An outflow boundary interacting with a seasonably warm and moist airmass triggered a line of strong to severe thunderstorms across western Illinois during the morning of May 18th. The storms pushed eastward across central Illinois, resulting in periodic damaging wind gusts mainly north of the I-70 corridor.
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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 outflow boundary interacting with a seasonably warm and moist airmass triggered a line of strong to severe thunderstorms across western Illinois during the morning of May 18th. The storms pushed eastward across central Illinois, resulting in periodic damaging wind gusts mainly north of the I-70 corridor. While the leading edge of the storms swept eastward into Indiana, the trailing flank became parallel with the prevailing flow and led to training cells and heavy rainfall along and south of I-70. Widespread amounts of 2 to 4 inches were common, with portions of southern Effingham County and northern Clay County picking up in excess of 5 inches. An observer 3 miles north-northwest of Bible Grove in far southern Effingham County measured 5.50. As a result of the excessive rainfall over the course of just a couple hours, flash flooding occurred across this area.
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 May 18, 4:44 AM CST, 2 hours 12 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Lincoln IL 544 AM CDT Mon May 18 2026 .KEY MESSAGES... - There is a Slight Risk (level 2 of 5) for severe weather areawide today. While all severe weather hazards will be possible, damaging wind gusts in excess of 60 mph will be the most likely. - Additional thunderstorms will develop along an advancing cold front on Tuesday, with a Slight Risk (level 2 of 5) for severe weather in areas east of Interstate 55. Once again, damaging wind gusts in excess of 60 mph will be the most likely hazard. && .DISCUSSION... Issued at 543 AM CDT Mon May 18 2026 ...Active Convective Complex This Morning... Radar analysis early this morning reveals a robust linear Mesoscale Convective System (MCS) stretching from north-central Wisconsin down through southeast Iowa, central Missouri, and into eastern Kansas. Strong, consolidating cold pools have allowed a leading outflow boundary to outrun the primary convective line. Convective-allowing models (CAMs) exhibit high confidence that this system will maintain its structural integrity as it pushes eastward into the central Illinois forecast area later this morning. Sustaining this morning activity is a potent 40-50 kt low-level jet (LLJ) parked directly over central Illinois. This feature, working in tandem with subtle mid-level shortwaves embedded within the southwest flow aloft, is providing ample synoptic lift and elevated instability (MUCAPE around 1500 J/kg). While weak deep- layer shear (> 30 kts) should keep the morning activity largely disorganized and sub-severe, mid-level dry air and localized evaporative cooling could help overcome the waning morning inversion, supporting isolated severe hail or localized downburst winds. As an interesting aside, numerous runs of the HRRR overnight depicted an area of 40-50 kt surface winds within the trailing stratiform region, in an otherwise unassuming area. While it is uncertain if the model is resolving a wake-low or meso-high feature, the trend bears close observation. If these winds materialize, a short- fused wind advisory or high wind warning may become necessary for a brief window this afternoon. ...Severe Potential This Afternoon... By early afternoon, attention shifts to areas near and east of a Taylorville-to- Champaign line. A compact shortwave trough is progged to lift northeastward out of southeast Missouri around 18z, enhancing background kinematic shear and dynamic forcing across a highly buoyant boundary layer. In this zone, temperatures climbing toward the 80-degree mark and dewpoints hovering near 70 degrees will yield SBCAPE values exceeding 2000 J/kg. While the incoming shortwave will likely spark an increase in convective coverage ahead of the main morning line, individual storm intensity remains somewhat conditional. An important limiting factor is that mid-level lapse rates will likely deteriorate through the afternoon as the residual Elevated Mixed Layer (EML) exits to the east. However, as deep- layer shear ticks upward across southeast Illinois later today, localized enhancements within the main convective line remain a possibility. This could yield bowing segments capable of producing the full spectrum of severe weather hazards as the line advances into the southeastern counties. The severe threat will not completely diminish after dark. Additional shortwaves interacting with the persistent 40-50 kt LLJ core will likely sustain elevated convective development ahead of the approaching cold front well into Tuesday morning. ...Conditional Severe Threat on Tuesday... Significant forecasting uncertainty shrouds the Tuesday period, primarily driven by nebulous synoptic forcing and the likelihood of extensive morning convective debris. If widespread cloud cover and rain persist deep into the morning hours, afternoon destabilization will be severely limited, rendering the severe weather threat highly conditional. At this juncture, the highest probability for boundary layer recovery exists near and south of the Interstate 72 corridor, extending through southeast Illinois ahead of the advancing cold front. Should adequate destabilization manifest, favorable instability and deep-layer shear profiles would initially support discrete supercellular structures. However, because the regional shear vectors are oriented nearly parallel to the surface frontal boundary, any discrete activity is expected to transition rapidly into a linear MCS as the front sweeps through Tuesday evening. ...Hydrological Concerns and High QPF Variability... Confidence remains exceptionally high that multiple rounds of convective rainfall will impact the entire region through Tuesday evening. However, the complex, repeated nature of this pattern introduces severe spatial discrepancies in expected precipitation totals. 48-hour HREF Localized Probability Match Mean (LPMM) QPF projections valid through 00z Wednesday demonstrate a stark variance, showing localized pockets picking up a mere quarter-inch while repeating strom cores could exceed 4.5 inches. Current model guidance continues to pinpoint the highest risk for these excessive, flood-producing rainfall totals along and south of the I-72 corridor, where repeated convective elements are most likely to anchor. ...Midweek Clearing Followed by a Wet Weekend Outlook... Wednesday through Thursday: A welcome pattern shift occurs mid- week as a cooler, significantly more stable post-frontal regime takes hold. Continental high pressure building into the Midwest will clear skies and lower humidity levels, offering a brief reprieve from the active weather. Friday through Sunday: The dry spell will be short-lived. Global deterministic models are in notably better agreement, signaling a return to a wetter, unsettled pattern by late week. As the surface high pressure slants eastward, a potent mid-level shortwave will advance across the central U.S. A steady plume of Gulf moisture combined with a series of minor shortwave impulses lifting northeast from the Southern Plains will keep central Illinois susceptible to multiple rounds of scattered showers. While weak kinematic profiles should heavily restrict the overall severe weather risk, a gradual build-up of instability over the weekend will support widespread thunderstorm development. && .AVIATION /12Z TAFS THROUGH 12Z TUESDAY/... Issued at 519 AM CDT Mon May 18 2026 A line of thunderstorms approaching from the west is expected to reach KPIA by 13Z, KSPI and KBMI by 15Z, and KDEC/KCMI by 16Z this morning. A three-hour TEMPO group has been included to account for IFR visibilities during the storms, with scattered showers likely to linger for several hours afterward under generally VFR conditions. Brief periods of degraded conditions are possible within the most intense storm cells. South winds are forecast to increase to 15-20 kts this morning, with gusts reaching 25-30 kts. Low-level wind shear is anticipated late tonight at regional terminals as 50 kt southwest winds return aloft. An additional round of thunderstorms will move in from the west overnight before sunrise; a PROB30 group has been added to address this potential. && .ILX WATCHES/WARNINGS/ADVISORIES... None. && KEY MESSAGES...MJA DISCUSSION...MJA AVIATION...MJA
Hazardous Weather Outlook National Weather Service Lincoln IL 500 AM CDT Mon May 18 2026 ILZ027>031-036>038-040>043-047>051-191100- Knox-Stark-Peoria-Marshall-Woodford-Fulton-Tazewell-McLean-Schuyler- Mason-Logan-De Witt-Cass-Menard-Scott-Morgan-Sangamon- 500 AM CDT Mon May 18 2026 This Hazardous Weather Outlook is for central Illinois and west central Illinois. .DAY ONE...Today and tonight. A broken line of thunderstorms will advance eastward to the I-55 corridor this morning with a risk for scattered damaging wind gusts and isolated large hail. A second line of thunderstorms associated with an approaching cold front will arrive late tonight. There is a continued risk for damaging wind gusts and hail. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Thunderstorms will continue into early afternoon Tuesday. There is a Slight Risk (level 2 of 5) for damaging wind gusts and hail. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed through noon today. Expected storm motion is toward the northeast around 35 mph. ILZ044>046-052>057-061>063-066>068-071>073-191100- Piatt-Champaign-Vermilion-Christian-Macon-Moultrie-Douglas-Coles- Edgar-Shelby-Cumberland-Clark-Effingham-Jasper-Crawford-Clay- Richland-Lawrence- 500 AM CDT Mon May 18 2026 This Hazardous Weather Outlook is for central Illinois, east central Illinois and southeast Illinois. .DAY ONE...Today and tonight. A broken line of thunderstorms will advance into east-central and southeast IL late this morning through afternoon with a risk for scattered damaging wind gusts, isolated large hail, and a tornado or two. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Another round of strong to severe thunderstorms is anticipated Tuesday morning through evening as a cold front pushes through the region. There is a Slight Risk (level 2 of 5) for damaging wind gusts and hail. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed late morning through afternoon today. Expected storm motion is toward the northeast around 35 mph. 37
The Lincoln radar (KILX), 77 km away, was scanning. The volume nearest the first event began at 12:55 UTC.
13 thunderstorm wind, 4 flash flood, 1 hail. Local standard time, as filed.
Significant tree damage occurred at Walnut Ridge Cemetery on the north side of Virginia.
An irrigation system was flipped over.
A large tree was blown onto powerlines.
A power pole was blown down across the road near Spring Lake.
A tree was blown onto a house.
A large tree was blown down near Limestone High School.
A 3.5 to 4-foot diameter tree was blown down across Stringtown Road near Hopedale.
Several large tree limbs were blown down.
A few trees were damaged.
A tree was blown down across a road.
A 66mph wind gust was measured at the Taylorville Airport (KTAZ).
A tree was blown over.
Water was flowing across numerous low-lying country roads in central and southern Effingham County. Debris from nearby farm fields was washed onto a few roads.
Water was flowing across several roads in Flora.
Water was flowing over a bridge in Bible Grove.
A building just west of downtown Louisville was flooded. Numerous side streets had water over them.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2026Every state in 2026This day in weather historyWarnings in Illinois, May 2026
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: 1340881, 1340882, 1340884, 1340885, 1340886, 1340887, 1340888, 1340889, 1340890, 1340891, 1340892, 1340893, 1340894, 1340895, 1340902, 1340903, 1340904, 1340905.