A fast moving complex of severe thunderstorms developed and tracked over much of eastern Iowa, northwest Illinois, and northeast Missouri, as an area of low pressure lifted northeast into northwest Iowa. Widespread damaging winds, large hail, frequent lightning, and a few brief tornadoes were reported.
Every event with a place to put it. Tap one for its entry below.
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 fast moving complex of severe thunderstorms developed and tracked over much of eastern Iowa, northwest Illinois, and northeast Missouri, as an area of low pressure lifted northeast into northwest Iowa. Widespread damaging winds, large hail, frequent lightning, and a few brief tornadoes were reported.
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 May 17, 1:38 AM CST, 3 hours 49 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 238 AM CDT Wed May 17 2017 .SYNOPSIS... Issued at 230 AM CDT Wed May 17 2017 At 230 AM CDT, showers and thunderstorms extended from northern Missouri, through central Iowa into portions of Minnesota and Wisconsin. A south breeze was gusting around 30 mph in some locations, helping keep early morning temperatures mainly in the low 70s. && .SHORT TERM...(Today and Tonight) ISSUED AT 230 AM CDT Wed May 17 2017 The main issues in the short term period are thunderstorm coverage/intensity and severe weather potential. In the near term, scattered thunderstorms should continue to spread into the western counties through daybreak, and eventually northeast across much of the forecast area before diminishing during the late morning. Relatively modest instability should keep the morning severe weather threat under control, although steep mid-level lapse rates suggest marginally severe hail may be possible. Attention then turns to the main event this afternoon and event. Various CAMS develop discrete cells and storm clusters early this afternoon, with strong to severe storms continuing into the early evening. A potent negatively tilted upper low will supply substantial kinematic forcing, and there is expected to be enough insolation to boost SBCAPE values near 2000 j/kg and perhaps a bit higher. Strong low level flow will result in very fast storm motions on the order of 45 mph and higher. Bufr soundings indicate strongly kinked hodographs with abundant low level shear and helicity, as well as an inverted-V profile. Bottom line for this afternoon/evening is the primary threats will be fast-moving storms with tornadoes and damaging winds as the main threats, and to a lesser extent, large hail. SPC has upgraded most of the forecast area to an enhanced risk for today. Storm coverage and intensity should wane after 10 pm. .LONG TERM...(Thursday through Tuesday) ISSUED AT 230 AM CDT Wed May 17 2017 The overall large scale signal continues to indicate an active weather pattern into next week. Temperatures look to be at or below normal and precipitation has the potential to average above normal. Quiet and dry conditions will be seen across the area on Thursday as the storm system exits the area. A dry cold front moving through the area during the day is expected to keep temperatures below normal over the northwest third of the area. Attention then turns to the next storm system. The next storm system consists of two parts that will affect the area roughly 1-1.5 days apart. There are disagreements among the model solutions as to the overall timing when each part moves through the area. Dprog/dt of the various models is indicating a slower arrival of the first part Thursday night/Friday which is being reflected more in the overall forecast. As of now Thursday evening will be dry across the area with a chance of rain over the southwest half of the area after midnight. If the current slowing trend continues, the possibility does exist that most of the area could remain dry Thursday night. If the slowing trend continues, then Friday morning would end up being dry for at least half of the area before rain moves into the area. The better rain chances look to be along/west of the Mississippi but the overall large signal shows broad lift across the area which would support a chance of rain. Friday night the second part of the system arrives. As before, this part of the system could also end up being slower as well. Unlike the first part, the rain threat for the second part would be across the entire area, especially late Friday night. Saturday on... The second part of the next system will move through the area Saturday/Saturday night. No one area is favored for rain during the day Saturday. However, areas along and east of the Mississippi show a stronger signal for rain Saturday night. The model consensus has likely pops for the entire area on Saturday and chance to likely pops Saturday night. Starting Sunday there is a significant difference of opinion between the global models. The CMC global develops another upper low over the area and keeps rain going Sunday into Monday. The GFS/ECMWF have no such system but do have very weak cyclonic flow aloft that could generate some diurnal showers. However, much of the area would remain dry. The differences between the GFS/ECMWF and the CMC global appear to be related to how energy in the northern and southern streams interact with the upper low out west later this week and when the next system upstream arrives to kick it out. The CMC global develops the upper low much further south than the GFS/ECMWF and the upstream system to kick it out into the Plains arrives slower. As a result of these differences, the model consensus has chance pops for the entire area on Sunday with slight chance pops across the northern third of the area Sunday night/Monday. If the GFS/ECMWF solutions turn out to be correct, then the Sunday into Monday time frame would end up being dry. Monday night/Tuesday the next storm system will slowly move through the Midwest. However, there are differences between the models on timing and the overall track. As a result, the model consensus has slight chance to chance pops Monday night and chance pops on Tuesday. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday Night) ISSUED AT 1151 PM CDT Tue May 16 2017 Widespread thunderstorms over central and western Iowa will likely decrease in intensity as they move into eastern Iowa tonight, but are appearing likely to reach the CID, DBQ and MLI terminals before sunrise with at least brief MVFR conditions. Scattered to isolated cells may linger until mid morning before dissipating. During the overnight, conditions may come close to low level wind shear thresholds due to strong southwest winds just above the surface. However, at this time it appears this vertical transition to stronger winds will not be sharp enough to justify a LLWS in the forecasts. Wednesday, most of the day looks to be VFR with gusty south winds at the surface. Scattered strong to severe thunderstorms are possible from mid afternoon through the evening. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && SYNOPSIS...RP Kinney SHORT TERM...RP Kinney LONG TERM...08 AVIATION...Sheets
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 302 AM CDT Wed May 17 2017 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-180815- 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- 302 AM CDT Wed May 17 2017 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...TONIGHT Scattered thunderstorms are expected this morning. The main threats are lightning and hail to penny size. More widespread thunderstorms are expected this afternoon and evening. Fast-moving storms could produce damaging winds around 70 mph and tornadoes. A secondary threat is large hail. A south wind will gust around 40 mph this afternoon. Drivers of high profile vehicles should use caution. Area rivers are experiencing flooding. Please see the latest Flood Statements and Flood Warnings for details. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY There is a risk of thunderstorms late Thursday night through Saturday evening. It is too early to determine the severe weather risk. .SPOTTER INFORMATION STATEMENT... Spotter activation is expected between 2 PM and 10 PM CDT today. RP Kinney/08
Special Weather Statement
National Weather Service Quad Cities IA/IL
123 AM CDT WED MAY 17 2017
IAC011-019-031-055-061-087-095-101-103-105-107-113-115-139-183-
170700-
Keokuk-Cedar-Benton-Washington-Delaware-Muscatine-Jefferson-Linn-
Henry-Louisa-Buchanan-Dubuque-Johnson-Jones-Iowa-
123 AM CDT WED MAY 17 2017
...ISOLATED THUNDERSTORMS AND STRONG OUTFLOW WINDS WILL MOVE THROUGH
PORTIONS OF EASTERN IOWA EARLY THIS MORNING...
At 117 AM CDT, radar indicated thunderstorms from Vinton to Marengo,
with outflow winds extending south through Williamsburg and
Sigourney. Storms were moving northeast at 50 mph.
Winds gusts around 40 mph and small hail are possible.
Locations impacted include...
Cedar Rapids, Iowa City, Washington, Independence, Anamosa, Vinton,
Manchester, Marengo, West Branch, Sigourney, Columbus Junction,
Mechanicsville, Stanwood, Marion, Coralville, North Liberty,
Hiawatha, Mount Vernon, Dyersville and Monticello.
This includes the following highways...
Interstate 80 in Iowa between mile markers 205 and 261.
Interstate 380 between mile markers 1 and 55.
Persons in campgrounds should consider seeking sturdy shelter until
these storms and strong winds pass.
LAT...LON 4151 9241 4153 9230 4229 9230 4230 9206
4264 9208 4265 9127 4236 9101 4114 9136
4113 9218 4116 9218 4116 9241
TIME...MOT...LOC 0617Z 232DEG 67KT 4240 9237 4184 9192 4120 9206
RP KINNEYThe Quad Cities radar (KDVN), 114 km away, was scanning. The volume nearest the first event began at 11:25 UTC.
46 thunderstorm wind, 23 hail, 4 tornado. Local standard time, as filed.
The local law enforcement reported extensive wind damage to trees, farm outbuildings, and one house and garage along Cedar Street for about 5 miles. Several hog confinement buildings lost parts of their roofs.
Tornado rated an EF-1 tornado with peak winds 110 mph, a path length of 1.27 miles, and a max width of 25 yards. This rapidly moving tornado moved almost due north damaging farm outbuildings and trees. It moved from Jefferson County into Washington County. This tornado was spotted and reported by local fire department spotters.
Tornado rated was an EF-1 tornado with peak winds 110 mph, a path length of 1.95 miles, and a max width of 25 yards. This rapidly moving tornado moved almost due north damaging farm outbuildings and trees. It moved from Jefferson County into Washington County. This tornado was spotted and reported by local fire department spotters.
The county emergency manager reported a tree was blown down in Birmingham onto a power line and another tree was downed onto Highway J16.
The local fire department reported a few medium sized tree branches were down.
A trained spotter reported 2 semis on Highway 34 were blown over.
Pictures of hail the size of golf balls were received via social media.
The local law enforcement reported some outbuildings. A shed, and a few windows and roofs were damaged.
A trained spotter reported several trees were damaged, and some boards were blown off the railroad walkway.
A trained spotter reported a large tree branch about 18 feet long was torn off a tree.
A trained spotter reported several tree branches down.
The local law enforcement reported a roof was off a shed, a garage, and hog and horse structures. Another garage was torn off a house. Trees and power lines were down with one tree down on a road.
The hail size was estimated from a picture on social media.
The county emergency manager reported power poles and trees were snapped from Ladora to Marengo. Some of these trees fell on houses and other buildings.
Tornado was rated was an EF-1 with peak winds of 110 mph, a path length of 5.95 miles, and a max width of 40 yards. This tornado spun up and tracked rapidly to the northeast. The tornado damaged numerous farm outbuildings, power lines and trees along its path.
Spotter reported a mix of stones between the size of dimes and quarters.
The spotter reported hail lasted 10 minutes and covered the ground.
A trained spotter reported a large tree was down. This report was relayed from Des Moines Weather Forecast Office.
Report was from a local resident using a personal weather instrument.
A public report was received of quarter sized hail, also winds up to 55 MPH and heavy rain.
The county emergency manager reported estimated winds up to 70 mph.
A picture was received from social media via Twitter of a roof blown off a home.
A trained spotter estimated wind gusts to 60 mph.
The county emergency manager reported winds up to 70 mph.
A trained spotter reported wind gusts up to 70 MPH.
A public report was received of estimated wind gusts to 65 mph.
The spotter reported the hail lasted for 1 minute.
A public report was received of a tree blown over.
A trained spotter reported wind gusts up to 70 mph.
Local broadcast media reported a swath of trees was blown down in Paris.
A trained spotter reported wind gusts up to 70 mph.
A trained spotter reported estimated winds of 60 to 70 mph with nearly horizontal rain.
The local fire department reported a measured wind gust of 77 knots.
The county emergency manager reported wind gusts of up to 70 mph.
The Washington Airport AWOS sensor measured this wind gust.
A measured wind gust from a Iowa Department of Transportation road sensor near highway 151.
Tornado was rated as EF-1 with peak winds of 100 mph, a path length of 2.14 miles, and a max width of 25 yards. This tornado was associated with a squall line. Numerous trees were damaged or uprooted with a few rotten trees snapped about 20 feet above the ground. Roofing damage was observed to a new home and garage at the beginning of its path.
The county emergency manager reported a tree had fallen on a house.
The spotter reported hail the size of peas to pennies.
The county emergency manager reported a parked semi was blown over and damage to farm outbuildings. Also power poles were down.
The county emergency manager received a report from the sheriff's office of a barn blown down in Lone Tree on 640th and SOO.
This report was from the county emergency manager who estimated wind gusts up to 75 mph.
A trained spotter reported a wind gust estimated to 70 mph.
The county emergency manager reported a measured wind gust of 63 knots.
A trained spotter reported estimated wind gusts to 60 mph along with very heavy rain.
A public report was received of a 60 foot tree that fell through a garage in town.
A trained spotter reported several farm buildings damaged near Dyersville.
The county emergency manager reported a measured wind gust of 68 knots.
A trained spotter reported a measured wind gust of 52 knots.
A trained spotter reported a tree split in half at the corner of Sun Valley Drive and Spring Street. On Green Street, several large tree branches were down.
A picture from the public of hail was received via Twitter. The time was estimated from radar.
Trained spotter reported quarter sized hail at the I-80 truck stop.
The Iowa Department of Transportation measured this wind gust near DeWitt Iowa.
The county emergency manager reported a hoop building had half of its soft roof torn off.
A trained spotter reported estimated winds of 50 to 60 mph.
The county emergency manager reported many trees and branches were blown down in the town of Camanche. At least one large tree fell on a house, causing $50,000 in damage.
A trained spotter reported estimated winds of 50 to 60 mph for 5 minutes.
Local amateur radio relayed a report of winds estimated at 50 to 60 mph.
A public report was received with a picture of hail using social media.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2017Every state in 2017This day in weather historyThe tornado archive for Iowa, 2017Warnings in Iowa, May 2017
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: 702922, 702825, 703265, 703267, 702918, 702908, 702904, 702837, 702826, 702911, 702915, 702827, 702833, 702909, 702995, 702998, 702878, 702835, 702838, 702840, 702999, 703274, 702842, 702851, 702925, 702926, 702927, 702846, 702930, 703000, 702931, 702933, 702935, 702965, 702853, 703001, 702936, 703002, 702939, 702941, and more.