An increase in monsoon moisture brought strong thunderstorms over northern Arizona. One thunderstorm produced a landspout tornado.
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The episode as NWS FGZ wrote it up.
An increase in monsoon moisture brought strong thunderstorms over northern Arizona. One thunderstorm produced a landspout tornado.
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 9, 2:20 PM MST, 10 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 220 PM MST Sat Sep 9 2023 .SYNOPSIS...Showers and thunderstorms with varying amounts of coverage will continue each day. The highest chances for rainfall will be during the first half of next week. Much drier weather is expected during the later half of next week. The increase in moisture early next week will put an end to our above average daytime temperatures. && .DISCUSSION...Sufficient moisture and instability has allowed scattered showers and thunderstorms to develop over the higher terrain of northern Arizona this afternoon. Given the thermodynamic forcing, think this activity will wane after sunset with the loss of daytime heating. Tonight through Sunday, quasi-zonal flow will develop over northern Arizona as a weak trough moves over the Great Basin and across the AZ/UT border. The latest CAMs prog isolated convection to develop over northern Arizona Sunday afternoon, with a little better coverage along the AZ/UT border proximate to the trough axis. Given the generally westerly flow, think the storm motion will be too fast for any appreciable flooding threat. By Monday, weak ridging aloft should allow for a more typical diurnal pattern to develop over northern Arizona, with around a 30 percent chance of thunderstorms along the higher terrain features. On Tuesday, the medium range models continue to prog the remnant moisture from TS Jova will get swept up in the westerly flow aloft ahead of an approaching trough. As the trough moves into the Great Basin, thunderstorm chances should increase significantly over northern Arizona. However, if skies are clouded over, that would significantly reduce the amount of instability needed for it to precipitate. For now went with NBM PoPs for Tuesday, but would not be surprised if this event became a high PoP/low QPF type event. We'll see. By Wedensday and Thursday, drier air should begin building into the region as upper level ridging develops over the Pacific coast. Lingering moisture and instability should suffice to keep small chances for thunderstorms each afternoon. However, impacts are expected to be minimal at this time. Friday and Saturday, mainly dry conditions are expected over northern Arizona as the aforementioned ridge gradually builds and crests over the Intermountain West by the weekend. && .AVIATION...For the 00z TAFs...VFR conditions will generally prevail over northern Arizona through the TAF period. Isolated to scattered thunderstorms will clear by 01-03z this evening. Isolated thunderstorms will then develop mainly along and north of I-40 Sunday afternoon. Variable wind gusts up to 35 kts will be possible with storm outflows. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Sunday through Monday...There will be a 20-30% chance of thunderstorms along and north of I-40 Sunday afternoon. By Monday afternoon, there will be a 20-30% chance of thundestorms along the Mogollon Rim and Bradshaw Mountains. Above normal temperatures are forecast Sunday, with near normal temperatures expected by Monday. Tuesday through Thursday...Tuesday afternoon will see the highest chances for precipitation over northern Arizona during the week. Precipitation chances will gradually decrease Wednesday, and again Thursday. Below normal high temperatures are forecast each day, with highs around the lower 70s in the higher elevations, and in the 80s in elevations below 5000 feet. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && PUBLIC...TM AVIATION...TM FIRE WEATHER...TM For Northern Arizona weather information visit weather.gov/flagstaff
The Flagstaff radar (KFSX), 116 km away, was scanning. The volume nearest the first event began at 21:27 UTC.
1 tornado. Local standard time, as filed.
A landspout was reported near Chino Valley and was on the ground for one to two minutes.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2023Every state in 2023This day in weather historyThe tornado archive for Arizona, 2023Warnings in Arizona, September 2023
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: 1131444.