A strong upper level trough moved into the region with favorable ingredients for strong thunderstorms. Widespread severe thunderstorms brought severe hail and winds to the region, causing minor damage to structures.
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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 BOI wrote it up.
A strong upper level trough moved into the region with favorable ingredients for strong thunderstorms. Widespread severe thunderstorms brought severe hail and winds to the region, causing minor damage to structures.
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 Boise, ID wrote its last area forecast discussion before the first event at May 16, 12:03 PM PST, 12 minutes earlier.
Area Forecast Discussion National Weather Service Boise ID 203 PM MDT Tue May 16 2023 .SHORT TERM...Tonight through Thursday night...A weak but important upper level trough will move across the area tonight through Wednesday night, bringing a continuation of isolated to scattered showers and thunderstorms. The main areas that will be impacted by these showers and storms will be the north tonight, area-wide Wednesday, and the east Wed night and Thu. The trough will be east of us Thursday, but close enough to help showers and storms form (20-40% chance in the West Central and Boise Mountain zones). Temperatures will remain above normal by around 10 degrees. Winds will be typical for this time of year, following the normal diurnal cycle, with the exception of gusts to 40 mph near storms. .LONG TERM...Friday through Tuesday...An upper level ridge will build over the western U.S. on Friday, yielding temperatures of 10-15 degrees above average for this time of year. Enough elevated moisture, combined with daytime heating, will be present to allow for a small chance of showers and thunderstorms Friday afternoon (15% chance or less), and again on Saturday (15-30% chance). Temperatures should peak on Saturday for the week as the axis of the ridge shifts eastward and enhances the southerly flow aloft. These temperatures will continue to support high elevation snowmelt and contribute to fast and cold river/stream flows and hydrological concerns. A large Pacific trough is currently forecast to move onshore into the Pacific Northwest sometime on Sunday, which would generate enough lift and moisture to increase the threat of showers and thunderstorms for both Sunday and Monday (20-35% chance). The models are struggling with the timing of the cold front with this trough, but agree that temperatures will trend cooler beginning early next week. && .AVIATION...Mainly VFR. Scattered showers and thunderstorms through this evening. Highest coverage of storms expected over Baker County, OR including KBKE, the west-central Idaho and Boise mountains including KMYL, and south-central Idaho including KTWF/KJER. Erratic gusts to 30-40 kt and small hail possible, along with brief MVFR, with stronger storms. Surface winds outside of storms: variable 10 kt or less. Winds aloft at 10k feet MSL: W-SW 10- 20 kt. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && www.weather.gov/Boise www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...SP LONG TERM....SH AVIATION.....SH
The Pendleton radar (KPDT), 132 km away, was scanning. The volume nearest the first event began at 20:16 UTC.
3 hail. Local standard time, as filed.
Hail covered the ground south of the city. Mostly small hail was pea to dime size but there were a few quarter size hail stones with the storm.
Severe hail spotted along with 0.88 inches of rainfall.
Severe hail around one inch shared via social media photos.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2023Every state in 2023This day in weather historyWarnings in Oregon, 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: 1099584, 1099585, 1099587.