A line of slow moving severe thunderstorms with damaging winds, large hail, and even one tornado, moved east across Iowa into Illinois the afternoon and evening of June 20th. These storms brought significant flash flooding to the the Quad Cities.
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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 DVN wrote it up.
A line of slow moving severe thunderstorms with damaging winds, large hail, and even one tornado, moved east across Iowa into Illinois the afternoon and evening of June 20th. These storms brought significant flash flooding to the the Quad Cities.
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 Quad Cities, IA wrote its last area forecast discussion before the first event at Jun 20, 11:34 AM CST, 1 hour 57 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 1234 PM CDT Wed Jun 20 2018 ...AVIATION UPDATE... .UPDATE... Issued at 1032 AM CDT Wed Jun 20 2018 Near full sun across the southwest half of the area is allowing temperatures to climb. At the same time, radar shows the precip from earlier this morning decaying rapidly. Thus the forecast has been updated to raise temperatures and lower very short term pops. The increased diurnal heating should allow a new round of showers/storms to develop this afternoon. The approaching upper level low will increase lift further and allow locally heavy rainfall to occur. Updated forecast to be out shortly. && .SYNOPSIS... Issued at 330 AM CDT Wed Jun 20 2018 The latest sfc analysis was indicating a weak low pressure center just west of the DSM area, with a quasi-stationary boundary undulating east-southeastward along and south of the I-80 corridor acrs the local area, and into northern Indiana. A large MCS/MCC was rolling east-southeastward acrs the central into southern plains, with secondary convergent zones producing west-east oriented narrow bands of convection currently acrs western IA. Aloft, the latest upper air analysis and water vapor imagery were indicating closed upper wave/low acrs central NE, with a lee side bump-up ridge axis right acrs the MS RVR Valley, probably helping suppress overnight convection locally. This as well as a rather weak west-southwest low level jet. Beyond today, the upstream upper low is still on track to bring waves of rainy weather to portions of the Midwest as it slow- rolls eastward through the end of the week. && .SHORT TERM...(Today and Tonight) ISSUED AT 330 AM CDT Wed Jun 20 2018 Low clouds and patchy fog will continue into the early portions of the first period, with such a saturated boundary layer with light LLVL flow. As a more southwest oriented low to mid level flow starts to edge east acrs IA and toward the local fcst area, see isolated to sctrd showers and thunderstorms developing more this morning generally in the vicinity of the frontal boundary, generally west of the Iowa City area, southeastward to Monmouth IL and Macomb. This activity will look to move north but decrease diurnally through the mid to late morning. Then as the upper low system slow-rolls east-southeast acrs the MO RVR valley through this evening, cyclonic diffluent southwesterly flow will sprawl eastward acrs the mid to upper MS RVR Valley this afternoon and evening, as well convergent lift. then depending on extent of heating and instability build up that can occur today, this process will look to produce a NNW-to-SSE oriented band of convection that will look to spiral eastward acrs the CWA by late afternoon and into the evening. With warm front continuing to waver acrs the local area for a type of triple-point, fcst soundings show a nice swath of low to mid level directional shear, although velocities marginal to moderate at best. If enough buoyancy of at least 1000-2000 J/KG can build up(a big "if", with expected MCS debris from out west spilling acrs the area for much of the morning into midday), the shear profile would support some strong to severe storms with rotating updrafts especially along the front or and other differential boundaries that can set up. This along with sounding indicated low LCL's of under 2000 FT AGL, agree with SPC that there may be some potential for supercells and at least a weak tornado or two developing just to the lee of the approaching LLVL low. Other modes of severe would also be possible especially downburst/damaging winds. Timing will be key as well, and it may be more optimum for supercell severe just to the west of the CWA, with bowing segments evolving from that activity into our area with more of a wind threat, but also a meso-vortice tornado possible on the warm front triple point. Along with the severe wx, another day of high PWAT feed of 1.8-2+ inches to fuel torrential rainfall and at high rates. The storms should be progressive helping limit residence time, but areas that get hit repeatedly may still have a localized flash flood threat into tonight. Some areas could get 1-2+ inches easily by Thu morning. Highs today a big challenge again wiht localized buts potential, with cloud cover and a moist BL fighting clearing breaks that would allow heating...and keeping in mind convective debris from the west. Will go with a range of mid 70s in the north, to the mid 80s in the south. The band of convection will pivot along and north of I-80 later tonight, with some signs of decreasing in intensity as it does. But will have to watch for more substantial rainfall bands trying to make it acrs the recent hard hit by heavy rainfall NW IL counties for renewed water trouble. Today and tonights rain and run-off to aggravate ongoing river flooding, and possibly set the stage for others to rise into the late week. Low temps tonight a secondary concern, but will be down in the 60s...along with more patchy fog possible where rain wanes and convergent flow condenses on a boundary. ..12.. .LONG TERM...(Thursday through next Tuesday) ISSUED AT 330 AM CDT Wed Jun 20 2018 Highlights of the long term period are continued wet weather and mostly below normal temperatures. Thursday and Friday: A slow moving H5 low will continue to rotate through the region with widespread rain and some scattered storms. Confidence remains high in widespread significant rain this period, while specific locations and basins impacted the most is less certain. Cannot rule out some isolated flash flooding with cumulative effects of several days of rain on already saturated ground, but the main issue will be the impact on rivers, which is discussed below. Rain will taper off Friday night as the upper low exits to the east. The severe weather risk is low. Expect highs in the 70s, below the normal highs of 80 to 85. Saturday and Sunday: A rather weak shortwave trough may support some showers and storms late Saturday into Sunday morning, especially across the south. Afternoon highs will warm slightly into the mid 70s to low 80s. Monday and Tuesday: Another potent H5 low will likely impact the forecast area this period. Specifics are still uncertain, but the risk of heavy rain and severe weather look greater than the weekend system. Temperatures will warm into the 80s to near 90 degrees by Tuesday. && .AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon) ISSUED AT 1230 PM CDT Wed Jun 20 2018 MVFR/IFR conditions will slowly improve to VFR through 00z/21 across eastern Iowa and northern Illinois. An approaching upper low will help generate SHRA/TSRA through at least 18z/21. Given the high moisture levels in the atmosphere, any TSRA/SHRA that affects a TAF site will have the potential to create brief MVFR if not IFR conditions. && .HYDROLOGY... Issued at 330 AM CDT Wed Jun 20 2018 Periods of heavy rain through Friday will likely have a significant impact on the river flooding situation in the area. Widespread 1 to 3 inch amounts still look reasonable, although confidence in favored areas for heaviest rain is still low. Nonetheless, we can expect delayed drops, renewed rises, and potentially higher crests at locations in or near flood, as well as additional flooding possible at new locations. With the expected rainfall, flooding is looking more likely on the Rock basin this week. A warning continue for Joslin while Moline is under a flood watch. Dewitt is currently forecast to remain in moderate flood for the next couple of days before falling, although this could change depending on how the weather plays out through Friday. In bank rises are also forecast along the mainstem Mississippi with increased input from the tribs. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && UPDATE...08 SYNOPSIS...12 SHORT TERM...12 LONG TERM...RP Kinney AVIATION...08 HYDROLOGY...RP Kinney
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 456 AM CDT Wed Jun 20 2018 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-211000- Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson- Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson- Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll- Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson- Warren-Hancock-McDonough-Scotland-Clark- 456 AM CDT Wed Jun 20 2018 This Hazardous Weather Outlook is for portions of north central Illinois...northwest Illinois...west central Illinois...east central Iowa...northeast Iowa...southeast Iowa and northeast Missouri. .DAY ONE...TODAY AND TONIGHT More rounds of scattered thunderstorms will occur across the area this morning, then again by late afternoon and into the evening. There will be a chance for some strong to severe storms with the afternoon and evening storms. The primary threat from these storms will be damaging winds, but there will also be a chance for an isolated tornado with any strong storm moving along a frontal boundary that is currently draped across the area along and south of Interstate 80. The Storm Prediction Center has placed areas generally along and south of a line from Cedar Rapids Iowa, to the Quad Cities, and to east of Galesburg Illinois, in a marginal risk for severe weather today and tonight. The storms will also have the capability of producing very heavy rainfall and at high rates. Areas that experience repeated thunderstorm activity will have the possibility of being impacted by flash flooding. The heavy rain will also aggravate any ongoing river and small stream flooding. A few area rivers are experiencing flooding. Please see the latest Flood Statements and Flood Warnings for details. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY Expect widespread rain and scattered thunderstorms Thursday and Friday. The severe weather risk is low. However, additional rounds of heavy rainfall on already saturated ground may lead to flooding problems, including isolated flash flooding. Flooding is expected to continue on some tributary rivers. Rounds of heavy rainfall may also cause additional river sites to rise later this week. Please see the latest Flood Statements and Flood Warnings for details. Thunderstorms are possible late Saturday into Sunday, and again late Monday into Tuesday. It is too early to determine the potential for severe weather. .SPOTTER INFORMATION STATEMENT... There is a chance that spotter activation will be needed today and tonight. 12/RP Kinney
Special Weather Statement
National Weather Service Quad Cities IA/IL
1152 AM CDT WED JUN 20 2018
ILC177-201945-
Stephenson-
1152 AM CDT WED JUN 20 2018
...Minor flooding ongoing along and near Yellow Creek...
On Wednesday morning, local emergency management reported ongoing
minor flooding on Yellow Creek and adjacent areas. It is reported
that river levels have not receded after the inital rise Monday
night and Tuesday and many acres of land have yet to drain into the
creek.
Rainfall amounts of 3.50 inches to 7.00 inches fell in the basin
Monday night into Tuesday morning.
Any additional rainfall prior to river levels receding will cause
additional flooding.
If you are driving and encounter a flooded roadway, Turn around,
don't drown. Most flood deaths occur in vehicles.
LAT...LON 4229 8976 4228 8970 4231 8956 4228 8954
4224 8967 4223 8976 4224 8981 4232 8991
4238 8987
TIME...MOT...LOC 1647Z 000DEG 0KT 4225 8975
BrooksSpecial Weather Statement
National Weather Service Quad Cities IA/IL
214 PM CDT WED JUN 20 2018
IAC087-095-101-107-111-177-183-MOC045-199-202015-
Henry-Van Buren-Keokuk-Washington-Jefferson-Iowa-Lee-Scotland-Clark-
214 PM CDT WED JUN 20 2018
...A LINE OF STRONG THUNDERSTORMS WILL AFFECT HENRY...VAN BUREN...
KEOKUK...WASHINGTON...JEFFERSON...SOUTHERN IOWA...LEE...SCOTLAND AND
CLARK COUNTIES UNTIL 315 PM CDT...
At 213 PM CDT, radar indicated strong thunderstorms were located
along a line extending from 7 miles northwest of What Cheer to near
Lockridge to near South Gorin. Movement was northeast at 25 mph.
Winds in excess of 40 mph and pea size hail are possible with these
storms.
Locations impacted include...
Fort Madison, Keokuk, Fairfield, Mount Pleasant, Washington, Kahoka,
Sigourney, Memphis, Keosauqua, Williamsburg, New London, Warsaw,
Wellman, Winfield, North English, West Point, Donnellson, Montrose,
Hedrick and Brighton.
This includes Interstate 80 in Iowa between mile markers 207 and 218.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
LAT...LON 4151 9241 4151 9230 4167 9230 4177 9214
4124 9148 4116 9148 4115 9137 4038 9142
4025 9150 4026 9195 4030 9195 4030 9215
4060 9226 4060 9218 4116 9218 4116 9241
TIME...MOT...LOC 1913Z 224DEG 20KT 4149 9245 4094 9177 4031 9202
GibbsThe Des Moines radar (KDMX), 127 km away, was scanning. The volume nearest the first event began at 19:30 UTC.
5 thunderstorm wind, 1 tornado, 1 funnel cloud, 1 flash flood. Local standard time, as filed.
A storm survey by the emergency manager found that an EF0 tornado occurred between Delta and Sigourney and moved northeast 6.3 miles before lifting. Damage to corn occurred along the path with winds estimated around 65 mph.
Three inch diameter tree branches down.
Power poles broken and crop damage reported through KCRG TV.
Large tree branches blown down.
A tree was blown down in northern Keokuk. The time was estimated by radar.
A small light pole was blown down with 2 inch diameter branches blown down nearby.
Widespread significant flash flooding reported throughout the city of Davenport. Numerous major and neighborhood streets 2 to 4 feet under water. Some cars were flooded up through hoods.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2018Every state in 2018This day in weather historyThe tornado archive for Iowa, 2018Warnings in Iowa, June 2018
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: 756013, 756014, 756015, 756016, 756017, 764637, 756018, 756012.