A large upper-level dome of high pressure brought hot and humid conditions to central Illinois on July 21st. A weak disturbance tracking along the northern periphery of the high triggered a cluster of strong to severe thunderstorms across central Wisconsin during the late afternoon.
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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.
A large upper-level dome of high pressure brought hot and humid conditions to central Illinois on July 21st. A weak disturbance tracking along the northern periphery of the high triggered a cluster of strong to severe thunderstorms across central Wisconsin during the late afternoon. These storms tracked southward toward the greatest instability and dropped into north-central Illinois by mid to late evening. While most of the storms produced winds of 40-50 mph, a few stronger cells caused minor wind damage near Downs in McLean 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 Jul 21, 10:17 PM CST, 13 minutes earlier.
Area Forecast Discussion National Weather Service Lincoln IL 1117 PM CDT THU JUL 21 2016 .UPDATE... Issued at 833 PM CDT Thu Jul 21 2016 Next convective system tracking south through northern Illinois early this evening looks like it will affect parts, if not all of our area overnight if you believe that last several runs of the HRRR. Looks as if the short term model latched on to these storms while they were in south central Wisconsin and seem to be doing well, albeit a bit on the slow side compared to reality. Looks like a well developed MCS with bowing segments will track south along the strong instability over our area this evening with the primary threat beging from damaging wind gusts and even the possibility for some hail based on the steep mid level lapse rates seen on the 00z ILX sounding. In addition, with the atmosphere loaded with moisture, PWAT values of around 1.8 inches, if these storms tend to train over a particular area, rainfall rates of 2 to 3 inches per hour will be possible which will produce flash flooding. Have made several changes to the grids with respect to the overall coverage and timing of storms in our area and it still may not be enough as the HRRR has been suggesting that the MCS will track south and affect most of our area through the early morning hours. Looks like the leading edge will push into our far northern areas over the next hour or so and continue to push south. Will be a bit more conservative at this point but may need to adjust the southward trends in the precip coverage over the next several hours along with the possibility for a new weather watch that may include a good portion of our area. Will continue to monitor that. Will have the updated zones out by 900 pm. && .SHORT TERM...(This evening through Friday) ISSUED AT 300 PM CDT Thu Jul 21 2016 A warm and muggy night is in store across central Illinois tonight. After high temperatures in the lower to middle 90s this afternoon, lows tonight will only drop into the middle to upper 70s. Aside from an isolated thunderstorm along/east of the I-55 corridor this afternoon, dry conditions will be the rule into this evening. As is typically the case this time of year, models are struggling to accurately forecast convective evolution. Solutions vary greatly...with some models going completely dry tonight and others suggesting a potential MCS across northern Illinois late. Current analysis shows an outflow boundary from storms that rolled through the Great Lakes earlier today extending from southern Wisconsin into northwest Indiana. With a weak 20-25kt 850mb jet flowing into the boundary, think clusters of thunderstorms may develop along/north of I-80 after midnight. These storms will tend to sink S/SE toward dawn, potentially spilling into the N/NW KILX CWA. Have tailored PoPs accordingly...with dry conditions everywhere through the evening followed by low chance along/north of I-74 well after midnight. .LONG TERM...(Friday night through Thursday) ISSUED AT 300 PM CDT Thu Jul 21 2016 A few showers and thunderstorms may be ongoing across the northern KILX CWA Friday morning, but these will likely dissipate after sunrise. Additional convection may develop along outflow boundaries left behind by the morning storms:however, with warm mid-level capping in place, do not think convection will become widespread. Most models suggest widely scattered thunderstorms everywhere except the SW CWA where cap will be strongest. Main story on Friday will be the continued heat and humidity, as high temperatures once again reach the middle 90s and heat index values climb into the 105-110 degree range. As upper-level ridging begins to weaken and mid-level temps cool slightly, areal coverage of thunderstorms may become a bit more robust on Saturday. Synoptic frontal boundary will remain well to the N/NW, so main forcing mechanism will be mesoscale outflow boundaries left behind by previous convection. Have carried low chance PoPs everywhere with highs topping out in the lower to middle 90s. Best rain chances still appear to be setting up Sunday/Sunday night as cold front approaches from the northwest. 12z Jul 21 models have now delayed FROPA, so rain chances will likely linger across at least the southern half of the CWA into Monday. After that, a cooler/drier airmass will settle into central Illinois on Tuesday and Wednesday with highs dropping back into the middle to upper 80s. As such, have maintained the Excessive Heat Warning everywhere through Saturday evening...and along/south of a Quincy to Danville line through Sunday evening. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1106 PM CDT Thu Jul 21 2016 Complex of storms affecting the PIA and BMI TAF sites will gradually shift south and affect our further south sites over the next 2 to 4 hours. Wind gusts to 35 kts will be possible with some of the stronger cells along with torrential rainfall and brief MVFR and possible IFR cigs/vsbys. We look for the complex of storms to settle south of the southern TAF sites by 09z. After that, there may be some fog that develops and brings vsbys down to MVFR category til 13z, and then VFR conditions are expected during the day Friday along with some more oppressive heat and humidity. Chances for additional storms continue on Friday but coverage looks to be quite spotty again so will not include anything with this forecast issuance for tomorrow afternoon/eve. Surface winds will be light southerly tonight, but variable in direction and quite gusty in and near the thunderstorms. Look for south to southwest winds of 8 to 13 kts on Friday. && .ILX Watches/Warnings/Advisories... Excessive Heat Warning until 7 PM CDT Sunday for ILZ040>057- 061>063-066>068-071>073. Excessive Heat Warning until 7 PM CDT Saturday for ILZ027>031- 036>038. && UPDATE...Smith SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Smith
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LINCOLN IL 302 PM CDT THU JUL 21 2016 ILZ027>031-036>038-221100- FULTON-KNOX-MARSHALL-MCLEAN-PEORIA-STARK-TAZEWELL-WOODFORD- 302 PM CDT THU JUL 21 2016 ...EXCESSIVE HEAT WARNING IN EFFECT UNTIL 7 PM CDT SATURDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS...NORTH CENTRAL ILLINOIS AND WEST CENTRAL ILLINOIS. .DAY ONE...THIS AFTERNOON AND TONIGHT ISOLATED THUNDERSTORMS ARE POSSIBLE LATE THIS AFTERNOON AND EARLY EVENING AND AGAIN LATE TONIGHT FROM I-74 NORTHEAST. SEVERE WEATHER IS NOT EXPECTED...BUT ANY STORMS COULD PRODUCE VERY HEAVY RAINFALL AND FREQUENT LIGHTNING. VERY HOT AND HUMID CONDITIONS WILL OCCUR THROUGH SUNSET...WITH PEAK HEAT INDICES OF 105 TO 113 DEGREES THROUGH 7 PM. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY VERY HOT AND HUMID WEATHER WILL CONTINUE FRIDAY THROUGH SATURDAY...WITH AFTERNOON HEAT INDICES OF 105 TO 113 DEGREES. SCATTERED THUNDERSTORMS WILL BE POSSIBLE FRIDAY THROUGH SUNDAY NIGHT. THERE IS A MARGINAL RISK FOR SEVERE STORMS FRIDAY AFTERNOON THROUGH SATURDAY NIGHT...WITH DAMAGING WINDS THE PRIMARY HAZARD. LOCALLY HEAVY RAINFALL AND FREQUENT LIGHTNING WILL ALSO BE POSSIBLE. ADDITIONAL THUNDERSTORMS ARE EXPECTED FROM WEDNESDAY THROUGH THURSDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. ILZ040>057-061>063-066>068-071>073-221100- CASS-CHAMPAIGN-CHRISTIAN-CLARK-CLAY-COLES-CRAWFORD-CUMBERLAND- DE WITT-DOUGLAS-EDGAR-EFFINGHAM-JASPER-LAWRENCE-LOGAN-MACON-MASON- MENARD-MORGAN-MOULTRIE-PIATT-RICHLAND-SANGAMON-SCHUYLER-SCOTT- SHELBY-VERMILION- 302 PM CDT THU JUL 21 2016 ...EXCESSIVE HEAT WARNING IN EFFECT UNTIL 7 PM CDT SUNDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS...EAST CENTRAL ILLINOIS...SOUTH CENTRAL ILLINOIS... SOUTHEAST ILLINOIS AND WEST CENTRAL ILLINOIS. .DAY ONE...THIS AFTERNOON AND TONIGHT AN ISOLATED THUNDERSTORM IS POSSIBLE LATE THIS AFTERNOON AND EARLY EVENING AND AGAIN LATE TONIGHT NORTHEAST OF I-74. SEVERE WEATHER IS NOT EXPECTED...BUT ANY STORMS COULD PRODUCE LOCALLY HEAVY RAINFALL AND FREQUENT LIGHTNING. VERY HOT AND HUMID CONDITIONS WILL OCCUR THROUGH SUNSET WITH PEAK HEAT INDICES OF 105 TO 113 DEGREES THROUGH 7 PM. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY VERY HOT AND HUMID WEATHER WILL CONTINUE FRIDAY THROUGH SUNDAY... WITH AFTERNOON HEAT INDICES OF 105 TO 113 DEGREES. ISOLATED THUNDERSTORMS WILL BE POSSIBLE FRIDAY ESPECIALLY FROM LINCOLN NORTHEAST. ISOLATED TO SCATTERED THUNDERSTORMS WILL OCCUR FRIDAY NIGHT THROUGH MONDAY. THERE IS A MARGINAL RISK FOR SEVERE STORMS SATURDAY AND SATURDAY NIGHT WITH DAMAGING WINDS THE PRIMARY HAZARD. LOCALLY HEAVY RAINFALL AND FREQUENT LIGHTNING WILL ALSO BE POSSIBLE. ADDITIONAL THUNDERSTORMS ARE EXPECTED FROM WEDNESDAY THROUGH THURSDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. 07
The Lincoln radar (KILX), 48 km away, was scanning. The volume nearest the first event began at 04:27 UTC.
1 thunderstorm wind. Local standard time, as filed.
Multiple trees were blown down in a residential area northwest of Downs.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2016Every state in 2016This day in weather historyWarnings in Illinois, July 2016
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: 646945.