Heavy rain caused localized flooding in parts of Chicago during the morning of September 26th.
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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 LOT wrote it up.
Heavy rain caused localized flooding in parts of Chicago during the morning of September 26th.
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 Chicago, IL wrote its last area forecast discussion before the first event at Sep 26, 5:32 AM CST, 3 hours 23 minutes earlier.
Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 632 AM CDT Tue Sep 26 2023 .SHORT TERM... Issued at 237 AM CDT Tue Sep 26 2023 Through Wednesday... A steady stream of showers and thunderstorms are ongoing over Winnebago and Boone County and southwestward to northern Lee County at the time this discussion was published. These storms are firing along a band of mid-level moisture that stretch back to the center of lower pressure over the southeastern Minnesota and northeastern Iowa border. The band itself has only moved this far east from the Mississippi River in the last two hours, meaning it is moving eastward fairly slowly. Showers and storms will like continue for the Wisconsin/Illinois border through Tuesday morning, which will likely result in a very wet commute for the Chicago metro area. Periods of moderate to heavy rain has been observed on radar. Localized ponding on roadways is possible, especially as new cells develop over the same area. Additionally in the immediate short term, isolated cells have developed on the southern edge of the band along a Tazewell to Livingston County line. At the moment, the similar flare up and dissipate due to the lesser amounts of deep moisture through the column with no lightning (yet). Big picture messaging for Tuesday and Wednesday has not changed. The aforementioned low will continue to move southeastward over eastern Iowa and north-central Illinois over the next 48 hours. Rain is likely through the forecast period. Small breaks in the rain may be possible as bands of higher moisture content rotate around the low as it descends. With precipitable water amounts in the 1 to 1.3 inch range, which is fairly robust for late September, sufficient CAPE, and descent mid level lapse rates expected to advect over northern Illinois, funnel clouds or even a brief tornado cannot be ruled out. Afternoon wind shear profiles range from 15 to 25 knots, and while for severe threats it would nice to be more robust, it is plenty adequate to possibly develop some hail with these storms. Additionally, with plenty DCAPE available as well, strong wind gusts are possible with the day's storms. The Storm Prediction Center put northern Illinois and northwest Indiana in a Marginal chance for severe weather (level 1 out of 5) as well as the Weather Prediction Center placing a marginal threat (level 1 out of 4) for excessive rainfall that can lead to flooding, especially for areas that have recently received heavy rains. While storms are expected over the next 48 hours, the one area of lower confidence is the exact timing that the system exits the area. The parent low has been moving very slowly. Admittedly models have been consistent passing the low to the east by Thursday morning, so there's no reason to deviate from that thinking. The main stronger storms are expected on Tuesday and then that threat moves to Indiana and western Ohio on Wednesday. Trends will be monitored in case the storm threat needs to be updated. Storm chances diminish overnight Wednesday into Thursday morning. DK && .LONG TERM... Issued at 226 AM CDT Tue Sep 26 2023 Thursday through Monday... Forecast concerns include a low chance for lingering showers Thursday and then an early Fall warmup through early next week. As the upper low moves east of the area on Thursday, there is a small chance for a few lingering showers, mainly across northwest IN though its possible that the bulk of any precip on Thursday will be east of the cwa. Most, possibly all of the area will likely be dry. Models remain in good agreement with an upper ridge building across the region from Thursday night into early next week. This will allow for dry and warm conditions with above normal temps. Blended highs are still generally in the upper 70s/near 80 and these could end up too cool. Easterly winds will keep the lakeshore areas cooler. cms && .AVIATION... For the 12Z TAFs... 632 AM...Forecast concerns include... Showers with periodic chances for thunderstorms. Low mvfr, possible ifr cigs Wednesday morning. Scattered showers continue to develop across northern IL this morning with thunder confined mainly north of the terminals. This trend may continue this morning with the best thunder potential north of Chicago terminals but thunder is still possible over the next few hours and have maintained tempo mention. The heaviest showers/storms may briefly reduce vis/cigs to ifr. A lull in the activity is expected midday/early afternoon and then another period of scattered thunderstorms is expected from mid afternoon to mid evening. This may end up being the best chance of thunder. Some of these storms may be strong/severe and may produce gusty/ erratic winds. Scattered showers are likely to continue tonight and into Wednesday morning along with the potential for thunder. Confidence is low for timing as well as thunder potential. Some patchy mvfr cigs have developed across northwest IL and these are expected to lift this morning with generally prevailing vfr cigs into this evening. Mvfr cigs are expected to develop late this evening and expand overnight and possibly lower to ifr by daybreak Wednesday, especially across northwest IL and RFD. Only medium confidence on cigs tonight. Prevailing winds will remain east/southeast through the period, with speeds perhaps into the 10-15kt range later today. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && Visit us at weather.gov/chicago Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSChicago www.twitter.com/NWSChicago www.youtube.com/NWSChicago
Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
348 AM CDT Tue Sep 26 2023
ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-270900-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-De Kalb-Kane-DuPage-
La Salle-Kendall-Grundy-Kankakee-Livingston-Iroquois-Ford-
Northern Cook-Central Cook-Southern Cook-Northern Will-
Southern Will-Eastern Will-Lake IN-Porter-Newton-Jasper-Benton-
348 AM CDT Tue Sep 26 2023 /448 AM EDT Tue Sep 26 2023/
This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.
.DAY ONE...Today and Tonight.
Weather hazards expected...
Elevated Thunderstorm Risk...with an associated:
Limited Tornado Risk.
Limited Hail Risk...up to 1 inch.
Limited Damaging Wind Risk...up to 60 mph.
Limited Flooding Risk.
DISCUSSION...
Waves of showers and thunderstorms will move through the area
today and tonight. The strongest storms may produce hail up to
1 inch in diameter, frequent cloud to ground lightning, a brief
tornado, and localized flooding in low-lying and poor drainage
areas. The best chance for strong to severe thunderstorms is
from early afternoon through the evening.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Wednesday...
Limited Thunderstorm Risk.
.SPOTTER INFORMATION STATEMENT...
Spotters may be needed this afternoon and evening.
GENERAL STORM MOTION OF THE DAY:
Moving toward the northeast 20 to 25 mph.
LMZ740>745-270900-
Winthrop Harbor to Wilmette Harbor IL-
Wilmette Harbor to Northerly Island IL-
Northerly Island to Calumet Harbor IL-
Calumet Harbor IL to Gary IN-Gary to Burns Harbor IN-
Burns Harbor to Michigan City IN-
348 AM CDT Tue Sep 26 2023
This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.
.DAY ONE...Today and Tonight.
Weather hazards expected...
Elevated Thunderstorm Risk...with an associated:
Limited Hail Risk...up to 1 inch.
Limited Thunderstorm Wind Gust Risk...up to 45 knots.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Wednesday...
Limited Thunderstorm Risk.
DK
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www.youtube.com/nwschicagoThe national radar mosaic for the moment the first event began.
3 flood. Local standard time, as filed.
Street flooding was reported in the Armour Square, Bridgeport and Douglas neighborhoods of Chicago.
State Street at 64th Street was temporarily impassable due to flooding and two stalled cars.
A viaduct was flooded with a few stalled cars in the 1500 block of East 47th Street between Lake Park Avenue and Lake Shore Drive.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2023Every state in 2023This day in weather historyWarnings in Illinois, 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: 1131807, 1131809, 1131810.