak transitional ridge is moving through Arizona today and is helping to suppress convective activity across much of the state. The exception is in Apache county where there's enough instability to maintain scattered thunderstorms. A few of these storms will produce isolated heavy rain. Elsewhere, low level clouds have been persistent through the afternoon but are gradually beginning to thin. Cool temperatures continue today while breezy southwest winds of 20-30 mph will also continue through early evening. Low clouds are likely to redevelop over the high terrain tonight with a few areas of patchy possible as well. A deepening trough and associated cool front will move through southern Utah and into Arizona tonight and will then remain over Arizona through Thursday night. This will continue the cool and unsettled weather pattern with daily chances for showers and thunderstorms. The biggest changes this afternoon were to increase the chance for showers tonight through Wednesday morning across far northern Arizona and then again Wednesday night/Thursday morning for areas mainly southeast of Flagstaff. Daytime temperatures will cool further for Wednesday and Thursday with the trough passage and additional cloud cover. Drier and warmer weather finally arrives by Friday when the aforementioned trough moves east of Arizona and high pressure builds over the region through the weekend. The coldest night looks to be Thursday night/Friday morning when a few higher elevation cold spots may drop below freezing temperatures. Otherwise, expect warming temperatures over the weekend. There's a possibility of another weak cut off low moving into the region early next week bringing additional rain chances, but we have low confidence in the timing of this feature right now. && .AVIATION...For the 00Z package...Breezy southwest winds continue this afternoon, weakening by 03z. IFR conditions may be interrupted briefly by MVFR as low stratus lingers over high terrain from KGCN-KSEZ. Scattered to isolated showers and storms will continue into the evening. Ceilings approach MVFR heights for higher elevations tomorrow morning, but there is some uncertainty around cloud heights. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Cool temperatures with winds out of the southwest Wednesday, becoming lighter and more variable by Thursday. A chance of rain remains in the forecast both days with precipitation shifting eastward by Thursday. Friday through Sunday...Northern Arizona will begin drying out on Friday with only isolated showers and storms expected towards the New Mexico border. Light winds and a warming trend will last through the weekend. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...MCT AVIATION...JM FIRE WEATHER...JM For Northern Arizona weather information visit weather.gov/flagstaff
Special Weather Statement
National Weather Service Flagstaff AZ
235 PM MST Tue Sep 28 2021
AZZ014-282200-
Little Colorado River Valley in Apache County-
235 PM MST Tue Sep 28 2021
...A strong thunderstorm will impact portions of Apache County
through 300 PM MST...
At 234 PM MST, Doppler radar was tracking a strong thunderstorm near
Concho, or 26 miles northeast of Show Low, moving east at 15 mph.
HAZARD...Winds in excess of 30 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Concho and Little Ortega Lake.
This includes State Route 61 between mile markers 363 and 379.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 3438 10974 3451 10969 3450 10942 3430 10952
TIME...MOT...LOC 2134Z 287DEG 14KT 3444 10964
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...30 MPH
DBThe Cedar City radar (KICX), 115 km away, was scanning. The volume nearest the first event began at 00:58 UTC.
1 hail. Local standard time, as filed.
A thunderstorm produce hail up to 1 and 3/4 inches in diameter about 9 miles west-southwest of Jacobs Lake.
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, September 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: 986786.