During the afternoon of July 11, a broken line of strong thunderstorms moved across the Chicago metro. While most of these storms remained sub-severe, one cell stood out among the rest producing a 68 mph wind gust recorded by the ASOS at Chicago Midway Airport and downing nearby trees and power lines.
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.
During the afternoon of July 11, a broken line of strong thunderstorms moved across the Chicago metro. While most of these storms remained sub-severe, one cell stood out among the rest producing a 68 mph wind gust recorded by the ASOS at Chicago Midway Airport and downing nearby trees and power lines. One home was also damaged when an attached garage was struck by lightning.
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 Jul 11, 12:18 PM CST, 1 hour 12 minutes earlier.
Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 118 PM CDT Tue Jul 11 2023 .MESOSCALE DISCUSSION... Issued at 118 PM CDT Tue Jul 11 2023 There are no major changes in forecast thinking through early this evening regarding scattered shower and thunderstorm development, a few of which could be severe. The well defined lake enhanced backdoor cold front is pushing south and southwest, fastest southward near the lake as is typical. With neutral to rising height tendencies at 500 mb, the enhanced lower level convergence associated with the front will be the primary source of lift for thunderstorm development. One item that is worth noting is a pocket of very dry mid-level air over Wisconsin, which can be seen on water vapor imagery and near term model guidance 700-500 mb RH. It appears dry air entrainment, perhaps lingering capping, and lack of stronger forcing, may have played a role in the very rapid decay of a shower passing across Kenosha County, WI mid way through the noon hour. Meanwhile, farther south over our area, the dry air is less prohibitive, with recent convective development (and detected lightning strikes) over far northeast Illinois and Chicago behind the lake enhanced front as of this writing. So it does appear locales from the approximate latitude of current convection (as of 1 PM) southward down to a bit south of the I-80 corridor will be most favored for scattered thunderstorm development through the late afternoon as the front settles inland. Effective bulk shear analyzed at 30-35 kt by the SPC RAP Mesoanalysis is forecast to remain roughly in that range the rest of today. This is sufficient for a few supercell structures given good veering with height. On the other hand, mid-level lapse rates are on the weaker end, between 5.5 C and 6.5 C/km, so that paired with less forcing and perhaps a bit of a dry air entrainment concern, appears to be a limiting factor intensity wise. Regarding severe threats, steep low level lapse rates and 1000+ DCAPE inland suggests downburst winds as the main threat, with any supercells also capable of producing hail up to quarter size. There may be a non-zero landspout threat given the very steep low-level lapse rates and surface vorticity near the advancing frontal boundary. If any concentrated corridor of thunderstorms can develop, that would lend to a shorter-lived hydro issue, though overall more concerned with the flash flood setup potential that may evolve tonight, discussed in the full short term AFD. Thunderstorm coverage and the associated strong to severe thunderstorm threat will likely quickly wane this evening between 7 pm and 9 pm CDT with diurnal decrease of instability amidst a continued lack of large scale forcing. Castro && .SHORT TERM... Issued at 343 AM CDT Tue Jul 11 2023 Through Wednesday... Key Forecast Messages: * Threat for at least some isolated to widely scattered strong thunderstorms across northeastern IL into far northwestern IN this afternoon and early evening. Primary threats from these storms aside from lightning would be locally strong wind gusts and possibly some marginally severe hail. * Increasing threat for training thunderstorms and an attendant flash flood threat late tonight into Wednesday morning. * A heavy rain threat is likely to persist through at least early afternoon on Wednesday. The threat of severe thunderstorms on Wednesday is highest for areas south of I-80, though uncertainty remains with the extent of this threat. A cold front current resides to our north from near Sheboygan, WI west-southwestward back into northeastern parts of IA. I did leave a stray chance for a storm or two in the forecast this morning for far northern sections of IL, but at this point would not expect much more that a brief isolated shower or storm making into far northern IL early this morning. The cold front is expected to surge down the southern half of Lake Michigan this morning before shifting inland across northeastern IL and far northwestern IN into the early afternoon hours. In advance of the front, diurnal heating/destabilization is expected to overcome any weak capping to support thunderstorm development across parts of the Chicago metro area potentially as early as 1 or 2 pm this afternoon. Large scale forcing for ascent is expected to remain subtle through the afternoon as upper level heights gradually rise. It thus appears that the coverage of storms may remain rather low (isolated to widely scattered) through the afternoon as storm development and maintenance will be almost exclusively driven by the lower-level frontal convergence. Nevertheless, any storms that do develop will be capable of having some organization, and a low end severe threat given an amply sheared environment along the southern fringe of a belt of 40+ kt mid-level flow across the Great Lakes. The main threat looks to be locally strong wind gusts, and possible an instance or two of marginally severe hail. Expect this activity to gradually sag southward towards the I-80 corridor later this afternoon before the activity begins to wane with dusk. The surface cold front is likely to set up somewhere near U.S. 24 (over a our far south) into tonight. After a dry period this evening, forecast guidance then forecasts the ramp-up of a southwesterly low-level jet late tonight into Wednesday morning in advance of an approaching convectively enhanced disturbance moving across IA. The induction of strong warm air advection along this low-level jet and to the north of the surface boundary is likely to support a narrow corridor favorable for elevated thunderstorm development somewhere right across northern IL. While the exact placement of these storms remains a bit unclear at this time, there is concern for a heavy rain and localized flash flood threat into late tonight into Wednesday as an easterly storm movement will parallel the front, potentially leading to training storms. We will have to monitor this threat closely as its possible these storms could occur over, or near the Chicago metro area. The convectively enhanced impulse over IA will translate eastward across northern IL during the late morning and afternoon hours of Wednesday. This is expected to drive a region of more widespread showers and some storms, with a continued heavy rain and flood threat through early afternoon. In addition to the heavy rain and flooding threat, we will also have to continue to monitor the threat for severe storms, particularly south of I-80 into Wednesday afternoon/evening as the potential exists for the backbuilding of thunderstorms back into the unstable airmass building into from the west. Uncertainty exists with how exactly this may unfold, but it appears winds off the surface will veer west-southwesterly in the wake of the impulse. This would likely support continued warm air advection, and the eastward advance of a very unstable airmass from the west. KJB && .LONG TERM... Issued at 301 AM CDT Tue Jul 11 2023 Wednesday night through Monday... By Wednesday evening, the potent shortwave trough progged to move through the area will have pushed well off to our east as will the densely scattered to widespread rain expected to accompany the wave earlier in the day. Well, at least according to just about all but one model. The NAM continues to be stubborn and holds off until the evening to bring the more aggressive shortwave through the region after resolving an initial, much milder shortwave in the morning. Being such an outlier among guidance though, I've pretty much neglected the model in the long term forecast. However, we may continue to see scattered instances of elevated convection through Wednesday evening and overnight with ample elevated instability in place through the night as well as 7-8 K/km mid level lapse rates, support from an encroaching LLJ, and a number of transient passing mid level vort lobes. The GFS, RAP, and Canadian even resolve a second little 700mb shortwave and notable localized vort max Thursday night tracking across central IL. Moisture availability is a big limiting factor, however, and just may inhibit precip development Thursday evening/night altogether. Mid level moisture will be somewhat sparse in the evening and that will only become more true through the night as some drier air works in which is a problem seeing as any activity would have to initiate above 700mb or so according to forecast soundings. Scattered chances improve a bit for Thursday afternoon once we destabilize enough to get surface-based convection going and are able to utilize a sufficient amount of moisture all pooled under 850mb. By this point however, support from features aloft will have dwindled by quite a lot. But, soundings look supportive for some scattered afternoon free convection. After another lull in activity is expected Thursday night, chances improve again for Friday. Guidance wants to bring in what looks to be a rather disorganized cold front Friday afternoon and evening. While forced ascent looks like it'd be less-than-impressive, forecast soundings during the afternoon again look favorable for perhaps some free convection, but any little boost from a boundary wouldn't hurt chances of course. The GFS is the most aggressive on coverage for Friday as it hints at another noteworthy shortwave moving across the area. Scattered rain chances will continue through the weekend as we remain in this overall unsettled synoptic pattern. Doom && .AVIATION... For the 18Z TAFs... Main Concerns in the TAF period: - Lake breeze marching west/south-west through the urban terminals of ORD and MDW. Continue pushing towards DPA this afternoon. - Increasing clouds associated with frontal system which will slide southward through the region, potentially initiating showers and scattered storms. - Another developing wave of showers and storms late tonight into early Wednesday morning, before the main disturbance tracks through the area midday Wednesday. The lake breeze is currently tracking west/south-west through the metropolitan terminals of ORD and MDW, with expectation of continued push through DPA this afternoon. Winds will shift from westerly to northeasterly pushing sustained 10-12kts with gusts possible in excess of 18-20kts at times. With this lake breeze, another frontal boundary is sliding southward through the region from the IL-WI border. This is where the potential for development of lower VFR to near MVFR ceilings will setup, and lead to the possibility of shower and storm development through this afternoon. Continued VCTS as no exact timing and location of cellular development is evident through any model progression. There will be break in activity this evening, however additional waves of precipitation are expected overnight and Wednesday. The frontal boundary will linger across portions of northern Illinois tonight, giving way to possible re-development of showers and maybe a rumble after 06-08z along and north of the Chicago and Rockford area terminals. Another Low pressure system will track through the upper Midwest Wednesday along the lingering boundary, bringing another opportunity for widespread showers and storms across northern Illinois midday Wednesday. Baker && .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
1250 PM CDT Tue Jul 11 2023
ILZ003>006-008-010>013-019>021-023-032-033-039-103>108-INZ001-002-
010-011-019-121800-
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-
1250 PM CDT Tue Jul 11 2023 /150 PM EDT Tue Jul 11 2023/
This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.
.DAY ONE...This Afternoon and Tonight.
Weather hazards expected...
Limited Thunderstorm Risk...with an associated:
Limited Hail Risk...up to quarter size.
Limited Damaging Wind Risk...up to 60 mph.
Limited Flooding Risk.
DISCUSSION...
Widely scattered thunderstorms are expected to develop across
parts of northern Illinois and far northwest Indiana along a cold
front during this afternoon, primarily I-80 and north. A few of
these thunderstorms could become strong to severe, capable of
producing locally damaging wind gusts and potentially an instance
or two of marginally severe hail. This activity is expected to
wane with sunset early this evening.
Additional thunderstorms are possible across northern IL after
midnight tonight. While severe weather is not expected with this
activity, heavy rainfall would be likely to accompany these
storms. A localized flash flood threat could thus develop across
parts of northern Illinois and far northwest Indiana late tonight,
especially if numerous storms move over the same area.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Wednesday...
Limited Severe Thunderstorm Risk.
Elevated Flooding Risk.
Thursday through Monday...
Limited Thunderstorm Risk.
DISCUSSION...
Slow-moving heavy rain producing showers and thunderstorms
will continue the threat of flash flooding into Wednesday
afternoon.
Another period of severe weather is also possible on
Wednesday, especially for locations south of I-80 in the
afternoon.
Intermittent thunderstorm chances will linger through the
remainder of the week and into the weekend.
.SPOTTER INFORMATION STATEMENT...
Spotter reports may be needed this afternoon.
GENERAL STORM MOTION OF THE DAY:
Moving toward the southeast at 20 to 30 mph.
LMZ740>745-121800-
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-
1250 PM CDT Tue Jul 11 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...This Afternoon and Tonight.
Weather hazards expected...
Limited Thunderstorm Risk...with an associated:
Limited Hail Risk...up to Penny size.
Limited Thunderstorm Wind Gust Risk...up to 45 knots.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Wednesday...
Limited Severe Thunderstorm Risk.
Thursday through Monday...
Limited Thunderstorm Risk.
Castro/KJB
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www.youtube.com/nwschicagoThe Chicago radar (KLOT), 32 km away, was scanning. The volume nearest the first event began at 19:29 UTC.
2 thunderstorm wind, 1 flood, 1 lightning. Local standard time, as filed.
Several roadways were reported to have flooded near Midway Airport, including a portion of I-55.
Trees and power lines were reported down near Midway Airport.
Lightning struck the attached garage of a home in Naperville starting a fire that spread throughout the garage and into the living space above. No injuries were reported, but damages were estimated at $40,000.
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, July 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: 1140662, 1126600, 1140655, 1142615.