An upper-level disturbance interacting with a dissipating frontal boundary triggered a few clusters of strong thunderstorms across west-central Illinois during the evening of August 16th. One of the cells produced gusty winds of around 60mph that blew a large tree branch into powerlines northwest of Groveland in Tazewell County.
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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 ILX wrote it up.
An upper-level disturbance interacting with a dissipating frontal boundary triggered a few clusters of strong thunderstorms across west-central Illinois during the evening of August 16th. One of the cells produced gusty winds of around 60mph that blew a large tree branch into powerlines northwest of Groveland in Tazewell County.
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 Lincoln, IL wrote its last area forecast discussion before the first event at Aug 16, 6:48 PM CST, 57 minutes earlier. Its key messages:
Area Forecast Discussion...Updated National Weather Service Lincoln IL 748 PM CDT Fri Aug 16 2024 .KEY MESSAGES... - Isolated (10-20% coverage) afternoon showers and storms linger through this weekend. Severe weather is not expected, but these storms will produce localized gusty winds. - Next work week, dry and seasonably cool conditions will prevail with no weather impacts expected. && .UPDATE... Issued at 747 PM CDT Fri Aug 16 2024 This evening, a weak surface trough is noted near the Illinois River Valley. Latest RAP indicates a narrow ribbon of moderate instability of 1500-2500 J/kg in the vicinity of this boundary as it moves across central Illinois late this evening and overnight. Weak convergence along the front and unfavorable diurnal timing will limit precip coverage along the front and most of the area will be dry tonight, but an isolated shower or storm remains possible. Temps are on track to drop into the mid to upper 60s. Deubelbeiss && .DISCUSSION... Issued at 108 PM CDT Fri Aug 16 2024 TODAY-TONIGHT: At 1pm, temps in the mid 80s and dewpoints in the low 70s were observed across central Illinois, with west winds around 10-15 mph. While the area remains rain-free at this time, multiple CAMs from the 12z HREF continue to advertise a brief shower or two developing at some point during the evening. SPC mesoanalysis suggests there's 2000-2500 J/kg SBCAPE in place, and with steep lapse rates any shower could generate brief gusty surface winds. However, coverage should be small (10-15%), with most of the area partly cloudy and seasonably humid (though not as humid as last night) through the evening. THIS WEEKEND: As the upper low lingers to our northeast, lobes of enhanced vorticity will pass over the Midwest to provide meso/synoptic lift for a few showers both tomorrow and possibly Sunday afternoons when low level lapse rates will be steep enough to yield a little instability (HREF mean is only around 500-1000 J/kg tomorrow north of I-70). CAMs generally suggest shower coverage will be more (10- 20%, highest I-74 corridor) tomorrow vs Sunday, when instability is lower as subsidence with an incoming ridge mixes drier air aloft to the surface. Surface gradients will be on the strong side both days, and given the aforementioned steep low level afternoon lapse rates, it will be seasonably breezy with northwest winds gusting 20-25 mph at times with stronger gusts over 30 mph expected from any shower. NEXT WORK WEEK: Models and their respective ensembles suggest the upper trough responsible for the cool and breezy weekend will take its sweet time meandering east. In addition, the GFS and ECMWF suggest a closed low will develop in its wake across the Ohio/Tennessee Valley Region and sink slowly southward mid-late week. This will maintain northerly flow and stable conditions through the work week, keeping the area dry and seasonably cool with NBM probabilities for temps above 80 degF generally lower than 40% (25%) Monday through Thursday (Tuesday and Wednesday). Looking at the LREF mean 500mb pattern, it appears a ridge will eventually expand towards the region from the Desert Southwest, but various cluster solutions imply ensemble spread in how long it takes the Midwest to start warming back up and to once again have notable (>15%) precip probabilities; this will likely be after the end of the forecast period, perhaps late in the weekend. Bumgardner && .AVIATION... (For the 00z TAFs through 00z Saturday Evening) Issued at 606 PM CDT Fri Aug 16 2024 VFR conditions and light W/SW winds 6kt or less are expected to prevail overnight, though there could be some variability in direction at times due to the low magnitude. A brief window of MVFR ceilings may build south towards central Illinois Saturday morning, but confidence is only high enough at PIA to include in the forecast. Outside of this potential, expect VFR conditions to prevail through the period. Winds will shift to WNW mid to late Saturday morning with some low end gusts of 18-20kt possible through the afternoon. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... None. &&
Hazardous Weather Outlook National Weather Service Lincoln IL 308 PM CDT Fri Aug 16 2024 ILZ027>031-037-038-042>046-052>057-061-171100- Knox-Stark-Peoria-Marshall-Woodford-Tazewell-McLean-Logan-De Witt- Piatt-Champaign-Vermilion-Christian-Macon-Moultrie-Douglas-Coles- Edgar-Shelby- 308 PM CDT Fri Aug 16 2024 This Hazardous Weather Outlook is for central Illinois and east central Illinois. .DAY ONE...Tonight. Isolated thunderstorms are possible early this evening, though the severe weather threat appears low at this time. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. Scattered thunderstorms are expected Saturday afternoon, and may also occur Sunday afternoon near the Indiana border. The severe weather threat is low. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated tonight. ILZ036-040-041-047>051-171100- Fulton-Schuyler-Mason-Cass-Menard-Scott-Morgan-Sangamon- 308 PM CDT Fri Aug 16 2024 This Hazardous Weather Outlook is for west central Illinois. .DAY ONE...Tonight. Isolated thunderstorms are possible early this evening, though the severe weather threat appears low at this time. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated tonight. ILZ062-063-066>068-071>073-171100- Cumberland-Clark-Effingham-Jasper-Crawford-Clay-Richland-Lawrence- 308 PM CDT Fri Aug 16 2024 This Hazardous Weather Outlook is for southeast Illinois. .DAY ONE...Tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. A few thunderstorms are possible Saturday and Sunday afternoons, mainly near the Indiana border, though the severe weather threat appears low at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated tonight. Geelhart
The Lincoln radar (KILX), 56 km away, was scanning. The volume nearest the first event began at 01:43 UTC.
2 thunderstorm wind. Local standard time, as filed.
A 20-foot long tree limb was blown down onto powerlines in the 2900 Block of Springfield Road.
A trained weather spotter estimated a wind gust of 60mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2024Every state in 2024This day in weather historyWarnings in Illinois, August 2024
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: 1212896, 1212894.