Scattered thunderstorms moved across parts of northern Illinois during the morning of September 6th producing heavy rain, localized flooding and localized wind damage.
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 LOT wrote it up.
Scattered thunderstorms moved across parts of northern Illinois during the morning of September 6th producing heavy rain, localized flooding and localized wind damage.
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 6, 1:14 AM CST, 2 hours 11 minutes earlier.
Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 214 AM CDT Wed Sep 6 2023 .SHORT TERM... Issued at 214 AM CDT Wed Sep 6 2023 Through Thursday... An early morning surface analysis depicts a 1004 mb surface low pressure system centered near Eau Claire, Wisconsin with an associated cold front stretching southward through far southeastern Minnesota, eastern Iowa, and eastern Missouri. Ahead of the cold front, it is a seasonably warm and muggy early September night with temperatures currently in the low to mid 70s (which are normal daytime highs for this time of year). We continue to watch for signs of sustained attempts for the nose a 30-35kt low-level jet between 925 and 800mb to initiate convection across central and northern Illinois. Recent AMDAR soundings from RFD/ORD/MDW continue to depict the presence of a dry layer between 900 and 700 mb. However, 1-minute GOES-16 nighttime microphysics imagery shows a subtle increase in ACCAS near I-39 where radar imagery occasionally depicts blips, signifying at least some degree of moistening is occurring within the aforementioned dry layer. Available high resolution model guidance continues to suggest a forecast scenario where convection rapidly develops near and moves over the Chicago metropolitan area between 5 and 9 AM, presumably out of the area of aforementioned ACCAS. Though, though time will tell if sufficient moistening actually takes place to support more than a single puff or two of sprinkles. At any rate, if a thunderstorm were to develop, the available instability bolstered by steep mid-level lapse rates of 7-8 K/km may provide enough oomph for an updraft pulse or two to spit out pea to quarter size hail. Again, such a threat will be over the Chicago metro between 5 and 9 AM. Beyond the threat for thunderstorms this morning, the surface cold front will sweep across the area after sunrise leading to breezy west winds and lowering humidity levels. With increasing stratocumulus clouds and cold air advection offsetting the normal influence of diurnal heating, highs today will range from the mid 70s west of I-39 to the mid 80s east of I-55. As mid-level temperatures cool within the core of the upper-level trough and subtle DCVA increases ahead of a secondary upper-level wave approaching from the west, low- to mid-level lapse rates may steepen sufficiently to support widely scattered showers this afternoon and evening, mainly north of I-80. Even so, this afternoon by no means looks like a washout. As the storm system and secondary wave depart tonight into Thursday, periods of partly to mostly cloudy skies, seasonably cool temperatures, and continued west to northwest winds will be the norm. Lows tonight will range from the upper 50s to lower 60s, and highs tomorrow will range from the upper 60s lakeside to lower 70s inland. Lowering inversion heights along the backside of the departing low should suppress the development of any showers on Thursday. Finally, persistent winds down the fetch of Lake Michigan will cause waves to build toward northwestern Indiana, leading to dangerous rip currents from Thursday morning through perhaps the early portion of the weekend. With the weather not expected to be exactly beach- worthy, we'll let the day shift take care of any nearshore and marine- based headlines. Borchardt && .LONG TERM... Issued at 214 AM CDT Wed Sep 6 2023 Thursday night through Tuesday... A 500 mb ridge over the Southern Plains continues to build through the end of the week setting up northwest flow over Northern Illinois. While in most cases the thought of northwest flow would lead to the potential for storms, drier air that is expected to advect over the region through the end of the week will keep rain out of the forecast starting late Thursday. Cooler air moving down the northwest flow from Canada will keep temperatures in the 60s and 70s, with overnight lows in the 50s and low 60s. The ridge is forecast to move slightly east over the weekend which could lead to a slight warming trend that could make for a possibility of low 80s in the day time highs for the weekend, but should not be much more than that. Though it is incredibly subjective, Thursday through Sunday is looking quite pleasant. By Sunday, the upper level pattern starts to morph over Alberta, Canada and a fairly broad shortwave trough descends southward from Canada toward the Great Lakes. 24 hours ago, models were suggesting it would pass through on Monday, but recent models trends has slowed the progression with in turn has resulted in PoPs being added to Tuesday as well as Monday. Weak instability and pulses in vorticity maxima will keep a slight chance for thunder in the forecast, but current limitations in shear and moisture puts confidence in severity low at the moment. Exact timing and strength can be reassessed closer in time; however, with model consistency suggesting the trough moving down, it keeps the potential for inclement whether in the forecast for the early part of next week. DK && .AVIATION... Issued at 1229 AM CDT Wed Sep 6 2023 For the 06Z TAFs... Aviation Forecast Concerns: * Maintained SHRA/TSRA coverage overnight with MVFR cigs through Wednesday morning. * South to southwest winds gusting between 20 to 25 knots through Wednesday afternoon. * Return of MVFR cigs Wendesday evening as winds diminish. A weak boundary has already pushed through the Chicago Metro area bringing light rain showers to area terminals. A cold front is moving through the Mississippi River Valley heading east through the overnight hours. Scattered storms are developing along the front producing lightning and locally moderate rainfall. With the scattered development, maintained the TEMPO group for area terminals. The question will be whether the storms pass directly over the terminal or pass to the north and south. While winds are mainly out of the south to southwest, they continue to over perform with gusts around 20 knots. Kept the stronger gusts in the TAF through at least the frontal passage. Cigs have also fallen to at or below 2000 feet for MVFR level conditions. with the extensive cloud deck reaching back to Eastern Iowa, chose to make the cigs prevailing through the overnight hours. Current expectations is for the front to have passed through the area by the 12Z TAF package. Winds are forecast to remain gusty and out of the southwest behind the front, but clouds should lift a little and break up to allow for VFR conditions. It is likely that there will still be moisture upstream around the Minnesota/Wisconsin border that can move east southeastward Wednesday afternoon. Cannot rule out the chance for a light sprinkle, but with a lack of forcing behind the front confidence was low enough to keep showers out of the TAF, but will be monitored through the day. With additional subsidence and the front being farther east, winds are forecasted to diminish after 00z and pivot to west to northwest. As the sun sets, clouds fill in for a return to MVFR cigs later on Wednesday evening. DK && .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 229 AM CDT Wed Sep 6 2023 ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002- 010-011-019-070730- 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- 229 AM CDT Wed Sep 6 2023 /329 AM EDT Wed Sep 6 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... Limited Thunderstorm Risk...with an associated: Limited Hail risk...up to quarter size hail. Limited Damaging Wind Risk...up to 50 mph. DISCUSSION... Scattered thunderstorms are possible late this evening and overnight. If any more intense thunderstorms are able to develop, a few may be capable of producing strong to locally damaging wind gusts and hail. The overall severe threat is low, however. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Thursday and Friday... High Swim Risk Lake Michigan beaches. Monday and Tuesday... Limited Thunderstorm Risk. DISCUSSION... .SPOTTER INFORMATION STATEMENT... Spotters are unlikely to be needed. GENERAL STORM MOTION OF THE DAY: Moving toward the east-northeast at 25 to 35 mph. LMZ740>745-070730- 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- 229 AM CDT Wed Sep 6 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... Limited Thunderstorm Risk. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Thursday and Friday... Hazardous conditions for small craft are likely. Tuesday... Limited Thunderstorm Risk. DK Visit us at www.weather.gov/chicago Follow us on Facebook, Twitter, and Youtube at: www.facebook.com/nwschicago www.twitter.com/nwschicago www.youtube.com/nwschicago
The Chicago radar (KLOT), 20 km away, was scanning. The volume nearest the first event began at 09:26 UTC.
4 thunderstorm wind, 1 flash flood. Local standard time, as filed.
Small to medium size tree limbs were blown down west of downtown Naperville, including near Aurora Road and River Road.
A photo shared on social media showed a snapped tree near a hospital. Other tree damage was observed nearby.
Small to medium size tree limbs were blown down.
A wind gust to 60 mph was measured.
Numerous viaducts and underpasses were flooded across the southern suburbs of Chicago. Rainfall amounts included 2.99 inches in Park Forest and 2.90 inches in Peotone.
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: 1120944, 1120942, 1120943, 1120939, 1120945.