An unusually moist pattern for mid-May was in place over Arizona with precipitable water values around 200-250% of normal. This allowed for the development of strong to severe thunderstorms.
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 unusually moist pattern for mid-May was in place over Arizona with precipitable water values around 200-250% of normal. This allowed for the development of strong to severe thunderstorms. Two thunderstorms produced severe hail on May 17 in different counties.
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 May 17, 9:10 AM MST, 4 hours 45 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 910 AM MST Wed May 17 2023 .SYNOPSIS...Afternoon and evening showers and thunderstorms will continue through the week and into the weekend. Daytime temperatures will be near to slightly above normal. Storm threats each day will include lightning, small hail, and gusty winds. Brief heavy rain will lead to localized runoff and minor flooding. && .DISCUSSION...The Four Corners high has become disorganized and weaker in the last 48 hours, due to a trough in south-central Canada that will serve to move the high westward in the coming days. This has helped to destabilize our airmass, while keeping moisture levels about the same. 12Z sounding at KFGZ indicates decent instability and above normal moisture, additionally, surface dewpoints are now in the 40s and 50s statewide. This will lead to another active day for our CWA, with stronger convection along the Mogollon Rim and White Mountains, moving southward. Convection in the northeastern zones will be slow to start, due to extensive debris cloud and showers in the area. A weak upper low also continues to churn over the western Gulf of California. This will remain in place through the weekend, as the mid-level high strengthens and consolidates over western Nevada. This will keep easterly flow aloft over our area, with low-level southerly flow, there will be nothing to scour the moisture out. This active pattern will continue into at least early next week and maybe longer, depending on the strength of the western trough advertised for next week. Stay tuned. No short term updates are planned this morning. && .AVIATION...For the 18Z TAF Package...Mainly VFR conditions are expected for the 24 hour TAF forecast period. SCT-NMRS SHRA/TSRA and ISOLD +TSRA, mainly from 18Z-03Z, will produce localized MVFR. Sfc winds generally light and variable, with gusts to 40-45kts possible near any thunderstorms and outflows. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Wednesday and Thursday...Expect scattered to numerous afternoon and evening showers and thunderstorms each day. Generally light winds, although outflows and thunderstorm gusts may exceed 40 mph at times. Friday through Sunday...Expect scattered afternoon and evening showers and thunderstorms each day. Generally light winds, although outflows and thunderstorm gusts may exceed 40 mph at times. Storm coverage may decrease slightly by Sunday. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...Peterson AVIATION...Peterson FIRE WEATHER...Peterson For Northern Arizona weather information visit weather.gov/flagstaff
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
110 PM MST WED MAY 17 2023
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0105 PM HAIL 2 ESE FLAGSTAFF AIRPORT 35.13N 111.63W
05/17/2023 E0.25 INCH COCONINO AZ NWS EMPLOYEE
&&
RKRThe Flagstaff radar (KFSX), 89 km away, was scanning. The volume nearest the first event began at 20:54 UTC.
2 hail. Local standard time, as filed.
A report from Facebook showed that 1 1/2 inch hail fell two miles east-northeast of Fort Valley.
A report of 1 1/2 inch diameter hail from 5 miles north of Walker was received.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2023Every state in 2023This day in weather historyWarnings in Arizona, May 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: 1098477, 1098478.