An upper-level short-wave helped lead to clusters of weak thunderstorms the morning of August 2. Early in the event, there were a couple of wind reports with a 71 mph wind measured at the Norfolk Airport.
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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 OAX wrote it up.
An upper-level short-wave helped lead to clusters of weak thunderstorms the morning of August 2. Early in the event, there were a couple of wind reports with a 71 mph wind measured at the Norfolk Airport. A moisture rich environment led to efficient downpours from thunderstorms. Additionally, clusters tracked over the same locations helping lead to high rainfall totals. There were several reports of 3 to 4 inches of rainfall which led to flash flooding across the area.
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 Omaha, NE wrote its last area forecast discussion before the first event at Aug 2, 3:20 AM CST, 1 hour 50 minutes earlier.
Area Forecast Discussion National Weather Service Omaha/Valley NE 420 AM CDT Wed Aug 2 2023 ...Updated Forecast Discussion... .DISCUSSION... Issued at 419 AM CDT Wed Aug 2 2023 Key Messages: - Heavy rain potential will continue through Wednesday morning, primarily focused across east central NE and southwest IA. - Potential for strong to severe storms across the region Saturday afternoon/night. - Cooler/dryer conditions expected for the end of this weekend/early next week. ...Today and Tonight... Ongoing morning convection across western Iowa and east central Nebraska is expected to continue through the morning hours. An MCS is also expected to move through southeast/east central Nebraska in this same time frame. Both regions of convection will produce regions of heavy rain with a risk for flash flooding, with the primary flooding risk across portions of southwestern Iowa. There is also the potential for strong to marginally severe wind gusts with the MCS, primarily before sun rise. These storms are in association with a weak midlevel disturbance that moved into the central Plains yesterday evening. As this system moves to the east over the course today, rain chances will shift to the east and move out of the region by this evening. While the highest risk for thunderstorms and heavy rain will be in the morning, lingering cloud cover and showers still appears likely through the afternoon today. There are no strong frontal boundaries associated with this system, so temperatures will remain slightly below average with highs in the low to mid 80s and humidity will remain high with dew points region wide in the low to mid 70s. ... Tomorrow and Tomorrow Night... Warm and humid conditions are expected to persist across the region through the day tomorrow. By late tomorrow night, another round of showers and thunderstorms appears possible as a weakening complex of storms should move into the region from the west/northwest. The biggest potential for rain should be after midnight and west of US-77. These storms are not expected to be severe. ...Friday through Tuesday... A shortwave trough is expected to eject into the northern Plains Friday night into Saturday and approach the region from the northwest. As such, there will be chances for storms across the region Friday night and Saturday evening/night. Thunderstorm coverage and intensity is expected to be higher for Saturday as this is when the surface low pressure associate with the upper level disturbance and its surface fronts are forecast to move through eastern NE/western IA. Storms are not anticipated to be severe Friday night, however the potential exists for strong to severe thunderstorms across the region Saturday evening/night. At this time, specific details on severe mode, intensity and timing are unclear. Behind the cold front that should pass through the area Saturday night, conditions should be cooler and drier with high temperatures in the upper 70s/low 80s and dew points in the mid 50s to lower 60s. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1155 PM CDT Tue Aug 1 2023 Mid-level clouds are finally sweeping east and dissipating, allowing the development of a IFR deck across the eastern half of the area overnight. Have kept these FL009-FL011 through daybreak for most locations. Have watched some BR develop in the northern half of the CWA. Expect to see vis slip as low as one mile or so at OFK. Have opted to keep the fog out of the TAF for OMA and LNK, but confidence is not high in that regard. Have slowed thunderstorm passage for OMA and have now included at LNK. The first few storms may fire northeast of these areas with a second wave pushing through between 10Z and 12Z. Heavy rain will be their primary threat. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && DISCUSSION...Darrah AVIATION...Nicolaisen
Hazardous Weather Outlook National Weather Service Omaha/Valley NE 431 AM CDT Wed Aug 2 2023 IAZ043-055-056-069-079-080-090-091-NEZ011-012-015>018-030>034- 042>045-050>053-065>068-078-088>093-022345- Monona-Harrison-Shelby-Pottawattamie-Mills-Montgomery-Fremont- Page-Knox-Cedar-Thurston-Antelope-Pierce-Wayne-Boone-Madison- Stanton-Cuming-Burt-Platte-Colfax-Dodge-Washington-Butler- Saunders-Douglas-Sarpy-Seward-Lancaster-Cass-Otoe-Saline- Jefferson-Gage-Johnson-Nemaha-Pawnee-Richardson- 431 AM CDT Wed Aug 2 2023 This Hazardous Weather Outlook is for portions of southwest Iowa...west central Iowa...east central Nebraska...northeast Nebraska and southeast Nebraska. .DAY ONE...Today and Tonight Widespread thunderstorms are expected across portions of east central Nebraska and southwest Iowa before noon today. The strongest storms have the risk of small hail and gusty winds. There is also a risk for localized flash flooding. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday There are nightly chances for thunderstorms through Saturday night. The overall threat for severe weather is low Thursday and Friday night, but a few storms could contain small hail, gusty winds, or localized heavy rainfall. There is a higher potential for strong to severe thunderstorms across the region Saturday evening/night. It's recommended to periodically check the forecast for updates. .SPOTTER INFORMATION STATEMENT... Spotters should not be needed tonight.
Special Weather Statement
National Weather Service Omaha/Valley Nebraska
159 AM CDT Wed Aug 2 2023
IAZ069-020715-
Pottawattamie IA-
159 AM CDT Wed Aug 2 2023
...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL POTTAWATTAMIE
COUNTY THROUGH 215 AM CDT...
At 159 AM CDT, Doppler radar was tracking a strong thunderstorm 8
miles south of Walnut, or 8 miles west of Atlantic, moving east at 10
mph.
HAZARD...Nickel size hail.
SOURCE...Radar indicated.
IMPACT...Minor hail damage to vegetation is possible.
This storm will remain over mainly rural areas of east central
Pottawattamie County.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4128 9528 4146 9527 4147 9516 4139 9515
4126 9516
TIME...MOT...LOC 0659Z 271DEG 8KT 4137 9518
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH
DeWaldSpecial Weather Statement
National Weather Service Omaha/Valley Nebraska
204 AM CDT Wed Aug 2 2023
IAZ069-020715-
Pottawattamie IA-
204 AM CDT Wed Aug 2 2023
...A STRONG THUNDERSTORM WILL IMPACT NORTH CENTRAL POTTAWATTAMIE
COUNTY THROUGH 215 AM CDT...
At 203 AM CDT, Doppler radar was tracking a strong thunderstorm near
Minden, or 18 miles southwest of Harlan, moving east at 25 mph.
HAZARD...Winds in excess of 30 mph and nickel size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down small tree branches and blow
around unsecured objects. Minor hail damage to vegetation
is possible.
Locations impacted include...
Neola, Shelby, Minden, and Arrowhead Park.
This includes Interstate 80 in Iowa between mile markers 20 and 34.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4137 9564 4150 9565 4150 9540 4137 9540
TIME...MOT...LOC 0703Z 264DEG 20KT 4143 9554
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH
DeWaldSpecial Weather Statement
National Weather Service Omaha/Valley Nebraska
206 AM CDT Wed Aug 2 2023
IAZ055-069-NEZ045-020715-
Pottawattamie IA-Harrison IA-Washington NE-
206 AM CDT Wed Aug 2 2023
...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN POTTAWATTAMIE...
SOUTHWESTERN HARRISON AND SOUTHEASTERN WASHINGTON COUNTIES THROUGH
215 AM CDT...
At 206 AM CDT, Doppler radar was tracking a strong thunderstorm 3
miles southwest of Missouri Valley, or 9 miles east of Blair, moving
southeast at 25 mph.
HAZARD...Winds in excess of 30 mph and nickel size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down small tree branches and blow
around unsecured objects. Minor hail damage to vegetation
is possible.
Locations impacted include...
Missouri Valley, Fort Calhoun, Modale, Desoto Bend National Wildlife
Refuge, Wilson Island State Park, and Historical Village Welcome
Center.
This includes Interstate 29 between mile markers 68 and 79.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4145 9607 4162 9606 4161 9578 4144 9579
TIME...MOT...LOC 0706Z 294DEG 20KT 4153 9595
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH
DeWaldThe Omaha radar (KOAX), 116 km away, was scanning. The volume nearest the first event began at 11:10 UTC.
2 thunderstorm wind, 2 flash flood. Local standard time, as filed.
Norfolk Airport ASOS measured a peak wind gust of 71 mph.
Emergency manager reported a 30-inch diameter tree snapped off.
Broadcast media relayed report of significant road flooding as well as flooding in yards from the public.
Public reported 5 to 6 inches of water flowing over Highway 30.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Nebraska in 2023Every state in 2023This day in weather historyWarnings in Nebraska, August 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: 1124293, 1124294, 1124296, 1124297.