During the morning of May 16th, a cluster of thunderstorms passed through the area, setting up a boundary in the center of the forecast area. It was this boundary that thunderstorms initiated on during the afternoon hours.
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The episode as NWS LSX wrote it up.
During the morning of May 16th, a cluster of thunderstorms passed through the area, setting up a boundary in the center of the forecast area. It was this boundary that thunderstorms initiated on during the afternoon hours. Convection quickly became linear before producing wind damage and mostly small hail in Washington and Marion counties.
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 St. Louis, MO wrote its last area forecast discussion before the first event at May 16, 12:21 PM CST, 2 hours 31 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Saint Louis MO 121 PM CDT Sat May 16 2026 .KEY MESSAGES... - Additional scattered thunderstorms are possible (20-30%) this afternoon and evening. The main risk is large hail and damaging winds. - Additional thunderstorm chances return early this week with a more widespread severe weather threat possible along a slow moving cold front Monday night into Tuesday. && .SHORT TERM... (Through Late Sunday Night) Issued at 112 PM CDT Sat May 16 2026 An upper level trough has moved onshore over the western CONUS, with a surface low over the Central High Plains and a warm front extending into Iowa. There was a secondary warm front/convergence zone draped along the I-70 corridor this morning, and this is what kicked off this morning's storms. These storms have reinforced a baroclinic zone across the CWA, with temps in the upper 60s across our north and pushing 80 in our south. As we move through the afternoon and into the evening, additional thunderstorm development will be largely focused to the north and west of the area, near the primary warm front. However, the above baroclinic zone may serve as a secondary focus for convection this afternoon, and a few of the most recent runs of the HRRR are hinting at that possibility. Given the weak forcing along this feature and lack of deep forcing, I don't expect widespread convection, but a few additional thunderstorms remain a possibility. If these storms do develop, MUCAPE around 2,500 J/kg and effective bulk shear around 30 kts may allow few of these storms to become strong enough the support large hail or damaging winds. The stronger convection expected to develop near NW MO should grow upscale and track to the ENE through the night. While previous runs of high-res guidance has largely kept these storms to our north, a few of the CAMs have begun pushing them a bit further south into our area. These storms may also pose a marginal threat for damaging winds and large hail as they diminish and move across NE MO and west-central IL this evening. Tomorrow, longwave troughing will amplify over the western CONUS, reinforcing deep southwesterly flow over the Mid-Mississippi Valley. Given the lack of any focused forcing for ascent, it appears likely that we'll see little to no precipitation and notably less cloud coverage than today. The increased insolation, coupled with the above deep southerly flow, should push temperatures quite a bit higher tomorrow. BSH && .LONG TERM... (Monday through Next Saturday) Issued at 112 PM CDT Sat May 16 2026 A compact shortwave will eject from the western CONUS trough on Monday, spurring cyclogenesis over the Central Plains. The resultant forcing for ascent from central KS through Iowa and into the Great Lakes will force another round of thunderstorms, largely to the north and west of our forecast area. These areas will also feature strong dynamics, which coupled with a very unstable airmass, will result in scattered/numerous strong to severe thunderstorms. The atmosphere will also be rather unstable over the Mid-Mississippi Valley, but without any focused forcing, anything more than widely scattered thunderstorms appear unlikely. Additionally, much more modest wind shear on our CWA will limit storm organization and severe potential. Our best chance for severe weather through Tuesday morning will be tied to whether the storms that develop to our northwest are able to grow upscale and persist as they advance into our forecast area. A cold front associated with Monday's surface low is expected to push through the region on Tuesday. Ahead of the front, instability should build into the 1000-2000 J/kg range, which coupled with the front, will result in the best chance for thunderstorms in the extended forecast. While the SPC convective outlook continues to highlight our area on Tuesday, I do see a couple of factors that may limit the potential for severe thunderstorms. First of all, the best deep layer dynamics are expected to remain well to the north of our forecast area, limiting deep layer shear to around 30kts ahead of the front. Secondly, it's unclear how storms from Monday night and Tuesday morning will unfold across the area and whether the atmosphere can recover before the frontal passage. Even if we do recover, the above wind shear would be only marginally supportive for severe thunderstorms. With that, the 15% contour from SPC seems appropriate, but I would not expect that to increase much, barring a notable change in the models. The above cold front should push the deep moisture our of our region, with the vast majority of guidance keeping dewpoints below 60 through the end of the week. Persistent weak zonal flow aloft may open the door for a few weak shortwaves to move through the region, but the lack of moisture will keep precipitation chances limited. BSH && .AVIATION... (For the 18z TAFs through 18z Sunday Afternoon) Issued at 1216 PM CDT Sat May 16 2026 The primary aviation concern are the ongoing storms near the STL metro and over NE MO and west-central IL. The storms near STL are rapidly decaying, but are still hanging onto some lightning. With that, I've just included an hour of -TSRA to cover the lightning threat, but no notable visby reduction as precipitation should be relative light. Further north, more robust convection has persisted generally just to the south and west of KUIN. Those storms should move over that terminal at some point in the first few hours of the TAF before gradually tapering off this afternoon. There will be a low (<30% chance) for storms through the afternoon, especially toward NE MO and west-central IL, before falling further this evening. Otherwise, VFR conditions should persist with southerly winds, becoming a bit gusty tomorrow. BSH && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && WFO LSX
Hazardous Weather Outlook National Weather Service St Louis MO 555 AM CDT Sat May 16 2026 ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027- 034>036-041-042-047>052-059>065-072>075-084-085-099-171100- Greene IL-Macoupin IL-Montgomery IL-Bond IL-Fayette IL-Clinton IL- Marion IL-Washington IL-Randolph IL-Adams IL-Brown IL-Pike IL- Calhoun IL-Jersey IL-Madison IL-Saint Clair IL-Monroe IL-Knox MO- Lewis MO-Shelby MO-Marion MO-Monroe MO-Ralls MO-Pike MO-Boone MO- Audrain MO-Moniteau MO-Cole MO-Osage MO-Callaway MO-Montgomery MO- Lincoln MO-Gasconade MO-Warren MO-Saint Charles MO-Franklin MO- Saint Louis MO-Saint Louis City MO-Jefferson MO-Crawford MO- Washington MO-Saint Francois MO-Sainte Genevieve MO-Iron MO- Madison MO-Reynolds MO- 555 AM CDT Sat May 16 2026 This Hazardous Weather Outlook is for portions of eastern and central Missouri as well as west central and southwest Illinois. .DAYS ONE THROUGH SEVEN...Today through Friday. More detailed information can be accessed at: https://www.weather.gov/media/lsx/DssPacket.pdf The Area Forecast Discussion is available at: https://forecast.weather.gov/ product.php?issuedby=LSX&product=AFD&site=lsx .KEY MESSAGES... - Showers and scattered thunderstorms are expected this morning with coverage forecast to gradually fade by this afternoon. The strongest storms could produce hail up to 1" and damaging wind gusts. - Thunderstorms are possible (20-30%) this afternoon and evening. The main risk is large hail with a lower potential for damaging winds. - Additional thunderstorm chances return early this week with a more widespread severe weather threat possible along a slow moving cold front Monday night into Tuesday. NOTE: Starting May 29, 2026, this outlook product will be discontinued. Please see the above products for more detailed forecast information. WFO LSX
The St Louis radar (KLSX), 114 km away, was scanning. The volume nearest the first event began at 20:52 UTC.
3 thunderstorm wind, 1 hail. Local standard time, as filed.
Thunderstorm winds blew over the awning to the Shell gas station near 12th Street.
Thunderstorm winds blew down power lines and trees near Odin. A transformer blew near Community Beach and Odin Road. To the south, the same thunderstorm caused minor roof damage to a home. In Centralia, power lines and trees were downed.
An NWS employee estimated 60 mph wind gusts near Ashley.
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: 1334113, 1334104, 1334108, 1334109.